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physiology > Ex Cells > Flashcards

Ex Cells Flashcards

1
Q

types of Excitable cells

A

Neurons
Sensory Cells
Most muscle cells

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2
Q

why are cells called excitable

A

Physiologic function relay critically on electrical events in their plasma membrane

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3
Q

what is an electrical event

A

A mechanism of cell-to-cell (intercellular) communication

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4
Q

speed of electrical events

A

Very rapid

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5
Q

what do electrical events allow

A

Precise timing of signals between cells

complex patterns of communication between cells

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6
Q

what do electrical events serve as a mechanism for

A

sensing environmental changes

triggering intracelular events

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7
Q

how can electrical events trigger intracellular events

A

rapid intracellular changes

accumulations over time (memory and learning)

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8
Q

the 3 physical components used for cell excitations

A

ECF
ICF
membrane

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9
Q

composition of the ECF

A

primarily ions, proteins, and other molecules

high NaCl

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10
Q

what is the ECF ionic concentration like

A

Similar to plasma in ionic composiition

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11
Q

Composiition of the ICF

A

ions

more proteins and other molecules

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12
Q

PRedoninant salt of the ICF

A

KCl

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13
Q

what allow cells to communicate

A

Inside and outside of cells are very different

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14
Q

what is the membrane composed of

A

phospholipid bilayer and proteins

equal amounts of protein and lipid with a small amount of carbs

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15
Q

what is premeability a characteristic of

A

The cell membrane

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16
Q

what is the permeability of a membrane to an ion

A

an index of the ability of the ion to cross the membrane

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17
Q

how does permeability affect cell excitation

A

Changes in permeability that are ion-specific and exquisitely timed

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18
Q

SImple diffusion

A

random diffusion down and electrical or concentration gradient

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19
Q

how well do non-polar molecules difuse

A

rapid through the membrane b/c it ids 50% lipids

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20
Q

how do ionspass the membrane

A

through channels which are proteins of several units with are ion-specific (generally)

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21
Q

What is flux

A

the amount of a substance cross a surface per unit of time

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22
Q

what way does diffusion occur between 2 compartments

A

Bi-direction

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23
Q

Net flux

A

difference between the 2 unidirection fluxes

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24
Q

what is something at diffusion equilibrium

A

when net flux equals 0

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25
Q

what is mediated transport

A

when something passes through the membrane but not directly

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26
Q

two types of mediated transport

A

Facilitaetd diffusion

active transport

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27
Q

energy need of facilitated diffusion

A

no energy

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28
Q

how does facilitated diffusion occur

A

membrane proteins serves as a carrier to translocate a molecule across the membrane

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29
Q

what types of molcules tend to use facilitated diffusion

A

large polar molecules

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30
Q

benifiti of facilitated diffusion

A

makes it hard for certain molecules to leave the cell

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31
Q

how does active transport work

A

molecule/ion bound to transporter in membrane using enegy to move up its concentration/electrical gradient

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32
Q

other name for active transporter

A

pumps

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33
Q

energy can affect what in active tranport

A

affinity of transporter for the ligant on one side of the membrane more than on the other side
rate of transporter conformational change

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34
Q

what happens in primary active-transport model

A

energy from hydrolgysis of ATP
transporter becomes phosphorylated changes affinity for solute (ligand)
increases transport rate

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35
Q

what happens in secondary active transport

A

uses energy in concetration gradient across membrane

transporter has 2 binding sites

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36
Q

steps in mediated transport

A

Ligand binds to transporter
transporter undergoes conformational change
ligand released on other side of membrane

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37
Q

factors that determine rate of flux

A

number of transporters in membrane
extrent of transporter saturation (transporter affinity,ligant concentration)
rate of transporter conformational change

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38
Q

types of channels

A

ligand-sensitive
voltage-sensitive
mechanosensitive

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39
Q

what is osmosis

A

Bulk flow of water acrosss a membrane

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40
Q

how does water diffuse

A

down its concentration gradient via aquaporins

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41
Q

osmolarity

A

the total solute concentration in a solution

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42
Q

osmolarity of ECF

A

300 mOsm

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43
Q

Isotonic

A

300 mOsm on Non-penetrating solutes in the ECF resulting in no change in cell volume

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44
Q

Hypotonic

A

less than 300mOsm of non-penetrating solutes in the ECF resulting in cell swelling

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45
Q

Hypertonic

A

greater than 300 mOsm of non-penetrating solutes in the ECF resulting in cell shrinking

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46
Q

difference in toniciity and osmoloarity

A

Toniciity is only non-penetrating

Osmolarity is non-penetating and penetrating

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47
Q

ligand sensitive channels

A

channel that binds to ligand to open

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48
Q

voltage-sensitive channel

A

changes by predominating charge diference

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49
Q

Mechanosensitve channels

A

bases on the mechanics of the envirnoment

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50
Q

Endocytosis

A

Engulfment of fluid and particles from the ECF

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51
Q

pinocytosis

A

Engulfment of small particles with or without a small volume of ECF

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52
Q

what does Pinocytosis

A

all cell types

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53
Q

phagocytosis

A

engulfment of large particels or cellular debris

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54
Q

what does phagocytosis

A

Special cells called phagocytes (usually at sites of tissue damage)

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55
Q

what is exocytosis

A

export of material from a cell (reverse of endocytosis)

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56
Q

what does Exocytosis lead to

A

replaces membrane patches internalixed through endocytosis

releases stuff from inside the cell

57
Q

what is a lotinside the cell

A

K
Ca
Organic
w

58
Q

what is a lot outside the cell

A

Na

Cl

59
Q

where is most of the Ca inside the cell

A

bound or sequestered (free Ca is very low)

60
Q

Voltage of a cell

A

Electrical charge difference between the inside and outside of a cell

61
Q

why must the plasma membrane have resistance

A

because the voltage of a resting cell is steady

62
Q

what happens when the resistance of the membrane changes

A

Ions cross the membrane leading to a curent

63
Q

Ohm’s Law

A

V=IR

64
Q

what is Conductance

A

The reciprocal of resitnace

65
Q

Nernst equation

A

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

z=valence

66
Q

what does the Nernst equation give

A

the hypothetical equilibtrium potention of a single ionic species

67
Q

what is the equalibrium potention of a single ionic species

A

the votlage across a cell membrane that exactly balances the forces in the concetration gradient of a permeable ion

68
Q

do diffusion potentials always stay the same

A

Can be transient, but also can be maintained at a steady level over time

69
Q

what causes the transient property of diffusion potentials

A

due to asymmetric ion flow of one or many ions between 2 compartments

70
Q

K and Na in and outside the cell

A

K higher inside

Na higher outside

71
Q

what ion is the membrane permiable

A

most permeable to K

72
Q

ratio of the permiability of K and Na

A

pK/PNa=60

73
Q

membrane potention

A

-70 mV

74
Q

what hold K inside

A

the charge (more negative inside) the cell

75
Q

what does K do to create a diffusion potential

A

K ions move down their concentration gradient leading to the development of a diffusion potential

76
Q

when is equilibrium found within the cell

A

when the force in the concentration gradient of K ions to move out of the cell is balanced by opposing force in electrical gradient

77
Q

what does the equilibrium do to the cell

A

keeps K ions inside the cell

78
Q

what is the equilibrium potental of K

A

about -100mV (close to the resting membrane potential of a cell)

79
Q

why is the resting membrane potential different than that of the equalibrium potential of K

A

other ions must contribute to the resting potental

80
Q

how does Na diffuse

A

Down its concetration gradient and electrical gradient

81
Q

diffuse of Na leads to what

of equilibrium potential

A

a resting membrane potential slightly lower than Equilibium of K

82
Q

is the resting membrane potential steady of transient

A

Steady

83
Q

does instaneous movement of ions cause the resting membrane potential

A

Not due to the instantaneous movement (due to the fact that ions have moved across the membrane)

84
Q

what keeps the resting membrane potential from decreasing (keeps homeostasis)

A

the Na/K ATPase pump moving K ions in and Na ions out

85
Q

depolarization

A

towrds 0 mV

86
Q

repolarization

A

toward resting potential

87
Q

Hyperpolarization

A

increase in membrane potential (more negative)

88
Q

how does Na/K ATPase pump do work

A

hydrolyzes ATP to do work(active transport)

89
Q

what would happen if Na/K ATPase were to go away

A

resting membrane potential would go back to 0mV

90
Q

Homeostasis

A

mechanism that have, as their goal, the maintenance of the body’s internal environment.
maintaining parameters of the internal environment at constant values

91
Q

eq potential of K

A

-101 mV

92
Q

eq potential of Na

A

+59 mV

93
Q

eq potential of Cl

A

-99 mV

94
Q

Action potential

A

A large transient change in membrane potential

95
Q

4 parts of the neuron

A

Dendrites
Cell body
Axon
Axon terminal

96
Q

stimulus leads to what in neuron

A

Depolarizaes membrane (dendrites)
Depolarizes cell body
AP first develops at initial segment
AP propagates along axon

97
Q

where is the initial segment

A

where the axon meets the cell body

98
Q

where the AP begins

A

Initial segnment

99
Q

is the AP transient or steady

A

transient

100
Q

steps of an AP

A

1 increased in the membrane permeability to Na ions
2 Na ions enter via channels driven by electrical and concentration gradients
3 membrane potential moves closer to 0 mV (depolarizes)
4 if depolarization reaches threshold, more Na votlage gated channels open
5 Na enters cells in a positive feed back cycle leading to the rising phase of an AP
6 eventually reaches +40mV
7 K chanells open and K leaves the cell
8 membrane potential abruptly reverses direction and returns in the falling phase of an AP
9 overshoot - hyperpolarization

101
Q

what kind of channels allow Na ions to enter during an AP

A

Voltage regulated Na-channels

102
Q

what is the movemeent of K driven by in an AP

A

concentration gradient and initiallly by electical gradient

103
Q

why does Na channels close (Na Inactivation

A

Close during falling phase baecause voltage regulated channels now experience a negative change

104
Q

length of depolarization and repolarization

A

1 ms

105
Q

after polarization phase

A

10 ms

106
Q

Do a lot of ions need to move to cause a great change in the membrane potential

A

no, only a few number of ions

107
Q

Latnet period

A

Very brief period between applying stmulus and beginning of depolarization during rising phase of an AP

108
Q

what occures during the latent phase

A

Channels are opening

109
Q

what does the peak of an AP approach

A

the ENa( about 58 mV)

110
Q

why does the Peak of an AP approach ENa

A

because the permiability of Na is very high during the rising phase of an AP
evnetually almost reaches where its ionic gradient is in eq with membrane potential

111
Q

what does the end of the repolarization phase come close to

A

EK

112
Q

why does the repolarization phase come close to Ek

A

becuase the permiability of K is high and crosses the membrane freely until its ionic gradient is in equilibium with membrane potential

113
Q

when a stimulus is insufficient to take membrane to threshold

A

Subthreshold stimulus

114
Q

when a stimultus is just sufficient to take membrane to threshold

A

Threshold stimulus

115
Q

when a stimulus is greater than a threshold stimulus

A

Suprathreshold stimulus

116
Q

where are subthreshold stimulus’s found

A

Confined to the immediate region of the membrane

117
Q

small depolarization or hyperpolarizations that do not move along the membrane

A

Local responses

118
Q

what are graded/local responses proportional to

A

Stimulus strenght

119
Q

absolute refractor period

A

Brief period when a second threshold stimulus of suprathreshold stimulus cannot elicit a second AP

120
Q

Relative refractory period

A

for a longer period after a AP suprathreshold stimulus can get an AP but threshold cannot

121
Q

what does Tetrodotoxin do

A

Binds to sodium channels and blocks sodium influx

122
Q

adaption

A

where 2 waves of depolarization can be applied to a cell at different rates of ramping and lead to different responses (square wave gives and AP and ramp does not)

123
Q

what causes adpation

A

property of channels called accommodation

124
Q

stimulus strength duration curve relates

A

less intense stimuli need more time to ilicit a response

125
Q

Rheobase

A

Magnitude of least intense stimulus that can elicit a response

126
Q

Utilization time

A

Duration required to elicit a response by a stimulus with a rheobase magnitude

127
Q

Chronaxie

A

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

128
Q

use of chronaxie

A

compare excitability of different cells

129
Q

what shape of stimuli do you need to get an AP

A

square wave

130
Q

what kind of current are electrotonic currents

A

passive currents (do not propagate)

131
Q

what happens if Electrotonic current are sufficient in magnitude

A

lead to an AP

132
Q

flow in stimulating electrodes

A

current flows from anode through the neuron to the cathode

133
Q

what does the cathode do

A

Causes cations to move toward it in both the ECF and inside the cells
the cations inside cell membrane are trapped in the membrane and depolarize the membane

134
Q

what does the anode do

A

Anode attracts anions

135
Q

layers of Schwann cell membrane

A

Myelin

136
Q

roll of myelin

A

electrical insulation do allow AP to travel faster and farther due to the AP skipping along the axon

137
Q

are large diameter axons faster or slower conducting

A

larger have higher velocities

138
Q

Recording the AP of a periferal nerve far and close

A

far: gives multiple AP due to different speeds
close: one large AP due to all the AP stacking up on each other

139
Q

where do AP occur in saltatory conduction

A

in the nodes of ranvier

physiology (32 decks)

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