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Systemic Physiology Unit 1 > Membranes (Unit 1) > Flashcards

Membranes (Unit 1) Flashcards

1
Q

plasma membrane

A

a lipid bilayer that is a barrier to water and water-soluble substances; gases move through easily

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2
Q

Relative extracellular/intracellular concentration of: Na+

A

high extracellular, low intracellular

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3
Q

Relative extracellular/intracellular concentration of: K+

A

low extracellular, high intracellular

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4
Q

Relative extracellular/intracellular concentration of: Ca2+

A

high extracellular, low intracellular

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5
Q

Relative extracellular/intracellular concentration of: Cl-

A

high extracellular, low intracellular

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6
Q

Relative extracellular/intracellular concentration of: PO4-

A

low extracellular, high intracellular

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7
Q

Relative extracellular/intracellular concentration of: Proteins

A

low extracellular, high intracellular

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8
Q

substances high extracellular:

A

Na+, Ca2+, Cl-

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9
Q

substances low extracellular:

A

K+, PO4-, Proteins

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10
Q

how substance can get through membrane:

A

simple diffusion (through membrane or pore), facilitated diffusion, active transport

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11
Q

Diffusion (passive transport) characteristics

A
  • Occurs down a concentration gradient
  • Through lipid bilayer or involves a protein “channel” or “carrier”
  • No additional energy required
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12
Q

Active Transport characteristics

A

• Establishes concentration gradient and continues to operate against a concentration
gradient
• Involves a protein “carrier” • Requires ENERGY (ATP)

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13
Q

Rate of diffusion is governed by:

A

• Amount of substance available
• Velocity of kinetic motion
• Number and sizes of
openings in the membrane through which the molecules or ions can move

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14
Q

ungated channels

A

Transport is determined by size, shape, and charge of channel and ion

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15
Q

Gated channels types

A

voltage-gated and ligand-gated

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16
Q

Voltage-gated

A

gate opens and closes depending on voltage (membrane potential) (e.g., voltage-gated Na+ channels)

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17
Q

Ligand-gated

A

gate opens and closes depending on binding of a chemical (e.g., nicotinic acetylcholine receptor channels)

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18
Q

simple diffusion

A

either through membrane directly (if lipid) or channel

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19
Q

facilitated diffusion

A

still taking advantage of gradient, but needs carrier protein

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20
Q

channel proteins

A

selectively permeable, can be opened and closed depending on a certain stimulus

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21
Q

aquaporins

A

select for water, made very narrow, water passes easily but other things too large

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22
Q

how are ion channels selectively permeable to specific ions?

A

ion get hydrated and the channels pull the hydration shell off of the ion – only works for the selected ion

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23
Q

patch-clamp technique

A

can measure channel activity and movement of ions in their native context; micropipette suctions to a cell and creates a seal (the patch) where electrical current can be recorded

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24
Q

rate of diffusion for simple diffusion

A

linear

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25
Q

rate of diffusion for facilitated diffusion (carrier proteins)

A

looks like log function then plateaus; due to the saturation of carrier proteins the rate eventually hits its Vmax

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26
Q

factors that affect net rate of diffusion

A
  1. chemical concentration gradient
  2. electrical (charged substances)
  3. pressure gradient (applies to fluid filtration)
27
Q

osmotically-active particles

A

exert attraction with water

28
Q

osmotic pressure

A

the pressure required to stop movement of water by osmosis across a selectively permeable membrane

29
Q

process of active transport through entire cell layers

A

The brush border on the luminal surfaces of the cells is permeable to both sodium ions and water. Therefore, sodium and water diffuse readily from the lumen into the interior of the cell. Then, at the basal and lateral membranes of the cells, sodium ions are actively transported into the extracellular fluid of the surrounding connective tissue and blood vessels.

30
Q

secondary active transport

A

depends on carrier protein that penetrates cell membrane; utilizes the energy stored due to gradient from a different substance

31
Q

types of secondary active transport

A
  1. co-transport

2. counter-transport

32
Q

co-transport and example

A

type of secondary transport that has ions moving in the same direction; example is sodium-glucose

33
Q

counter-transport and example

A

type of secondary transport that has ions moving in opposite direction across membrane; example is Na+-Ca2+ exchanger

34
Q

membrane potential and abbreviation

A

difference in charge across membrane; abbreviated Vm (voltage membrane)

35
Q

where does membrane potential come from?

A
  1. activity of sodium-potassium pump (electrogenic)

2. diffusion of ions across membrane

36
Q

leak channel

A

not gated, allows free passage of ions

37
Q

Ek

A

potassium equilibrium potential (diffusion potential)

38
Q

active transport through entire cell sheet: locations

A
  1. intestinal epithelium (important for food getting to blood)
  2. epithelium of renal tubules
  3. epithelium of all exocrine glands
  4. epithelium of the gallbladder
  5. membrane of the choroid plexus of the brain
39
Q

ENa

A

sodium equilibrium potential (diffusion potential)

40
Q

diffusion potential

A

Electrical charge that develops across a selectively permeable membrane when ions diffuse down their concentration gradient

41
Q

membrane potential of potassium

A

-94 mV

42
Q

membrane potential of sodium

A

+61 mV

43
Q

measuring membrane potential

A

taking glass electrode with small tip to puncture nerve cells; detects movement of ions of cell fluid and read on voltage meter

44
Q

where is the polarization in a cell?

A

we see the polarization right at the cell membrane

45
Q

origin of resting membrane potential

A
  1. Na+-K+ pump (quarter to a third)

2. diffusion of K+ through leak channels

46
Q

action potential in neurons

A

rapid changes in membrane potential that spread rapidly along nerve cell membrane; change in membrane potential that elicits an action

47
Q

Three phases of action potential

A
  1. cell at rest (-90mV, cell unstimulated)
  2. depolarization
  3. repolarization
48
Q

depolarization stage

A

membrane suddenly permeable to Na+ ions causing rapid diffusion of Na+ ions into the cell – this neutralizes the cell (or can get slightly positive)

49
Q

repolarization stage

A

sodium channels close and potassium channels open which reestablishes the normal negative resting membrane potential

50
Q

resting membrane potential

A

the difference in membrane charge at rest

51
Q

Hodgkin and Huxley

A

figured out that you could impale axon to measure cell potential and also cause artificial action potential; 1st to record electrical activity in neuron (action potential)

52
Q

1st people to record electrical activity in neuron and record action potential

A

Hodgkin and Huxley

53
Q

action potentials that look different

A
  1. Certain excitable cells’ APs do not repolarize immediately—there is a plateau during the depolarization phase
  2. Certain excitable cells’ APs show rhythmicity—spontaneous self-induction at a specific rate
54
Q

axon

A

central core of the nerve fiber, membranes of axon is the membrane that conducts action potential

55
Q

axoplasm

A

filling of axon center, viscid intracellular fluid

56
Q

myelin sheath

A

surrounds axon, often much thicker than axon

57
Q

node of Ranvier

A

located 1-3 mm along length of myelin sheath, 2-3 micrometer long area of uninsulation where ions can easily flow through the axon membrane between EC and IC fluid inside the axon; at juncture between two successive Schwann cells

58
Q

Schwann cell function

A

insulate nerve fibers

59
Q

saltatory conduction advantages

A

improved velocity (jumping for point to point) and conserved energy due to insulation

60
Q

acute local potential

A

local depolarization

61
Q

acute subthreshold potential

A

an acute local potential that fails to elicit an action potential

62
Q

absolute refractory period

A

the period during which a second action potential cannot be elicited, even with a strong stimulus

63
Q

absolute refractory period length of time for large myelinated fiber

A

1/2500 second

Systemic Physiology Unit 1 (4 decks)

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