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Summer Physio > Excitable Cells > Flashcards

Excitable Cells Flashcards

1
Q

3 electrical events

A

cell to cell communication (intercellular)
sensing environmental changes
triggering intracellular events

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2
Q

extracellular fluid composition

A

ions, proteins, HIGH NaCl

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3
Q

Intracellular fluid composition

A

ions, lots of proteins, HIGH KCl

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4
Q

what allows cells to communicate with each other?

A

major difference between inside and outside of cell (Na outside, K inside)

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5
Q

3 major parts of cell excitation

A

extracellular fluid
intracellular fluid
cell membrane

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6
Q

types of movements that occur across cell membrane

A 
Simple Diffusion
mediated transport
osmosis
endocytosis
exocytosis
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7
Q

simple diffusion

A

random diffusion, down a concentration gradient.

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8
Q

what kind of molecules can simply diffuse?

A

organic molecules or ions.

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9
Q

organic molecules that can simple diffuse

A

non polar organic because solubility in lipid is high. membrane 50% lipid composition

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10
Q

ion simple diffusion uses what

A

ion channels, which are proteins themselves, several subunits generally and ion-specific (K channels).

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11
Q

examples of non polar substances are

A

O2, CO2, fatty acids, steroid hormones

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12
Q

Amount of substance crossing a suface per unit time is termed what

A

flux

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13
Q

diffusion equilibrium

A

flux=0

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14
Q

diffusion between a substance between two compartments is always ______

A

bi-directional

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15
Q

mediated transport

A

ligand binds to a transporter in the membrane, transporter undergoes a conformational change and ligand is released on the other side of the membrane

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16
Q

two types of mediated transport

A

facilitated diffusion

active transport

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17
Q

facilitated diffusion and example

A

NO energy. glucose, large and polar molecules

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18
Q

active transport

A

requires energy, moves up concentration/electrical gradient

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19
Q

active transport also called what

A

pumps

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20
Q

energy can affect what in active transport

A
  1. affinity of the transporter for the ligand on one side of the membrane more than on the other side
  2. rate of transporter conformational change
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21
Q

primary active transport and example

A

uses metabolic energy to transport molecules. uses ATP, most called ATPases. Na/K pump best example

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22
Q

secondary active transport and example

A

different source of energy, NO direct coupling of ATP, uses electrochemical potential difference created by pumping ions out of the cell is used, TWO binding sites. Amino Acids use Na concentration gradient

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23
Q

3 factors determine the rate of flux

A
  1. number of transporters
  2. extent of transporter saturation, which, in turn is affected by
    a. transporter affinity
    b. ligand concentration
  3. rate of transporter conformational change
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24
Q

types of channels

A 
ligand sensitive (chemical)
voltage sensitive (voltage)
mechanosensitive- atria of heart
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25
Q

osmosis

A

bulk flow of water across membrane, lead to cell swelling/shrinkage

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26
Q

how does water cross membranes

A

channels called aquaporins

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27
Q

osmolarity

A

total solute concentration in a solution. 1 osmol= 1 mole of solute

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28
Q

1 mole of NaCl = ___ osmoles

A

2

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29
Q

osmolarity of extracellular fluid =

A

300 mOsm.

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30
Q

isotonic

A

= 300 mOsm. of non-penetrating solutes - no change in cell volume

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31
Q

hypotonic

A

< 300 mOsm. of non-penetrating solutes - cell swells

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32
Q

hypertonic

A

> 300 mOsm. of non-penetrating solutes - cell shrinks

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33
Q

isoosmotic

A

= 300 mOsm. of non-penetrating plus penetrating solutes

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34
Q

hypoosmotic

A

< 300 mOsm of non-penetrating plus penetrating solutes

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35
Q

hyperosmotic

A

> 300 mOsm. of non-penetrating plus penetrating solutes

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36
Q

what kinds of cells can pinocytosis? phagocytosis?

A

all cells can pinocytosis, specialized cells called phagocytes use phagocytosis

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37
Q

intra/extracellular K

A

intra- 124

extra- 2.25

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38
Q

intra/extracellular of Na

A

intra- 10.4

extra- 109

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39
Q

intra/extracellular of Cl

A

intra- 1.5

extra- 77.5

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40
Q

intra/extracellular of Ca

A

intra- 4.9* most is bound or sequestered

extra- 2.1

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41
Q

intra/extracellular of organic anions

A

intra- 74

extra- 13

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42
Q

Ohm’s law

A

V = IR

43
Q

in a cell….voltage is, resistance is, and current is…

A 
V = charge difference between inside and outside of cell
R = membrane
I = ion movement, in to out, out to in.
44
Q

Conductance (G) =

A

reciprocal of resistance G = I/V

45
Q

conductance and resistance are ____ related to each other and are _____ properties

A

inversely, membrane

46
Q

Nernst equation

A

E = (58/z) log10 [X1]/[X2]

z is the valance of the ion

47
Q

nernest equation yields what

A

equilibrium potential (equilibrium voltage) - of a single ionic species, is the voltage across a cell membrane that exactly balances the force in the concentration gradient of a permeable ion

48
Q

log10 of .1 =

A

-1

49
Q

log10 of 1 =

A

0

50
Q

log10 of 10 =

A

1

51
Q

log10 of 100 =

A

2

52
Q

what is due to asymmetric ion flow and can disappear over time?

A

diffusion potentials

53
Q

resting membrane potentials

A

membrane of a resting cell is most permeable to K. K ions diffuse across a typical cell membrane 60 times more readily than do Na ions

54
Q

which ion is higher concentration inside the cell?

A

K

55
Q

which ion is higher concentration outside the cell?

A

Na

56
Q

are rest what way to Na and K ions diffuse

A

K diffuse out of the cell

Na diffuse into the cell

57
Q

resting membrane potential number

A
  • 90 mV
    Equilibrium potential of K is -100 mV, the difference comes from the small amount of Na coming into the cell. this number is steady, so this diffusion potential is not transient.
58
Q

depolarization (or hypopolarization)

A

change in membrane potential towards 0mV

59
Q

repolarization

A

change in membrane potential towards negative voltage direction

60
Q

hyperpolarization

A

change in membrane potential, becoming more negative from the resting value (i.e. > -90)

61
Q

Sodium Potasium Pump

A

ATPase pump. maintains concentration gradient for Na and K. 3 Na out for 2K in. without this pump the potential would slowly go to 0 mV. example of homeostasis

62
Q

does it take a large or small number of ions to cause a change in membrane potential?

A

very small number, relative intra and extracellular concentrations remain the same.

63
Q

large and very rapid changes in membrane potential

A

action potentials.

64
Q

most common places of action potentials

A

neurons and muscle cells

65
Q

action potentials _____ over a distance of the cell membrane

A

propagated

66
Q

examples of stimuli

A

light, temperature, and sources of pain.

67
Q

stimuli process

A

—> change in ion permeability (increased Na) —> membrane depoloarizes

68
Q

where is the first change in membrane potential associated with the stimulus

A

dendrites, then cell body

69
Q

first place the AP developes

A

initial segment, then travels down the axon.

70
Q

step 1 of AP

A

increase in membrane permeability to Na ions

71
Q

step 2 of AP

A

Na ions travel down concentration and electrical gradients through Na channels. carry + charge with them

72
Q

step 3 of AP

A

membrane potential moves closer to 0 mV

73
Q

step 4 of AP

A

if potential threshold is reached additional Na channels open (they are voltage-gated)

74
Q

step 5 of AP

A

even more Na enters the cell, positive feedback cycle, all part of rising phase.

75
Q

step 6 of AP

A

membrane potential very rapidly moves towards O mV then to 40 mV.

76
Q

step 7 of AP

A

K channels open. K ions move from inside to outside. mem. potential reverses direction, falling phase. Na channels close as well (repolarization)

77
Q

step 8 of AP

A

hyperpolarization. (after polarization phase)

78
Q

time line of events

A

depolarization and repolarization in 1 ms

after polarization > 10 ms

79
Q

latent period

A

between AP’s. where neuron can’t depolarize

80
Q

equilibrium potential for Na is what

A

58 mV, the peak of the AP approaches this.

81
Q

peak of AP approaches what, the end of the depolarization phase is close to what

A

peak approaches equilibrium potential for Na (58)

end of repole. approaches equilibrium potential of K

82
Q

sub threshold stimulus, threshold stimulus, spurathreshold stimulus

A

sub- stimuli isn’t strong enough
just sufficient
stimulus is greater than threshold stimulus

83
Q

all action potentials are ____-or-_____

A

all or nothing

84
Q

graded potentials

A

amplitudes are graded with the strength of the stimulus. weak stimuli that are sub threshold and not propagated.

85
Q

absolute refractory period

A

brief period after the AP when a second threshold stimulus or supra threshold cannot elicit a second AP.

86
Q

relative refractory period

A

when a supra threshold can elicit another AP but a threshold stimulus still cannot. even longer time

87
Q

refractory periods impose what

A

limits on the frequency at which cells can fire AP, important in heart.

88
Q

neural adaptation

A

is a change over time in the responsiveness of the sensory system to a constant stimulus. hand on table, sense table at first but then slowly stop sensing it.

89
Q

accommodation

A

transition from closed state to the open state of the channels is dependent on the rate of stimulus change.

90
Q

adaptation is a property of the ____ and it is due to accommodation of ion _____

A

neuron

channels

91
Q

stimulus parameters

A
  1. intensity
  2. duration
  3. rate of change
  4. frequency
92
Q

Rhenobase

A

magnitude of the least intense stimulus that can elicit a response

93
Q

utilization time

A

duration required to elicit a response by a stimulus with a rhenobase magnitude

94
Q

chronaxie

A

duration required to elicit a response for a stimulus that has a magnitude that is twice the rhenobase magnitude.

95
Q

electronic currents (local currents)

A

passive currents, do NOT propagate, can generate AP though. “Electrotonic potentials represent changes to the neuron’s membrane potential that do not lead to the generation of new current by action potentials” small neurons, in longer axons local currents initiate action potentials

96
Q

salutatory conduction

A

AP’s skip along the axon from node of ranvier to another node.

97
Q

A alpha function diameter velocity

A

motor, proprioception
12-20 micrometers
70-120 m/s

98
Q

A beta function diameter and velocity

A

touch, pressure
5-12 micrometers
30-70 m/s

99
Q

A gamma function diameter and velocity

A

muscle spindles
3-6 micrometers
15-30 m/s

100
Q

A delta function diameter and velocity

A

pain, cold, touch
2-5 micrometers
12-30 m/s

101
Q

B fiber function, diameter, and velocity

A

preganglionic autonomic
<3 micrometers
3-15 m/s

102
Q

C dorsal root

A

pain, temp, mechanoreceptors, reflexes
.4-1.2 micrometers
.5-2 m/s

103
Q

C sympathetic

A

postganglionic, sympathetic
.3-1.3 micrometers
.7-2.3 m/s

Summer Physio (4 decks)

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