Action Potential

Question 1

difference between charges on each side of neuron’s plasma membrane @ rest

Answer 1

• 70 mV (millivolts)

- charge inside membrane = 70 less than outside

Question 2

resting potential

Answer 2

• polarization of neuron’s plasma membrane at rest
• maintained via sodium-potassium pump
• sodium + potassium gates closed

Question 3

sodium-potassium pump

Answer 3

• active transport process (against grain of diffusion)
• 3 Na+ ions pumped out, 2K+ ions pumped in
• uneven #s & diffusion rates –> higher charge outside membrane than inside

Question 4

action potential overview

Answer 4

• rapid change in polarity that occurs when axon stimulated to conduct a nerve impulse
• self-propagating
• all or nothing response

Question 5

phases of action potential

Answer 5

1. Resting Potential
2. Depolarization
3. Repolarization
4. Afterpolarization

Question 6

depolarization

Answer 6

• sodium gates open
• sodium rushes into axon
• voltage rises to 0, then to +40mV

Question 7

repolarization

Answer 7

• sodium gates close
• potassium gates open
• potassium rushes out of axon
• negative voltage returns to inside of axon

Question 8

afterpolarization

Answer 8

• aka hyperpolarization
• potassium gates slow to close
• undershoot of potential voltage ( < -70mV) then increases back to -70mV to return to resting potential

Question 9

intensity of sensation depends on:

Answer 9

• # neurons stimulated

- frequency with which the neurons stimulated

Question 10

how neurotransmitters work

Answer 10

nerve impulse reaches end of axon

• -> volt-gated calcium channels to open
• -> Ca +2 rushes in
• -> vesicles containing neurotransmitters fuse with the plasma membrane & release them into synapse
• -> neurotransmitter binds with receptor on next neuron

Question 11

inhibition

Answer 11

processes, such as enzymes inactivating neurotransmitters, that prevent continuous stimulation of post-synaptic membranes

Question 12

acetylcholine

Answer 12

neurotransmitter found at NMJs in PNS

Question 13

acetylcholinesterase

Answer 13

enzyme that breaks down acetylcholine

Question 14

dopamine

Answer 14

• neurotransmitter produced in brain

- specialized to regulate emotional responses and muscle tone

Question 15

neuromuscular junction (NMJ)

Answer 15

synapse between motor neuron and muscle tissue (where motor neuron ends on a muscle instead of another neuron)

Question 16

NMJ’s process of making muscle contract

Answer 16

1. nerve impulse sent by presynaptic motor neuron to muscle
2. nerve impulse reaches muscle fiber @ NMJ
3. acetylcholine released into synapse, binds to receptors on muscle fiber, causing sodium channels to open
4. Na+ rushes out of cell, triggering action potential that stimulates sarcoplasmic reticulum of muscle fiber
5. sarcoplasmic reticulum releases calcium ions, causing muscle to contract