Upload 9.06 Nerve Impulse Notes to eBackpack

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• Upload 9.06 Nerve Impulse Notes to eBackpack

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Nerve Impulses
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• 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
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• Nerve impulses have a domino effect.
• Through a chain of chemical events, the dendrites
  pick up an impulse thats shuttled through the
  axon and transmitted to the next neuron.

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

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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

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

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Step 3Repolarization

• K channels in the membrane open
• K diffuse outward, repolarizing the membrane

• Repolarizing animation

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Step 4Action 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

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Summary of Nerve Impulse

• Nerve impulse summary video

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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!!!!
------------
------- ---- ---
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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

Axon
2. What branch is this?

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Complete Nerve Impulse Homework
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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.

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Structures of the synapse
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Presynaptic cell
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Synaptic knob
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Postsynaptic cell
Axon, Dendrite, Mitochondria, Neurotransmitter,
Receptor site, Synaptic cleft, Synaptic knob,
Synaptic vesicle
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Whats happening?
Arrival of the nerve impulse
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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
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• The synapse animation

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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

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• 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?

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Dramatize it!
Dendrite
neurotransmitters
Na
receptor
receptor
Axon
synapse
Dendrite
Cell Body
Cell Body
Cl-
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)