1. The Nervous System and Neurons

2. Nervous System Network of connected cells, tissue, and organs
Controls thoughts, movement, life processes
Quick responses
Ex: Sunny day  pupils shrinking

3. CNS and PNS

4. Neurons AKA: Highly specialized nerve cells 4 Main Parts
Transfer electrical impulses to and from the brain
4 Main Parts
Cell body: contains nucleus and organelles
Dendrites: branches that receive messages from neighboring cells
Axon: extension that carries messages away from the cell body
Axon Terminal: End of neuron

5. Three Types of Neurons:
1) Sensory
Detect stimuli and transmit signals to/from the brain
Detect sense (sight, smell, sound, taste, touch)

6. Three Types of Neurons:
2) Interneuron
Located in the brain
Receive signals from the sensory neurons

7. Three Types of Neurons:
3) Motor
Pass messages to other tissue
Ex: Nerve attached to muscle
Muscle reacts by contracting

8. Resting Potential Defined: Neuron at rest Neuron interior is negativeK+
Interior K+ K+ K+ K+ K+ K+ K+ K+
Defined: Neuron at rest
Neuron exterior is positive in charge
Due to abundance of Na+ outside
Neuron interior is negative
Due to abundance of proteins and…
Some K+ inside the cell

9. Action Potential
Defined: The electrical impulse that is triggered & moves quickly down an axon

10. Action Potential
Defined: The electrical impulse that is triggered & moves quickly down an axon
Generating the Impulse
Na + channels in the membrane open and allow Na+ to diffuse into the cell
Area becomes positively charged (impulse)
After the Impulse
K+ channels open to allow K+ to exit the cell
Area returns to negative charge
Process continues down the axon

11. impulse

12. Normally negative charge
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Na+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ + K+ K+ K+ K+ + K+ K+ K+ + K+ K+ K+ K+ K+ K+
Normally negative charge K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+
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13. The impulse moves down the length of the axon.
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Na+ - - - - - - - - - - - + K+ + K+ + K+ + K+ + K+ + K+ + K+ + K+ + - - - - - - - - - - - - - - - - - - - - -
The impulse moves down the length of the axon.

14. Cleaning Up the Mess Who? What? How? When? Where? Why? Na + /K + pump
Na+ is pumped back out of the cell…
K + is pumped back into the cell
How?
Active transport (REQUIRES ATP)
When?
After the impulse has passed
Where?
Located in cell membrane
Why?
To restore the initial charge inside & outside the cell

15. Na+
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17. Synapse Defined: Gap between neurons
Problem: Impulse cannot cross the gap
Solution: Neurotransmitters (chemical signals) are sent from one neuron to another
Steps:
1) Impulse reaches axon terminal (end)
2) Vesicle releases neurotransmitters into synapse, which attach to receptors on neighboring neuron
3) Na+ Channels open on dendrite of neighboring neuron… creates new impulse
Neurotransmitter proteins

19. Vesicle exits the cell and dissolves
Na+
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Vesicle exits the cell and dissolves
impulse
impulse
impulse K+ K+ K+
Impulse reaches the axon terminal
Dendrite of another cell
Terminal end of one cell

20. Neurotransmitters cause Na+ channels to open… creating new impulse
Neurotransmitters diffuse across the synapse and attach to receptors of a neighboring neuron
Na+
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impulse
impulse
impulse
impulse K K K
Dendrite of another cell
Terminal end of one cell

21. Brain Feet …. …. …. …. impulse impulse impulse impulse impulse
neurotransmitters
impulse ….
neurotransmitters
impulse ….
neurotransmitters
impulse ….
neurotransmitters
impulse
Feet

22. Impulses eventually reach the muscles…
and causes MOVEMENT!

23. Review
1. What is the function of the nervous system? 2. List the 4 main parts and describe the purpose of the 4 main parts of a neuron. 3. The nervous system is divided into 2 parts. What are they and what do they include? 4. Describe the internal and external environment of a neuron in resting potential. How is resting potential reached? 5. What is a synapse and why is it a problem for neurons? 6. To what part of the nervous system do motor neurons, interneurons, and sensory neurons belong? 7. When an impulse is within a neuron it is electrical. When the signal moves to the next neuron it is _________________. What is the specific name for this signal? 8. Describe how an action potential moves down a neuron.