Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Cardiology Block 1 > Action Potentials > Flashcards

Action Potentials Flashcards

1
Q

Homeostasis is a relatively stable condition of the internal environment that results from ______ system actions.

A

Homeostasis is a relatively stable condition of the internal environment that results from regulatory system actions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe the fluid distribution of an average 70 kg male:

A

Total body water is 42 L (about 55-60% of body weight)

Intracellular fluid (28 L):

  • Main cell compartment - 26 L
  • Blood cells - 2 L

Extracellular fluid (14 L)

  • Plasma - 3 L
  • Interstitial Fluid - 11 L
  • Transcellular - <1 L
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

_____ is the total solute concentration of a solution regardless of the chemical composition of the solutes.

A

Osmolarity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Osmolarity is the total solute concentration of a solution regardless of the ______ composition of the solutes.

A

Osmolarity is the total solute concentration of a solution regardless of the chemical composition of the solutes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Osmolarity is measured in ______

A

osmoles/L

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Hypoosmotic:

A

Less than 275 mOsm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Isoosmotic:

A

275-295 mOsm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Hyperosmotic:

A

More than 295 mOsm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

The higher the osmolarity, the _____ the water concentration

A

lower

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

If the membrane separating the compartments is _______ to water and _____ to solute, such as in a cell, the volume of the compartments can shrink or swell as water moves, but solute remains fixed.

A

If the membrane separating the compartments is permeable to water and impermeable to solute, such as in a cell, the volume of the compartments can shrink or swell as water moves, but solute remains fixed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What happens to a cell when placed in a hypertonic solution?

A

Cell shrinks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What happens when a cell is placed in an isotonic solution?

A

No change in cell volume

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What happens when a cell is placed in a hypotonic solution?

A

Cell swells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the Nernst equation?

A

Ex = (60/z) · log (xout/xin)

(units: mV)

x is an ion (Na+, K+, Cl-, Ca2+)

z is the charge of that ion

xout is the concentration of x in ECF

xin is the concentration of x in cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

When is the nernst equation not applicable?

A

When the membrane is permeable to more than one ion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

2 major determinants of membrane potential at any given time:

A

Ion gradients

Relative permeability of membrane to those ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

The _____ equation applies to multiple ions and their permeabilities (to determine the resting membrane potential)

A

Goldman-Hodgkin-Katz equation

(don’t memorize equation)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the resting membrane potential for potassium?

A

-85 mV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the resting membrane potential for Na?

A

+59 mV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the resting membrane potential of neurons and skeletal muscle cells?

A

Between -40 to -85 mV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Ca++ channels open in the membrane of a normal mammalian cell with a resting membrane potential of -65 mV. Which of the following will occur?

A. Ca++ moves out of the cell into the extracellular fluid.

B. The membrane potential will become more negative.

C. The membrane potential will become more positive.

D. Both A & C are correct

A

C. The membrane potential will become more positive.

(increasing the permeability will allow Ca to enter the cell, which will move the equilibrium potential closer to the + membrane potential)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Cl- channels open in the membrane of a normal mammalian cell with a resting membrane potential of -66.6 mV. The intracellular concentration of Cl- is 9 mM; the extracellular concentration is 116 mM. Which of the following will occur?

A. There will be no net flux of Cl- into or out of the cell.

B. The membrane potential will become more positive.

C. The membrane potential will become more negative.

A

A. There will be no net flux of Cl- into or out of the cell.

(The resting membrane potential is at the equilibrium potential - so no net flux)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Compare/contrast the nernst and goldman-hodgkin-katz equations:

A
  • The Nernst equation defines the equilibrium potential for a given ion gradient across a membrane permeable to only that ion.
  • The Goldman-Hodgkin-Katz equation defines the membrane potential for multiple ions and their gradients across a membrane permeable to multiple ions.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Label the chart:

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

______ is the voltage required to get enough voltage gated-Na+ channels to open to initiate the all-or-none behavior of the action potential.

A

Threshold is the voltage required to get enough voltage gated-Na+ channels to open to initiate the all-or-none behavior of the action potential.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

A ______ stimulus fails to fire an action potential

A

Subthreshold

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Subthreshold stimuli are due to the opening of _____ or _______ channels.

A

Subthreshold stimuli are due to the opening of ligand-gated or stimulus-gated channels.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

A _______ helps activate voltage gated Na channels

A

positive feedback loop

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Describe the relative permeabilities during an action potential:

A

K+ channels open much more slowly than Na+, and they continue to remain open for more time than the Na channels.

Also see that as we lose the permeability to the Na channel, the permeability to the K channel keeps going and hyperpolarizes the cell.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

After voltage- gated Na channels open, they will enter a state of ______, where they’re not responsive and won’t allow more Na to enter.

A

After voltage- gated Na channels open, they will enter a state of inactivation, where they’re not responsive and won’t allow more Na to enter.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Repolarization of the membrane potential occurs due to: (2)

A
  • inactivation of voltage-gated Na+ channels AND
  • opening of the voltage-gated K+ channels.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Because voltage-gated K+ channels close slowly, the membrane potential _______ past the resting membrane potential.

A

Because voltage-gated K+ channels close slowly, the membrane potential hyperpolarizes past the resting membrane potential.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Roughly how many ion molecules are moved across the membrane during an action potential?

A
  • The movement of only a few ion molecules is responsible for the action potential.
  • It is estimated that only 1 in 100,000 K+ present in the cell leaves during an action potential!
  • A similar number of Na+ enters from the ECF.

(Thus the Na-K-ATPase oesn’t have to work incredibly hard to restore ionic gradients after an action potential)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Assume the extracellular concentration of Na+ is 145 mM and the intracellular concentration is 15 mM. At the peak of the action potential, what value is the intracellular concentration of Na+ closest to?

A. 145 mM

B. 15 mM

C. 80 mM

A

B. 15 mM

Only 1 in 100,000 molecules actually move across the membrane. This is a miniscule concentration of ions, so the intracellular concentration doesn’t really change.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

The _______ period is when all Na+ channels are either open or inactivated.

A

The absolute refractory period is when all Na+ channels are either open or inactivated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

The _______ period is when K+ permeability is elevated and some Na+ channels are still inactivated

A

The relative refractory period is when K+ permeability is elevated and some Na+ channels are still inactivated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

_____ propagate without degradation over long distances.

A

Action potentials

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

_____ cells in the peripheral nervous system and _____ in the central nervous system myelinate axons.

A

Schwann cells in the peripheral nervous system and oligodendrocytes in the central nervous system myelinate axons.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

The wraps of myelin increase the _____ of the membrane resulting in less leakage of current out of the axon.

A

The wraps of myelin increase the resistance of the membrane resulting in less leakage of current out of the axon.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

______ increases the speed of conduction of the action potential along the length of the axon.

A

Myelination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Myelination increases the speed and efficiency of AP propagation is up to ____x faster than unmyelinated axons.

A

Myelination increases the speed and efficiency of AP propagation is up to 50x faster than unmyelinated axons.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Define saltatory conduction:

A

Wave of depolarization in a myelinated axon “jumps” from node of Ranvier to node of Ranvier

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

The larger the diameter, the ____ the conduction velocity.

A

faster

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

The larger the diameter of the axon, the ____ the wrapping of myelin

A

greater

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

What is the initiation site for action potentials?

A

The axon hillock

  • The axon hillock is the initial segment of axon.
  • Voltage-gated Na+ channels are highly concentrated in this region of the neuron.
  • Easier to depolarize membrane here.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Voltage-gated Na channels are highly concentrated at the ______

A

Nodes of ranvier

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

_______ channels are highly concentrated at the nodes of Ranvier

A

Voltage-gated Na channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q
A

A

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

What are the two types of synapses?

A

Electrical (less common in the nervous system)

Chemical (most common in the nervous system)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

Electrical synapses occur between a _____ and a _____

A

Electrical synapses occur between a neuron and another cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

______ occurs between electrical synapses, linking the cells.

A

Gap junctions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

______ are present in the membrane of each cell which line up to form channels with 2 nm pores. These are formed by 6 _______.

A

Connexons are present in the membrane of each cell which line up to form channels with 2 nm pores. These are formed by 6 connexins.

53
Q

What type of synapse is occuring at each site?

A
54
Q

A chemical synapse occurs between a ____ and a ____.

A

A chemical synapse occurs between a neuron and a neuron.

OR

between a neuron and a non-neuronal effector cell

e.g.

–Skeletal muscle = “neuromuscular junction” (NMJ)

–Non-neural effector cell = “neuroeffector junction”

55
Q

A chemical synapse is transmitted via a neuron propagating an action potential which invades the _______

A

A chemical synapse is transmitted via a neuron propagating an action potential which invades the axon terminal

56
Q

Presynaptic features of a neuron:

A

Presynaptic features:

  1. Axon swelling
  2. Synaptic vesicles
  3. Mitochondria
  4. Pre-synaptic density
57
Q

A rise in ____ triggers fusion of synaptic vesicles with the presynaptic membrane.

A

Calcium (Ca++)

58
Q

An action potential arrives at the presynaptic terminal, opening ____ channels.

A

An action potential arrives at the presynaptic terminal, opening Ca++ channels.

59
Q

Chemical synapse which links a neuron and a skeletal muscle cell = _____

A

neuromuscular junction

60
Q

The _____ distribute at the top of the junctional folds at them NMJ while the ________ are located at the bottoms of junctional folds and on the longitudinal surface.

A

The Ach receptors distribute at the top of the junctional folds at them NMJ while the voltage-gated Na+ channels are located at the bottoms of junctional folds and on the longitudinal surface.

61
Q

The Ach receptors distribute at the ____of the junctional folds at the NMJ while the voltage-gated Na+ channels are located at the ____ of junctional folds and on the _____ surface.

A

The Ach receptors distribute at the top of the junctional folds at the NMJ while the voltage-gated Na+ channels are located at the bottoms of junctional folds and on the longitudinal surface.

62
Q

To enhance the action of ACh at the NMJ:

A. increase the activity of acetylcholinesterase

B. decrease the activity of acetylcholinesterase

C. decrease the Ca++ entry into the presynaptic terminal

D. block the postsynaptic receptor

A

B. decrease the activity of acetylcholinesterase

63
Q

At the NMJ, the EPSP is called WHAT?

A

End Plate Potential (EPP)

64
Q

What determines whether a post-synaptic response is an IPSP or EPSP?

A
  • Neurotransmitter released
  • Receptor at the post-synaptic cell
  • Whether ion channels open or close (either directly or indirectly)
  • Selectivity properties of channels
  • Ions present and their gradients across the membrane

Example: The ACh receptor at the NMJ is a non-selective cation channel. When ACh binds its receptor, the channel opens and Na+ and K+ flow across the membrane. Because the driving force is greatest on Na+ towards its equilibrium potential, the membrane depolarizes as a graded potential.

65
Q

When graded potentials exceed _____ an action potential is generated.

A

When graded potentials exceed threshold an action potential is generated.

66
Q

When graded potentials exceed threshold a(n) ______ is generated.

A

When graded potentials exceed threshold an action potential is generated.

67
Q

Graded potentials at the NMJ are always _____.

A

excitatory

68
Q

Key characteristics of graded potentials:

A

Transient changes in membrane potential

  • EPSPs move the membrane potential toward threshold for an action potential
  • IPSPs stabilize or move the membrane potential away from threshold for an action potential

Amplitude of membrane potential can vary

Decays over distance

Can summate

  • Spatial summation
  • Temporal summation
69
Q
A

Choice B - AA; CC

70
Q
A

Choice C - A&B; A&C

71
Q

Complete the table:

A
72
Q

Neurotransmitter release through exocytosis of synaptic vesicle contents is regulated by WHAT

A

Calcium

73
Q

Muscle fiber contraction in response to stimulation is regulated by WHAT?

A

Calcium

74
Q

How is calcium removed from the neuron?

A

Ca/Na exchangers

Plasma membrane Ca-ATPase

SERCA pumps (Smooth ER Calcium ATPases)

75
Q

An increase in intracellular Ca++ is essential for presynaptic release of neurotransmitter. Where does the additional Ca++ come from, mainly?

A. Endoplasmic reticulum

B. Sarcoplasmic reticulum

C. Mitochondria

D. Voltage-gated Ca++ channels

A

D. Voltage-gated Ca++ channels

76
Q

If the Na+/K+ ATPase is poisoned:

A.intracellular [K+] will increase.

B.cytosolic [Ca++] will increase.

C.Intracellular [Na+] will increase.

D.B and C are correct.

E.All of the above are correct.

A

D. B and C are correct.

(cytosolic [Ca++] will increase and intracellular [Na+] will increase).

77
Q

Within the myofiber are ______, which contain _____.

A

Within the myofiber are myofibrils, which contain myofilaments.

78
Q

The _____ is the smallest contractile unit of the skeletal muscle

A

sarcomere

79
Q

Triads are composed of what?

A

Two SR terminal cisternae and a T tubule

80
Q

What is a neuromuscular junction?

A

A synapse between a somatic motor neuron and a skeletal muscle fiber

81
Q

What is a motor endplate?

A

the post-synaptic region of the skeletal muscle cell at the neuromuscular junction

82
Q

What is a motor unit?

A

All the muscle fibers innervated by one somatic motor neuron.

A somatic motor neuron may innervate more than one muscle fiber (motor unit). HOWEVER a muscle fiber is innervated by only one somatic motor neuron, in humans.

83
Q
A
84
Q

Explain what happens at an NMJ after acetylcholine has been release from the presynaptic neuron:

A
  1. Acetylcholine diffuses across synaptic cleft and binds to nicotinic acetylcholine receptor channels
  2. Receptor channels open increasing the permeability of subsynaptic membrane to Na+and K+
  3. Na+ influx exceeds K+ efflux producing a depolarizing graded potential termed the end-plate potential (EPP)
  4. EPP exceeds threshold and initiates muscle action potential; voltage-gated Na+ channels open as the sarcolemma depolarizes
  5. Muscle action potential is conducted along sarcolemma and into transverse tubules
  6. Voltage-gated L-type Ca++ channels in the T-tubules (DHP receptors) open; Causes Ca++ release channels (Ryanodine receptors) in SR to open
  7. Ca++ diffuses out of the sarcoplasmic reticulum
  8. [Ca++] near sarcomeres increases.
  9. Cross-bridges form; contraction begins
85
Q

Depolarization of the sarcolemma is propagated down the T-tubules, opening the _____

A

DHP Receptors

86
Q

In skeletal muscle contraction, mechanical coupling of DHP receptors to _______ causes Ca++ to move out of SR into cytosol

A

Ryanodine receptors

87
Q

Calcium binding to _____ removes the blocking action of _____, allowing cross bridges binding between actin and myosin.

A

Calcium binding to troponin removes the blocking action of tropomyosin, allowing cross bridges binding between actin and myosin.

88
Q

Calcium release from the ___ in response to a single action potential is sufficient to bind all sites on ____ to expose the actin binding sites for maximum cross-bridge binding in a skeletal muscle.

A

Calcium release from the SR in response to a single action potential is sufficient to bind all sites on troponin to expose the actin binding sites for maximum cross-bridge binding in a skeletal muscle.

This differs with other muscle types

89
Q

Does smooth muscle have sarcomeres?

A

No - no Z bands, but do have dense bodies

90
Q

Key points about vascular smooth muscle:

A
  • Surrounds some blood vessels, controlling diameter of the blood vessel lumen, regulates blood flow through vessel
  • Does not fire action potentials
  • Under involuntary control:
  • Hormones
  • Neurotransmitters
    • Autonomic Nervous System
  • Local stimuli
91
Q

Multiunit smooth muscle cells have _____ electrical coupling between cells, vs. single unit smooth muscle cells which have _____ electrical coupling between cells. Explain.

A

Multiunit smooth muscle cells have little electrical coupling between cells, vs. single unit smooth muscle cells which have extensive electrical coupling between cells. Explain.

92
Q

Ca++ binds ____ which activates Myosin light chain kinase (MLCK)

A

Ca++ binds calmodulin which activates Myosin light chain kinase (MLCK)

93
Q

Ca++ binds calmodulin which activates _____

A

Ca++ binds calmodulin which activates Myosin light chain kinase (MLCK)

94
Q

_______ phosphorylates myosin leading to cross-bridge formation and thus, contraction. ______ dephosphorylates myosin causing cross bridges to uncouple and thus resulting in relaxation.

____ is active constituitively.

A

Myosin light chain kinase (MLCK) phosphorylates myosin leading to cross-bridge formation and thus, contraction. Myosin light chain phosphatase (MLCP) dephosphorylates myosin causing cross bridges to uncouple and thus resulting in relaxation.

MLCP is active constituitively.

95
Q

Myosin light chain kinase (MLCK) ______ myosin leading to cross-bridge formation and thus, ____. Myosin light chain phosphatase (MLCP) _____ myosin causing cross bridges to uncouple and thus resulting in _____.

____ is active constituitively.

A

Myosin light chain kinase (MLCK) phosphorylates myosin leading to cross-bridge formation and thus, contraction. Myosin light chain phosphatase (MLCP) dephosphorylates myosin causing cross bridges to uncouple and thus resulting in relaxation.

MLCP is active constituitively.

96
Q

____ muscle contraction is slow and energy efficient

A

Smooth muscle

  • Cross-bridge activation is slow compared to skeletal muscle.*
  • Smooth muscle form of myosin has a very low rate of ATPase activity relative to skeletal muscle.*
  • Shortening is slower than in skeletal muscle.*
  • Smooth muscle cells do not fatigue during prolonged activity due to low rate of energy utilization.*
97
Q

The tension generated by a smooth muscle cell can be graded by varying ______ concentration

A

The tension generated by a smooth muscle cell can be graded by varying cytosolic Ca++ concentration

Elevated Intracellular Ca++ = elevated number of bound cross-bridges = elevated tension developed

98
Q

______ is the most potent endogenous vasodilator known.

A

Nitrous Oxide

99
Q

Nitric oxide produced by _______ diffuses into vascular smooth muscle cells resulting in relaxation and vasodilation

A

Nitric oxide produced by vascular endothelial cells diffuses into vascular smooth muscle cells resulting in relaxation and vasodilation

100
Q

Nitric oxide produced by vascular endothelial cells diffuses into vascular smooth muscle cells resulting in ______ and _____

A

Nitric oxide produced by vascular endothelial cells diffuses into vascular smooth muscle cells resulting in relaxation and vasodilation

101
Q

Ca++ entry into the cytosol of a smooth muscle cell:

A. increases nitric oxide activation of guanylate cyclase.

B. favors the actions of MLCP.

C. favors phosphorylation of MLC.

A

C. favors phosphorylation of MLC.

102
Q

Nitrous Oxide stimulates production of ___ through soluble guanylate cyclase, which activates ____, which then stimulates the reuptake of cytosolic Ca2+ and the opening of calcium-activated _____ channels. Cytosolic Ca++ levels fall and ____ activity decreases.

A

Nitrous Oxide stimulates production of cGMP through soluble guanylate cyclase, which activates protein kinase G, which then stimulates the reuptake of cytosolic Ca2+ and the opening of calcium-activated potassium channels. Cytosolic Ca++ levels fall and MLCK activity decreases.

103
Q

Interalated discs contain ____ and ____

A

Desmosomes for strength

Gap junctions for low resistance pathways for action potential spread

104
Q

_______ connect atrial myocytes with other atrial myocytes
and ventricular myocytes with other ventricular myocytes

A

Gap junctions connect atrial myocytes with other atrial myocytes
and ventricular myocytes with other ventricular myocytes

(However, atrial myocytes are not connected to ventricular myocytes)

105
Q

The atria are electrically insulated from the ventricles except at the _____.

A

The atria are electrically insulated from the ventricles except at the AV node.

106
Q

The _____ is the only path for excitation from the atria to ventricles.

A

The AV node is the only path for excitation from the atria to ventricles.

107
Q

AV nodal cells conduct action potentials _____.

A

AV nodal cells conduct action potentials slowly.

(This allows for a delay between atrial and ventricular contraction, allowing more time for ventricular filling)

108
Q

What is the conduction pathway starting from the AV node?

A

AV node

Bundle of His

left and right bundle branches

Purkinje fibers

(rapid conduction allows action potentials to rapidly spread throughout the ventricles)

109
Q

Ventricular contraction starts in the _____, then spreads to the _____.

A

Ventricular contraction starts in the apex, then spreads to the ventricular walls.

110
Q

Are action potentials fired between heartbeats?

A

No - pacemaker cells are depolarizing but no action potentials are firing.

111
Q

Generally, what occurs at each labeled stage?

A
112
Q

What channels are opened/closed during phase 4 of the cardiac action potential?

A

IR potassium channels are open, allowing K+ to exit the cell

(also called “very leaky channels” or “inward rectifier K+ channels”)

113
Q

What channels are opened/closed during phase 0 of the cardiac action potential?

A

Voltage-gated Na channels open

IR K channels are becoming blocked

114
Q

What channels are opened/closed during phase 1 of the cardiac action potential?

A

Transient outward K channels open

Voltage-gated Ca channels aka L type Ca channels aka DHP receptors begin to open

Voltage gated Na channels inactivating

115
Q

What channels are opened/closed during phase 2 of the cardiac action potential?

A

Voltage gated Ca channels aka L type Ca channels aka DHP receptors open

Delayed Rectifier K channels (DR K channels) opening

Transient outward K channels inactivating

Voltage-gated Na channels inactivated

116
Q

What channels are opened/closed during phase 3 of the cardiac action potential?

A

Voltage gated Ca channels inavtivating

Delayed Rectifier K channels open

Transient outward K channels inactivated

117
Q

During phase 1 and 2 (depolarization) of cardiac action potentials, ___ channels inactivate while ___ and ___ channels activate.

A

During phase 1 and 2 (depolarization) of cardiac action potentials, Na channels inactivate while Ca and K channels activate.

118
Q

During phase 3 of the cardiac action potential, ___ channels inactivate and ___ channels continue to open.

A

During phase 3 of the cardiac action potential, Ca channels inactivate and K channels continue to open.

119
Q

Cardiac action potential threshold is about ____mV

A

-75 mV

120
Q

Explain calcium entry into the cardiac muscle cell

A

L-type Calcium channels are opened during phase 2 (opening during phase 1 and inactivating during phase 3). This allows for calcium to enter the cell.

Entry of calcium via these channels causes a calcium induced calcium release from the SR

121
Q

Increased ______ results in greater strength of contraction.

A

Increased cytosolic calcium results in greater strength of contraction.

122
Q

Cardiac muscle relaxation occurs when calcium is removed from the cytosol. How is calcium removed?

A

Sarcolemma

  • Na+-dependent 2nd active Ca++ transporters (Na+/Ca++ exchanger)
  • Ca++ - ATPases
  • Na+/K+- ATPases

Membrane of SR

  • Ca++- ATPases (SERCA pumps
123
Q

SERCA pump function decreases in a cardiac ventricular myocyte. Which of the following could occur?

A. Cytosolic [Ca++] decreases.

B. Cross bridge cycling increases.

C. Ca++ binding to troponin decreases.

A

B. Cross bridge cycling increases.

124
Q

Label the channels that are open during each stage of the pacemaker cell action potential:

A
125
Q

Hyperpolarization-activated cyclic nucleotide-gated (HCN) aka “funny” channels are permeable to both __ and __. These open at _____ potentials and close as membrane ____ in sinoatrial node action potentials.

A

Hyperpolarization-activated cyclic nucleotide-gated (HCN) aka “funny” channels are permeable to both Na+ and K+. These open at negative potentials and close as membrane depolarizes in sinoatrial node action potentials.

126
Q

Hyperpolarization-activated cyclic nucleotide-gated (HCN) aka “funny” channels are sensitive to __ and __.

A

Hyperpolarization-activated cyclic nucleotide-gated (HCN) aka “funny” channels are sensitive to NE and EPI.

127
Q

The ventricular action potential is ____ than than a neuronal action potential.

A

The ventricular action potential is slower than than a neuronal action potential.

128
Q

What is the resting membrane potential for the sinoatrial node?

A

There is not one

Cardiology Block 1 (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions