1. Upload 9.06 Nerve Impulse Notes to eBackpack

2. Nerve Impulses

3. How does an impulse travel along a nerve pathway
How does an impulse travel along a nerve pathway? Review “Best of”, filling in your notes as you go.
Effector
Interneuron
Motor neuron
Receptor
Sensory neuron
Stimulus C B F D E A

4. Nerve impulses have a domino effect.
Through a chain of chemical events, the dendrites pick up an impulse that’s shuttled through the axon and transmitted to the next neuron.

5. Introductory animation
The entire impulse passes through a neuron in about 7 milliseconds- faster than a lightning strike.
Introductory animation

6. Step 1 Resting Potential (the nerve fiber is not sending a signal)
NaK pumps in the cell membrane actively transport 3 Na+ ions out of the cell for every 2 K+ ions pumped into the cell
The result- the interior of the cell is negatively charged with respect to the exterior- polarization
Resting potential animation and quiz

8. Step 2 Depolarization A threshold stimulus is received.
(the stimulation level that must be exceeded to elicit a nerve impulse)
Na+ channels in the membrane open and Na+ diffuses inward depolarizing the membrane

9. Depolarization animation
What charge are sodium ions? +
What will happen to the charge inside of the neuron?
It will become more +
Depolarization animation

10. Step 3 Repolarization K+ channels in the membrane open
K+ diffuse outward, repolarizing the membrane
Repolarizing animation

11. Step 4 Action Potential
The resulting action potential causes a local bioelectric current that stimulates adjacent portions of the membrane
The wave of action potential travels the length of the nerve fiber as a nerve impulse
Action potential propagation animation

12. Summary of Nerve Impulse
Nerve impulse summary video

13. Dramatizing an Action Potential
2. What happens to the charge during an action potential?
1. What is the name of the stimulus that causes an action potential?
Threshold stimulus!!!!

14. Dramatizing an Action Potential
3. During rest, what is the charge on the outside of the cell membrane?
Resting
1. What part of the neuron does this rectangle represent?
Neuron
Cell Body
2. What branch is this?
Axon

15. Complete Nerve Impulse Homework

16. The Synapse
A synapse or synaptic cleft is a gap that separates the axon of one neuron and the dendrites of the next neuron.
*Neurons do not touch.
Chemicals carry
messages across
the synapse.

17. Structures of the synapse1
Presynaptic cell 2
Synaptic
knob 3 7 8 4 6 5
Postsynaptic cell
Axon, Dendrite, Mitochondria, Neurotransmitter, Receptor site, Synaptic cleft, Synaptic knob, Synaptic vesicle

18. What’s happening?
Arrival of the nerve impulse

19. Neurotransmitter binds to receptor
Arrival of the nerve impulse
Opening of the
calcium channels
Binding of Ca2+ to synaptic vesicles, neurotransmitter released into the gap
Neurotransmitter binds to
receptor
Na+ enter the Ligand-gated channel
Action potential generated in postsynaptic neuron

21. The synapse animation

22. Synaptic transmission
Excitatory
“+” charged ions are released into postsynaptic neuron
May trigger a nerve impulse
Inhibitory
“-” charged ions are released into postsynaptic neuron
Less likely a threshold stimulus will be reached

23. Something else to think about…
Something else to think about….. The synaptic knobs of a thousand or more neurons may communicate with the dendrites and cell body of a single postsynaptic neuron. What will happen if both excitatory and inhibitory signals are received?

24. Dramatize it! Needed: Presynaptic Neuron Postsynaptic Neuron
Dendrite
neurotransmitters
receptor
Na+
receptor
Axon
synapse
Dendrite
Cell Body
Cl-
Cell Body
Needed:
Presynaptic Neuron
Dendrite (1 student)
Cell Body (1 student)
Axon (Row 3)
Calcium (1 student)
Synaptic Vesicles (4 students)
Neurotransmitters (2 students)
Synaptic knob
Postsynaptic Neuron
Receptors (4 students)
Sodium Ion (1-2 students)
Chlorine Ion (1-2 student)
Dendrite Branch (3 students)
Cell body (1 student)