The Nervous SystemMedical Biology

Mission Hills High School

Functions of the Nervous System

Sensory Integrative Motor

Divisions of the Nervous System

The nervous system is divided into- Central Nervous System (CNS), containing the brain and spinal cord- The Peripheral Nervous System (PNS), containing the nerves and ganglia

The Peripheral Nervous System

contains… cranial nerves

which arise from the brain

Spinal nerves which arise from the spinal cord as well as many branches

Nerve Tissue

The nerve tissue is composed of two types of cells: -neurons, which conduct impulses, and…-neuroglia which support the neurons

Neurons Structural and functional

units of the nerve system Perform sensory, integrative

and motor functions-sensory: ability to sense (receive) information-Integrative: ability to process the information received and arrive at a desire to respond.-Motor: ability to initiate a response with body movement or secretion of a product.

Lots of types of neurons

Structure of neurons

Each contain a cell body with a nucleus

Numerous dendrites: receive and send information to the cell body

A single axon: moves impulse from dendrites and body to dendrites or body of other neurons.

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3

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1. Cell Body

Part of the neuron that contains the nucleus

2. Nucleus

The nucleus is the control center of the cell and contains the genetic information in the form of DNA

3. Dendrites

Dendrites carry impulses (from another cell’s axon tips) toward the cell body

4. Axon

The axon carries impulses away from the cell body.

5. Axon Tip(s)

The axon tips release chemicals that enable the impulse to cross the synapse

Axon Tips

6. Synapse

The space between the axon tip and the next dendrite. It is also called the synaptic cleft.

Label and tell the function of each neuron part

Myelin in PNS and CNS

Axons in large peripheral nerves contain a fatty, supportive sheath called myelin sheath

Presence of myelin makes nerve tissue appear white (white matter)

In CNS spinal cord, unmyelinated nerve tissue appear gray (grey matter)

What makes up the brain, the spinal cord or your peripheral nerves?

Neurons are “the cell”

Cell body Nucleus Axon Dendrite What do you think

surrounds the cell? What other

organelles would be needed?

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

How are neurons connected?

Synapses!!

Why are neurons connected?

More neuron connections!

AXON

The synapse - where the action happens

The next cell’s plasma membrane

What is this in the membrane?

Transport protein

Close up look at your synapse (The Gray Matter)

How does the Synapse carry the signal?

1. impulse travels down the axon (The White Matter)2. Vesicles with neurotransmitters move toward the

membrane 3. Neurotransmitters are released and diffuse toward

the next cell’s plasma membrane4. The chemicals open up the transport proteins and

allow the signal to pass to the next cell

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23 4

The synapse carries a signal from cell to cell

There are lots of proteins and chemicals in your body to do the work

Why is it important that it is an electrical current?

How many synapses are in one neuron? 1,000 to 10,000!!

What do you think can change neurons and their

connections? Accident

s Drugs Alcohol Disease

Drugs and alcohol bind important receptors on neurons

Repeated binding causes the neuron to die

Drugs = neuron death

Alcohol damages dendrites - can repair after abstinence

Alcohol blocks receptors and slows down transmission

100 Billion or so neurons - what’s the problem with some of them dying?• Cells multiply all the time

- will your neurons?• Does everyone react the

same way to accidents, or drugs and alcohol?

• Do all organisms react the same to all stimulus?

• Which of your activities use your neurons?

What if neurons die here?

or hereor here

or here

or here