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Physiology S2 > T2: Cardiac Cycle > Flashcards

T2: Cardiac Cycle Flashcards

1
Q

What 3 major types of cardiac muscle is the heart composed of?

A
  • atrial muscle
  • ventricular muscle
  • specialized excitatory and conductive muscle fibers
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2
Q

What is the structure of cardiac myocytes?

A
  • striated (thin actin and thick myosin fillaments)
  • no gap junctions
  • intecallated disks
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3
Q

What is the name of the valves seperating the atria and ventricles?

A

atrioventricular valves
left: mitral valve
right: tricuspid valve

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4
Q

What valve does blood exit the heart through?

A
  • pulmonary valve (to pulmonary trunk)
  • aortic valve (to aorta)
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5
Q

What does the cardiac conduction system contain?

A
  • sinoatrial node
  • atrioventricular node
  • bundle of His (atrioventricular bundle)
  • purkinje fibers
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6
Q

What is the pacemaker? What does it do?

A
  • the sinoatrial node
  • sends electrical impulses which initiate the heart beat
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7
Q

What does the atrioventricular node do?

A

delays the SA node’s electrical signal

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8
Q

What does the bundle of His do?

A
  • recieves electrical signals from the AV node
  • carries electrical impulses to the Purkinje fibers
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9
Q

What are Purkinje fibers? What are their functions?

A
  • branches of specialized nerve cells
  • send electrical impulses to the right and left ventricles
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10
Q

What does each cardiac cycle have? What phases? What occurs during each phase?

A

Diastolic phase:
- relaxation
- filling of heart with blood

Systolic phase:
- contraction
- exiting of blood

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11
Q

Explain the steps of the cardiac cycle?

A

1) atrial systole
2) ventricular systole
3) atrial diastole
4) ventricular diastole

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12
Q

What are the three phases of ventricular systole?

A

1) isovolumic contraction (pressure builds in the ventricle)
2) ventricular ejection (ventricles eject blood)
3) isovolumic relaxation

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13
Q

What happens during ventricular contraction?

A

atria relax (atrial diastole)

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14
Q

State, in order, the different phases of the cardiac cycle.

A
  • atrial diastole
  • atrial systole
  • isovolumic contraction
  • ventricular ejection
  • isovolumic relaxation
  • ventricular filling
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15
Q

Approximately how long is a heart cycle?

A

0.8 seconds

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16
Q

Why is diastole important?

A
  • for chambers to refill again (without it, there wouldn’t be blood to push out during the next systole)
  • essential for proper blood circulation
  • essential for the nourishing of the body’s tissues and organs
17
Q

What are the 3 stages of a single heart beat?

A
  • atrial depolarization
  • ventricular depolarization
  • atrial and ventricular repolarization
18
Q

What nervous system controls the firing of the sinus node to trigger the start of the cardiac cycle?

A

autonomic nervous system

19
Q

What is an electrocardiogram (ECG)?

A

a graphic record of the electrical activities of the heart, as monitored at specific location son the body surface

20
Q

What are ECG’s used for?

A

diagnosing cardiac arrhythmias

21
Q

What are cardiac arrhythmias?

A

abnormal patterns of cardiac electrical activity

22
Q

State the different parts of the ECG.

A

1) P wave
2) PR interval
3) QRS complex
4) ST segment
5) T wave

23
Q

What does the P-wave refer to?

A
  • atrial depolarization
  • SA node trigerring
24
Q

What does the PR-inteval refer to?

A
  • delay of the AV node
  • alows filling of ventricles
25
Q

What does the QRS-complex refer to?

A
  • depolarization of the ventricles
  • triggers the main pumping contractions
26
Q

What does the ST-segment refer to?

A
  • beginning of ventricle repolarization
  • should be flat
27
Q

What does the T-wave refer to?

A
  • ventricular repolarization
28
Q

Does the heart undergo tetany or summation?

A

NO!
no tetany or summation possible as the heart has a long absolute REFRACTORY PERIOD.

29
Q

What is tetany?

A

involuntary muscle contractions and overly stimulated peripheral nerves

30
Q

What is summation?

A

the additive effect of electrical impulses in multiple numbers coming on a neuromuscular junction

31
Q

What does the “starling’s law” state?

A

the more the heart is filled during diastole, the greater the volume pumped out.

32
Q

What is “cardiac output”?

A

the amount of blood that the heart pumps in a unit of time (usually ml or L per minute)

33
Q

What is “stroke volume”?

A

the amount of blood pumped out of the heart with each individual beat of the heart

34
Q

How is cardiac output calculated?

A

stroke volume x heart rate

  • units: ml/minute
35
Q

What is “tachycardia”?

A

abnormally fast heart beat

36
Q

What is “bradycardia”?

A

abnormally slow heart beat

37
Q

What are “atrial fibrillations”?

A
  • the irregular contraction of atria
  • blood cannot effectively flow out of atria
38
Q

What are “ventricular fibrillations”?

A
  • the irregular contraction of ventricles
  • blood cannot effectively flow out of ventricles
  • leads to death unless corrected

Physiology S2 (17 decks)

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