1. Neurons & the Nervous System

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

3. What must happen in order to pick up the apple?
Light reflects off the apple and into your eyes…
Photoreceptors (rods and cones) send a signal to your brain…
Your brain receives the signals and sends another signal down your spine…
Down your arm…
To your hand…
Hand muscles react to those signals and grab the apple

4. Neurons AKA: Nerve Cells
Function: Transfer electrical impulses to/from the brain
3 Main Parts
Cell body: contains nucleus and organelles
Dendrites: branches that receive impulses from neighboring cells
Axon: extension that carries impulse away from the cell body
Cell Body
Dendrites
Axon

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

6. Three Types of Neurons:
1) Sensory
Detect stimuli and transmit signals to/from the brain
Detect sense (sight, smell, sound, taste, touch)
2) Interneuron
Located in the brain
Receive signals from the sensory neurons

7. Three Types of Neurons:
Muscle cell
Motor Neuron
1) Sensory
Detect stimuli and transmit signals to/from the brain
Detect sense (sight, smell, sound, taste, touch)
2) Interneuron
Located in the brain
Receive signals from the sensory neurons
3) Motor
Pass signal to other tissue
Ex: Nerve attached to muscle
Muscle reacts by contracting/stretching

8. - - - - - - - - - - - Resting Potential Defined: Neuron at rest
An electrode can be inserted to measure the internal charge
Exterior
Lets zoom into the cell membrane of this neuron… - - K+
Interior - - -
-70mV -
Defined: Neuron at rest
Neuron Interior = negative charge due to cytoplasm proteins (although K+ inside) - K+ K+ - - - - K+

9. Resting Potential Defined: Neuron at rest
Exterior
Na+
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Interior
Defined: Neuron at rest
Neuron Interior = negative charge due to cytoplasm proteins (although K+ inside)
Neuron Exterior = positive charge due to abundance of Na+ ions

10. - - - - - - - - - - - - - - - - - - - - - - - - - - Resting Potential
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Exterior
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Na+ - - - - K+
Interior - K+ K+ - K+ - - - - - - K+ - - - K+ - K+ - - - K+ - - - - - K+ - K+ K+ - K+

11. Action Potential
Defined: Electrical impulse is triggered & moves quickly down axon
Analogy:
An action potential is like people doing “the wave” at a sporting event.

12. Action Potential
Defined: electrical impulse 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
Na+
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-90mv K+
-40mv K+
+50mv K+ K+ K+

13. Here is an action potential (impulse) moving down a neuron…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+
Lets zoom in… 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+ K+
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14. -40mV: Na channels open & positive Na+ ions diffuse inside
+50mV: Na channels close & K channels open. K+ ions diffuse outside.
Na+
-90mV: K channels close & Na channels open. Na+ ions diffuse inside.
Na+
+50mV: Na channels close & K channels open. K+ ions diffuse outside.
Na+
Na+
-90mV: K channels close & Na channels open. Na+ ions diffuse inside.
Na+
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+50mV
+50mV K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+
+50mV K+ K+ K+ K+
impulse K+ K+ K+ K+
impulse K+ K+ K+
impulse 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+
-90mV
-90mV
-90mV K+ K+ K+ K+ K+ K+
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15. The impulse moves down the length of the axon.
Na+
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Na+ - - - - - - - - - - - + K+ + K+ + K+ + K+ + K+ + K+ + K+ + K+ + - - - - - - - - - - - - - - - - - - - - -
The impulse moves down the length of the axon.

16. Too much potassium (K+) on the outside of the cell
Na+
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Problem:
Too much potassium (K+) on the outside of the cell
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Problem:
Too much sodium (Na+) on the inside of the cell
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17. Cleaning Up the Mess Who? Na/K pump How? Active transport (use of ATP)
What?
Na is pumped back out of the cell…
K is pumped back into the cell
When?
After the impulse has passed
Where?
Located in cell membrane
Why?
To restore the initial charge inside & outside the cell K+ K+ K+ K+ K+
heat A P P
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18. Na+
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19. 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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20. Lets continue moving the impulse…Na Na Na
Lets continue moving the impulse… Na Na
vesicle
receptor
Lets zoom in again…

21. Synapse Defined: Gap between neurons
vesicle
receptor K K
Defined: Gap between neurons
Problem: Impulse cannot cross the gap
Solution: Neurotransmitter proteins sent from one cell to another
Steps:
1) Impulse reaches axon terminal (end)
2) Neurotransmitters (from vesicles) attach to neighboring receptors
3) Na channels open on neighboring cell…new impulse created

22. Synapse Defined: Gap between neurons
vesicle K K
Defined: Gap between neurons
Problem: Impulse cannot cross the gap
Solution: Neurotransmitter proteins sent from one cell to another
Steps:
1) Impulse reaches axon terminal (end)
2) Neurotransmitters (from vesicles) attach to neighboring receptors
3) Na channels open on neighboring cell…new impulse created

23. -40mV: Na channels open & positive Na+ ions diffuse inside
+50mV: Na channels close & K channels open. K+ ions diffuse outside.
Na+
-90mV: K channels close & Na channels open. Na+ ions diffuse inside.
Na+
+50mV: Na channels close & K channels open. K+ ions diffuse outside.
Na+
Na+
-90mV: K channels close & Na channels open. Na+ ions diffuse inside.
Na+
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+50mV
+50mV K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+
+50mV K+ K+ K+ K+
impulse K+ K+ K+ K+
impulse K+ K+ K+
impulse 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+
-90mV
-90mV
-90mV K+ K+ K+ K+ K+ K+
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24. Synapse Neurotransmitters are released across the synapse Na Na Na Na
vesicle
receptor K K
The impulse reaches the terminal end…

25. A new impulse is triggered
Synapse Na Na
vesicle K K
A new impulse is triggered

26. Brain . . . . . . . . . . . .
Feet

27. Impulses eventually reach the muscles…
Muscle cell
and causes MOVEMENT!

28. Practice Quiz What is the function of the nervous system?
Name the 3 types of neurons.
List the 3 main parts and describe their purpose.
Describe the internal and external environment of a neuron in resting potential.
What is a synapse and why is it a problem for neurons?
What are the roles of the following during an action potential?
Na+ ions, K+ ions, Neurotransmitters, Receptors, Na/K pump
Explain (paragraph form) how an action potential is passed from one neuron to another.