# data[].attributes.body
P3: Outline the organisation of the nervous system.
P4: Outline the organisation of the endocrine system.
M2: Explain the functions of the nervous system.
M3: Explain the functions of the endocrine system.
D2: Explain the
interrelationships between the nervous and the endocrine systems.

# data[].attributes.body
The nervous system is an organ system that coordinates voluntary and involuntary movements and responses by exchanging signals between different parts of the body.
The brain and the spinal cord form the control centre known as the central nervous system. This is where information is processed and decisions are made. The sensory nerves and sense organs of the peripheral nervous system monitor  conditions inside and outside of the body and send this information to the CNS. Efferent nerves in the PNS carry signals from the control centre to the muscles, glands, and organs to regulate their functions.

# data[].attributes.body
1. Afferent neurons. Also known as sensory neurons, afferent neurons transmit sensory signals to the central nervous system from receptors in the body.

2. Efferent neurons. Also known as motor neurons, efferent neurons transmit signals from the central nervous system to effectors in the body such as muscles and glands.

3. Interneurons. Interneurons form complex networks within the central nervous system to integrate the information received from afferent neurons and to direct the function of the body through efferent neurons.

# data[].attributes.body
Neuroglia, also known as the glial cells, acting to aid the cells of the nervous system. Each neuron in the body is surrounded by anywhere from 6 to 60 neuroglia that protect, feed, and insulate the neuron, because neurons are extremely specialized cells that are essential to body function and almost never reproduce, neuroglia are vital to maintaining a functional nervous system.

# data[].attributes.body
The brain is a soft, wrinkled organ that is located inside the cranial cavity, where skull surround and protect it. The approximately 100 billion neurons of the brain form the main control centre of the body. The brain and spinal cord together form the central nervous system, where information is processed and responses originate. The brain, the seat of higher mental functions such as consciousness, memory, planning, and voluntary actions, also controls lower body functions such as the maintenance of respiration, heart rate, blood pressure, and digestion.

# data[].attributes.body
The spinal cord is a long, thin mass of bundled neurons that carries the information through the vertebral cavity of the spine beginning at the medulla of the brain on its superior end and continuing inferiorly to the lumbar region of the spine. In the lumbar region, the spinal cord separates into a bundle of individual nerves called the cauda equina that continues inferiorly to the sacrum and coccyx. The white matter of the spinal cord functions as the main conduit of nerve signals to the body from the brain. The grey matter of the spinal cord integrates reflexes to stimuli.

# data[].attributes.body
Nerves are bundles of axons in the peripheral nervous system that act as information highways to carry signals between the brain and spinal cord and the rest of the body. Each axon is wrapped in a connective tissue sheath called the endoneurium. Individual axons of the nerve are bundled into groups of axons called fascicles, wrapped in a sheath of connective tissue called the perineurium. Finally, many fascicles are wrapped together in another layer of connective tissue called the epineurium to form a whole nerve. The wrapping of nerves with connective tissue helps to protect the axons and to increase the speed of their communication within the body.

# data[].attributes.body
Some of the nerves in the body are specialized for carrying information in only one direction, similar to a one-way street. Nerves that carry information from sensory receptors to the central nervous system only are called afferent nerves. Other neurons, known as efferent nerves, carry signals only from the central nervous system to effectors such as muscles and glands. Finally, some nerves are mixed nerves that contain both afferent and efferent axons. Mixed nerves function like 2-way streets where afferent axons act as lanes heading toward the central nervous system and efferent axons act as lanes heading away from the central nervous system.

# data[].attributes.body
Extending from the inferior side of the brain are 12 pairs of cranial nerves. Each cranial nerve pair is identified by a Roman numeral 1 to 12 based upon its location along the anterior-posterior axis of the brain. Each nerve also has a descriptive name that identifies its function or location. The cranial nerves provide a direct connection to the brain for the special sense organs, muscles of the head, neck, and shoulders, the heart, and the gastrointestinal tract.

# data[].attributes.body
Extending from the left and right sides of the spinal cord are 31 pairs of spinal nerves. The spinal nerves are mixed nerves that carry both sensory and motor signals between the spinal cord and specific regions of the body. The 31 spinal nerves are split into 5 groups named for the 5 regions of the vertebral column. Thus, there are 8 pairs of cervical nerves, 12 pairs of thoracic nerves, 5 pairs of lumbar nerves, 5 pairs of sacral nerves, and 1 pair of coccygeal nerves. Each spinal nerve exits from the spinal cord through the intervertebral foramen between a pair of vertebrae or between the C1 vertebra and the occipital nerve of the skull.

# data[].attributes.body
The nervous system has 3 main functions: sensory, integration, and motor.

# data[].attributes.headline
Functions of the Nervous System: Sensory.

# data[].attributes.subject
Functions of the Nervous System: Sensory.

# data[].attributes.body
The sensory function of the nervous system involves collecting information from sensory receptors that monitor the body’s internal and external conditions. These signals are then passed on to the central nervous system for further processing by afferent neurons.

# data[].attributes.headline
Functions of the Nervous System: Integration.

# data[].attributes.subject
Functions of the Nervous System: Integration.

# data[].attributes.body
The process of integration is the processing of the many sensory signals that are passed into the CNS at any given time. These signals are evaluated, compared, used for decision making, discarded or committed to memory as deemed appropriate. Integration takes place in the grey matter of the brain and spinal cord and is performed by interneurons. Many interneurons work together to form complex networks that provide this processing power.

# data[].attributes.body
Once the networks of interneurons in the CNS evaluate sensory information and decide on an action, they stimulate efferent neurons. Efferent neurons (also called motor neurons) carry signals from the grey matter of the CNS through the nerves of the peripheral nervous system to effector cells. The effector may be smooth, cardiac, or skeletal muscle tissue or glandular tissue. The effector then releases a hormone or moves a part of the body to respond to the stimulus.

# data[].attributes.headline
Divisions of the Nervous System: The Central Nervous System.

# data[].attributes.subject
Divisions of the Nervous System: The Central Nervous System.

# data[].attributes.body
The brain and spinal cord together form the central nervous system, or CNS. The CNS acts as the control centre of the body by providing its processing, memory, and regulation systems. The CNS takes in all of the conscious and subconscious sensory information from the body’s sensory receptors to stay aware of the body’s internal and external conditions. Using this sensory information, it makes decisions about both conscious and subconscious actions to take to maintain the body’s homeostasis and ensure its survival. The CNS is also responsible for the higher functions of the nervous system such as language, creativity, expression, emotions, and personality. The brain is the seat of consciousness and determines who we are as individuals.

# data[].attributes.headline
Divisions of the Nervous System: Peripheral Nervous System.

# data[].attributes.subject
Divisions of the Nervous System: Peripheral Nervous System.

# data[].attributes.body
The peripheral nervous system includes all of the parts of the nervous system outside of the brain and spinal cord. These parts include all of the cranial and spinal nerves, ganglia, and sensory receptors.

# data[].attributes.headline
Divisions of the Nervous System: Somatic Nervous System.

# data[].attributes.subject
Divisions of the Nervous System: Somatic Nervous System.

# data[].attributes.body
The somatic nervous system is a division of the PNS that includes all of the voluntary efferent neurons. The SNS is the only consciously controlled part of the PNS and is responsible for stimulating skeletal muscles in the body.

# data[].attributes.headline
Divisions of the Nervous System: Autonomic Nervous System.

# data[].attributes.subject
Divisions of the Nervous System: Autonomic Nervous System.

# data[].attributes.body
The autonomic nervous system is a division of the PNS that includes all of the involuntary efferent neurons. The ANS controls subconscious effectors such as visceral muscle tissue, cardiac muscle tissue, and glandular tissue.

There are 2 divisions of the autonomic nervous system in the body: the sympathetic and parasympathetic divisions.

# data[].attributes.body
Sympathetic. The sympathetic division forms the body’s 'fight or flight' response to stress, danger, excitement, exercise, emotions, and embarrassment. The sympathetic division increases respiration and heart rate, releases adrenaline and other stress hormones, and decreases digestion to cope with these situations.

# data[].attributes.body
The parasympathetic division forms the body’s 'rest and digest' response when the body is relaxed, resting, or feeding. The parasympathetic works to undo the work of the sympathetic division after a stressful situation. Among other functions, the parasympathetic division works to decrease respiration and heart rate, increase digestion, and permit the elimination of wastes.

# data[].attributes.body
Reflexes are fast, involuntary responses to stimuli. The most well known reflex is the patellar reflex, which is checked when a physicians taps on a patient’s knee during a physical examination. Reflexes are integrated in the grEy matter of the spinal cord or in the brain stem. Reflexes allow the body to respond to stimuli very quickly by sending responses to effectors before the nerve signals reach the conscious parts of the brain. This explains why people will often pull their hands away from a hot object before they realize they are in pain.

# data[].attributes.body
At rest, neurons maintain a concentration of sodium ions outside of the cell and potassium ions inside of the cell. This concentration is maintained by the sodium-potassium pump of the cell membrane which pumps 3 sodium ions out of the cell for every 2 potassium ions that are pumped into the cell. The ion concentration results in a resting electrical potential of -70 millivolts (mV), which means that the inside of the cell has a negative charge compared to its surroundings.

# data[].attributes.body
If a stimulus permits enough positive ions to enter a region of the cell to cause it to reach -55 mV, that region of the cell will open its voltage-gated sodium channels and allow sodium ions to diffuse into the cell. -55 mV is the threshold potential for neurons as this is the “trigger” voltage that they must reach to cross the threshold into forming an action potential.

# data[].attributes.body
Sodium carries a positive charge that causes the cell to become depolarized (positively charged) compared to its normal negative charge. The voltage for depolarization of all neurons is +30 mV. The depolarization of the cell is the AP that is transmitted by the neuron as a nerve signal. The positive ions spread into neighbouring regions of the cell, initiating a new AP in those regions as they reach -55 mV. The AP continues to spread down the cell membrane of the neuron until it reaches the end of an axon.

# data[].attributes.body
After the depolarization voltage of +30 mV is reached, voltage-gated potassium ion channels open, allowing positive potassium ions to diffuse out of the cell. The loss of potassium along with the pumping of sodium ions back out of the cell through the sodium-potassium pump restores the cell to the -55 mV resting potential. At this point the neuron is ready to start a new action potential.

# data[].attributes.body
The anterior pituitary gland is the true glandular part of the pituitary gland. The function of the anterior pituitary gland is controlled by the releasing and inhibiting hormones of the hypothalamus. The anterior pituitary produces 6 important hormones:

Thyroid stimulating hormone (TSH), as its name suggests, is a tropic hormone responsible for the stimulation of the thyroid gland.

Adrenocorticotropic hormone (ACTH) stimulates the adrenal cortex, the outer part of the adrenal gland, to produce its hormones.

Follicle stimulating hormone (FSH) stimulates the follicle cells of the gonads to produce gametes—ova in females and sperm in males.

Luteinizing hormone (LH) stimulates the gonads to produce the sex hormones—estrogens in females and testosterone in males.

Human growth hormone (HGH) affects many target cells throughout the body by stimulating their growth, repair, and reproduction.

Prolactin (PRL) has many effects on the body, chief of which is that it stimulates the mammary glands of the breast to produce milk.

# data[].attributes.body
The pineal gland is a small pinecone-shaped mass of glandular tissue found just posterior to the thalamus of the brain. The pineal gland produces the hormone melatonin that helps to regulate the human sleep-wake cycle known as the circadian rhythm. The activity of the pineal gland is inhibited by stimulation from the photoreceptors of the retina. This light sensitivity causes melatonin to be produced only in low light or darkness. Increased melatonin production causes humans to feel drowsy at night time when the pineal gland is active.

# data[].attributes.body
The pituitary gland, also known as the hypophysis, is a small pea-sized lump of tissue connected to the inferior portion of the hypothalamus of the brain. Many blood vessels surround the pituitary gland to carry the hormones it releases throughout the body. Situated in a small depression in the sphenoid bone called the sella turcica, the pituitary gland is actually made of 2 completely separate structures: the posterior and anterior pituitary glands.

# data[].attributes.body
The endocrine system includes all of the glands of the body and the hormones produced by those glands. The glands are controlled directly by stimulation from the nervous system as well as by chemical receptors in the blood and hormones produced by other glands. By regulating the functions of organs in the body, these glands help to maintain the body’s homeostasis. Cellular metabolism, reproduction, sexual development, sugar and mineral homeostasis, heart rate, and digestion are among  the many processes regulated by the actions of hormones.

# data[].attributes.body
The hypothalamus is a part of the brain located superior and anterior to the brain stem and inferior to the thalamus. It serves many different functions in the nervous system, and is also responsible for the direct control of the endocrine system through the pituitary gland. The hypothalamus contains special cells called neurosecretory cells and these are the neurons that secrete hormones:

Thyrotropin-releasing hormone (TRH)

Growth hormone-releasing hormone (GHRH)

Growth hormone-inhibiting hormone (GHIH)

Gonadotropin-releasing hormone (GnRH)

Corticotropin-releasing hormone (CRH)

Oxytocin

Antidiuretic hormone (ADH)

All of the releasing and inhibiting hormones affect the function of the anterior pituitary gland. TRH stimulates the anterior pituitary gland to release thyroid-stimulating hormone. GHRH and GHIH work to regulate the release of growth hormone—GHRH stimulates growth hormone release, GHIH inhibits its release. GnRH stimulates the release of follicle stimulating hormone and luteinizing hormone while CRH stimulates the release of adrenocorticotropic hormone. The last two hormones—oxytocin and antidiuretic hormone—are produced by the hypothalamus and transported to the posterior pituitary, where they are stored and later released.

# data[].attributes.body
The posterior pituitary gland is actually not glandular tissue at all, but nervous tissue instead. The posterior pituitary is a small extension of the hypothalamus through which the axons of some of the neurosecretory cells of the hypothalamus extend. These neurosecretory cells create 2 hormones in the hypothalamus that are stored and released by the posterior pituitary:

Oxytocin triggers uterine contractions during childbirth and the release of milk during breastfeeding.

Antidiuretic hormone prevents water loss in the body by increasing the re-uptake of water in the kidneys and reducing blood flow to sweat glands.

# data[].attributes.body
The thyroid gland is a butterfly-shaped gland located at the base of the neck and wrapped around the lateral sides of the trachea. The thyroid gland produces 3 major hormones:

Calcitonin

Triiodothyronine (T3)

Thyroxine (T4)

Calcitonin is released when calcium ion levels in the blood rise above a certain set point. Calcitonin functions to reduce the concentration of calcium ions in the blood by aiding the absorption of calcium into the matrix of bones. The hormones T3 and T4 work together to regulate the body’s metabolic rate. Increased levels of T3 and T4 lead to increased cellular activity and energy usage in the body.

# data[].attributes.body
The parathyroid glands are 4 small masses of glandular tissue found on the posterior side of the thyroid gland. The parathyroid glands produce the hormone parathyroid hormone, which is involved in calcium ion homeostasis. PTH is released from the parathyroid glands when calcium ion levels in the blood drop below a set point. PTH stimulates the osteoclasts to break down the calcium containing bone matrix to release free calcium ions into the bloodstream. PTH also triggers the kidneys to return calcium ions filtered out of the blood back to the bloodstream so that it is conserved.

# data[].attributes.body
The adrenal glands are a pair of roughly triangular glands found immediately superior to the kidneys. The adrenal glands are each made of 2 distinct layers, each with their own unique functions: the outer adrenal cortex and inner adrenal medulla.

# data[].attributes.body
The adrenal cortex produces many cortical hormones in 3 classes: glucocorticoids, mineralocorticoids, and androgens.

Glucocorticoids have many diverse functions, including the breakdown of proteins and lipids to produce glucose. Glucocorticoids also function to reduce inflammation and immune response.

Mineralocorticoids, as their name suggests, are a group of hormones that help to regulate the concentration of mineral ions in the body.

Androgens, such as testosterone, are produced at low levels in the adrenal cortex to regulate the growth and activity of cells that are receptive to male hormones. In adult males, the amount of androgens produced by the testes is many times greater than the amount produced by the adrenal cortex, leading to the appearance of male secondary sex characteristics.

# data[].attributes.body
The gonads: ovaries in females and testes in males are responsible for producing the sex hormones of the body. These sex hormones determine the secondary sex characteristics of adult females and adult males.

The testes are a pair of ellipsoid organs found in the scrotum of males that produce the androgen testosterone in males after the start of puberty. Testosterone has effects on many parts of the body, including the muscles, bones, sex organs, and hair follicles. This hormone causes growth and increases in strength of the bones and muscles, including the accelerated growth of long bones during adolescence. During puberty, testosterone controls the growth and development of the sex organs and body hair of males, including pubic, chest, and facial hair. In men who have inherited genes for baldness testosterone triggers the onset of androgenic alopecia, commonly known as male pattern baldness.

The ovaries are a pair of almond-shaped glands located in the pelvic body cavity lateral and superior to the uterus in females. The ovaries produce the female sex hormones progesterone and oestrogen. Progesterone is most active in females during ovulation and pregnancy where it maintains appropriate conditions in the human body to support a developing fetus. Oestrogen are a group of related hormones that function as the primary female sex hormones. The release of oestrogen during puberty triggers the development of female secondary sex characteristics such as uterine development, breast development, and the growth of pubic hair. Oestrogen also triggers the increased growth of bones during adolescence that lead to adult height and proportions.

# data[].attributes.body
The adrenal medulla produces the hormones epinephrine and norepinephrine under stimulation by the sympathetic division of the autonomic nervous system. Both of these hormones help to increase the flow of blood to the brain and muscles to improve the 'fight-or-flight' response to stress. These hormones also work to increase heart rate, breathing rate, and blood pressure while decreasing the flow of blood to and function of organs that are not involved in responding to emergencies.

# data[].attributes.body
The pancreas is a large gland located in the abdominal cavity just inferior and posterior to the stomach. The pancreas is considered to be a heterocrine gland as it contains both endocrine and exocrine tissue. The endocrine cells of the pancreas make up just about 1% of the total mass of the pancreas and are found in small groups throughout the pancreas called islets of Langerhans. Within these islets are 2 types of cellsalpha and beta cells. The alpha cells produce the hormone glucagon, which is responsible for raising blood glucose levels. Glucagon triggers muscle and liver cells to break down the polysaccharide glycogen to release glucose into the bloodstream. The beta cells produce the hormone insulin, which is responsible for lowering blood glucose levels after a meal. Insulin triggers the absorption of glucose from the blood into cells, where it is added to glycogen molecules for storage.

# data[].attributes.body
The thymus is a soft, triangular-shaped organ found in the chest posterior to the sternum. The thymus produces hormones called thymosins that help to train and develop T-lymphocytes during fetal development and childhood. The T-lymphocytes produced in the thymus go on to protect the body from pathogens throughout a person’s entire life. The thymus becomes inactive during puberty and is slowly replaced by adipose tissue throughout a person’s life.

# data[].attributes.headline
Relationship between the Endocrine System and Nervous System:

# data[].attributes.subject
Relationship between the Endocrine System and Nervous System:

# data[].attributes.body
The endocrine system works alongside of the nervous system to form the control systems of the body. The nervous system provides a very fast and narrowly targeted system to turn on specific glands and muscles throughout the body. The endocrine system, on the other hand, is much slower acting, but has very widespread, long lasting, and powerful effects. Hormones are distributed by glands through the bloodstream to the entire body, affecting any cell with a receptor for a particular hormone. Most hormones affect cells in several organs or throughout the entire body, leading to many diverse and powerful responses.

# data[].attributes.body
Once hormones have been produced by glands, they are distributed through the body via the bloodstream. As hormones travel through the body, they pass through cells or along the plasma membranes of cells until they encounter a receptor for that particular hormone. Hormones can only affect target cells that have the appropriate receptors. This property of hormones is known as specificity. Hormone specificity explains how each hormone can have specific effects in widespread parts of the body.

Many hormones produced by the endocrine system are classified as tropic hormones. A tropic hormone is a hormone that is able to trigger the release of another hormone in another gland. Tropic hormones provide a pathway of control for hormone production as well as a way for glands to be controlled in distant regions of the body. Many of the hormones produced by the pituitary gland, such as TSH, ACTH, and FSH are tropic hormones.

# data[].attributes.body
The levels of hormones in the body can be regulated by several factors. The nervous system can control hormone levels through the action of the hypothalamus and its releasing and inhibiting hormones. For example, TRH produced by the hypothalamus stimulates the anterior pituitary to produce TSH. Tropic hormones provide another level of control for the release of hormones. For example, TSH is a tropic hormone that stimulates the thyroid gland to produce T3 and T4. Nutrition can also control the levels of hormones in the body. For example, the thyroid hormones T3 and T4 require 3 or 4 iodine atoms, respectively, to be produced. In people lacking iodine in their diet, they will fail to produce sufficient levels of thyroid hormones to maintain a healthy metabolic rate. Finally, the number of receptors present in cells can be varied by cells in response to hormones. Cells that are exposed to high levels of hormones for extended periods of time can begin to reduce the number of receptors that they produce, leading to reduced hormonal control of the cell.

# data[].attributes.headline
Interrelationship between the Nervous System and the Endocrine System:

# data[].attributes.subject
Interrelationship between the Nervous System and the Endocrine System:

# data[].attributes.body
The hypothalamus plays a significant role in the endocrine system. It is responsible for maintaining your body’s internal balance, which is known as homeostasis. To do this, the hypothalamus helps stimulate or inhibit many of your body’s key processes, including:

Heart rate and blood pressure

Body temperature

Fluid and electrolyte balance, including thirst

Appetite and body weight

Glandular secretions of the stomach and intestines

Production of substances that influence the pituitary gland to release hormones

Sleep cycles

# data[].attributes.body
The fight-or-flight response, also known as the acute stress response, refers to a physiological reaction that occurs in the presence of something that is terrifying, either mentally or physically. The response is triggered by the release of hormones that prepare your body to protect itself.
To produce the fight-or-flight response, the hypothalamus activates two systems: the sympathetic nervous system and the adrenal-cortical system. The sympathetic nervous system uses nerve pathways to initiate reactions in the body, and the adrenal-cortical system uses the bloodstream. The sympathetic nervous system sends out impulses to glands and smooth muscles and tells the adrenal medulla to release epinephrine (adrenaline) and norepinephrine (noradrenaline) into the bloodstream. These stress hormones cause several changes in the body, including an increase in heart rate and blood pressure.

# data[].attributes.body
Kim Ann Zimmermann. (2018). Nervous System. Available: https://www.livescience.com/22665-nervous-system.html. Last accessed 16th May 2018.

# data[].attributes.headline
Interrelationship between the Nervous System and the Endocrine System:

# data[].attributes.subject
Interrelationship between the Nervous System and the Endocrine System:

# data[].attributes.body
The hypothalamus is involved in many functions of the autonomic nervous system, as it receives information from nearly all parts of the nervous system.

# data[].attributes.body
Solomon D. Erulkar Thomas L. Lentz . (2018). Nervous System. Available: https://www.britannica.com/science/nervous-system. Last accessed 16th May 2018.

# data[].attributes.body
Kim Ann Zimmermann. (2018). Endocrine System. Available: https://www.livescience.com/26496-endocrine-system.html. Last accessed 16th May 2018.

# data[].attributes.body
Hormone Health Network. (2018). The Endocrine System. Available: https://www.hormone.org/hormones-and-health/the-endocrine-system. Last accessed 16th May 2018.

# data[].attributes.body
Young Diggers. (2018). The fight or flight response. Available: http://www.youngdiggers.com.au/fight-or-flight. Last accessed 16th May 2018.

# data[].attributes.body
Harvard Medical School. (2011). Understanding the stress response. Available: https://www.health.harvard.edu/staying-healthy/understanding-the-stress-response. Last accessed 16th May 2018.