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SF1.07 Electrophysiology (ZACHOW) > Electrophysiology > Flashcards

Electrophysiology Flashcards

1
Q

What causes currents and the flow of charge in cells?

A
  • ions
  • cation = (+) charge
  • anion = (-) charge
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2
Q

Test utilized to measure ion levels:

A
  • complete metabolic panel (CMP)
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3
Q

Cell and tissue function is controlled by:

A
  • ionic flux
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4
Q

Nomenclature of current in a cell:

A
  • I(ion abbreviation)
    • e.g. INa+
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5
Q

Ionic gradients confer distribution of charge across plasma membranes. This distribution of charge allows for:

A
  • electrogenecity
    • the ability to generate electrical current
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6
Q

Electrogenic tissues can create:

A
  • action potentials via the use of anions and cations in the tissue
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7
Q

Major electrogenic tissues in the body:

A
  • heart
  • skeletal muscle
  • neurons
  • GI smooth muscle
  • vascular smooth muscle
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8
Q

Distribution of charge across the membrane of a motor neuron in the resting state:

A
  • Inside cell (cytoplasm)
    • little sodium
    • little calcium
    • a lot potassium
  • Outside cell (interstitium):
    • a lot sodium
    • a lot calcium
    • little potassium

SODIUM AND CALCIUM WANT TO MOVE INTO CELL.

POTASSIUM WANTS TO MOVE OUT OF CELL.

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9
Q

Electromotive force is:

A
  • the desire/potential for something to move
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10
Q

What is the electromotive force present across the membranes of motor neurons?

A
  • Interstitium is more positive than the cytoplasm.
  • Interstitium contains more sodium and calcium.
  • Sodium and calcium want to move down their gradient into the cell.
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11
Q

At rest, there is passive flux of K+ and Na+ through the plasma membrane of motor neurons. How is the electrochemical gradient across motor neuron membranes maintained at rest?

A
  • Na+/K+ ATP-dependent pump.
    • Moves 3 Na+ out of cell and 2 K+ into cell.
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12
Q

State of a motor neuron at rest:

A
  • Hyperpolarized (-80mV).
  • Na+/K+ ATP-dependent pump active.
  • Voltage-gated K+ channel inactive.
  • Voltage-gated Na+ channel inactive.
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13
Q

Potential stimuli that can cause an action potential:

A
  • electrical
  • chemical
  • mechanical
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14
Q

Process of motor neuron depolarization:

A
  1. Stimuli causes activation of some voltage-gated Na+ channels
  2. Slight influx of Na+.
  3. Threshold value reached, majority of voltage-gated Na+ channels open.
  4. Na+ rushes in and depolarizes cell.
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15
Q

Motor neuron depolarization is _______ dependent.

A
  • Sodium dependent.
  • Positive charge rushes into cell.
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16
Q

Motor neuron repolarization is _______ dependent.

A
  • Potassium dependent.
  • Positive charge rushes out of cell.
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17
Q

The two fail-safe mechanisms of voltage-gated ion channels:

A
  • voltage-dependent (only open at certain voltages)
  • time dependent (close after some time open)
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18
Q

The three phases of a motor neuron action potential:

A
  1. Depolarization (Na+ rushes in)
  2. Repolarization (K+ rushes out)
  3. Refraction (inactive; recovery stage)
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19
Q

Timing and types of refractory phases:

A
  • Follows repolarization.
  • absolute and relative
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20
Q

Absolute refraction:

A
  • Na+ channels inactive.
  • No stimulus will elicit a second action potential regardless of stimulus strength.
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21
Q

Relative refraction:

A
  • some Na+ channels resting.
  • second AP can be elicited if a stronger than normal stimulus is applied.
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22
Q

Steps in motor neuron action potential:

A
  1. Refraction period ends.
  2. Stimulus activates some voltage-gated Na+ channels.
  3. Threshold reached.
  4. Voltage-gated Na+ channels open; sodium rushes in.
  5. Depolarization (more positive).
  6. Voltage-gated Na+ channels close.
  7. Voltage-gated K+ channels open; potassium rushes out.
  8. Repolarization (more negative).
  9. Hyperpolarization/Refraction.
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23
Q

The excitability of neuromuscular tissue is dependent on:

A
  • difference between the resting potential and the threshold potential.
24
Q

The resting potential of electrogenic cells is set by:

A
  • ratio of intercellular K+ to extracellular K+
  • an important component of this is the passive flux of K+ through the plasma membrane at rest.
25
Q

Effect of increased extracellular K+ levels on action potentials?

A
  • Passive flux of K+ impeded.
  • More K+ (positive charge) retained intercellularly.
  • Cells begin to depolarize due to increased intercellular positive charge.
  • Action potentials fired at wrong times, cells become refractory, irregular electrical transmission occurs.
26
Q

Altering a neurons resting membrane potential by varying the levels of potassium (too high or too low) in the body will result in:

A
  • impeding the neuron’s ability to fire an AP
27
Q

The two types of action potentials in the heart:

A
  1. Pacemaker potentials (SA node)
  2. Plateau potentials (myocardium)
28
Q

Where do pacemaker potentials occur in the heart?

A
  • SA node
29
Q

Where do plateau potentials occur in the heart?

A
  • myocardium (ventricles and atria)
30
Q

The first step of a pacemaker potential is:

A
  • slow depolarization
    • dependent on:
      • T-type calcium channels (slow influx)
      • HCN+ sodium channels (slow influx)
      • Outflux of potassium
31
Q

The slow depolarization of a pacemaker potential is dependent on:

A
  • T-type calcium channels (slow influx)
  • HCN+ sodium channels (slow influx)
  • Outflux of potassium

Above are antagonistic, which leads to a slow depolarization.

32
Q
A

Threshold.

33
Q

Depolarization of pacemaker cells in the SA node (pacemaker potentials) is _____ dependent.

A

Calcium-dependent.

34
Q

Repolarization of pacemaker cells in the SA node (pacemaker potentials) is _____ dependent.

A

Potassium-dependent.

35
Q

Steps in pacemaker potential in SA node:

A
  1. Slow depolarization.
    • T-type Ca2+; HCN+ Na+; outflux K+
  2. Rapid depolarization at -50mV.
    • T-type Ca2+
  3. Repolarization.
    • voltage-gated K+; K+ outflux
36
Q

The trigger of pacemaker potentials in the SA node is:

A
  • spontaneous.
  • no stimulus required.
37
Q

The four phases of plateau potentials:

A
  • Phase 0: depolarization
  • Phase 1: transient repolarization
  • Phase 2: transient repolarization
  • Phase 3: transient repolarization
  • Phase 4: refraction
38
Q

What channels are responsible for the repolarization of myocardium cells following a plateau potential?

A
  • Calcium channels.
  • Three isoforms of potassium channels.
    • Each isoform opens at a different voltage.
39
Q

Depolarization of myocardium cells in the heart (plateau potentials) is _____ dependent.

A

sodium

40
Q

Steps in plateau potential in myocardium cells:

A
  1. Phase 0:
    • voltage-gated sodium channels open
    • depolarization
  2. Phase 1:
    • isoform (1) potassium channel opens
    • transient repolarization
  3. Phase 2:
    • isoform (2) potassium channel opens
    • voltage-gated calcium channels open
    • transient repolarization
  4. Phase 3:
    • isoform (3) potassium channel opens
    • transient repolarization
  5. Phase 4:
    • refraction
41
Q

In general, what results in depolarization of an electrogenic cell?

A

inward positive charge

42
Q

In general, what results in repolarization/hyperpolarization of an electrogenic cell?

A

outward positive charge

OR

inward negative charge

43
Q

Arrhythmias are due to:

A
  • disruptions in voltage-gated channels functions in the heart.
  • affects depolarization and repolarization.
  • can be treated with drugs that target specific ion channels in the heart in specific regions.
44
Q

Pathway of pain transmission:

A
  1. Pain-evoking stimulus
  2. Nociceptors (pain receptors)
  3. AP in afferent pain nerves
  4. Relay of AP to dorsal horn
  5. Relay of AP to thalamus
45
Q

Mechanism of lidocaine:

A
  • lidocaine blocks voltage-gated sodium channels from the interior
  • threshold cannot be achieved
  • AP does not occur in response to pain
46
Q

alpha toxins are:

A

ACh receptor antagonists

47
Q

Beta bungarotoxins are:

A

Cholinesterase inhibitors

48
Q

Botulinus toxins and tetanus block:

A

ACh release

49
Q

Tetrodotoxin blocks:

A

neuronal and cardiac voltage-gated Na+ channels

50
Q

Dendrotoxin blocks:

A

motor neuron voltage-gated K+ channels

51
Q

Steps in release of synaptic vesicles from an axon terminal:

A
  1. AP reaches axon terminal
  2. Voltage-gated calcium channels open
  3. Calcium rushes in
  4. Synaptic vesicles are mobilized and released into the synaptic cleft where they release neurotransmitters
  5. Neurotransmitters bind to receptors on post-synaptic dendrite
52
Q

Which is faster at a nerve terminal, ionotrophic or metabotrophic transmission?

A

ionotrophic

53
Q

Ionotrophic transmission:

A
  • Very fast.
  • No ligand-receptor binding or intracellular signaling required to activate ion channels.
54
Q

Metabotropic transmission:

A
  • Fast, but slower than ionotrophic.
  • Ligand-receptor binding or intracellular signaling REQUIRED to activate ion channels.
55
Q

GABA function:

A
  • inhibitory neurotransmitter
  • activates chlorine(-) channels in neurons.
  • negative charge rushes in, neuron becomes more hyperpolarized and further from the threshold value for depolarization.
56
Q

Glutamate function:

A
  • excitatory neurotransmitter
  • activates membrane sodium(+) and calcium(+) channels.
  • positive charge rushes in, cells become closer to threshold value for depolarization.
57
Q

How does the parasympathetic nervous system slow the heart rate?

A
  • metabotrophic transmission causes outflux of K+.
  • cells become more hyperpolarized, further from depolarization threshold.
  • heart rate slows due to slower AP rate.

SF1.07 Electrophysiology (ZACHOW) (1 decks)

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