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physiology 2 > excitable cells > Flashcards

excitable cells Flashcards

1
Q

voltage-gated channel

A

respond to changes in potential by changing conformation
- allows ion influx/efflux

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1
Q

ligand-gated channel

A

bind neurotransmitters and ions
- opens in response to ligand binding

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2
Q

ion distribution

A
  • large amounts of Na+ outside the cell
    -large amounts of K+ inside the cell
  • intracellular proteins (A-) are negatively charged and unable to leave the cell
  • ICF is more negatively charged than the ECF
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3
Q

ion permeability

A

cell membrane is more permeable to potassium than sodium
(K+ is King of the Kastle)

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4
Q

concentration gradient

A

Na+ wants to enter the cell
K+ wants to leave the cell

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5
Q

electrical gradient

A

Na+ wants to enter the cell
K+ wants to stay in the cell

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6
Q

membrane potential

A

separation of positive and negative charges across the plasma membrane

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7
Q

resting membrane potential

A

the membrane potential of ells in non-excitable tissues and also excitable tissues at rest

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8
Q

what is the average resting membrane potential

A

-70 mV

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9
Q

equilibrium potential

A

electrical gradient balances with the concentration gradient, no net movement

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10
Q

nernst equation

A

E= 61 log [outside]/[inside]

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11
Q

potassium equilibrium potential

A

-90mV
(if the membrane potential were to reach -90mV, the electrical and concentration gradients would be balanced and there would be no net movement of K+)

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12
Q

sodium equilibrium potential

A

61mV
(if the membrane potential were to reach 61mV, the electrical and concentration gradients would be balanced and there would be no net movement of Na+)

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13
Q

which ion is resting membrane potential determined by?

A

POTASSIUM

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14
Q

hypokalemia

A

Low ECF [K+]
- concentration gradient: increases
- electrical gradient: increases in magnitude
- equilibrium potential for K+: more negative
- RMP: more negative (harder to reach threshold= less excitable)

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15
Q

hyperkalemia

A

High ECF [K+]
- concentration gradient: decreases
- electrical gradient: decreases in magnitude
- equilibrium potential for K+: less negative
- RMP: less negative (easier to reach threshold= more excitable)

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16
Q

excitatory graded potentials

A

brings the membrane potential closer to the threshold (hypopolarizes)

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17
Q

inhibitory graded potentials

A

brings the membrane potential further from threshold (hyperpolarizes)

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18
Q

action potentials

A

an excitable cell membrane that is depolarized to threshold potential (-50mV)
get less negative ;)

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19
Q

graded potentials

A

hyperpolarize
get less negative ;)
-can turn into an action potential if it hyperpolarizes an excitable cell membrane to threshold

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20
Q

threshold

A

caused by graded potentials - triggers opening of voltage-gated channels

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21
Q

depolarization

A

rapid influx of Na+- membrane become less negative

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22
Q

repolarization

A

rapid efflux of K+ - membrane becomes more negative

23
Q

hyperpolarization

A

membrane potential drops below RMP (caused by slow closure of voltage gated K+ channels)

24
Q

how do action potentials propagate

A

they go in ONE direction and they do NOT diminish

25
Q

absolute refractory periods

A

the period in which a cell cannot undergo another action potential
- starts at threshold and ends whenever sodium gates reset

26
Q

relative refractory periods

A

a cell can undergo an action potential but it is harder than usual because the membrane potential is below RMP
- refractory periods ensure one-way propagation of action potentials

27
Q

contiguous conductions

A

conduction in unmyelinated fibers that begins at the axon hillock
- the action potential spreads along every portion of the membrane

28
Q

myelin

A

thick layers of lipids that cover axons at regular intervals
purpose: insulator that prevents leakage current

29
Q

myelin-forming cells are

A

schwann cells (PNS) and oligodendrocytes (CNS)

30
Q

nodes of ranvier

A

a bare patch of membranes that are between myelinated regions
- current can flow or jump across nodes

31
Q

saltatory conduction

A

(saltatory = to jump)
- in myelinated nerve fibers
- an action potential at one node produces an action potential at the next node (the impulse “jumps” from node to node skipping over the myelinated section of the axon)
- 50 x faster than contiguous

32
Q

conduction velocity of small unmyelinated fibers

A

SLOW
- seen in digestive tract
- pain fibers- Slow C type- lingering pain

33
Q

conduction velocity of large myelinated cells

A

FAST
- skeletal fibers
- pain fibers- fast A type- part of reflex, sharp pain

34
Q

regeneration fibers of the PNS

A

schwann cells guide the peripheral axon to re-establish connection

35
Q

which type of cells can regenerate and repair neurons

A

schwann cells in the PNS

36
Q

regeneration fibers of the CNS

A

oligodendrocytes retract their arms, losing the neuronal pathway

37
Q

examples of demyelinating diseases

A

guillain-barre syndrome and MS

38
Q

what is lost in MS and guillain- barre syndrome

A

loss of saltatory conduction and loss of axonal action potential conduction due to their being no myelin sheath

39
Q

synapse

A

the junction between neurons

40
Q

electrical synapses

A

neurons connected directly by gap junctions

41
Q

chemical synapses

A

chemical messenger transmitted across the junction separating neurons
(most common)

42
Q

when does the neurotransmitter combine with a glutamate receptor?

A

excitatory post synaptic potentials

43
Q

what happens during excitatory post synaptic potentials

A

ligand gated Sodium channel opens
- sodium goes into the cell and the cell becomes more positive (hypOpolarization)

44
Q

when does the neurotransmitter combine with a GABA receptor?

A

inhibitory post synaptic potentials

45
Q

what happens during inhibitory post synaptic potentials

A

ligand gated potassium channel opens
- potassium goes out if the cell and the cell becomes more negative
ligand gated chlorine channel opens
- chlorine goes into the cell and the cell becomes more negative
(hypERpolarization)

46
Q

temporal summation

A

EPSP or IPSP from a single and repeatedly firing presynaptic input that occur close together in time so they add together

*one kid repeating mom over and over

47
Q

spatial summation

A

EPSP or IPSP simultaneously firing from different presynaptic inputs

*multiple kids saying mom at the same time

48
Q

what happens if an excitatory input dominates during summation

A

the cell is brought closer to threshold

49
Q

what happens if an inhibitory input dominates during summation

A

the cell is taken further from threshold

50
Q

what happens if inhibitory and excitatory input is balanced during summation

A

the membrane potential remains close to resting

51
Q

summation of all inputs

A

grand post synaptic potential

52
Q

neuropeptides

A

large molecules made up of 2 to 40 amino acids

53
Q

neuromodulator

A

act slowly to produce long-term changes at the synapse

54
Q

where are neuropeptides synthesized

A

golgi

55
Q

where are classical neurotransmitters synthesized

A

cytosol

physiology 2 (2 decks)

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