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Craneal Nerves

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AMILCAR HERRERA, ESTEBAN MIRANDA,MARCOS MIRANDA, ARIEL TORO, YOUTUBERS xd lol y=0

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NERVOUS SYSTEM

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Uploaded by Lizbeth Chano on 2017-07-17.

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Neurons, cell body, processes, classification.

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Neurons, cell body, processes, classification.

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Essential features of neurons:

• The purpose of neurons is to receive, process, and transfer information. This information is made up of chemical or electrical signals

• They are unidirectional

• It’s an ‘all-in-one’ transfer of information (see Neuronal Signaling section)

• Mature neurons do not regenerate in the CNS if their soma (cell body) is damaged. However, the dendrites can regenerate, and sometimes the axons can generate also. (This allows other neurons to assume the function of damaged ones.) Regeneration in the PNS is more probable and successful.

• Mature neurons do not proliferate after birth,however, progenitor (stem) cells are found in the brain and can divide after birth. Progenitor cells can become neurons or glial cells.

There are 3 main types of neurons:

• Sensory neurons (afferent neurons) transfer information from the external environment to the CNS

• Motor neurons (efferent neurons) transfer information from the CNS to external environment

• Interneurons, or association neurons, process information in the CNS and transfers the information from one neuron to the other within the CNS

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Unipolar Neuron : Has only one process extending from the soma, branching into dendrites or axon terminals (typical of invertebrate animals)

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One axon but many dendrites extending directly from the soma (used for motor and sensory processing). This is the prototypical neuron

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Anatomy quiz that focuses specifically on the parts of a neuron, such as the axon and dendrite.

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Neurons are divided into three parts: dendrites, soma, and axon

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Neurons are divided into three parts: dendrites, soma, and axon

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The ‘input’ of the neuron:
Receive information from other neurons or the external environment and transfer to the cell body (soma) or axons
Are numerous, relatively short, and branch extensively in a tree-like fashion
Dendrite means tree in Greek
Dendrites have numerous spines on them, and provide a greater surface area for other neurons to synapse on, i.e., attach to.
Dendrites receive information from other cells at these synapses. This makes dendrites postsynaptic.
The connection between axons that synapse on dendrites is called axodendritic
The connection between dendrites that synapse on other dendrites is called dendrodendritic
Soma
The cell’s body:
Has typical cell components used for cell maintenance:
the membrane (a lipid bilayer), which separates and protects the cell from its environment;
the nucleus (with a large nucleolus), which contains the genetic information of the cell;
endoplasmic reticulum and ribosomes, where proteins are produced;
mitochondria, the energy power houses of the cell;
golgi apparatus, where proteins are packaged in vesicles for secretion outside the cell;
and other miscellaneous organelles.
The soma is usually large
Soma means body in Greek

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Wraps its membrane around the axons in concentric circles to form myelin, a white and shiny fatty substance, in the CNS. This squeezes out all the cytoplasm from that region, leaving only the lipid-bilayer. This vastly improves electrical conduction in the axon (see Neuronal Signaling section)

Offer nourishment to the neurons

Wraps itself around several axons at once. See cross section cutting vertically though three axons and an oligodendrocyte

Many are needed to cover the whole length of an axon

Schwann Cells

Like oligodendrocytes, they form myelin sheaths around axons, but in the PNS.

A Schwann cell wraps itself around only one axon

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Are irregular-shaped

Are small (hence, micro)

Are mobile

Are phagocytic, which means they engulf and consume foreign microorganisms and damaged or dead neurons.

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Glia, short for neuroglial cells, provide support to the nervous system:

Their purpose is to provide metabolic support, insulate, protect, reinforce, repair, and cleanup damaged areas

They probably do not conduct information, though they perhaps offer some integration function of their own, but currently this is in question. As of today we do not yet completely understand their function

Glial cells are much more numerous than neurons. In some places they outnumber neurons 3 to 1. In other places, they are 10 to 50 times more numerous. In total, neurons only form 10% of the nervous system

They are found in both the CNS and the PNS, but there are different types in each

Neuroglia means "nerve glue"

Unlike neurons, glia proliferate (overproduction of glia is what causes brain tumor)

The different types of glia:

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The ‘output’ of the neuron:

Transfer information to other neurons

Begin at the axon hillock, which is a swelling at the junction of the axon and soma where there are many Na+ channels and the action potential starts (see Neuronal Signaling section)

Are usually long (some reaching several feet)

Axon means axis in Greek

Have terminal boutons at the end of the axon where the synapse is located

This makes axons presynaptic

This swelling at the terminal bouton is where the neuron synapses with another neuron

Contains numerous vesicles which hold neurotransmitter

Has many Ca2+ channels in the membrane

Forms presynaptic membrane in any kind of axonal synapse

The space between the terminal boutons and the next cell is known as the synaptic cleft, and is approximately 20 nm thick.

Most are myelinated:

Have myelin sheaths that are made by Schwann cells or oligodendrocytes

Myelin acts as insulator to help conduction of action potential

There are openings between the Schwann cells called Nodes of Ranvier. These help with the conduction of action potentials

Some are not myelinated

Typical of shorter axons

Axons synapse on other cells in various forms:

Axoaxonal: Axon is connected to another neuron’s axon

Axodendritic: Axon is connected to another neuron’s dendrites

Axosomatic: Axon is connected directly to another neuron’s soma

In neuromuscular junctions, axons synapse directly on muscles.

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autonomic nervous system quiz. sensory nervous system quiz

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A quiz on the general organization of the nervous system, using interactive animations and diagrams.

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From the ProEdify TEAS V prep course, this is part 1 of the lesson on the nervous system. In this introduction to the nervous system, we discuss the primary functions of the nervous system and its role in maintaining bodily homeostasis. In the later part of the video we discuss the basic structure of the nervous system.

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https://youtu.be/IOQ6eU0-tcw

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Uploaded by Andrea Valdez on 2017-07-18.

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Nervous System. 1.	Functions and divisions of the nervous system. 

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Nervous System. 1.	Functions and divisions of the nervous system. 

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To learn how the nervous system functions, you must learn how the nervous system is put together.

The nervous system can be divided into several connected systems that function together. Let's start with a simple division:

The nervous system is divided into the central nervous system and peripheral nervous system.

Central Nervous System

The central nervous system is divided into two parts: the

brain and the spinal cord. The average adult human brain weighs 1.3 to 1.4 kg (approximately 3 pounds). The brain contains about 100 billion nerve cells (neurons) and trillions of "support cells" called glia. The spinal cord is about 43 cm long in adult women and 45 cm long in adult men and weighs about 35-40 grams. The vertebral column, the collection of bones (back bone) that houses the spinal cord, is about 70 cm long. Therefore, the spinal cord is much shorter than the vertebral column.

Functions of the CNS are to process and coordinate:
·         Sensory data from inside and outside body

·         Motor commands control activities of peripheral organs (e.g., skeletal muscles)

Higher functions of brain intelligence, memory, learning, emotion

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THE CNS AND PNS: THE MAIN DIVISIONS OF THE NERVOUS SYSTEM

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the peripheral nervous system (PNS) gets all information into the brain (and therefore to the mind) and controls directly all responses you make. It consists of the nerves going to and from the central nervous system. A nerve is a bundle of axons, the part of a neuron (nerve cell) that is specialized for communication.