1. The Nervous System chapter 37
direction of impulse
The Nervous System chapter 37
info into cell
Gathering, analyzing and responding to stimuli - information from internal and external environment - via nerve cells, aka neurons
neuron
info to next cell
All domains of life detect and respond; only animals have a NS

2. The Nerve Impulse the message takes two forms
An electrical message is conducted down the axons of neurons
A chemical message bridges the gap - the synapse - between neurons, continuing communication

3. Membrane (Resting) Potential potential energy due to a difference in charge
Greater + charge outside the cell
Effect: charge inside cell is negative relative to environment; cell is polarized -70mV at rest
Lower +charge inside cell
K+ diffusion channels are open, ‘leak’ ions out
Na+/K+ pump moves Na+ out of cells, K+ in
• Na+/K+ move in facilitated and active transport
• Transport proteins are gated channels, triggered first by signal, then changes in voltage

4. Action Potential drives the impulse down the axon
Stimulus/signal open Na+ gates, begin localized depolarization of the membrane
Depolarization causes neighboring Na+ channels to open, impulse moves forward
Adjacent Na+ channels close, K+ gated channels open, membrane is repolarized

5. Action Potential not just any stimulus will do
Na+ gates open
Na+ gates close
K+ gates open
Not enough stimulus to reach threshold, gates do not open
no registering of stimulus, no impulse

6. Myelin Sheath insulates the Axon impulse travels faster
Schwann cells
wrap around
the axon, creating ‘insulating’ myelin sheath, for faster transmission
No ion channels in sheathed regions
only at Nodes
of Ranvier
No sheath? Muscular Dystrophy

7. The synapse A chemical message
Action potential
axon
neurotransmitter vessicle
re-uptake of neurotransmitter
neurotransmitter molecules
Ex: acetylcholine, norepinephine, seratonin,
dendrite
exocytosis
Action potential restarts
receptors

8. functional analogy – student after school5 4 2 1 7 3 6
A = 1, 3, 7
B = 4
C = 2
D = 6
E = 5
A. hanging out at home, watching TV
B. a friend texts; you answer it, make plans
C. your mom calls; you don’t answer
D. you take a short nap
E. you meet up with your friend, act on the plan