Chapter 12: Action Potentials

Question 1

How do the cells of nerve and muscle tissues communicate?

Answer 1

action potentials or graded potentials

Question 2

action potentials or nerve impulses allow?

Answer 2

communication over short + long distances

Question 3

graded potentials allow?

Answer 3

communication over short distances only

Question 4

what is the resting membrane potential that action potentials rely on?

Answer 4

-70 mV

Question 5

membrane potential

Answer 5

electrical voltage across the membrane

Question 6

2 basic types of ion channels

Answer 6

leakage and gated

Question 7

what are leakage channels open to?

more of which?

Answer 7

sodium and potassium

• more potassium than sodium

Question 8

gated channels respond to?

Answer 8

a direct change in the membrane potential

Question 9

ligand-gated channels respond to?

examples

Answer 9

a specific chemical stimulus

• ex: sodium, chlorine, calcium, potassium, mechanical pressures

Question 10

mechanicaly-gated ion channels respond to?

Answer 10

mechanical vibration or pressure

Question 11

What is the chemical permeability of a resting membrane?

Answer 11

the unequal distribution of potassium ions inside the cell membrane and sodium ions outside the cell membrane in the cell membrane in the ECF

potassium=inside

sodium=outside

Question 12

typical value for the resting membrane potential?

Answer 12

-70 mV polarized

Question 13

how id th resting membrane potential determined?

Answer 13

by the unequal distribution of ions across the plasma membrane + the selective permeability of the membrane to Na and K

Question 14

potassium permeability is ___x more than sodium

Answer 14

100

Question 15

action potential or impulse is a?

what occurs during action potential?

Answer 15

sequence of rapidly occurring events that decrease and eventually reverse the membrane potential (depolarization)

• then restore it to resting (repolarization)
• during action potential, voltage gated Na + K channels open in sequence

Question 16

all or none principle

Answer 16

if a neuron reaches threshold, an action potential is always generated

Question 17

what occurs during hyperpolarization?

Answer 17

b/c not all K gates closed, some remain open shortly

• dont close until resting membrane potential reaches -70 again

Question 18

refractory period

when can action potential be generated again?

Answer 18

when membrane cant respond to 2nd stimulus

• neuron is unabe to generate another ation potential until original Na and K concentrations are reestablished (restored through Na, K pump)
  
  • Na ions pumped against gradient, K ions pumped in

Question 19

absolute refractory period

Answer 19

membrane cant respond to 2nd stimulus no matter how strong it is (1-2 ms)

Question 20

relative refractory period

Answer 20

membrane can respond to 2nd stimulus if its stronger than the 1st

Question 21

how do local anasthetics and certain neurotoxins (botox) affect the muscle

Answer 21

prevent opening of voltage-gated Na channels so nerve impulses cant pass the obstructed region + reach CNS

Question 22

saltatory conduction in nerve fiber

Answer 22

myelinated segments of the nerve fiber remain electrically inactive and the impulse jumps from node to node as each area depolarizes

Question 23

propagation speed of a nerve impulse is related fiber ____ and to _____, not _____

Answer 23

diameter, myelin sheath, stimulus strength

Question 24

what fibers conduct nerve impulses at the fastest rate? how fast?

Answer 24

large, myelinated, type A, 250 mph or 100 mps

Question 25

what fibers conduct the slowest nerve impulses?

Answer 25

small diameter, non myelinated, 1 mps

Question 26

where can a neuron synapse?

Answer 26

cell body, dendrite, another axon

Question 27

synapse interacts with?

Answer 27

functional interaction btwn 2 neurons or neuron + effector (muscle, gland)

Question 28

presynaptic neuron transmits____ toward_____

Answer 28

impulse twds synapse

Question 29

post synaptic neuron recieves ______ from ______

Answer 29

impulse from presynaptic neuron

Question 30

synaptic cleft

Answer 30

space btwn pre and post synaptic neuron