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circulation part two Flashcards

1
Q

Depolarization of the heart is

A

rhythmic and spontaneous

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2
Q

what ensures the heart contracts as a unit

A

gap junctions

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3
Q

cardiac muscle contraction graph parts

A

beginning; Na+ influx shoots to top (depolarization)
plateau where Ca2+ leaks slowly
rushes down where Ca2+ closes and k+ opens (repolarization)

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4
Q

E-C coupling occurs as

A

Ca2+ binds to troponin and sliding of the filaments begins

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5
Q

Duration of the Action Potential and the contractile phase is what in comparison to skeletal muscle

A

Duration of the Action Potential and the contractile phase is much greater in cardiac muscle than in skeletal muscle

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6
Q

Intrinsic cardiac conduction system

A

A network of noncontractile (autorhythmic) cells that initiate and distribute impulses to coordinate the depolarization and contraction of the heart

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7
Q

the self excitable myocytes act as

A

nerves

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8
Q

the self excitable myocytes have two important roles

A

forming the conduction system of the heart and acting as pacemakers within the system

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9
Q

autorhythmicity

A

spontaneously depolarize at a given rate. once one group of A cells start an action potential, all the cells around it also depolarize

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10
Q

SA node fires how often

A

every .8 seconds, or 75 action potentials per minute

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11
Q

autorhythmic cells reasoning with graph

A

Have unstable resting potentials (pacemaker potentials or prepotentials) due to open slow Na+ channels
At threshold, Ca2+ channels open
Explosive Ca2+ influx produces the rising phase of the action potential
Repolarization results from inactivation of Ca2+ channels and opening of voltage-gated K+ channels

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12
Q

Heart Physiology: Sequence of Excitation

A 
SA node 
AV node
AV bundle 
right and left bundle branches 
perkinje fibers
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13
Q

what Depolarizes faster than any other part of the myocardium

A

SA node

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14
Q

whatDelays impulses approximately 0.1 second

A

AV node

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15
Q

how often does AV node fire

A

Depolarizes 50 times per minute in absence of SAnode input

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16
Q

what is the Only electrical connection between the atria and ventricles

A

AV bundle

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17
Q

how often do AV bundle and purkinje fibers depolarize

A

AV bundle and Purkinje fibers depolarize only 30times per minute in absence of AV node input

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18
Q

Defects in the intrinsic conduction system may result in

A

Arrhythmias
Uncoordinated atrial and ventricular contractions
Fibrillation

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19
Q

Arrhythmias

A

irregular heart rhythms

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20
Q

Fibrillation

A

rapid, irregular contractions; useless for pumping blood

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21
Q

Defective SA node may result in

A

Ectopic focus: abnormal pacemaker takes over

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22
Q

Defective AV node may result in

A

Partial or total heart block

Few or no impulses from SA node reach the ventricles

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23
Q

Heartbeat is modified by the

A

autonomic nervous system

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24
Q

Cardiac centers are located in the

A

medulla oblongata

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25
Q

what does Cardioacceleratory center do

A

innervates SA and AV nodes, heart muscle, and coronary arteries through sympathetic neurons

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26
Q

what does Cardioinhibitory center do

A

inhibits SA and AV nodes through parasympathetic fibers in the vagus nerves

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27
Q

The vagus nerve

(parasympathetic does what

A

decreases heart rate

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28
Q

Sympathetic cardiac

nerves does what

A

increase heart rate

and force of contraction

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29
Q

Electrocardiogram (ECG or EKG

A

a composite of all the action potentials

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30
Q

EKG three waves

A

P wave: depolarization of SA node
QRS complex: ventricular depolarization
T wave: ventricular repolarization
(go over pictures on powerpoint)

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31
Q

EKG six steps

A 
Depolarization of the Atria
Repolarization of the Atria
Septal Depolarization
Apical Depolarization
Late Left Ventricular Depolarization
Repolarization of the Ventricle
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32
Q

Junctional rhythm.

A

p waves absent, weird t waves, look at pictures

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33
Q

Second-degree heart block.

A

Some P waves are not conducted through the AV node; more P than QRS waves are seen

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34
Q

Ventricular fibrillation

A

These chaotic, grossly irregular ECG

deflections are seen in acute heart attack and electrical shock.

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35
Q

lub

A

First sound occurs as AV valves close and signifies beginning of systole

36
Q

dub

A

Second sound occurs when SL valves close at the beginning of ventricular diastole

37
Q

Heart murmurs

A

abnormal heart sounds most often indicative of valve problems

38
Q

Cardiac cycle

A

all events associated with blood flow through the heart during one complete heartbeat

39
Q

Systole

A

contraction

40
Q

diastole

41
Q

Phases of the Cardiac Cycle

A

Ventricular filling
Ventricular systole
Isovolumetric relaxation occurs in early diastole

42
Q

Ventricular filling

A

takes place in mid-to-late diastole
AV valves are open
80% of blood passively flows into ventricles
Atrial systole occurs, delivering the remaining 20%

43
Q

End diastolic volume (EDV

A

volume of blood in each ventricle at the end of ventricular diastole

44
Q

Ventricular systole

A

Atria relax and ventricles begin to contract
Rising ventricular pressure results in closing of AV valves
Isovolumetric contraction phase (all valves are closed)
In ejection phase, ventricular pressure exceeds pressure in the large arteries, forcing the SL valves open

45
Q

End systolic volume (ESV

A

volume of blood remaining in each ventricle

46
Q

Isovolumetric relaxation occurs in early diastole

A

Ventricles relax
Backflow of blood in aorta and pulmonary trunk closes SL valves and causes dicrotic notch (brief rise in aortic pressure)

47
Q

dont forget!!!

A

go over graphs

48
Q

Cardiac Output (CO

A

Volume of blood pumped by each ventricle in one minute

49
Q

CO =

A

heart rate (HR) x stroke volume (SV)

50
Q

heart rate

A

number of beats per minute

51
Q

stroke volume

A

volume of blood pumped out by a ventricle with each beat

52
Q

At rest

CO (ml/min)

A

HR (75 beats/min) × SV (70 ml/beat)

= 5.25 L/min

53
Q

Maximal CO

A

is 4–5 times higher than resting CO in nonathletic people

54
Q

Maximal CO may reach — in athletic people

A

35L/min in trained athletes

55
Q

Cardiac reserve:

A

difference between resting and maximal CO

56
Q

SV = formula

A

EDV – ESV

57
Q

Three main factors affect SV

A

Preload
Contractility
Afterload

58
Q

starlings law of the heart

A

the more the heart muscle is stretched before contraction (preload), the more forcefully the heart will contract

59
Q

Preload

A

degree of stretch of cardiac muscle cells before they contract

60
Q

cardiac muscle cells stretching

A

At rest, cardiac muscle cells are shorter than optimal length
Slow heartbeat and exercise increase venous return
Increased venous return distends (stretches) the ventricles and increases contraction force

61
Q

Contractility

A

contractile strength at a given muscle length, independent of muscle stretch and EDV

62
Q

Positive inotropic agents increase contractility

A

Increased Ca2+ influx due to sympathetic stimulation

Hormones (thyroxine, glucagon, and epinephrine)

63
Q

Negative inotropic agents decrease contractility

A

Acidosis
Increased extracellular K+
Calcium channel blockers

64
Q

Afterload

A

pressure that must be overcome for ventricles to eject blood

65
Q

what does hypertension increased afterload result in

A

resulting in increased ESV and reduced SV

66
Q

how do Positive and negative chronotropic factors affect heart rate

A

Positive chronotropic factors increase heart rate

Negative chronotropic factors decrease heart rate

67
Q

sympathetic nervous system is activated by

A

emotional or physical stressors

68
Q

what does Norepinephrine do

A

causes the pacemaker to fire more rapidly (and at the same time increases contractility)

69
Q

what does Acetylcholine do

A

Acetylcholine hyperpolarizes pacemaker cells by opening K+ channels

70
Q

at rest is the heart parasympathetic or sympathetic

A

The heart at rest exhibits vagal tone (parasympathetic)

71
Q

Atrial (Bainbridge) reflex:

A

a sympathetic reflex initiated by increased venous return

72
Q

Stretch of the atrial walls stimulates

A

the SAnode

Also stimulates atrial stretch receptors activating sympathetic reflexes

73
Q

what does Epinephrine do

A

enhances heart rate and contractility

74
Q

what does Thyroxine do

A

increases heart rate and enhances the effects of norepinephrine and epinephrine

75
Q

Other Factors that Influence Heart Rate

A 
Age
Gender
Exercise
Body temperature
hormones
ions
76
Q

Tachycardia

A

abnormally fast heart rate (>100bpm)

77
Q

tachycardia can lead to

A

may lead to fibrillation if persistent

78
Q

Bradycardia

A

heart rate slower than 60bpm

79
Q

Bradycardia can lead to

A

May result in grossly inadequate blood circulation

May be desirable result of endurance training

80
Q

Congestive Heart Failure (CHF)

A

Progressive condition where the CO is so low that blood circulation is inadequate to meet tissue needs

81
Q

Congestive Heart Failure (CHF) caused by

A

Coronary atherosclerosis
Persistent high blood pressure
Multiple myocardial infarcts
Dilated cardiomyopathy (DCM)

82
Q

Age-Related Changes Affecting the Heart

A

Sclerosis and thickening of valve flaps
Decline in cardiac reserve
Fibrosis of cardiac muscle
Atherosclerosis

83
Q

systolic blood pressure

A

higher pressure measured during left ventricular systole when the aortic valve is open

84
Q

diastolic blood pressure

A

lower pressure measured during left ventricular diastole when the valve is closed

85
Q

normal blood pressure

A

about 120mm Hg systolic over 80 mmHg diastolic in healthy adult. females normally 10mmHg less `

Anatomy (29 decks)

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