35.2. Controls and coordinates functions throughout the body. Responds to external and internal...
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Transcript of 35.2. Controls and coordinates functions throughout the body. Responds to external and internal...
![Page 1: 35.2. Controls and coordinates functions throughout the body. Responds to external and internal messages. The body’s communication system.](https://reader036.fdocuments.in/reader036/viewer/2022062308/56649f085503460f94c1d26e/html5/thumbnails/1.jpg)
THE NERVOUS SYSTEM35.2
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Controls and coordinates functions throughout the body.
Responds to external and internal messages.
The body’s communication system
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NEURONS
•Specialized cells of the nervous system• Transmit electrical signals called impulses in only one direction.•3 types
– sensory neurons-send signals from sensory receptors brain– motor neurons – send signals from the brain muscles & glands– interneurons –carry impulses between sensory & motor neurons
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NEURON ANATOMY
Axon terminals
Nodes
Myelin sheath
Cell body
Axon Dendrites
Nucleus
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FUNCTIONS
Axons – carry impulses away from the cell body
Myelin sheath – an insulating membrane surrounding the axon
Cell body – where the metabolic activity of the cell takes place
Dendrites – carry impulses from the environment to the cell body
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NERVE IMPULSE – RESTING NEURON • A nerve impulse is similar to the flow of electrical current through a wire.• When the neuron is NOT sending an impulse, the inside is negative and the outside is positive
Na+ and K+ ions move across the cellMembrane via the sodium-potassium pump
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The Moving impulse An impulse begins when a neuron is
stimulated by another neuron or the environment
Action potential - When an impulse is sent the charge reverses inside the cell – it becomes positive
Threshold – the amount of stimulus required to activate the neuron
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The moving impulse
An impulse begins when a neuron is stimulated strong enough to reach a threshold. The impulse travels rapidly down the axon towards the terminal end.
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THE SYNAPSE • Where impulses are transferred from one neuron to another.•Chemicals diffuse across a small gap between the cells •Neurotransmitters- are the chemicals that transfer impulses from one neuron to another.•Receptors of the neighboring neuron pick up the chemical message, and a new impulse begins.
axon
Neuro-transmitter
Direction of impulse
receptor
Axon terminal
vesicle
Dendrite ofAdjacent neuron
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In a fraction of a second after binding to the receptors, the neur0transmitter molecules are released.
They are re-absorbed back into the axon terminal
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What are the 4 parts of a neuron?
What is a threshold?How does a message move
from one neuron to another?
Review questions