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Thanks for a great class!

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Association, Commissural, and Projection Fibers

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Association, Commissural, and Projection Fibers

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Internal Cerebrum (Association, Commissural, Projection Fibers, Basal Ganglion)

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How to learn major parts of the brain quickly

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"If we imagine our brain as a peach, on the cross section of that peach we’d see the outer skin, the flesh, and an inner stone. The skin is analogous to the cerebral cortex, the fleshy part is the deep white matter, and the stone represents the subcortical structures.

Subcortical structures are a group of diverse neural formations deep within the brain, which include the diencephalon, pituitary gland, limbic structures and basal ganglia. They are involved in complex activities such as memory, emotion, pleasure, and hormone production. They act as information hubs of the nervous system, as they relay and modulate information passing to different areas of the brain." - Source

Here is a superior view of the subcortical (below-the-cortex) structures, aka, the peach pit.

https://www.youtube.com/watch?v=Na_4HZLvFiM

The video above reviews the thalamus, hypothalamus, epithalamus, and subthalamus

The thalamus is going to send sensory information from the sense organs to the appropriate cortical lobe (acting as the switchboard) to make sure sensory information gets where it needs to go. For example, the thalamus will route visual signals from the eyes to the occipital lobe for processing, etc.

The epithalamus contains the pineal gland. Nuclei within the epithalamus also send signals to the limbic system responsible for emotion.

The hypothalamus directly controls the release of hormones from the pituitary gland; (it does this by releasing its hormones in a downstream axis. It helps to regulate body temperature (sweating and shivering), the sensation of hunger/satiety, thirst, and the internal clock or circadian rhythm.

The subthalamus is ventral to the thalamus and, confusingly, contains the subthalamic nucleus as one of its components. Technically, the STN is part of the basal ganglia. We aren't going to go into immense detail - but for now, it is helpful to know that the subthalamus helps to regulate movement.

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Author: Onome Okpe * Reviewer: Gordana Sendić MD
Last reviewed: October 30, 2023
Reading time: 8 minutes

Commissural pathways are white matter fiber bundles that bridge the midline and connect identical cortical structures in the opposite hemispheres of the brain.

In contrast to commisural fibers, there are association fibers, that connect different cortical regions within the same hemisphere, and projection fibers, that connect a cortecal region to lower parts of the brain or the spinal cord.

The most recognised and well understood commissural pathways are the corpus callosum, anterior commissure, posterior commissure, habenular commissure, and the hippocampal commissure (commissure of the fornix).

The main function of commissural pathways is to ensure integration of functions between left and right structures of the brain. Thus, they are involved in manyfunctionsincluding cognitive functions like memory and several motor and perceptual functions.

This article will discuss the anatomy and function of commissural pathways.

Definition

White matter fiber bundles that bridge the midline and connect identical cortical structures in the opposite hemispheres of the brain.

Main commissures

Corpus callosum, anterior commissure, posterior commissure, habenular commissure, and the hippocampal commissure (commissure of fornix).

Corpus callosum

Parts: Body, genu and splenium
Function: Connects corresponding regions of almost all parts of the cerebral cortex of the two hemispheres

Anterior commissure

Parts: Anterior and posterior bundle
Function: Connects structures of the olfactory pathway, the frontal cortex, temporal pole and parahippocampal gyri

Posterior commissure

Function: Connects the language processing centres of both cerebral hemispheres

Habenular commissure

Function: Connects the habenular nuclei of the two cerebral hemispheres

Hippocampal commissure

Function: Connects the hippocampi of the two cerebral hemispheres

General function

Integration of functions between left and right structures of the brain.
Involved in memory and several motor and perceptual functions.

Corpus callosum

The corpus callosum is the main and largest of the commisural pathways that connects the right and left cerebral hemispheres. During embryonic development, this commissural pathway may fail to develop, leading to a congenital condition called split brain effect as the two cerebral hemispheres are not connected. An after-birth or 'postnatal' implication of this condition is that if one hand, for example, is trained to perform an act, the other hand may not be able to do so.

The absence of a fully developed corpus callosum have a significant relationship with impaired verbal processing speed and problem-solving.

The corpus callosum is subdivided into 3 parts. The central part is called the body or trunk. The anterior end is bent on itself to form the genu, while the elongated posterior end is known as the splenium. These are the major parts of the corpus callosum, but they are are divisible into sub-parts for localization of structures.

A thin lamina of nerve fibres, which form the rostrum of the corpus callosum, connects the genu to the upper end of the lamina terminalis. The corpus callosum is intimately related to the lateral ventricle, and its lower surface gives attachment to the septum pellucidum. As a true commissural pathway, its fibres interconnect the corresponding regions of almost all parts of the cerebral cortex of the two hemispheres.

[Coronal section of the brain (thalamus level): White matter structures]

From the genu, fibres run forwards into the frontal lobes, the fibres of the two sides forming a fork-like structure called the forceps minor. Many fibres of the splenium run backwards into the occipital lobe to form a similar structure called the forceps major (each half of this structure bulges into the posterior horn of the corresponding lateral ventricle, forming the bulb of the posterior horn).

Fibres of the trunk of the corpus callosum (and some from the splenium) run laterally, and intersect the fibres of the corona radiata as they do so. As fibres of the trunk and of the splenium pass laterally, they form a flattened band referred to as the tapetum which is closely related to the posterior and inferior horn of the lateral ventricle.

Anterior commissure

The anterior commissure is located in the anterior wall of the third ventricle at the upper end of the lamina terminalis. It runs across the midline in front of the anterior columns of the , above the basal forebrain and beneath the medial and ventral aspect of the anterior limb of the internal capsule.

The anterior commissure is divided into an anterior and a posterior bundle when traced laterally, and the posterior half passes underneath the lentiform nucleus of the basal ganglia.

This commissural pathway mainly interconnectsthe regions of the two cerebral hemispheres concerned with the olfactory pathway such as the olfactory bulb, the anterior olfactory nucleus, the piriform cortex, the entorhinal area, the anterior perforated substance, and the amygdaloid complex.

The anterior commissures also links other parts of the two hemispheres such as caudal part of the orbital frontal cortex, the temporal pole, the rostral superior temporal region, the major part of the inferotemporalarea, the parahippocampal gyri and other regions of the two temporal lobes, as well as the frontal lobesof the two hemispheres.

Posterior commissure

The posterior commissural pathway is major part of the epithalamus and forms one of the stalks that attach the pineal body (pineal gland) to the posterior wall of the third ventricle.

The posterior commissure is the inferior lamina or stalk of the pineal gland and is important in language processing and connects the language processing centres of both cerebral hemispheres. It is closely related in function to the splenium of the corpus callosum, and injury to it may lead to disorders such as alexia.

Habenular commissure

The superior lamina or stalk of the pineal body is called the habenular commissure and connects the habenular nuclei of the two cerebral hemispheres. Thus it is also a vital part of the epithalamus.

Commissure of fornix

The hippocampal commissure, or commissure of fornix, is a bundle of fibres interconnecting the hippocampi of the two cerebral hemispheres. More specifically, this commissure connects a part of the body of the fornix called the crus on both sides of the midline.

The fornix, which is composed predominantly of fibres arising from the hippocampus, has a body that when traced posteriorly divides at the middle line into two parts called crura (pleural of crus).

The commissure of the fornix is one of the four bundles of fibres contained in the fornix of the brain. The remaining three being the postcommissural fornix lying behind the anterior commissure, the precommissural fornix, which descends anteriorly to the anterior commissure, and a bundle of fibres running above the splenium of the corpus callosum. This bundle of running fibres is referred to as the dorsal fornix.

References:

S. Standring: Gray's Anatomy - The Anatomical Basis of Clinical Practice, 40th edition, (2008), p. 227, 239 - 241, 326, 356 - 357, 380, 385.

Illustrators:

Corpus callosum (sagittal view) - Paul Kim

Corpus callosum (ventrolateral view) - Paul Kim

Anterior commissure (sagittal view) - Paul Kim

Posterior commissure (sagittal view) - Paul Kim

Habenular commissure (sagittal view) - Paul Kim

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Did you know that the brain hemispheres are connected by bundles of fibres known as commissural pathways? These are the fascinating topic of this article!

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You might have heard artists say they're right-brained or mathematicians say they're left-brained. Maybe when you were a kid someone noticed you were left-handed and told you that meant you were creative. The idea that some of us are "left-brained" and others are "right-brained" is extremely popular. But, like so many other appealing ideas, the science doesn't support it. People use both halves of their brain equally, and even within an individual person, creative and analytical thinking require both the left and right brain. I only learned this about a month ago, and as a 25-year-old graduate student working in neuroscience, I was shocked and embarrassed by my naiveté. I had heard so many professors, physicians and even scientists use the terms "right-brained" and "left-brained." How could an idea with such little basis in reality have taken such a strong root? In this article, I discuss left brain right brain research, discoveries leading to the development of the brain laterality myth, studies disproving it and theories as to what makes this particular myth so hard to shake.

History Sets the Stage: The Left Brain Right Brain Myth

The idea that the right and left halves of our bodies might be different arose very early in human history. Early humans discovered that there was a near universal preference for the right hand. Not only did this suggest some asymmetry in our anatomy, but it also quickly led to the association of right with positive values and left with sinister, negative values. It's why we use the phrase "right-hand man" to mean someone we trust and, conversely, why the word "sinister" comes from the Latin root for "left." This went as far as the severe stigmatization of left-handed individuals. Left-handed people were associated with everything society hated, including black magic and sexual deviance, and many were forced to use their right hand as dominant. ¹ Later, when we figured out that the right half of the body is controlled by the left half of the brain, the left hemisphere was naturally seen as more important and dominant.

It wasn't until the 1800s that humans discovered certain brain regions were responsible for certain functions. When a 19th century railroad worker named Phineas Gage shattered his frontal lobe, the once amiable, calm man became angry and irritable. Based on this, scientists who studied Phineas came to believe that the frontal lobe was specialized for emotion and impulse control. ² Determining function based on the behavioral deficits that result from a lesion in a particular area is known as "lesion deficit analysis" and is still practiced today. This technique eventually led to the discovery that speech is based mostly in the left brain.

After enough of these discoveries were made, the theory "functional specialization" arose, which suggests that certain functions rely on specific brain regions. ² Although this theory is well-supported, it was particularly vulnerable to hyperbole and metaphoric interpretation by nonscientists. In fact, the theory of functional specialization set the perfect stage for the experiments that jump-started the brain laterality myth, known as the split-brain experiments.

Left Brain, Right Brain: The Split-Brain Experiments

During a split-brain surgery, the connective tract joining the two hemispheres of the brain is cut, resulting in two completely separated halves or "hemispheres." In the 1960s, some of the first split-brain surgeries were performed on people with epilepsy, as separating the two halves of the brain was an effective treatment in reducing seizure frequency in these patients. ¹ This presented scientists with an unprecedented opportunity to investigate the unique functions of each half of the brain in a controlled system. From these experiments, the investigators discerned that, for the most part, the left half of the brain outperformed the right in language and rhythm, while the right half was superior in discerning spatial orientation, emotion and melodies. ³ This work won Roger W. Sperry the Nobel Prize in Physiology and Medicine in 1981. ¹

Since the 1960s, new technologies have allowed scientists to look at the brain with higher resolution. These new techniques demonstrate that, although there appears to be some specialization between the hemispheres of the brain, it is a lot more complex than previously thought, certainly more complex than is painted by the left-brain/right-brain ideology. ² Both creative and analytical thought activate both hemispheres equally. Some specific discrete tasks are lateralized, but during complex cognitive processes both hemispheres are involved and communicate. Lefties and righties alike use both hemispheres of their brains equally. ¹ So why do so many people believe that the two halves of our brain embody opposite ways of thinking, and that individual people have a dominant side? Although nuanced, the answer has to do with marketing and an inherently human drive to categorize.

The Rebirth of a Familiar False Dichotomy

By the 1970s, educational circles believed that traditional teaching practices reflected a tragic lack of effort to develop the right brain in children. The literary field advocated for "writing with right brain to release expressive powers." ³ Many artists and musicians turned to brain laterality for curricular and theoretical guidance. For many, the idea that there was an untapped well of creativity in the right, submissive halves of our brains was appealing. ⁴ In 1979, American artist, teacher and author Betty Edwards published her book Drawing on the Right Side of the Brain, in which she asserted that her success in drawing was due to an ability to switch into the "right mode" of her brain and tap into her creativity and emotional intelligence. Indeed, even today polarities of the brain are broadly invoked in art, business, education, literary theory and other facets of culture. 1,2

Is there something particularly alluring about the idea of brain laterality? There is no doubt that these ideas are good for business. ³ "Whole-brain learning" products appeal to anyone looking to improve in their chosen field. Additionally, categorizing oneself as right- or left-brained may satisfy a human craving for order. Similar to astrological signs, labeling ourselves by dominant brain hemisphere gives us the security of a defined personality type, capable of explaining actions in the past and predicting the future.

Another factor could be our tendency to define creativity and analytical thinking as opposites. This is known as the "cognitive-affective" dichotomy, which is rooted in early religious teachings. ⁴ Within this ideology there are two mutually exclusive and antagonistic forms of human thought and behavior - reason and emotion. We see variations on this theme throughout time and space again and again. Platonic idealism versus sensualism. The Freudian id versus superego. Science versus art. We repeatedly take two facets of the human experience and pit them against one another. Reason and emotion may be different, but as is the case with the halves of our brain, differences do not imply dichotomies. So resist the urge to define yourself and others as right- or left-brained, analytical or creative, emotional or reasonable. These characteristics co-exist in all of us, allowing us to exhibit a broad range of human behavior. Cry at sappy movies, paint masterpieces, do multivariable calculus and read business reports knowing that your whole brain is supporting you.
References

1. Corballis, M. C. (2014). Left brain, right brain: facts and fantasies. PLoS biology, 12(1), e1001767.

2. Helding, L. (2014). Singing with your whole brain: The right brain/left brain dichotomy. Journal of Singing, 71(1), 83.

3. Della Sala, S. (Ed.). (2007). Tall tales about the mind and brain: Separating fact from fiction. Oxford University Press, USA.

4. Wieder, C. G. (1984). The left-brain/right-brain model of mind: Ancient myth in modern garb. Visual Arts Research, 10(2), 66-72.

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Left- vs. Right-Brained: Why the Brain Laterality Myth Persists | Biomedical Odyssey

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You might have heard artists say they're right-brained or mathematicians say they're left-brained. Maybe when you were a kid someone noticed you were left-handed and told you that meant you were creative. The idea that some of us are "left-brained" and others are "right-brained" is extremely popular.

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Author: Reviewer: Edwin Ocran MBChB, MSc * Dimitrios Mytilinaios MD, PhD
Last reviewed: October 30, 2023
Reading time: 21 minutes

The cerebral cortex (cortex of the brain) is the outer grey matter layer that completely covers the surface of the two cerebral hemispheres. It is about 2 to 4 mm thick and contains an aggregation of nerve cell bodies. This layer is thrown into complex folds, with elevations called gyri and grooves known as sulci.

The cerebral cortex is quite distinct from the cerebrum (forebrain) which describes the two cerebral hemispheres (right and left), the largest part of the brain. The cerebrum consists of the outer grey matter (cerebral cortex), an inner mass of white matter made up of myelinated axons, which forms the bulk of the deeper structures of the cerebral hemispheres, and subcortical structures which include the diencephalon, pituitary gland, limbic structures and the basal ganglia.

The cerebral cortex is organized into distinct functional areas made up of sensory, motor and association areas. It has a broad range of functions including perception and awareness of sensory information, planning, and initiation of motor activity. It also plays a key role in higher cognitive functions, such as decision making, motivation, attention, learning, memory, problem-solving, and conceptual thinking.

This article will discuss the anatomy and functions of the cerebral cortex.

Definition

Outer gray matter layer of the cerebral hemispheres

Lobes

Each hemisphere is divided into six lobes: frontal, parietal, temporal, occipital, insular and limbic.

Principal sulci

Lateral sulcus (Sylvian fissure): Separates the temporal lobe from the frontal and parietal lobes
Central sulcus: Divides the frontal and parietal lobes
Parietooccipital sulcus: Separates the parietal and occipital lobes
Cingulate sulcus: Separates the limbic lobe from the frontal and parietal lobes
Collateral sulcus: Between the limbic lobe and temporal lobe

Principal gyri

Frontal lobe: Precentral gyrus, superior, middle and inferior frontal gyri
Parietal lobe: Postcentral gyrus, superior parietal lobule, inferior parietal lobule (supramarginal and angular gyri)
Temporal lobe: Superior, middle and inferior temporal gyri
Occipital lobe: Superior, middle and inferior occipital gyri, cuneus, lingual gyrus
Insular lobe: Gyrus breves, gyrus longus
Limbic lobe: Subcallosal, cingulate, parahippocampal gyri

Principal cortical areas/functional units

Frontal lobe: Prefrontal cortex, premotor cortex, primary motor cortex (Brodmann area 6), Broca's area (Brodmann areas 44 and 45)
Parietal lobe: Primary somatosensory cortex
Temporal lobe: Primary auditory cortex, Wernicke's area
Occipital lobe: Primary visual cortex (Brodmann Area 17)

Blood supply

Cortical branches of the anterior, middle and posterior cerebral arteries

Functions

Control of voluntary movement, attention, learning, memory, motivation, planning decision making, problem-solving, conceptual thinking, perception of sensory stimuli, language processing, visual processing and comprehension, modulation of emotion

Structure

The cerebral cortex is a dense layer of neuronal cell bodies that lines the outer surface of the cerebral hemispheres, just below the cranial pia mater of the meninges. This layer has a convoluted appearance
with many elevated ridges of tissue called gyri, alternating with grooves called sulci. This structural conformation is an important feature of the cerebral cortex because it increases the surface area of the cortex, and thus the number of neurons within it, allowing larger processing and cognitive abilities within the cerebral hemispheres.

Lobes of the cerebral cortex

The cerebral cortex is divided into six lobes based on the organization of major sulci. Each lobe has gyri that contain neuronal cell bodies involved in specific functions. Four of these lobes, the frontal, parietal, temporal and occipital lobes take their names from the overlying cranial bones. The insular lobe is located deep to the lateral sulcus, while the limbic lobe is located on the medial aspect of the hemisphere. The boundaries of these lobes are defined by major sulci that separate one region of the cerebral cortex from the other.

The major sulci on the lateral surface of each cerebral hemisphere are the lateral sulcus (Sylvian fissure) which separates the temporal lobe from the frontal and parietal lobes, and the central sulcus which divides the frontal and parietal lobes. Notable sulci on the medial surface of the cerebral hemisphere include the parietooccipital sulcus which separates the parietal and occipital lobes, the cingulate sulcus which separates the limbic lobe from the frontal and parietal lobes, and the collateral sulcus which separates the limbic lobe from the temporal lobe. The insular lobe, which lies at the base of the lateral sulcus, is separated from the surrounding frontal, parietal, and temporal lobes by the circular sulcus of the insula.

Histology of the cerebral cortex

Microscopically, the cerebral cortex is composed of cell bodies of billions of neurons, their dendrites, myelinated and unmyelinated axons which altogether form a unique, multilayered arrangement. In addition, it contains a dense population of supporting glial cells which include oligodendrocytes, astrocytes, microglia, and ependymal cells, and blood vessels. The neuronal cells of the cortex consist of six main cell types. These are the pyramidal cells (the main output neurons of the cerebral cortex), fusiform cells, stellate (granular) cells, basket cells, horizontal cells of Cajal-Retzius and cells of Martinotti. Histologically, the cerebral cortex is organized into six layers or horizontal laminae based on the size and shape of the neuronal bodies. These layers are designated by Roman numerals, and from superficial (at the pial surface) to deep, they are the:

Molecular (plexiform) layer (I): Contains mainly nerve axons and a few scattered horizontal cells of Cajal-Retzius

External granular layer (II): Composed of a varying density stellate (granular) cells and pyramidal cells

External pyramidal layer (III): Contains predominantly pyramidal cells of varying sizes

Internal granular layer (IV): Consists mostly of the stellate cells and a smaller portion of the pyramidal cells. It is usually the narrowest layer

Internal pyramidal layer (V): Contains mainly medium-sized to large pyramidal cells

Multiform (fusiform) layer (VI): Composed different types of neuron types, mostly fusiform cells with less dominant pyramidal cells and interneurons

[Cells and layers of the cerebral cortex]

Columnar organization of the cerebral cortex

The cerebral cortex can also be functionally divided into vertical formations that are called columns. These represent the functional units of the cortex and are capable of memorizing relations and performing more complex operations than a single neuron. Each column is oriented perpendicular to the cortical surface and it consists of all of the 6 cellular layers. Neurons are tightly connected inside one column, but also share connections with the adjacent and distant columns, and with the subcortical structures as well, particularly the thalamus.

Functional areas of the cerebral cortex

Additionally, the cerebral cortex can be divided into three functional areas: primary, secondary and associative. The cortical areas responsible for the elementary functions of either motor or sensory are primary areas. Secondary areas are located around every primary area and receive afferent projections from the corresponding primary areas and the thalamus. They are responsible for integrating the raw signal from the primary areas with the information received from the thalamus, to refine the primary area stimuli. Association areas, on the other hand, are cortical areas that integrate, process and analyze different kinds of stimuli that reach the brain and are involved in mediating higher mental functions.

Phylogenetic types of cortex

Different regions of the cerebral cortex can be categorized based on evolutionary history and relationships into three groups, the allocortex, mesocortex, and neocortex (isocortex).

The allocortex is the most ancient type of cortex and is composed of the archicortex and the paleocortex. It consists of three cellular layers: polymorphic, pyramidal and the molecular layer, and is associated with the limbic system. The paleocortex contains three to five layers of cells and mediates the sense of smell.

The mesocortex is a transitional form between the allocortex and isocortex. It contains three to six layers and is found in the insula, cingulate and parahippocampal gyri.

The neocortex, as its name suggests, is the most recent cortical region and makes up to 90% of the human cortex. It includes all of the lobes of the cortex except the limbic lobe and consists of six layers of cells or laminae.

Check out our videos, articles, illustrations and quizzes in this study unit to learn more about the histology of the cerebral cortex:

Brodmann areas

The cerebral cortex is divided into smaller areas structurally by sulci based on its histological structure and cellular organization. The resulting smaller regions are known as Brodmann areas. There are a total of 52 areas which have been shown to have distinct neuronal organization and have also been correlated to various cortical functions.

Frontal lobe

Primary motor cortex (Area 4), premotor cortex and supplementary motor cortex (Area 6), frontal eye field (Area 8), prefrontal cortex (Areas 9, 10)

Parietal lobe

Primary somatosensory cortex (Areas 1, 2, 3), somatosensory association cortex (Areas 5, 7), angular and supramarginal gyri (Areas 39, 40)

Temporal lobe

Primary auditory cortex (Areas 41, 42), secondary auditory cortex (Area 22)

Occipital lobe

Primary visual cortex (Area 17), secondary visual cortex (Area 18), associative visual cortex (Area 19)

Special Brodmann areas

Wernicke's area (22, 39, 40) - language comprehension
Broca's area (44, 45) - motor speech

The Brodmann areas can sometimes be challenging to understand! Take advantage of the videos, articles, illustrations and quizzes included in this study unit to learn the material from different perspectives.

Principal gyri of the cerebral cortex

The cerebral cortex has several notable gyri on each lobe which carry out its multitude of functions.

Frontal lobe

The frontal lobe is the largest lobe of the cortex and contains four main gyri located on its lateral surface: the precentral gyrus, superior, middle and the inferior frontal gyri. The precentral gyrus lies between the central and precentral sulci. It contains the primary motor cortex (Brodmann area 4), and is involved in integrating signals from different brain regions to modulate voluntary movement to the body and limbs on the contralateral side.

The superior frontal gyrus lies anterior to the precentral sulcus while the middle frontal gyrus lies between the superior and the inferior frontal sulci. The inferior frontal gyrus lies in the inferolateral surface of the frontal lobe below the inferior frontal sulcus, which separates it from the middle frontal gyrus. It is divided into three parts, a pars opercularis, pars triangularis, and pars orbitalis. In the dominant hemisphere, this region contains the Broca's speech area and is important in the motor component of speech production.

Parietal lobe

The parietal lobe contains the postcentral gyrus, superior and inferior parietal lobules. The postcentral gyrus is known as the somatosensory cortex (Brodmann area 3,1,2). It lies between the central and postcentral sulci and is the region of the cerebral cortex that receives and integrates sensory information related to touch and the sensing of body position and movement. The inferior parietal lobule (Brodmann area 39,40) consists of two gyri, the supramarginal gyrus and the angular gyrus. The supramarginal gyrus is located superior to the posterior aspect of the lateral fissure. The angular gyrus lies just posterior to the supramarginal gyrus. Both gyri are involved in auditory and visual perception and form part of Wernicke's area, which is a functional unit of the cerebral cortex that plays an important role in the comprehension of spoken language.

The superior parietal lobule (Brodmann area 5,7) is separated from the inferior parietal lobule by the intraparietal sulcus. This region is involved in integrating sensory and motor functions and provides input to the premotor cortex.

Temporal lobe

The temporal lobe consists of the superior, middle and inferior temporal gyri, separated by superior and inferior temporal sulci. The superior temporal gyrus contains a specialized region called the transverse temporal gyri of Heschl, which is also known as the primary auditory area (Brodmann area 41, 42). This region of the cerebral cortex is primarily responsible for the reception of auditory information. Posterior to the primary auditory area in the superior temporal gyrus, lies the auditory association area (Brodmann area 22), which is responsible for the interpretation of sounds and for the association of the auditory input with other sensory information. The posterior part of this region, in the dominant hemisphere (usually the left), contributes to Wernicke's area, which is important in the comprehension of language. The middle temporal gyrus is associated with the perception of movement within the visual field, while the inferior temporal gyrus plays a role in facial recognition.

Occipital lobe

The occipital lobe forms the caudal aspect of the cerebral hemisphere. Its lateral surface often exhibits significant variability in the sulci resulting in either two or three occipital gyri (superior, middle and inferior). On the medial surface of the occipital lobe, the calcarine sulcus separates the cuneus which lies above the sulcus from the lingual gyrus below. The regions of both gyri adjacent to the calcarine sulcus form the primary visual cortex (Brodmann area 17), which is responsible for the integration and perception of visual information.

Insular lobe

The insular lobe is buried deep to the lateral fissure. It contains a group of short gyri in its rostral region called short gyri (gyri breves) and another group of long gyri in its caudal region called l ong gyri (gyri longi). These sets of gyri are separated from each other by the central sulcus of the insula. The insular cortex is involved in receiving and processing and integration of various types of information, including taste sensation, visceral sensation, pain sensation, and vestibular function.

Limbic lobe

The limbic lobe is a ring of cortex on the medial aspect of each hemisphere that surrounds the corpus callosum. It forms part of the larger limbic system which is involved in emotional and behavioral expression. The limbic lobe is composed of the subcallosal, cingulate, and parahippocampal gyri.

The subcallosal gyrus lies below the rostrum of the corpus callosum. This area also corresponds with sections of Brodmann areas 24, 25, and 32, and is believed to be involved in depression.

The cingulate gyrus lies directly above the corpus callosum. It continues anteriorly around the genu of the corpus callosum, blending with the subcallosal gyrus. Posteriorly, the cingulate gyrus wraps around the splenium of the corpus callosum. It is separated from the corpus callosum by callosal sulcus, while the cingulate sulcus separates it from the frontal and parietal lobes. The cingulate gyrus is involved in modulating emotion, as well as in visceral motor processes.

The parahippocampal gyrus lies between the parahippocampal sulcus and the collateral sulcus which continues anteriorly as the rhinal sulcus. It contains the hippocampal formation and extends anteromedially as the uncus which contains the amygdala. The parahippocampal gyrus provides a path of communication between the hippocampus and all cortical association areas through which afferent impulses enter the hippocampus.The anatomy of the brain can be quite challenging. Learn neuroanatomy faster with our brain quizzes and diagrams!

The anatomy of the brain can be quite challenging. Learn neuroanatomy faster with our brain quizzes and diagrams!

Blood supply

The cerebral cortex receives its blood supply from cortical branches of the anterior, middle, and posterior cerebral arteries. The anterior and middle cerebral arteries arise as terminal branches of the internal carotid artery, while the posterior cerebral artery is a terminal branch of the basilar artery. The middle cerebral artery supplies mainly the lateral surface of the cerebral hemisphere, whereas the occipital lobe and the inferior temporal gyrus receive blood supply from the posterior cerebral artery. Branches from all three arteries supply the medial and inferior surfaces of each hemisphere.

Function

The cerebral cortex is organized into different functional areas/units that process various stimuli and are responsible for specific brain functions including sensory, motor and higher intellectual functions. Its neurons receive input from several subcortical structures conveyed by the thalamus as well as from other cortical regions via association fibers. Neuronal fibers from the cerebral cortex, in turn, project to several structures in the central nervous system including other cortical areas, the thalamus, basal nuclei, brainstem nuclei, pontine nuclei, cerebellum and spinal cord. These functional areas are located in the various lobes of the cerebral cortex.

The frontal lobe contains the prefrontal cortex, premotor cortex, primary motor cortex (Brodmann area 6), Broca's area (Brodmann areas 44 and 45). This lobe is responsible for the control of voluntary movement, and is involved in attention, short term memory tasks, motivation, planning and also contributes to personality traits.

The parietal lobe is responsible for integrating proprioceptive and mechanoceptive stimuli, and also plays a role in language processing. It contains the primary somatosensory cortex (Brodmann areas 3,2,1), somatosensory association cortex (Brodmann areas 5, 7), and the inferior parietal lobule which forms part of the Wernicke's area.

The occipital lobe contains the primary visual cortex (Brodmann Area 17) and is the center for visual processing.

The temporal lobe is involved in decoding sensory input into derived meanings for retention of visual memory and language comprehension. It contains the primary auditory cortex and Wernicke's area.

The insular cortex plays a role in the processing and integration of taste sensation, visceral and pain sensation and vestibular functions.

The limbic lobe contains areas that are concerned with the modulation of emotions, modulation of visceral and autonomic functions, learning, and memory.

Now that you've completed this article, take this quiz to solidify your knowledge about the basic structure and function of the brain!

Sources

All content published on Kenhub is reviewed by medical and anatomy experts. The information we provide is grounded on academic literature and peer-reviewed research. Kenhub does not provide medical advice. You can learn more about our content creation and review standards by reading our content quality guidelines.

References

Haines, D. E., Mihailoff, G. A., Cunningham, W., Schenk, M., Armstrong, G. W., & Runyan, C. P. (2018). Fundamental neuroscience for basic and clinical applications. Philadelphia, PA: Elsevier.

Mancall, E., Brock, D. & Gray, H. (2011). Gray's clinical neuroanatomy: the anatomic basis for clinical neuroscience. Philadelphia: Elsevier/Saunders.

Nolte, J. (2009). The human brain: an introduction to its functional anatomy. Philadelphia, PA: Mosby/Elsevier.

Nolte, J. & Angevine, J. (2013). The human brain in photographs and diagrams. Philadelphia, Pa: Elsevier Saunders.

Standring, S. (2016). Gray's anatomy: the anatomical basis of clinical practice. Philadelphia: Elsevier Limited.

Javed, K., Reddy, V., & Lui, F. (2019). Neuroanatomy, cerebral cortex.

Cerebral cortex: want to learn more about it?

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The cerebral cortex is the part of the brain responsible for higher cognitive abilities. Learn more about its structure and functions at Kenhub!

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Author: Reviewer: Alice Ferng B.S., MD, PhD * Dimitrios Mytilinaios MD, PhD
Last reviewed: October 30, 2023
Reading time: 12 minutes

Originally defined and numbered into 52 regions by the German anatomist Korbinian Brodmann in the early 1900's, the Brodmann areas of the cerebral cortex are defined by its cytoarchitecture (histological structure and cellular organization).

It is important to remember that the same Brodmann area numbers in humans and primates often do not translate to other species. In addition, these Brodmann areas have been widely redefined, discussed, debated, and refined exhaustively based on cytoarchitecture, cortical functions, and brain plasticity.

Areas 1, 2, 3

Primary somatosensory cortex (postcentral gyrus)

Area 4

Primary motor cortex (precentral gyrus)

Area 5

Somatosensory association cortex

Area 6

Premotor and supplementary motor cortex

Area 9

Dorsolateral/anterior prefrontal cortex (motor planning, and organization)

Area 10

Anterior prefrontal cortex (memory retrieval)

Area 17

Primary visual cortex

Area 22

Primary auditory cortex

Area 37

Occipitotemporal (fusiform) gyrus

Areas 22, 39, 40

Wernicke's area (language comprehension)

Areas 44, 45

Broca's area (motor speech programming)

This article will discuss the Brodmann areas and their function.

1. Anatomical basis

2. Important Brodmann areas

1. Areas 1,2,3

2. Area 4

3. Area 5

4. Area 6

5. Area 9

6. Area 10

7. Area 17

8. Area 22

9. Area 37

10. Areas 22, 39, 40

11. Areas 44,45

3. All Brodmann areas

4. Lesions of Brodmann areas

1. Areas 1,2,3

2. Area 4

3. Area 5

4. Area 6

5. Area 9

6. Area 10

7. Area 17

8. Area 22

9. Areas 22, 39, 40

10. Areas 44, 45

5. Sources

Anatomical basis

The Brodmann areas were initially based on the cytoarchitectural organization of neurons in the cerebral cortex.

Specifically, it was observed that they were organized in distinct groups once the cells were stained using the Nissl method (which consists of basic dyes, notably staining the rough endoplasmic reticulum-also known as Nissl substance-dark blue). Many of these areas of distinct neuronal organization have since been correlated to various cortical functions.

Since there are 52 distinct Brodmann regions, only a few of the major regions will be further elaborated in this article. However, a list of all areas defined can be found below for reference.

Neuroanatomy is big topic, so it's important to start with a solid foundation. Have you already mastered the basics? Our free diagrams and quizzes on the parts of the brain are a great place to get started.

Important Brodmann areas

Areas 1,2,3

Primary somatosensory cortex (or Postcentral gyrus) - this is numbered rostral to caudal as 3,1,2. This region is associated with several senses, such as the ones for:

localization of touch, temperature, vibration, pain

sensory perception (two-point discrimination, proprioception, etc.) especially the legs, trunk, arms, hands, face and lips

skilled and coordinated orofacial movement (i.e. whistling)

motor learning

Area 4

This are is also known as the p rimary motor cortex (or Precentral gyrus) (may possibly include part of Area 6). It is responsible for executing motor movements, which includes contralateral finger/hand/wrist or orofacial movements, learned motor sequences, breathing control, and voluntary blinking.

Precentral gyrus (cross section)

Area 5

Somatosensory association cortex - Brodmann area 5 is part of the parietal cortex. Associated functions include:

stereopsis

line bisection judgments

processing chaotic patterns

using spatial imagery in deductive reasoning

motor execution

bimanual manipulation

working memory

language processing

visuomotor attention

pain perception

tactile localization

saccadic eye movement

Area 6

Premotor and Supplementary Motor Cortex - this region is critical for the sensory guidance of movement and control of proximal and trunk muscles, and contributes to the planning of complex and coordinated motor movements. This area plays a large role in motor, language, and memory functions, including:

motor sequencing/planning

laughter/smiling

interlimb coordination

movement learning and initiation

motor imagery

speech motor programming

language processing and switching

speech perception

object naming

lip-reading

word retrieval

lexical decision on words and pseudowords

syntactical processing

working memory

mnemonic rehearsal

episodic long-term memory

topographic memory

visuospatial and visuomotor attention

attention to human voices

Note: The "Motor Association Cortex" includes areas 6, 8, 44, and 45. This association cortex is involved in movement throughout the body, including motor speech movements.

Area 9

Dorsolateral/anterior prefrontal cortex (DLPFC) - This region is the highest cortical area responsible for motor planning, organization, and regulation, and sustaining attention and working memory. The DLPFC plays an important role in:

integrating sensory and mnemonic information

regulation of intellectual function and action

the act of deception and lying

In sum, all complex mental activities require crosstalk between cortical and subcortical circuits that are connected to the DLPFC.

Area 10

Anterior prefrontal cortex - involved in strategic processes of memory retrieval and executive functions, such as

reasoning

task flexibility

problem solving

planning

execution

working memory

processing emotional stimuli

inferential reasoning

decision making

calculation of numerical processes

There is a significant role of Areas 9 and 10 in memory encoding and retrieval, and area 10 is thought to control and manipulate event and time-based prospective memory (metamemory), and allow "intentional forgetting."

Area 10 is also involved in attending to sensory stimulation and use of language (generating sentences, word-stem completion, verbal fluency, syntactic processing, and metaphor comprehension).

Area 17

Primary visual cortex (V1) - the visual cortex is located in the occipital lobe in the back of the brain, and contains a well-defined map of the spatial information required for vision.

Area 22

Primary auditory cortex / Superior Temporal Gyrus (part of Wernicke's area) - this region is situated close to the external ear and involves complex language and auditory processing.

Area 37

Fusiform Gyrus / Occipitotemporal Gyrus - this region is largely involved in:

processing of color information

face and body recognition

word and number recognition

Areas 22, 39, 40

Wernicke's area - the gyri that comprise this area may be larger or smaller in different people and itis responsible for speech fluency. More precisely, this area allows you to string words together in complete and sensical sentences. An easy way to temember is to think of "Wordy Wernicke".

Areas 44,45

Broca's area - this region is associated with the praxis of speech (motor speech programming). This includes:

being able to put together the binding elements of language

selecting information among competing sources

sequencing motor/expressive elements

cognitive control mechanisms for syntactic processing of sentences

construction of complex sentences and speech patterns

You can remember it by thinking of "Broken boca" where boca means 'mouth' in Spanish.

All Brodmann areas

Areas 3, 1 & 2 - Primary Somatosensory Cortex (frequently referred to as Areas 3, 1, 2 by convention)

Area 4 - Primary Motor Cortex

Area 5 - Somatosensory Association Cortex

Area 6 - Premotor cortex and Supplementary Motor Cortex (Secondary Motor Cortex) (Supplementary motor area)

Area 7 - Somatosensory Association Cortex

Area 8 - Includes Frontal eye fields

Area 9 - Dorsolateral prefrontal cortex

Area 10 - Anterior prefrontal cortex (most rostral part of superior and middle frontal gyri)

Area 11 - Orbitofrontal area (orbital and rectus gyri, plus part of the rostral part of the superior frontal gyrus)

Area 12 - Orbitofrontal area (used to be part of BA11, refers to the area between the superior frontal gyrus and the inferior rostral sulcus)

Area 13 and Area 14* - Insular cortex

Area 15* - Anterior Temporal Lobe

Area 16 - Insular cortex

Area 17 - Primary visual cortex (V1)

Area 18 - Secondary visual cortex (V2)

Area 19 - Associative visual cortex (V3,V4,V5)

Area 20 - Inferior temporal gyrus

Area 21 - Middle temporal gyrus

Area 22 - Superior temporal gyrus, of which the caudal part is usually considered to contain the Wernicke's area

Area 23 - Ventral posterior cingulate cortex

Area 24 - Ventral anterior cingulate cortex.

Area 25 - Subgenual area (part of the Ventromedial prefrontal cortex)[4]

Area 26 - Ectosplenial portion of the retrosplenial region of the cerebral cortex

Area 27 - Piriform cortex

Area 28 - Ventral entorhinal cortex

Area 29 - Retrosplenial cingulate cortex

Area 30 - Part of cingulate cortex

Area 31 - Dorsal Posterior cingulate cortex

Area 32 - Dorsal anterior cingulate cortex

Area 33 - Part of anterior cingulate cortex

Area 34 - Dorsal entorhinal cortex (on the Parahippocampal gyrus)

Area 35 - Perirhinal cortex (in the rhinal sulcus)

Area 36 - Ectorhinal area, now part of the perirhinal cortex (in the rhinal sulcus)

Area 37 - Fusiform gyrus

Area 38 - Temporopolar area (most rostral part of the superior and middle temporal gyri)

Area 39 - Angular gyrus, considered by some to be part of Wernicke's area

Area 40 - Supramarginal gyrus considered by some to be part of Wernicke's area

Areas 41 and 42 - Auditory cortex

Area 43 - Primary gustatory cortex

Area 44 - Pars opercularis, part of the inferior frontal gyrus and part of Broca's area

Area 45 - Pars triangularis, part of the inferior frontal gyrus and part of Broca's area

Area 46 - Dorsolateral prefrontal cortex

Area 47 - Pars orbitalis, part of the inferior frontal gyrus

Area 48 - Retrosubicular area (a small part of the medial surface of the temporal lobe)

Area 49 - Parasubicular area in a rodent

Area 52 - Parainsular area (at the junction of the temporal lobe and the insula)

(*) Area only found in non-human primates.

Dive into our Brodmann area quiz and test your knowledge!

agraphesthesia

astereognosia

loss of vibration, proprioception and fine touch (since 3rd order neurons of the medial-lemniscal pathway cannot synapse in the cerebral cortex)

potentially hemineglect if the non-dominant hemisphere is affected.

difficulty finding words

semantic paraphasias

prosopagnosia (the acquired inability to recognize faces)

disturbances in drawing

References:

John Nolte: The Human Brain: An Introduction To Its Functional Anatomy, 6th edition, Mosby.

Illustrators:

Brodmann areas (overview) - Paul Kim

Precentral gyrus (cross section) - Paul Kim

Brodmann areas: want to learn more about it?

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This is an article covering the anatomy and functions of the different regions of the brain called Brodmann areas. Learn this topic now at Kenhub!

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https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6354324/

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Recent advances in understanding the role of the basal ganglia

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The basal ganglia are a complex subcortical structure that is principally involved in the selection and implementation of purposeful actions in response to external and internal cues. The basal ganglia set the pattern for facilitation of voluntary movements…

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To make sense of difficult science, Michael Kofi Esson often turns to art.

When he's struggling to understand the immune system or a rare disease, music and poetry serve as an anchor.

"It helps calm me down and actively choose what to focus on," says Esson, a second-year student at the Medical College of Wisconsin.

Esson, who was born in Ghana, also thinks his brain is better at absorbing all that science because of the years he spent playing the trumpet and studying Afrobeat musicians like Fela Kuti.

"There has to be some kind of greater connectivity that [art] imparts on the brain," Esson says.

That idea - that art has a measurable effect on the brain and its structure - has support from a growing number of scientific studies.

"Creativity is making new connections, new synapses," says Ivy Ross, who is vice president of hardware design at Google and co-author of the new book, Your Brain on Art: How the Arts Transform Us.

Ross co-wrote the book with Susan Magsamen, director of the International Arts and Mind Lab at Johns Hopkins University School of Medicine. Magsamen says art's effect on the brain is most dramatic in children.

"Children that are playing music, their brain structure actually changes and their cerebral cortex actually gets larger," Magsamen says.

In Your Brain on Art, Magsamen and Ross describe how a person's neural circuitry changes in response to activities like learning a new song, or a new dance step, or how to play a character on stage.

They also explain why a growing number of researchers believe these changes result in a brain that is better prepared to acquire a wide range of skills, including math and science.

A brain trained to flex

Music, dance, drawing, storytelling - all of these have been a part of human cultures for tens of thousands of years. As a result, "we're really wired for art," Magsamen says.

And when we make art, she says, we increase the brain's plasticity - its ability to adapt in response to new experiences.

"Children who engage in the arts are better learners," Ross says. "Students with access to art education are five times less likely to drop out of school and four times more likely to be recognized with high achievement."

The arts also can teach the brain skills that it's unlikely to get in a classroom, Ross says.

"I was a dancer for like 12 years and I really think it gave me a sense of form and negative space," she says.

Those brain circuits probably helped in her wide-ranging career, she says, which includes designing jewelry that's part of the permanent collection at the Smithsonian.

Dancing also seems to improve mental health, Magsamen says.

"Even just 15 minutes of dance reduces stress and anxiety," she says, noting that the activity causes the brain to release "feel-good" hormones like endorphins, serotonin and dopamine.

Measuring art's effects

The link between arts and academic achievement has been noted by educators for many years. But it's only in the past couple of decades that technology has allowed scientists to see some of the changes in the brain that explain why.

In 2010, for example, scientists used functional magnetic resonance imaging to show that professional musicians had greater plasticity than nonmusicians in the hippocampus, an area involved in storing and retrieving information.

"The arts provide children with the kind of brain development that's really important for building strong neural pathways," Magsamen says, including pathways involved in focus, memory and creativity.

Esson, the medical student, may have been using some of those pathways when he found a novel way to study difficult concepts in chemistry.

"I wrote [poems] about acid-base reactions," he says, with a laugh. "Oh my god, just so nerdy."

A failing grade for arts in school

Despite growing evidence that arts can improve performance in many other areas, activities like music and drawing have fallen out of favor in education and our culture, Ross says.

"We optimize for productivity and push the arts aside," she says. "We thought we'd be happy. And the truth is, we're not."

So people like Michael Kofi Esson are trying to find a balance.

Now at the end of his second year of medical school, Esson spends his days on science. But sometimes late at night, he still writes poems, including one that ends with this thought about how art and the brain both create their own version of reality.
Deception is art,
An art the brain has mastered.
Although art is a lie,
It is the brain's truth
Although art is deception,
it is the brain's reality.
The brain is a lie,
a lie so beautiful, it is art.
Esson hopes that one day he will write poems about the patients he treats. For now, though, he's still mostly an observer.

"I get to talk to them. But at the end of the day, they come for the doctor, not for me," he says. "Once I'm actually in that position, I think I want to bring the patient into the poems."

And perhaps bring some of the poems to his patients.

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Building a better brain through music, dance and poetry

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To make sense of difficult science, Michael Kofi Esson often turns to art. When he's struggling to understand the immune system or a rare disease, music and poetry serve as an anchor. "It helps calm me down and actively choose what to focus on," says Esson, a second-year student at the Medical College of Wisconsin.

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Review: Four Areas of the Cerebrum and Functions

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Review: Four Areas of the Cerebrum and Functions

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025 The 4 Lobes of the Cerebrum and their functions

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The Science of Creativity & How to Enhance Creative Innovation - Huberman Lab

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In this episode, I explain how the brain engages in creative thinking and, based on that mechanistic understanding, the tools to improve one's ability to think creatively and innovate in any area.

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Okay. This online quiz is called Label Parts of the Brain. It was created by member ninalahoti and has 12 questions.

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anatomy of the lobes and specific of the brain

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This online quiz is called Brain Structure Identification. It was created by member KeeneyQuest and has 13 questions.

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Endocrine Hormones and Related Disorders

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Endocrine Hormones and Related Disorders

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Hypothalamus

Maintaining Homeostasis

Four F’s

Endocrine regulations of growth, metabolism, and reproductive organs

Autonomic Regulation

Regulation of circadian rhythms (suprachiasmatic nuclei)

Master gland:

Growth Hormone Releasing Hormone

Growth Hormone Inhibiting Hormone

Thyrotropin Releasing Hormone

Corticotropin Releasing Hormone

Gonadotropin-Releasing Hormone

Prolactin Releasing Hormone

Prolactin Inhibition Hormone

Diabetes Insipidus: The regulation of urine production occurs in the hypothalamus, which produces ADH (Antidiuretic (ADH) in the supraoptic and paraventricular nuclei. After synthesis, the hormone is transported in neurosecretory granules down the axon of the hypothalamic neuron to the posterior lobe of the pituitary gland where it is stored for later release.

Posterior Pituitary Gland

Antidiuretic Hormone (ADH) / Vasopressin

Increases water absorption in the kidneys.

Affects drinking behavior to regulate fluid balance.

Produced by osmoreceptor cells in the Paraventricular and Supraoptic nuclei of the hypothalamus.

Released in the posterior pituitary and transported to target organs via capillaries.

Oxytocin

Induces uterine contractions during childbirth.

Triggers breast milk ejection during lactation.

Released during bonding experiences.

Originates from the hypothalamus and is stored and released by the posterior pituitary gland.

Anterior Pituitary Gland

Thyroid-stimulating hormone (TSH)

Basics

Also known as thyrotropin.

It is stimulated by thyrotropin-releasing hormone (TRH) from the hypothalamus.

It is inhibited by somatostatin from the hypothalamus.

TSH stimulates the thyroid gland to secrete thyroxine (T4) by binding to G-protein-coupled receptors (GPCRs) on thyroid cells.

Disorders

Hyperthyroidism (Graves' Disease):

The immune system attacks the thyroid gland, causing overproduction of thyroxine (T4).

Symptoms: protrusion of eyes, reddish skin on lower legs, fatigue, insomnia, weight loss, increased appetite, excessive urination, and impaired kidney function.

Hypothyroidism (can be caused by autoimmune Hashimoto’s disease, but not always):

Symptoms: fatigue, cold sensitivity, constipation, dry skin, puffy face, brittle nails, hair loss, tongue enlargement, weight gain, muscle and joint pain, weakness, menstrual irregularities, depression, and memory lapses.

Increased TSH - since the APT is trying to send a message to the thyroid to produce more hormones

Some individuals have conversion disorders from T4 —> T3, the active version of the hormone.

Adrenocorticotropic Hormone (ACTH)

Basics

ACTH acts on adrenal cortex cells, stimulating them to produce glucocorticoids (like cortisol), mineralocorticoids (like aldosterone), and androgens (like testosterone).

Glucocorticoids raise blood sugar levels by stimulating gluconeogenesis in the liver.

Cortisol plays a role in glucose metabolism, blood pressure regulation, insulin release, immune function, and inflammatory response.

Effects of Cortisol

Positive Effects (Small increases):

Energy burst, heightened memory, increased immunity, lowered pain sensitivity, maintenance of homeostasis

Adverse Effects (High or Protracted levels):

Impaired cognitive performance, suppressed thyroid function, hyperglycemia, decreased bone density, muscle tissue loss, hypertension, lowered immunity, slow wound healing, increased abdominal fat, risk of heart attacks, strokes, metabolic syndrome, and cholesterol imbalances

Disorders

Cushing Syndrome:

Often caused by hypersecretion of ACTH.

Symptoms: severe fatigue, weak muscles, high blood pressure, high blood glucose, and increased thirst.

Prolactin -lactation

Growth Hormones (GH)

Body growth, insulin-like growth factor 1

Basics

Controlled by Growth Hormone-Releasing Hormone (GHRH) or Growth Hormone-Inhibiting Hormone.

Human Growth Hormone (HGH; also known as somatotropin).

GH-secreting cells are stimulated by the intermittent arrival of GHRH from the preoptic and anterior hypothalamus.

GH promotes body growth by binding to liver cell receptors, stimulating them to release Insulin-Like Growth Factor-1 (IGF-1; also known as somatomedin), which acts directly on the ends of the long bones to promote growth.

Disorders

In Childhood:

Hyposecretion leads to stunted but well-proportioned growth (small stature).

Hindered growth can result from an inability to respond to GH due to:

Mutant genes encoding GHRH or GH receptors.

Homozygosity for a disabling mutation in STAT5b, part of the downstream signaling after GH binds its receptor.

Hypersecretion leads to gigantism.

In Adults:

Hypersecretion of GH or GHRH leads to acromegaly, characterized by enlargement of hands, feet, nose, lips, ears, and a general thickening of the skin. Other symptoms include a thick, deep voice, slowed speech, generalized skull expansion, pronounced brow protrusion, and ocular distension.

Gonadotropins

Luteinizing hormone – ovulation, progesterone, testosterone

Follicle Stimulation hormone – follicle, estrogen, sperm