Unit 8: Communication and Control

The Nervous System

Communication and Control

• Together the nervous and endocrine systems continually monitor conditions inside and outside of the body and adjust function to maintain homeostasis

• The endocrine system produces hormones which travel through blood act fairly slowly on target tissues

• The nervous system produces impulses and neurotransmitters which act extremely fast to send messages along nerves

Weird Science• Our nervous system creates tiny electrical currents to send messages around the body.

• What if we could generate large and powerful currents and shoot them from our bodies, like a great or evil superpower?

• That would be pretty awesome, right?• Well, we can’t. But there are a few animals that have that power. Most famously, the electric eel.

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Electric Eel• Not really an eel. It’s a knifefish.

• capable of producing one amp of current driven by up to 750 volts - enough to kill eight people.

• used for navigation, communication, attracting a mate and to stun or even kill prey.

• How do they do it? And how do they not shock themselves?

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What are the 3 basic functions of the nervous system?

• 1) sensory function (detect internal & external stimuli)

• 2) integrative function (processing, analyzing storing information)

• 3) motor function (carry info from brain/SC to muscles and organs, response)

Organization of the nervous system

Structures of the nervous system

• Billions of neurons & neuroglia

• Brain & cranial nerves• Spinal cord & spinal nerves• Ganglia: small masses of nervous tissue

What is a nerve?

• A bundle of up to thousands of neuron axons + associated connective tissue & blood vessels

What is a neuron?

• Functional, conductive unit of the nervous system

• Nerve cell

Neuroglia

• Other cells of the nervous system

• Do not generate or carry nerve impulses

• Can grow and multiply, unlike neurons

• Glioma is a tumor of the neuroglia

Myelination

• Lipid & protein coating around axons

• Produced by Schwann cells in PNS or oligodendrites in CNS

• Nodes of Ranvier= gaps in the myelin at intervals

• White matter= myelinated neurons• Gray matter= unmyelinated neurons

Where are white & gray matter found?

brain spinal cord

The Impulse

• Electrical signal passed along neurons

• Action potentials travel long distances

• Generation & conduction of an action potential depend on movement of ions across the cell membrane

Ion channels

1. Leakage channels: always open, K+ and Na+ constantly able to diffuse in & out

2. Gated channels: open & close in response to stimuli, creating electric excitability1. Change in voltage2. Response to chemical stimulus3. Response to mechanical stimulation

(vibration, pressure, stretching, etc.)