#8 The Nervous System, Part 1

Its Anatomy and Organization, how it Comunicates, and what happens when it gets Damaged.

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<Nervous System Functions>

The sensory receptors on your skin detect those eight little legs - that information is your sensory input.

From there your nervous system processes that input, and decides what should be done about it.

The response that occurs when your nervous system activates certain parts of your body.

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<Organization of Central and Peripheral Nervous Systems>

The central nervous system is your brain and spinal cord - the main control center.

It's what decided to remove the spider, and gave the order to your hand.

Your peripheral system is composed of all the nerves that branch off from the brain and spine that allow your central nervous system to communicate with the rest of your body.

The motor division also includes the somatic, or voluntary nervous system, that rules your skeletal muscle movement, and the autonomic, or involuntary nervous system, that keeps your heart beating, and your lungs breathing, and your stomach churning.

That autonomic system, too, has its own complementary forces.

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<Neurons&Glial Cells>

Glial Cell Types
provide support, nutition, insulation, and help with signal transmission in the nervous system.

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<Central Nervous System Glial Cells>

Star-shaped astrocytes are found in your central nervous system and are your most abundant and versatile glial cells.

They anchor neurons to their blood supply, and govern the exchange of materials between neurons and capillaries.

Ependymal cells line cavities in your brain and spinal cord and create, secrete, and circulate cerebrospinal fluid that fills those cavities and cushions those organs.

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<Peripheral Nervous System Glial Cells>

Satellite cells do mainly in the peripheral system what astrocyte cells do in the central system - they surround and support neuron cell bodies.

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<Cool Neuron Facts>

1. Nuerons are some of the longest-lived cells in your body.

2. Neurons are irreplaceable.

3. Neurons have huge appetites.

About 25 percent of the calories that you take in every day are consumed by your brain's activity.

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<Neuron Structure>

The bushy, branch-like things projecting out from the soma are dendrites.

The axons transmit electrical impulses away from the cell body to other cells.

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<Classifying Neuron Structures>

The main feature we look at is how many processes extend out from the cell body.

A "process" in this case being a projecting part of an organic structure.

99 percent of all your neurons are multipolar neurons, with three or more processes sticking out from the soma - including one axon, and a bunch of dendrites.

bipolar neurons have two processes - an axon and a single dendrite - extending from opposite sides of the cell body.

Unipolar neurons, on the other hand, have just one process, and are found mostly in your sensory receptors.

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<Classifying Neuron Functionality>

Which way an impulse travels through a neuron in relation to the brain and spine.

Our sensesory, or afferent, neurons pick up messages and transmit impulses from sensory receptors in say, the skin or internal organs, and send them toward the central nervous system.

Most sensory neurons are unipolar.

There are interneurons, or association neurons, which live in the central nervous system and transmit impulses between those sensory and motor neurons.

Interneurons are the most abundant of your body's neurons and are mostly multipolar.