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Module 3: CPR > CV Physiology > Flashcards

CV Physiology Flashcards

1
Q

What are the functions of the cardiovascular system?

A

Supplies oxygen, metabolic fuel and heat; removes metabolic products and excess heat.

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2
Q

What does neural control do in the CV system?

A

Maintains constant arterial pressure.

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3
Q

What does local control do in the CV system?

A

Supplies nutrients to meet metabolic demand; exerted at the tissue site.

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4
Q

Where is blood pressure lowest?

A

Right atrium.

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5
Q

SYSTEMIC vascular resistance = ?

A

cardiac output (L/min)

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6
Q

PULMONARY vascular resistance = ?

A

(mean pulmonary arterial pressure - left atrial pressure) / cardiac output

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7
Q

Equation for pressure: P = ?

A

P = QR, where Q is flow and R is resistance.

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8
Q

R = ?

A

P/Q

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9
Q

Q = ?

A

P/R

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10
Q

Resistance increases as diameter _________.

A

Decreases. (except for the capillaries, because together the have lots of total cross-sectional area)

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11
Q

Resistance is highest in the ____________.

A

Arterioles.

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12
Q

What percentage of total blood volume is located in the venous system?

A

70%.

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13
Q

Velocity = ?

A

Velocity (cm/s) = flow (cm3/s) / cross-sectional area (cm2)

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14
Q

In which vessels is the ratio of wall thickness to lumen diameter greatest?

A

Arterioles.

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15
Q

Where is cross-sectional area greatest?

A

Capillaries.

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16
Q

Where is velocity lowest?

A

Capillaries.

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17
Q

Compliance = ?

A

Change in volume / change in pressure

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18
Q

What are the three types of cardiac action potentials?

A

Ventricular, atrial and nodal.

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19
Q

Which cardiac action potential is longest in duration?

A

Nodal.

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20
Q

What is Phase 0 of the cardiac action potential? What are the primary ions responsible?

A

Rapid depolarization, or the upstroke. Na+ in ventricular and atrial cells; Ca2+ in nodal cells.

21
Q

What is Phase 1 of the cardiac action potential?

A

Brief, partial repolarization in ventricular and atrial cells.

22
Q

What is Phase 2 of the cardiac action potential in ventricular cells? Atrial cells?

A

Plateau phase in ventricular action potential; it’s abbreviated in the atrial action potential.

23
Q

What is Phase 3 of the cardiac action potential? Which ion channels are involved?

A

Repolarization; K+ channels.

24
Q

What is Phase 4 of the cardiac action potential?

A

Resting potential in ventricular and atrial cells; pacemaker potential in nodal cells.

25
Q

In Phase 4 of ventricular action potential, which channels are open? What is the effect?

A

Both voltage-gated K+ channels like iK1 inward rectifying channels and potassium leak channels. They stabilize the membrane near potassium equilibrium potential.

26
Q

When the membrane depolarizes, what happens to iK1 channels? What is the effect?

A

They are plugged by Mg2+ and polyamines? K+ permeability decreases.

27
Q

Which channels are responsible for Phase 0 rapid depolarization in ventricular cells? What is the effect?

A

Voltage-gated, fast Na+ channels. Inward sodium current causes rapid depolarization toward sodium equilibrium potential.

28
Q

At which voltage does Phase 2 start in ventricular cells? Which channels close?

A

0 mV. ito1 channels close.

29
Q

When ito1 channels are closed during Phase 2, which channels open? What is the effect?

A

Voltage-gated slow iCa channels open, allowing calcium to enter down concentration gradient leading to excitation-contraction coupling in the myocyte.

30
Q

At the end of the plateu phase and beginning of Phase 3, which channel inactivates?

A

iCa inactivates.

31
Q

Which channels open during Phase 3 repolarization? What happens?

A

Voltage-gated potassium channels, iKr and iKs. They open slowly and K+ begins to leave and repolarize the cell.

32
Q

What happens to iK1 channels in Phase 3?

A

They are unplugged (previosly plugged by Mg2+) and allow more K+ to leave the cell.

33
Q

What causes the refractory period?

A

Inactivation of fast, voltage-gated Na+ channels. They close upon depolarization and cannot reopen until the cell is back at resting potential.

34
Q

What are the differences between nodal and ventricular action potentials?

A

Resting potential is not constant in nodal action potentials; cells depolarize between action potentials producing pacemaker potential. Phase 4 is rarely hyperpolarized past -60mV in nodal cells vs. -90 mV in ventricular cells. Nodal cells have a slower rate of depolarization during Phase 0. Nodal action potentials do not have Phases 1 and 2.

35
Q

Describe Phase 0 of nodal action potentials.

A

It follows membrane depolarization to threshold by Phase 4 pacemaker potentials, then at threshold slow, voltage-gated iCa channels open leading to the upstroke. Ca2+ enters depolarizing the cell to +10 - +20 mV. iCa channels are inactivated near the peak of the action potential.

36
Q

What happens in Phase 3 of nodal action potentials?

A

Repolarization: iK outward rectifiers open; K+ leaves and the membrane repolarizes.

37
Q

Phase 4 in the nodal cells is known as what?

A

Pacemaker potential.

38
Q

Is depolarization from adjacent cells required in nodal cells?

A

No, permeabilities of Na+, K+ and Ca2+ spontaneously change .

39
Q

What happens near the maximum negative voltage in Phase 4 of nodal action potentials?

A

Voltage-gated outward rectifiers close, so outward K+ currents decrease; inward currents begin depolarization; voltage-gated iCaT channels open and Ca2+ enters the cell, depolarizing it; voltage-gated Na+ channels open further depolarizing membrane toward threshold.

40
Q

Parasympathetic control of the heart is performed by which nerve? Which neurotransmitter?

A

Vagus. ACh.

41
Q

ACh __________ heart rate. How?

A

Decreases. By decreasing Na+ and Ca2+ permeability and increasing K+ permeability leading to hyperpolarization, decreasing the slope of pacemaker potential and modifying threshold. This decreases probability of slow, voltage-gated iCa opening. So, pacemaker potential starts more negative, depolarizes more slowly and has further to depolarize to reach threshold.

42
Q

Which neurotransmitter controls sympathetic innervation of the heart?

A

Norepinephrine.

43
Q

What is norepinephrine’s effect on the heart? How?

A

It increases heart rate by increasing the slope of pacemaker potential (opening of Na+ and Ca2+ channels, closing K+ channels), leading to faster depolarization and allowing it to reach threshold faster.

44
Q

Define EKG.

A

Vectorial summation of all cardiac action potentials at any one instant of time during the cardiac cycle.

45
Q

Which part of a syncytium repolarizes first?

A

The part that depolarized last.

46
Q

If voltage is positive, the axis and vector are pointing in the ________ direction. If voltage is negative?

A

Same. Opposite.

47
Q

The instant vectorial sum of the vectors produced by the polarization states and orientations of individual cardiomyocytes is known as ______.

A

Mean Cardiac Vector.

48
Q

If all cells are polarized, MCV is _____. Depolarized? Some depolarized, some polarized.

A

Zero. Zero. Nonzero.

49
Q

Greater mass of heart changing polarization state leads to ___________.

A

Greater magnitude of mean cardiac vector.

Module 3: CPR (1 decks)

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