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SU17: Physiology > Excitable Cells > Flashcards

Excitable Cells Flashcards

1
Q

________, ________ and most ________ are often referred to as “excitable cells.”

A

Neurons, sensory cells, and most muscle cells…

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2
Q

What is the definition of an excitable cell?

A

It’s physiologic functions relies critically on electrical events in their plasma membrane.

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3
Q

Electrical events in cells can cause three different actions. What are they?

A
  1. Communication
  2. Sensing environmental changes
  3. Triggering intracellular events
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4
Q

What are the three environments involved in cell excitation?

A
  1. ECF
  2. Membrane
  3. Intracellular fluid
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5
Q

____ has a high concentration of NaCl.

A

ECF

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6
Q

____ has a high concentration of KCl.

A

Intracellular fluid

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7
Q

Changes in permeability that are ______ and ________, are essential to excitation in cells.

A

ion-specific; exquisitely timed

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8
Q

The amount of a substance crossing a surface per unit of time is ____.

A

flux

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9
Q

The system is in ______ ______ when the net flux is 0.

A

diffusion equilibrium

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10
Q

What are the two forms of mediated transport?

A
  1. Facilitated diffusion (no energy)

2. Active transport (requires energy)

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11
Q

What is an example of facilitated diffusion?

A

Glucose transporters

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12
Q

T/F: Active transport can move molecules UP a concentration gradient.

A

TRUE

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13
Q

What are two examples of active transport?

A
  1. Na+ out of cells

2. K+ into cells

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14
Q

What is secondary active transport?

A

Energy from ion gradient is used to transport something else in the same direction.

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15
Q

What three factors determine flux of transport?

A
  1. Number of transporters in membrane
  2. Transporter saturation
  3. Rate of transporter conformational change
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16
Q

What are three types of channels?

A
  1. Ligand-sensitive
  2. Voltage-sensitive
  3. Mechanosensitive
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17
Q

T/F: If you place a cell in a hypotonic solution the cell will shrink.

A

FALSE

Swell

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18
Q

Which type of endocytosis is performed by all cells?

A

Pinocytosis

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19
Q

T/F: Cl- ions are much more abundant outside of the cell.

A

TRUE

20
Q

The difference in electrical charge between the inside and outside of a cell is _____.

A

Voltage

21
Q

Ion movement creates a ______.

A

current

22
Q

What is Ohm’s law?

A

V=IR

V = voltage
I = current
R = resistance
23
Q

T/F: Conductance = current.

A

FALSE

24
Q

T/F: Conductance is the reciprocal of resistance.

A

TRUE

25
Q

What is the purpose of the Nernst equation?

A

Balance a concentration gradient with a voltage gradient

26
Q

T/F: Diffusion potentials can be transient (disappear over time).

A

True

27
Q

T/F: A diffusion potential can be maintained at a steady level over time.

A

True

28
Q

__+ ions diffuse much more readily than __+ ions.

A

K; Na

29
Q

Explain the resting membrane potential.

A

K+ ions move out of cell until electrical gradient balances concentration gradient (Na+ ions also move into the cell at a lower rate than K+ moving out)

30
Q

T/F: The resting membrane potential is a transient potential.

A

FALSE

It is a steady potential

31
Q

What is the function of the Na+/K+-ATPase pump?

A

Move K+ ions back into the cell and Na+ ions out of the cell

32
Q

An _____ _____ is a large transient change in membrane potential.

A

Action potential

33
Q

How does an action potential begin?

A

Stimulus depolarizes dendrites -> depolarize cell body -> AP develops and moves along axon

34
Q

What are the steps involved in an action potential up to the rising phase?

A
  1. Increase in Na+ permeability
  2. Na+ enters through voltage-regulated Na channels
  3. Membrane potential moves to 0 mV
  4. More channels continue to open as charge goes up (rising phase)
35
Q

What are the steps of an action potential after the rising phase?

A
  1. Membrane potential approaches and overshoots 0mV (+40mV)
  2. K+ channels open and ions leave the cell
  3. Potential goes back down and Na channels close (falling phase)
  4. Afterpolarization
36
Q

A _______ stimulus will not push the membrane to a threshold.

A

Subthreshold

37
Q

What is a graded potential?

A

A local response to a subthreshold stimulus

38
Q

What types of stimuli result in action potentials?

A

Threshold or suprathreshold

39
Q

T/F: During the absolute refractory period, a suprathreshold stimulus can cause a second action potential.

A

FALSE

40
Q

T/F: During the relative refractory period a suprathreshold stimulus can elicit a second action potential.

A

TRUE

41
Q

T/F: A weaker stimulus needs to be applied for a longer duration to cause an AP?

A

TRUE

42
Q

The weakest stimulus that can elicit a response is the ______ and it must be given for a duration referred to as the _____ ____.

A

Rheobase; utilization time

43
Q

The ______ is the duration a stimulus with twice the strength of the rheobase must be given.

A

chronaxie

44
Q

What charge of ions will move toward the cathode?

A

Positive charges

45
Q

T/F: The current of positive charges moves from the anode to the cathode.

A

TRUE

46
Q

Axons with ________ diameters have higher velocities of conduction.

A

larger

47
Q

T/F: A(alpha) neurons are the largest and C sympathetic neurons are the smallest.

A

True

SU17: Physiology (9 decks)

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