Chapter 20 THE HEART Flashcards Preview

Anatomy and Physiology > Chapter 20 THE HEART > Flashcards

Flashcards in Chapter 20 THE HEART Deck (64):
1

2

heart factoids

size of fist, less than a pound, beats an av of 100,000 times a day

3

Pulmonary Circuit pump

pumps sCo2 rich blood and O2 deficient, to the lungs. Blood is pumped through the lungs by the heart to reverse these gasses in the blood

4

Systemic circuit pump

blood returns to heart from lungs rich in O2 and low in Co2 and is pumped to rest of the body

5

Arteries

efferent vessels that carry blood away from the heart

6

Veins

Afferent, carry blood to the heart

7

Capillaries

Connect arteries and veins, referred to as exchange vessels

8

Cavity where the heart is located

mediastinum, between plural cavities

9

Apex

tip of the heart lies just above the diaphragm, left of the midline

10

Base

wide and directed towart the right shoulder
(base is on top)

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Pericardium

double walled fibrous sac the encloses the heart

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fibrous pericardium

loosely fitting, superficial part of sac anchoring

13

parietal pericardium

lines internal surface of the fibrous pericardium

14

Visceral Pericardium (epicardium)

upon the heart...layer covers surface of heart

15

serous fluid

fluid between parietal, visceral layers, prevents friction

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myocardium

cardiac muscle layer, contracting part of the heart

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Myocardium characteristics

pg. 3

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intercalated discs

membranes of adjacent cells are held together by desmosomes and linked by gap junctions; this propagates action potentials

19

endocardium

inner most layer. most internal layer, made of simple squamous epithelium, provides a smooth surface to prevent clotting

20

Chambers of the heart

pg. 3, fig 20-6

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Flow of blood, ex. cr.

pg. 4-6

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Coronary vessels

blood supply to the myocardium

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coronary arteries

first branches of the ascending aorta supplying nutrient/oxygen rich blood to myocardium

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arterial anastomomosis

joining up of vessels to maintain good blood supply despite fluctuation in pressure

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coronary veins

arteries merge with veins that will return blood to the right atrium

26

Cardiac conduction pathway

beating of the heart is regulated by electrical activity of the myocardium cardiac muscle cells contract spontaneously; the heart generates its own heartbeat called automaticity

27

conducting system cells

control/coordinate heartbeat through action potential

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contractile cell

produce contractions that propel blood

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The entire heart contracts in what series

1st the atria, then the ventricles; there is lag time between the beginning of the electrical impulse and the contraction (calcium entering sarcoplasm)

30

Impulse route

pg. 7 fig 20-12

31

electrocardiogram

electrical events in the cardiac cycle can be recorded (EKG or ECG)

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P wave

depolarizing of atria

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QRS complex

ventricles depolarize contraction of ventricles. happens shortly after that

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T wave

ventricles repolarizing

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P-R interval

from the start of atrial depolarization to the start of the QRS complex

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Q-T interval

from the time the ventricles depolarize to the time that they repolarize

37

Action Potential of cardiac muscle
1.Rapid depolarization

cause: Na+ entry
duration: 3-5 msec
ends with: closure of voltage-gated fast sodium channels

38

Action Potential of cardiac muscle
2. The Plateau

cause: Ca2+ entry
Duration: 175 msec
ends with: closure of slow calcium channels

39

Action Potential of cardiac muscle
3. Repolarization

cause: K+ loss
Duration: 75 msec
Ends with: closure of slow potassium channels

40

Energy for cardiac contractions

aerobic reactions occur when mitochondria break down fatty acids and glucose and in the presence of O2 convert them to ATP, O2 is stored in myogloblin for normal circulation

41

Cardiac Cycle

sequences of events in one heart beat= simultaneous contraction of the two atria followed by the simultaneous contraction of the ventricles, followed by a rest period

42

Systole

contraction

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diastole

relaxation

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cardia cycle, Atrial systole
3:

1. blood flows passively to rgt. atrium & ventricle during atrial & ventricular diastole
2. pressure builds as more blood enters rgt. atrium & it contracts, filling ventricles to capacity
3. atrial diastole occurs

45

Ventricular systole
ventricles enter_____ at the same time the atria enter _____

systole
diastole

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Ventricular systole (phase #1)

forces the L and R AV valves closed but there is not enough pressure to eject blood into arteries...pressure continues to rise until it exceeds pressure in the arterial trunks

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Ventricular systole (phase #2, called ventricular ejection)

ventricle contract strong enough to send blood into aortic and pulmonary trunks

48

stroke volume of heart

amount of blood pumped by ventricle per beat, 60-80 mL of blood

49

Ejection fraction

the percent of blood in a ventricle that is pumped during ventricle systole = pumps out 60% of the blood

50

End systolic volume

amount of blood remaining in the ventricle when semilunar valves closed

51

what gives the heart a rest for every beat?

ventricular diastole paired with atrial diastole

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S1- the lubb-loudest and longest

ventricular systole CLOSING the AV valves

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S2-dupp-ventricular diastole

closure of the aortic and pulmonary semilunar valves

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S3-blood flowing into the?

ventricles

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S4

atrial contraction

56

Pulse=heart rate, a healthy adult has a resting heart rate of

60-80 beats per min, which is also the rate of depolarization of the SA node

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child pulse

100 beats per min

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Infant pulse

120 beats per min

59

athletes pulse

35-50 beats per min

60

Cardiac output

amount of blood pumped by a ventricle in one min. determined by stroke volume x heart rate

61

average cardiac output

5-6 liters per min.

62

starling's law of the heart

the more the cardiac muscle fibers are stretched the more forcefully they contract

63

venous return

the amount of blood returning to the heart through veins; if the amount increases the atrial walls stretch causing a more rapid depolarization

64

Factors affecting heart rate, autonomic innervation

parasympathetic and sympathetic divisions innervate the heart innnervating both the SA and AV nodes, the atrial muscles fibers and ventricular muscle cells