Structures and Functions of the Nervous System

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Structure and Function

Learning Targets:• Classify the major structures of the nervous

system (R)• List the general functions of the nervous

system (K)

Nervous System

Anatomy Physiology

Organs are divided into two groups:1. Central Nervous System (CNS) a. Brain b. Spinal Cord

2. Peripheral Nervous System (PNS) a. Nerves

A

B

C

Nervous System

Anatomy Physiology

Together, organs perform 3 main functions1. Sensory monitor internal and external environment2. Integration information from the sensory nerves is integrated into the CNS by neurons3. Motor Output stimulation of muscles or glands to move or secrete substances

Nervous Tissue

Learning Target: Identify and state the function of the components of nervous tissue. (K)

1. Neuron (Nerve Cell) a. specialized to react to physical and chemical changes in their surrounding b. Excitable- transmit information in the form of electrochemical changes called nerve impulses along nerve fibers to other neurons and other types of cells c. Structures of a neuron-

1) Cell Body- contains the nucleus and organelles

2) Dendrites- receive info from other neurons

3) Axons- send impulses away from the cell body

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2

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Fun Fact:A cell body diameter ranges from 5 - 135 µm An axon diameter ranges from 1 - 20 µm The axons length ranges from 2 mm - 1 m.

Let's scale this up!

The classroom

will equal 1 cell body

How far would this axon travel out of the room? Up to 1.6 km (1 mile)- That’s all the way to the HC library!!!!

2. Neuroglial cells-a. Specialize to support the neuron

b. Non-excitable-do not send impulses

c. Four types in the CNS

1) Astrocytes– form connections between blood vessels and neurons

A tissue sample from the brain. The area where the astrocyte connects to the blood vessel is called a foot process.

2) Oligodendrocytes-insulate neurons, form the myelin sheath

Electron micrograph showing branched oligodendrocytes with processes extending to several underlying axons

3. Microglial cells- engulf microbes and remove wastes

Activated microglial cells in a rat brain. When activated, these cells are phagocytic helping to removing damaged or dying cells.

4. Ependymal cells- help circulate cerebrospinal fluid

Ependymal cells found in the 3rd ventricle of the brain of a 32 week old fetus.

d. 2 types in the PNS 1) Satellite cells- surround and control the chemical environment of the neuron 2) Schwann- insulate the neuron, form the myelin sheath

What is the name of the similar cell in the CNS?

Fun Fact: For every nerve cell in your body there are 50 glial cells.

If a person looses brain cells every day, how does a child's brain increase in mass from 400 g to 1400g in adulthood?

1. The number of glia cells increases tremendously.2. More synapses are formed.

*When glia cells reproduce uncontrollably, a person has cancer.

Homework:

9.04 Neuron worksheet

Let’s pick four people for the review.