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Structure and Function Test 1 > Intro to Electrophysiology > Flashcards

Intro to Electrophysiology Flashcards

1
Q

A voltage difference or separation of charge between the internal and external surfaces of the plasma membrane

A

Membrane potential

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2
Q

At rest, the membrane is

A

Polar

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3
Q

In general, the internal surface region of the plasma membrane has what charge?

A

Negative

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4
Q

In general, the extracellular surface region of the plasma membrane has what charge?

A

Positive

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5
Q

The inner surface of the plasma membrane is negative relative to the

-does not mean it is loaded with negative charge

A

Extracellular surface

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6
Q

The resting membrane potential of a large nerve is maintained at approximately

A
  • 90 mV

- means inner membrane is 90 mV less positive than outer

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7
Q

The flow of charge (ions)

A

Current

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8
Q

The resting membrane potential is due in large part to the membrane distribution of

A

Na+ and K+

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9
Q

Located inside the cell and help establish the resting membrane potential

A

Negatively charged proteins and Cl-

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10
Q

Generated any time an ion translocates across the cell membrane

A

Current (I)

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11
Q

Cell and tissue function is controlled by

A

Ion flux

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12
Q

In a resting motor neuron, there is a high intracellular concentration of K+ as compared to a high extracellular concentration of

A

Na+

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13
Q

Because of its chemical concentration gradient, there is a strong driving force for the translocation of K+ out of the cell through

A

K+ leak channels

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14
Q

Na+ and K+ are moved across the membrane against their concentration gradients by the

-maintains net negative charge on inner face of membrane

A

Na+/K+ ATPase (3 Na+ out, 2 K+ in)

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15
Q

How many ATP molecules are used during each ATPase cycle?

A

One

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16
Q

The tendency for an ion to move in one direction or another

A

Electromotive Force (EMF)

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17
Q

Dependent on the intra- and extracellular concentrations of Na+, K+, and Cl-, as well as membrane permeability of these ions

A

EMF

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18
Q

By maintaining RMP at around -90 mV, there exists a tremendous electrochemical gradient for the movement of Na+ inward, which is the defining characteristic of

A

Membrane depolarization during action potential

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19
Q

What are four electrogenic tissues that are dependent oupon anions (Cl-) and cations (Na+, K+, Mg2+, and Ca2+) for electrogenecity?

A

Heart, Skeletal muscle, Neurons, Vascular smooth muscle, and GI smooth muscle

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20
Q

The resting membrane potential is set by the membranes concentration gradient for

A

K+ out of the cell

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21
Q

The larger the K+ concentration gradient (i.e. the ratio of intracellular K+ to extracellular K+), the greater the

A

Nagtivity in the cell

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22
Q

When the the plasma [K+] is elevated (i.e. during hyperkalemia), the concentration gradient across the cell membrane is lowered; and this drives the

A

Resting membrane potential to be less negative (Membrane depolarizes)

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23
Q

Neurons communicate via the electrochemical phenomenon known as an

A

Action potential

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24
Q

The plasma membranes of neural and muscle cells contain voltage-gated Na+, K+, Cl-, and/or Ca2+ channels that open/close when there is a specific change in

A

Membrane potential

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25
Q

Causes the initial upward phase of the action potential (membrane depolarization)

A

Na+ flux

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26
Q

The action potential can be recorded and measured as

A

Electric current (INa+)

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27
Q

Rapid (< 0.1 msec) changes in membrane potential that result from alterations in the permeability of the membrane to Na+ and K

A

Neuronal Action Potentials

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28
Q

What are the three phases of the action potential?

A
  1. ) Resting
  2. ) Depolarization
  3. ) Repolarization
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29
Q

When the nerve fiber is at resting membrane potential

A

Resting phase

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30
Q

Characterized by acute changes in the membrane potential, which result in increased permeability of the plasma membrane to Na+ due to inactivation of resting voltage gated Na+ channels

A

Depolarization phase

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31
Q

Describe the depolarization phase of an action potential

A

Na+ rushes into the cell through open (active) Na+ gated channels, this results in the membrane potential becoming less negative, and more Na+ channels are activated, thus increasing influx of Na+

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32
Q

The membrane potential at which I-Na+ overcomes any opposing forces to inward I-Na+ and I-Na+ becomes self-reinforcing rapidly driving membrane potential toward the Nernst equilibrium potential for Na+

A

Threshold potential (Usually around -70 - -60 mV)

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33
Q

The changes in membrane potential resulting from depolarization induce the opening of

A

Voltage-gated K+ channels

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34
Q

Peak opening of the voltage gated K+ channels has occured at around

A

60 mV

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35
Q

What happens during the Repolarization phase?

A

Na+ channels close, but K+ channels remain open for a while allowing the membrane potential to become more negative. Then Na+/K+ ATP restore the resting membrane potential

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36
Q

Voltage-gated Na+ channels have 2 gates in series.

  1. ) One is located more toward the extracellular side and is called the
  2. ) One is located more towards the cytoplasmic side and is called the
A
  1. ) Activation gate

2. ) Inactivation gate

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37
Q

If either gate of the Na+ voltage-gated channel is closed, then the channel is

A

Inactive

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38
Q

What is the resting conformation of a Na+ channel?

A

Activation gates = closed

Inactivation gates = open

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39
Q

This specific conformation is important because Na+ channels can only be activated from the

A

Resting conformation

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40
Q

The majority of activation gates rapidly open in response to the

A

Threshold potential (about -60 mV)

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41
Q

During repolarization, both gates of the Na+ channel are

A

Closed (inactive conformation)

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42
Q

In the event of elevated extracellular K+
(i.e. severe enough hyperkalemia), RMP will be driven less negative; in so doing lessening the potential difference between

A

Resting membrane potential (RMP) and threshold

43
Q

Decreasing the potential difference between RMP and threshold has what effect on neuromuscular tissue?

A

Makes them more excitable (irritable)

44
Q

This excitability is very short lived because hyperkalemia depolarizes neuromuscular tissues and promotes inactivation of

A

Resting Na+ channels

-impedes generation of action potentials

45
Q

Are comprised of a single gate

-possess both a voltage and time dependency

A

K+ Channels

46
Q

During RMP, the gate is closed and the voltage-gated K+ channel is

A

Inactive (resting)

47
Q

Upon depolarization to suprathreshold levels (> -60 mV), the K+ gate opens somewhat gradually, with the greatest percentage of K+ channels open around

A

60 mV

48
Q

K+ channels change between conformations slowly. As membrane potential returns towards RMP, voltage-gated K_ channels remain open for several msec, resulting in a brief period of

A

Membrane Hyperpolarization

49
Q

Another contributor to the generation of an action potential

A

Calcium

50
Q

In cardiac myocytes and smooth muscle cells, the depolarization scheme is dominated by

A

Ca+ pumps/channels

51
Q

By comparison to voltage-gated Na+ channels, voltage-gated Ca2+ channels are

A

Slow activating

52
Q

What are the two important types of calcium channels?

A

L (long) type and T (transient) type

53
Q

Activate and inactivate over more negative membrane potentials and therefore assist in the pacemaker function of the sinoatrial node

A

T-type channels

54
Q

Have a high threshold for activation (> -30 mV), and sustain the plateau phase of the action potential found in cardiac myocytes and vascular smooth muscle

A

L-type channels

55
Q

Under normal circumstances, any even that depolarizes membrane potential to threshold level will initiate an

A

Action potential

56
Q

Not all depolarizations reach

A

Threshold

57
Q

A subthreshold stimulus initiates subthreshold alterations in membrane potential by activating

-allows for Na+ influx

A

LIGAND-gated Na+ channels

58
Q

Subthreshold changes in membrane potential are referred to as

-Proportional in amplitude to the stimulus strength

A

Graded potentials

59
Q

Graded potentials can sum to reach

A

Threshold

60
Q

The excitability of neuromuscular tissue is dependent upon the difference between

A

Resting potential (Em) and Threshold potential (Et)

= Em - Et

61
Q

Another action potential can not be initiated when the Na+ channels are

A

Closed (inactive)

62
Q

Period of time following peak action potential, where all voltage-gated Na+ channels are inactive (closed)

-extends until sufficient numbers of voltage-gated Na+
channels return to the resting conformation

A

Absolute refractory period

63
Q

The recovery phase where enough Na+ channels have returned to resting that a relatively strong (suprathreshold) stimulus can initiate another action potential

A

Relative refractory period

64
Q

Sodium that has entered the neuron (during depolarization) spreads to neighboring sections of the

A

Plasma Membrane

65
Q

The migration of Na+ to neighboring sections of the plasma membrane induces which three things?

A
  1. ) Depolarization of adjacent regions to threshold
  2. ) Activation of restive voltage-gated Na+ channels
  3. ) The resultant action potential in adjacent areas of membrane
66
Q

Thus, an action potential is propagated from the initial activation site, along the membrane, via a series of

A

Na+-induced depolarizations

67
Q

Travel to the nerve terminus and/or soma and stimulate a response such as the release of neurotransmitters, or the opening of other types of voltage-gated ion channels (e.g., Ca2+ channels)

A

Action potentials

68
Q

A phospholipid/cholesterol based substance that is formed by Schwann cells within certain types of neuronal tissue

A

Myelin

69
Q

The presence of the myelin sheath prevents conductivity, hence AP are not generated within

A

Myelin

70
Q

Within myelinated neurons, an action potential can only be generated within the

A

Nodes of Ranvier

71
Q

Propagation of an action potential from node to node

-requires less energy than the cable-like conduction in non-myelinated neurons

A

Saltatory conduction

72
Q

The maintenance of normal cardiac rate and rhythm is directed by the pacemaker activity of a population of electrogenic cells collectively known as the

A

Sinoatrial node

73
Q

Undergo rythmic depolarization and repolarization in the absence of innervation

A

SA nodes

74
Q

The concerted activities of T-type Ca2+ channels, Na+ HCN channels, and K+ channels enables inward ICa2+ and If (funny current = Na+) and outward IK+ within the

A

SA node

75
Q

To begin one pacemaker cycle, inward ICa2+ and If, combined with outward IK+, enable a

A

Gradual depolarization

76
Q

As the membrane potential creeps toward -55 mV, voltage-gated Ca2+ channels are increasingly activated, producing a rapid upstroke in

A

Action potential

77
Q

T-type Ca2+ channels inactivate through the depolarization phase, and at about 0 mV HCN channels are inactivated, shutting down If, and thus allowing repolarization via

A

Ik+

78
Q

Repolarization leads to a brief period of hyperpolarization which is necessary to reactivate

A

HCN channels

79
Q

Relatively long duration APs which are named due to a characteristic plateau-shaped phase following depolarization

-ex: potentials regulating cardiomycete contractility

A

Plateau Potential

80
Q

The plateau of the plateau potential is the result of K+ channels, which cause repolarization, being countered by

A

Ca2+ channels (activated by Na+ AP)

81
Q

Somatic sensory receptors that mediate the pain signal

-activated during injury by factors such as bradykinin, substance P, etc

A

Nociceptors

82
Q

The sensations of acute and chronic somatic pain are mediated by

A

Nociceptors

83
Q

Nociceptor afferents (nerve fibers relaying into the central nervous system) consist of

A

Myelinated and unmyelinated fibers

84
Q

The myelinated fibers are type Aδ fibers, which mediate the relay of so-called

A

Fast pain (Sharp/intense pain)

85
Q

Working with type Aδ fibers are the populations of small diameter, unmyelinated, slow conducting pain afferents called

A

Type C fibers

86
Q

Relay the sensation of dull, burning pain

A

Type C fibers

87
Q

Pain afferents feed into the dorsal horn of the spinal cord and ascend specific tracts to the

A

Thalamus

88
Q

Work by reversibly blocking action potentials in pain afferents

A

Local Anesthetics

89
Q

In general these agents exist as weak bases (deprotonated) at physiologic pH (7.4), are lipid-soluble, and because of their hydrophobic nature preferentially
enter small diameter pain afferents

A

Local Anesthetics

90
Q

Local anesthetic molecules are ionized by the acidic intracellular pH of the neuron, which enables them to bind

A

Voltage-gated Na+ channels (confers inactive conformation)

91
Q

The process whereby action potentials are relayed between neurons and/or between neurons and affector tissues

A

Synaptic transmission

92
Q

Neuromuscular transmission utilizes the neurotransmitter

A

Acetylcholine (ACh)

93
Q

There are numerous neurotransmitters used for neuroneuronal transmission. The ubiquitous excitatory neurotransmitters are

A

Gluamate and aspartate

94
Q

Common inhibitory neurotransmitters are

A

GABA and glycine

95
Q

Chemical synaptic transmission is subcategorized into

A

Ionotropic and metabotropic

96
Q

Utilizes neurotransmitters to activate ligand-gated ion channels residing in the post synaptic membrane

A

Ionotropic transmission

97
Q

An example of an excitatory ionotropic system

-found in skeletal muscle

A

Nicotenic-cholinergice receptor (ACh = neurotransmitter)

98
Q

What is faster, ionotropic or metabotropic transmission?

A

Ionotropic

99
Q

Relies upon not only the release of chemical neurotransmitters, but the activation of receptor-mediated signaling in the effector tissue by the neurotransmitters

A

Metabotropic transmission

100
Q

The AChmediated activation of cholinergic-muscarinic receptors within the sinoatrial node, which results in K= exiting the cell, used to control heart rate is an example of

A

Metabotropic transmission

101
Q

Terminated by enzymatic dissociation of the neurotransmitters and/or re-uptake of the neurotransmitter by the pre-synaptic terminus

A

Neuronal Transmission

102
Q

Can occur following the sustained stimulation of

neuronal transmission, such as what would occur in the presence of a cholinesterase inhibitor

A

Synaptic fatigue

103
Q

Results from exhaustion of neurotransmitter reserves, desensitization of the postsynaptic receptors, and/or disruptions in local ionic gradients within the post synaptic neuron such that the stimulatory signal is dampened or terminated

A

Synaptic fatigue

104
Q

ACh binding to the nicotinic-cholinergic receptor induces a conformational change in the channel receptor structure, which increases its permeability to

A

Na+, Ca2+, and K+

Structure and Function Test 1 (61 decks)

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