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Heart, Circulation, Respiratory > Heart > Flashcards

Heart Flashcards

1
Q

What are the two separate pumps of the heart?

A

The right heart pumps blood to the lungs, and the left heart pumps blood to the surrounding organs.

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2
Q

What are the two chambers of each heart pump?

A

An atrium and a ventricle.

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3
Q

What ensures regular and continuous heart contractions?

A

Special mechanisms in the heart transmit action potentials to all parts of the heart muscle.

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4
Q

What are the three layers of the heart?

A
  • Endocardium
  • Myocardium
  • Epicardium
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5
Q

What is the function of the fibrous tissue surrounding the atrioventricular (A-V) valves?

A

It separates the atria from the ventricles and prevents action potentials from passing between them.

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6
Q

What is the duration of the normal unresponsive period of the ventricle?

A

0.25-0.30 seconds.

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7
Q

What is the significance of calcium ions in cardiac muscle contraction?

A

Calcium ions play a crucial role in the excitation-contraction coupling mechanism.

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8
Q

What is the cardiac cycle?

A

The events that occur from the beginning of one heartbeat to the beginning of the next.

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9
Q

What are the two main phases of the cardiac cycle?

A
  • Diastole (relaxation)
  • Systole (contraction)
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10
Q

What does the P wave in an electrocardiogram represent?

A

The spread of depolarization to the atria.

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11
Q

What happens during the isovolumetric contraction phase?

A

Ventricular contraction begins, and ventricular pressure rises while A-V valves are closed.

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12
Q

What is end-diastolic volume typically?

A

110-120 ml.

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13
Q

What is stroke volume?

A

70 ml.

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14
Q

What is the ejection fraction?

A

The fraction of the end-diastolic volume that is ejected, usually equal to about 0.6 (or 60 percent).

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15
Q

What are the phases of the volume-pressure diagram during the cardiac cycle?

A
  • Period of filling (A→B)
  • Isovolumetric contraction period (B→C)
  • Period of ejection (C→D)
  • Isovolumetric relaxation period (D→A)
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16
Q

What is preload?

A

The end-diastolic pressure when the ventricle has become filled.

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17
Q

What is afterload?

A

The pressure in the aorta leading from the ventricle.

18
Q

True or False: The heart pumps only 4-6 liters of blood per minute in a resting person.

A

True.

19
Q

What regulates the volume pumped by the heart?

A
  • Intrinsic regulation in response to blood volume changes
  • Regulation by the autonomic nervous system
20
Q

What is the role of specialized signal and conduction fibers in the heart?

A

They exhibit automatic and rhythmic firings or transmit action potentials.

21
Q

What are the stages of action potentials in cardiac muscle?

A
  • Stage 0: Depolarization
  • Stage 1: Initial repolarization
  • Stage 2: Plateau
  • Stage 3: Rapid repolarization
  • Stage 4: Resting membrane potential
22
Q

What is the impact of calcium ion concentration on heart muscle contraction?

A

The force of contraction largely depends on the concentration of calcium ions in the extracellular fluid.

23
Q

What is the refractory period in cardiac muscle?

A

Cardiac muscle does not respond if restimulated during an action potential.

24
Q

What is the significance of actin-myosin filaments and intercalated discs?

A

They are key components of cardiac muscle structure.

25
Q

What is the normal resting heart pumping rate in liters per minute?

A

4-6 liters per minute

26
Q

What are the two main ways the volume pumped by the heart is regulated?

A
  • Intrinsic regulation of the pumping function of the heart
  • Regulation by the autonomic nervous system
27
Q

What does the Frank-Starling mechanism state about heart muscle stretching?

A

The more the heart muscle is stretched during filling, the greater the force of contraction and the amount of blood pumped

28
Q

What determines the amount of blood pumped by the heart per minute?

A

Venous return

29
Q

How does sympathetic stimulation affect cardiac output?

A

It may increase cardiac output by more than 100%

30
Q

What is the effect of strong sympathetic stimulation on heart rate?

A

It can increase the heart rate from 70 beats per minute to 180-200, or even 250 beats per minute

31
Q

What happens when strong impulses from the parasympathetic nerve fibers reach the heart?

A

They can stop the heartbeat for a few seconds, then resume at 20-40 beats per minute

32
Q

What is the effect of an increase in ECF potassium ion concentration on heart rate?

A

It causes a slowing of the heart rate

33
Q

What happens to the heart rate when body temperature increases?

A

The heart rate increases

34
Q

What effect does an increase in arterial pressure have on cardiac output?

A

It does not decrease cardiac output up to a certain limit

35
Q

Fill in the blank: The effect of _______ ions on heart function leads to spastic contraction.

A

Calcium

36
Q

What is the consequence of increasing potassium concentration to 8-12 meq/L?

A

It may cause death by disrupting the rhythm of the heart

37
Q

What is the primary role of the autonomic nervous system in heart regulation?

A

It regulates the heart’s pumping force and speed

38
Q

True or False: The sympathetic nerve fibers to the heart discharge continuously at a high rate.

A

False

39
Q

What happens to the force of contraction of the heart with strong vagus stimuli?

A

It can reduce the force of contraction by 20-30%

40
Q

What is the primary physiological limit described by the Frank-Starling mechanism?

A

The heart pumps all the blood that returns to it by way of the veins

41
Q

What is the result of decreased resting membrane potential of cardiac muscle fibers due to increased potassium?

A

It weakens the heart contraction

Heart, Circulation, Respiratory (1 decks)

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