Graded And Action Potentials

Front 1

what are the 4 different types of ion channels?

Back 1

Ligand gated
voltage gated
background
mechanosensitive

Front 2

which ion channels are responsible for generating graded potentials?

Back 2

ligand gated
mechanosensitive

Front 3

which ion channel is responsible for generating action potentials?

Back 3

voltage gated

Front 4

which ion channel is responsible for maintaining the resting membrane potential?

Back 4

background

Front 5

what causes the magnitude of the graded potential to change?

Back 5

the magnitude of the stimulus

Front 6

what is the difference in propagation paths between graded and action potentials?

Back 6

graded- bidirectional
action- unidirectional

Front 7

what is the difference in conduction between action and graded potentials?

Back 7

graded- decremental and bidirectional
action- non-decremental and unidirectional

Front 8

what is the difference in the location of graded potentials vs action potentials?

Back 8

graded- in the cell body or at a neuromuscular jxn

action- at the axon hillock and along the axon. or along the muscle fiber (sarcolemma)

Front 9

what are the two types of postsynaptic, graded potentials?

Back 9

excititory- EPSP
inhibitory- IPSP

Front 10

What is a GPSP and what does it mean?

Back 10

Grand Postsynaptic Potential

it is the culmination of all presynaptic stimuli at any given time

Front 11

what is temporal summation?

Back 11

one way of bringing a post synaptic neuron to threshold.
it is the summation of repeated firings from a single presynaptic neuron

Front 12

what is spatial summation?

Back 12

one way of bringing a post synaptic neuron to threshold.
it is the summation of repeated firings from multiple presynaptic neurons

Front 13

what are the 4 types of voltage gated channels?

Back 13

Na+, K+, Ca+, and DHP

Front 14

what are the differences between a Na+ and K+ voltage gated ion channel?

Back 14

Na+ channels have an activation and inactivation gate. K+ channels only have activation gates.

the activation gates of Na+ channels open rapidly when threshold is reached. K+ channels are also triggered at threshold, but they have a delayed response

Front 15

what events are triggered to happen when an action potential threshold is reached?

Back 15

Na+ and K+ activation gates are triggered to open
Na+ inactivation gates are triggered to close.

Front 16

why doesnt the Na+ inactivation gate prevent siganal propagation if it is triggered to close at the same time as the activation gate?

Back 16

because the inactivation gate closes slowly

Front 17

why doesnt the K+ channel prevent signal propagation if its activation gate is triggered at the same time as Na+'s?

Back 17

because its response is delayed

Front 18

about how large must a graded potential be in order to create an action potential?

Back 18

10 to 15mV

Front 19

are depolarizing signals excititory or inhibitory?

Back 19

Excitatory

Front 20

are polarizing signals excititory or inhibitory?

Back 20

inhibitory

Front 21

where is the highest concentration of voltage gated ion channels located within a neuron?

Back 21

at the axon hillock

Front 22

during depolarization, what is the relationship between Na+ movement and K+ movement?

Back 22

Na+ movement into the cell exceeds the K+ movement out of the cell

Front 23

during repolarization, what is the relationship between Na+ movement and K+ movement?

Back 23

Na+ movement into the cell is less than the K+ movement out of the cell

Front 24

what type of feedback is established at the threshold of a Na+ channel?

Back 24

positive feedback

Front 25

what restores a cell to resting membrane potential after hyperpolarization?

Back 25

the Na+/K+ pump

Front 26

Why does tetrodotoxin prevent nerve impulses?

Back 26

it binds to the extracellular pore opening of voltage gated Na+ channels and prevents action potentials from occuring

Front 27

what event, within an action potential, are you inhibiting by blocking a voltage gated Na+ channel?

Back 27

depolarization

Front 28

how does topical lidocaine work?

Back 28

blocks voltage gated sodium channels

Front 29

what is the difference between an absolute and relative refractory period?

Back 29

Absolute- no stimulus can elicit an action potential
Relative- only a massive stimulus can elicit an action potential

Front 30

why is it impossible to generate an action potential during an absolute refractory period?

Back 30

because all of the inactivation gates of voltage gated Na+ channels are closed. impossible to depolarize the membrane

Front 31

why is it harder than normal, but possible, to generate an action potential during the relative refractory period?

Back 31

do to the increased permiability of the membrane to K+ and the partial/residual inactivation of voltage gated Na+ channels

Front 32

what happens to muscles during hyperkalemic conditions?

Back 32

spontaneous muscle contractions that eventually lead to total muscle paralysis.

Front 33

Why do hyperkalemic conditions lead to muscle paralysis?

Back 33

high conc of ECF K+ prevents K+ channels from repolarizing the cell. this continuous state of depolarization causes Na+ channels to be inactivated, further decreasing the cells ability to create an action potential.

Front 34

what determines the speed of conduction?

Back 34

the diameter of a neuron and the degree of myelination.

Front 35

which sends a signal faster, a saltatory or contiguous axon?

Back 35

saltatory.

Front 36

why do saltatory axons send signals faster?

Back 36

because they are myelinated. the myelin acts as a capacitor and allows for signals to jump sections of the axon

Front 37

what do contiguous axons lack?

Back 37

myelination

Front 38

how much faster are myelinated fibers than unmyelinated ones of the same size?

Back 38

50 times

Front 39

what are the myelinating cells of the CNS?

Back 39

oligodendricytes

Front 40

what are the myelinating cells of the PNS?

Back 40

schwann cells

Front 41

If action potentials have an invariable intensity, how do you alter the intensity of a signal?

Back 41

by increasing or decreasing the frequency of impulse transmission

Front 42

how do plasma Ca+ levels effect the generation of action potentials?

Back 42

it alters the threshold of activation

Front 43

what happens to the threshold under high plasma Ca+ levels?

Back 43

the threshold is increased

Front 44

what happens to the threshold under low plasma Ca+ levels?

Back 44

the threshold is decreased

Front 45

why do plasma Ca+ levels have an effect on threshold?

Back 45

Ca+ can bind to phospholipids and make the plasma membrane less excitable, effectively decreasing the sensitivity of voltage gated Na+ channels

Front 46

What plasma components effect the amount of free calcium?

Back 46

Albumin
small anions (Phosphate, bicarbonate, and citrate)

Front 47

what effect does hyperparathyroidism have on plasma Ca+ levels?

Back 47

increases Ca+ levels

Front 48

what effect does hypoparathyroidism have on plasma Ca+ levels?

Back 48

decreases Ca+ levels

Front 49

what effect does hyperparathyroidism have on plasma phosphate levels?

Back 49

decreases Phosphate levels

Front 50

what effect does hypoparathyroidism have on plasma phosphate levels?

Back 50

increases Phosphate levels

Front 51

What effect does an acidic plasma condition have on the amount of free Ca+ levels?

Back 51

H+ will compete with Ca+ binding sites on albumin and cause an increase in free plasma Ca+

Front 52

What effect does an alkaline plasma condition have on the amount of free Ca+ levels?

Back 52

The excess OH- will tie up free H+, reducing Ca+ binding site competition. This decreases plasma Ca+ concentrations