Nervous tissue 12-2

Question 1

action potentials

Answer 1

• only occur on excitable membranes
• self propagating
• exhibit all or nothing behavior

Question 2

graded (local) potentials

Answer 2

• act locally
• all cell membranes can generate
• strength is related to strength signal
• get weaker the further they get from original signal
• can be excitatory or inhibitory

Question 3

what is a graded potential?

Answer 3

a change in potential that decreases with distance and varies in strength based on the strength of the stimulus

Question 4

depoloarization

Answer 4

becomes less negative

Question 5

hyperpolarization

Answer 5

becomes more negative

Question 6

repolarization

Answer 6

shifts back toward typical resting potential

Question 7

what is an action potential?

Answer 7

appears when region of excitable membrane depolarizes; begins at axon hillock

Question 8

what are the steps of action potential?

Answer 8

1. resting membrane potential
2. activate voltage gated sodium channels and depolarization of membrane
3. sodium channel inactivation
4. Potassium channel activation and membrane re polarization
5. return to normal permeability

Question 9

refractory period

Answer 9

lasts from time action potential begins until normal resting potential returns

Question 10

absolute refractory period

Answer 10

neuron can’t refire; sodium channels are either open or inactivated

Question 11

relative refractory period

Answer 11

sodium channels are closed but can become reactivated; potassium channels are still open so new stimulus must cause more sodium entry than potassium exit

Question 12

continuous propagation

Answer 12

spread of action potential across entire membrane in series of small steps

Question 13

saltatory propogation

Answer 13

action potential spreads from node to node, skipping internodal membrane

Question 14

synapse

Answer 14

site of intercellular communication