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Human Anatomy BIO244 > Cardiac Physiology > Flashcards

Cardiac Physiology Flashcards

1
Q

How does heart muscle contract?

A

Stimulated by nerves and is self-excitable
The entire muscle contracts as a unit
Long (250 ms) absolute refractory period

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2
Q

What is the general structure of cardiac muscle tissue?

A

Intercalated discs connect the cells together to allow contraction as a unit

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3
Q

How is cardiac muscle arranged?

A

Spiral arrangement around the heart chambers, contraction reduces the diameter– apex of ventricles gets pulled up

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4
Q

What do the SA and AV nodes provide for the heart?

A

Rhythmic and automatic beating, initiate action potentials in heart muscles, they have unstable resting potentials called pacemaker potentias

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5
Q

What do pacemaker potentials do?

A

Depolarize slowly

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6
Q

What does the SA node do?

A

Contraction of the atria and stimulates the AV node (in right wall of right atrium)

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7
Q

What does the AV node do?

A

Contraction of the ventricles (in left wall of right atrium)

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8
Q

How many impulses does the SA node generate per minute?

A

70-80 times

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9
Q

What does the AV node do in the sequence of excitation

A

delays the impulse 0.1 seconds to allow atria to contract

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10
Q

How long do the atria and ventricles contract for?

A

Atria (0.1)

Ventricles (0.3)

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11
Q

Where are the nodes of the heart?

A

Both in the right atrium

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12
Q

Where do bundle branches carry the impulse?

A

To the apex

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13
Q

Where do the Purkinje fibers carry the impulse to?

A

To the apex then the ventricular walls

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14
Q

What happens when the SA node fails?

A

AV node takes over at 50 BPM

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15
Q

What happens if the AV node is damaged?

A

Ventricle impulse is blocked, atria keep pumping normally but ventricles contract at 30 bpm via the Purkinjie fibers

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16
Q

What does an ectopic focus of the SA node mean?

A

AV node takes over and makes the RHR 50 BPM, adequate to deliver blood

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17
Q

What does an ectopic focus of the AV node mean?

A

Purkinje fibers have to take over as the pacemaker, only produce RHR 30 BPM, not enough to deliver blood–requires artificial pacemaker

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18
Q

What are the steps of the EKG?

A

P wave
QRS complex
T wave
Atrial repolarization

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19
Q

What is the P wave?

A

Atrial depolarization

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20
Q

What is the QRS complex?

A

Ventricular depolarization

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21
Q

What is the T wave?

A

Ventricular repolarization

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22
Q

What is atrial repolarizaiton?

A

Atrial repolarization (masked by QRS complex)

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23
Q

What stimulates the heart?

A

The cardioacceleratory center of the medulla via the sympathetic system

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24
Q

What inhibits the heart?

A

The cardioinhibitory center of the medulla via the parasympathetic system

25
Q

What is the “lub-dup” sound of the heart?

A

First sound is AV valves closing, Second sound is the closing of the semilunar valves

26
Q

What is ventricular diastole?

A

Ventricular filling, first passive (80%) then atrial contraction fills the ventricles

27
Q

What is ventricular systole?

A

AV valves close, semilunar vales open and ventricles eject blood through them

28
Q

What closes the semilunar valves?

A

Backflow of blood in aorta and pulmonary trunk

29
Q

What is fibrillation?

A

Chambers contracting out of sequence

30
Q

What type of fibrillation is more serious?

A

Ventricular fibrillation

31
Q

How does the SA node signal start the whole contraction of the heart?

A

SA node stimulates both atria to contract, that signal jumps to the AV node which causes depolarization of the ventricles

32
Q

Why do diastole and systole overlap?

A

For quick and efficient heart beats

33
Q

What is Cardiac Output?

A

Amount of blood pumped by each ventricle in one minute, product of HR and stroke volume

34
Q

What is stroke volume?

A

Amount of blood pumped out by a ventricle with each beat

35
Q

What is the cardiac reserve?

A

The difference between resting and maximal CO

36
Q

What is EDV?

A

Amount of blood collected in a ventricle during diastole

37
Q

What is ESV?

A

Amount of blood remaining in a ventricle after contraction

38
Q

What is the ejection fraction?

A

SV/EDV, the fraction ejected

39
Q

How is SV calculated?

A

EDV - ESV

40
Q

What factors affect stroke volume?

A

Preload
Contractility
Afterload

41
Q

What is preload?

A

Amount ventricles are stretched by contained blood

42
Q

What is afterload?

A

Back pressure exerted by blood in the large arteries leaving the heart

43
Q

What is the Frank-Starling Law of the Heart?

A

Preload of cardiac muscle before they contract is the critical factor controlling stroke volume

44
Q

How much preload is normal?

A

130 ml of blood

45
Q

What factors increase contractility?

A

Hormones
Calcium and some drugs
Increased stimuli

46
Q

What factors decrease contractility?

A

Acidosis
Increased potassium
Calcium channel blockers

47
Q

What is a murmur?

A

Abnormal heart sound, from turbulent blood flow, most commonly a heart valve malfunction

48
Q

What is a stenotic valve?

A

Stiffened, does no open completely, and allows backflow

49
Q

What is an incompetent valve?

A

Scarred or damaged, doesn’t close completely, allows backflow

50
Q

What causes valve conditions?

A

Rheumatic fever

51
Q

How is the sympathetic system activated?

A

stress, anxiety, excitement, exercise

52
Q

How is the parasympathetic system activated?

A

acetylcholine, dominates the autonomic stimulation of the heart and slows down heart rate

53
Q

How does the vagus nerve affect the heart?

A

Release ACh
Binds to cholinergic receptors
Decreases membrane permeability
Slows heart rate and force

54
Q

How do the sympathetic nerves affect the heart?

A

Release norepinephrine
Bind to adrenergic receptors
Increases membrane permeability
Increases heart rate and force

55
Q

What do beta blockers do?

A

lower BP

56
Q

What does venous return do?

A

Increased venous return increases pre-systolic stretching of cardiac muscle

57
Q

What does thyroxine do?

A

Increases speed and force of heart contractions increases transcription of genes, increases contractile proteins in cardiac muscle

58
Q

What do the carotid and aortic sinuses do?

A

Measure BP

59
Q

What do the carotid and aortic bodies do?

A

Monitor pH, pCO2, and pO2

Human Anatomy BIO244 (32 decks)

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