Excitable Cells

Question 1

what is action potential?

Answer 1

a brief flip flop in polarity across the membrane

Question 2

why is action potential important?

Answer 2

it is how nerves and muscles contract

Question 3

how does sodium ions enter the cell?

Answer 3

through facilitated diffusion

Question 4

why does the cell loose positive charge?

Answer 4

potassium moves out the cell, therefore the cell looses the positive charge

Question 5

what happens during the depolarizing stage

Answer 5

there is a change in sodium; positive charge is entering the cell

Question 6

what happens during the repolarizing stage

Answer 6

there is a change in potassium; moves out the cell

Question 7

what is the threshold

Answer 7

-55

Question 8

what is the resting membrane potential

Answer 8

-70

Question 9

what is the peak

Answer 9

+30

Question 10

is action potential graded or not graded

Answer 10

not graded; meaning all the responses are identical once the threshold is met

Question 11

what channels open during depolarization

Answer 11

voltage-gated ion channels open so the axon keeps gaining positive charge

Question 12

when does the refractory period take place

Answer 12

beginning of hyperpolarization

Question 13

do concentration gradients change during an action potential

Answer 13

the overall concentration gradients for Na+ and K+ do not change during an action potential

Question 14

is action potential required

Answer 14

nerves have to have action potential in order to function properly

Question 15

what does absolute refractory mean

Answer 15

the cell cant respond at all

Question 16

what does relative refractory mean

Answer 16

the cell needs a bigger stimulus then usual to reach threshold

Question 17

are leaky potassium channels always open ?

Answer 17

yes

Question 18

what kind of stimulus is needed during the refractory period

Answer 18

a larger stimulus because its farther from threshold

Question 19

what is the purpose of an inactivation gate

Answer 19

prevents the cell from being stimulated again until you are done with action potential

Question 20

when do the inactivation gates slide into place

Answer 20

at the peak

Question 21

what does propagate mean

Answer 21

to make more

Question 22

where do action potentials take place

Answer 22

in the axon

Question 23

what is the cell membrane mostly made of

Answer 23

phospholipids

Question 24

what is the axon covered in

Answer 24

mylein

Question 25

why is mylein covering the axon important

Answer 25

it increases speed, because it insulates the axon

Question 26

why kind of charge flows under the myelin

Answer 26

positive charge

Question 27

what occurs when there is a small space where the mylein isnt covering the axon

Answer 27

the sodium channels are open and the membrane reaches peak

Question 28

what is velocity

Answer 28

how fast the axon conducts information

Question 29

whats the difference between a myelinated axon and an unmyelinated axon?

Answer 29

a myelinated axon carries information faster with less friction, while covering more area (its thicker)

Question 30

what kind of diffusion is ion movement

Answer 30

passive diffusion

Question 31

what happens once threshold is met

Answer 31

sodium enters

Question 32

which channels open first

Answer 32

sodium channels, then potassium

Question 33

what is passive diffusion

Answer 33

type of membrane transport that does not require energy to move substances across cell membranes

Question 34

which ion channels happen on the synaptic knob

Answer 34

voltage-gated calcium channels

Question 35

what does blood calcium reflect

Answer 35

extracellular calcium

Question 36

what is the importance of calcium

Answer 36

calcium helps the vesicles migrate to the synaptic cleft; calcium also helps to trigger the neurotransmitters to be released

Question 37

what does exocytosis mean

Answer 37

to move something out of the cell

Question 38

what are the steps of exocytosis

Answer 38

the cell manufacturers the neurotransmitters, the neurotransmitters are packaged within the vesicle, the vesicle fuses with the cell membrane and becomes a part of it, the calcium stimulates the vesicles to move to the synaptic cleft and then the neurotransmitter is released from the cell

Question 39

what happens to the neurotransmitter once exocytosis process is over

Answer 39

once the neurotransmitter binds to the voltage channel, some of the neurotransmitters are removed by an enzyme out of the synaptic cleft while some neurotransmitters are recycled so they will go back by a process called endocytosis

Question 40

where is electrical synapses found

Answer 40

cardiac muscle and smooth muscle

Question 41

why are gap junctions important in cardiac muscle and smooth muscle

Answer 41

because they allow for an exchange of cytoplasmic products