nervous system + review

Question 1

Which is the best description of why neurons have an absolute refractory period at the end of an action potential.

Answer 1

Because voltage-gated Na+ channels cannot open until after the membrane repolarizes (I.e. reaches approximately resting potential).

Question 2

Which of the following is the best comparison of signaling via a chemical vs electrical synapse?

Answer 2

Signaling via a chemical synapse takes longer than signaling via an electrical synapse

Question 3

Based on class discussion, which of the following would completely block transmission across all chemical synapses?

Answer 3

Blocking the activity of voltage gated Ca 2+ gated channels

Question 4

Synaptic transmission via GABA receptor

Answer 4

Always results in an IPSP in the post synaptic cell, however hyperpolarization or depolarization might occur

Question 5

plateau

Answer 5

the maximum value of the output value that can be produced by the effector

Question 6

threshold

Answer 6

the value of an output above which the system will automatically and rapidly drive the output variable to plateau

Question 7

transport

Answer 7

three major processes
1. pressure: force per unit area
2. concentration gradients
3. electrical charges

Question 8

simple diffusion

Answer 8

direct diffusion of lipid-soluble subtances across the plasma membrane, CO2, O2, thyroid, steroid hormones

Question 9

diffusion through protein channels

Answer 9

ion channels + water channels + uniporter carriers

Question 10

uniporter carrier example from class

Answer 10

the glucose transporters (GLUT 1-4)

Question 11

co - transporters

Answer 11

move substances in the same direction across the membrane

Question 12

exchangers

Answer 12

move substances in the opposite direction across the membrane

Question 13

endocytosis

Answer 13

engulfment of extracellular materials (phagocytosis), removal of spanning proteins from the plasma membrane

Question 14

exocytosis

Answer 14

release of the messengers from intracellular vesicles, insertion of spanning proteins into plasma membrane

Question 15

lipid soluble messegers

Answer 15

diffuse into cells, binding receptors in the cytoplasm or nucleas (steroid hormones, estrogen, cortisol)

Question 16

water soluble messengers

Answer 16

bind transmembrane protein receptors, two main classes include ionotropic and metabotropic

Question 17

myelin sheath

Answer 17

lipid-rich tissue that insulates the axon and improves the rate of signal transmission. stretches of myelin are separated by nodes of ranvier, which contain all the channels needed to propogate action potentials

Question 18

the sodium potassium pump

Answer 18

3 sodium are pumped out, and 2 sodium are pumped in - establishes the sodium and potassium concentration gradients that eventually lead to resting potential.

Question 19

describe leak channels. At rest, signifigantly more ______ leak channels are open as compared to _______

Answer 19

channels that are open at rest and alow their specific ions to flow. potassium, sodium

Question 20

Resting potential for potassium is

Answer 20

-90

Question 21

Resting potential for sodium is

Answer 21

+60

Question 22

describe the giant squid experiment

Answer 22

a recording electrode was placed an extracellular saline, and the voltage was measured. following this, the recording electrode was placed in the cell where the resting potential was determined

Question 23

describe the initiation of an action potential

Answer 23

something (such as an EPSP) prompts the depolarization of the cell. note: if, at this point the threshold is not reached, then it will return back to resting potential after some time

Question 24

what happens when the voltage reaches threshold?

Answer 24

V-gated sodium channels start to open up. at the peak of the action potential, the conductance of the sodium is greater than the conductance of the potassium, membrane potential approaches ENa. However, Ek > 0 and there are potassium leak channels it doesn’t quite reach 60 mV.

Question 25

what happens when the voltage reaches the peak?

Answer 25

The V-gated potassium channels open and the V-gated sodium channels become inactive, beginning a repolarization phase. During this, Gk >> GNa, meaning that much more potassium flows out of the cell than sodium into the cell meaning that the membrane voltage approaches Ek again.

Question 26

why do neurons have an absolute refractory period at the end of an action potential?

Answer 26

Voltage-gated Na+ channels cannot open until after the membrane repolarizes

Question 27

Do Ek or ENa change during the course of an action potential?

Answer 27

No