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BIO 232 Anatomy OIT > Lecture Quiz 7 > Flashcards

Lecture Quiz 7 Flashcards

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1
Q

What is autorhythmicity?

A

the ability to spontaneously generate an action potential

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2
Q

Describe the resting potentials in pacemaker cells

A

unstable
aka pacemaker potentials
initiate action potentials in the heart

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3
Q

Where are the pacemaker cells located?

A

sinoatrial node
atrioventricular node
right and left bundle branches - bundle of His
purkinje fibers aka subendocardial conducting network

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4
Q

What happens during the resting potential phase in pacemaker cells?

A

phase 4
unstable
slow leakage of Na+ ions causes the depolarization of the membrane at the end of the resting state

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5
Q

What happens during the depolarization phase in pacemaker cells?

A

phase 0

occurs due to the calcium influx (not sodium)

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6
Q

What do pacemaker potentials lack in comparison to cardiomyocytes?

A

early depolarization and plateau phases

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7
Q

What happens during the repolarization phase in pacemaker cells?

A

phase 3

occurs when K channels open allowing K+ to leave the cell

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8
Q

What are the rhythms at the SA node and what is the rate of conduction?

A

60-100 per minute

0.5 m/s

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9
Q

What are the rhythms at the AV node and what is the rate of conduction?

A

40-60 per minute

0.05 m/sec

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10
Q

What are the rhythms at the bundle branches and purkinje fibers and what is the rate of conduction?

A

20-40 per minute
bundles - 2 m/sec
purkinje - 4 m/s

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11
Q

What is the ultimate pacemaker in the heart and why?

A

SA node has the highest or fastest rhythm, therefore it sets the rate of contraction for the entire heart

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12
Q

How many impulses are generated on average?

A

SA node

70 impulses/min

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13
Q

Describe the pathway of an impulse in the heart

A

SA -> AV node
AV node delays impulse for 0.1 second
impulse passes to ventricles via bundle of His
AV bundle splits into two pathways in the interventriculur septum (bundle branches)
bundle branches carry impulse towards apex of heart
Purkinje fivers carry impulse to ventricular wall

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14
Q

Give an overview of the extrinsic innervation of the heart

A

heart is stimulated by the sympathetic cardio acceleratory center
heart is inhibited by the parasympathetic cardioinhibitory center

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15
Q

What does thryoid hormone do in the heart?

A

increases sensitivity of the heart to epinephrine

sympathetic stimulation

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16
Q

What does the P wave represent in an EKG?

A

depolarization of the SA node and atrial depolarization, followed by contraction

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17
Q

What does the QRS complex represent in an EKG?

A

ventricular depolarization followed by ventricular contraction

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18
Q

What does the T wave represent in an EKG?

A

ventricular repolarization followed by ventricular relaxation

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19
Q

What is the normal range for heartrate?

A

60-100 bpm

lower or higher and you are in bradycardia or tachycardia respectively

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20
Q

What does the cardiac cycle refer to?

A

All events associated with blood flow through the heart

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21
Q

What is systole?

A

contraction of heart muscle

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22
Q

What is diastole?

A

relaxation of heart muscle

23
Q

How do conduction and contraction differ?

A

conduction of AP is an electrical event

contraction of the myocardium is a mechanical event

24
Q

What parts of the heart contract at what time?

A

both atria and ventricles contract at the same time

25
Q

How does blood move?

A

down the pressure gradient

from higher pressure to lower pressure

26
Q

What controls the valves?

A

pressure changes make the valves open and close

27
Q

What generates heart noise?

A

closure of valves

28
Q

Describe what happens when the heart makes sound?

A

first sound - AV valves close, beginning systole

second sound - semilunar valves close, end of systole and start of diastole

29
Q

What can be said about the cardiac systole regards to the ventricles?

A

cardiac systole includes isovolumetric contraction and cardiac ejection
it occurs between heart sounds 1 and 2

30
Q

What can be said about cardiac diastole in regards to the ventricles?

A

cardiac diastole includes isovolumetric relaxation, ventricular filling, and atrial systole
occurs between heart sounds 2 and 1

31
Q

What happens during ventricular filling in the left ventricle?

A

ventricular pressure drops below atrial pressure
mitral valve opens
blood flows from atrium into ventricle, filling it
blood pressure in the heart is low
blood enters the atria and flows into ventricles

32
Q

What happens during atrial systole?

A

SA node fires
impulse spreads through the atrium, causing its depolarization (P wave)
atrium contracts last bit of blood into ventricle
impulse spreads to AV node

33
Q

What happens during isovolumetric contraction?

A

impulse spreads to the ventricle causing its depolatization (QRS complex)
ventricles contract, causing pressure in the chamber to rise
mitral valves close (heart sound 1)
pressure in aorta higher so aortic valve remains closed
no blood flow in or out

34
Q

What happens during cardiac ejection?

A

pressure in the ventricle rises
when it exceeds aortic pressure, aortic valve opens
blood is ejected from the heart
ventricular contraction is isotonic
ventricular muscle repolarizes (T wave) and begins to relax
pressure in ventricle slowly declines

35
Q

What happens during isovolumetric relaxation?

A

pressure in the ventricle drops below aortic pressure
aortic valve closes (heart sound 2)
all valves are closed
relaxation continues and the ventricle pressure drops rapidly

36
Q

What is cardiac output?

A

the amount of blood pumped by each ventricle in one minute

37
Q

How is cardiac output measured?

A

ejected volume of blood/minute

heart rate * stroke volume

38
Q

What is normal cardiac input and what could it increase to?

A

5 L/min

can increase to 30 L/min with exercise

39
Q

What are two factors that affect cardiac output?

A

heart rate and stroke volume

40
Q

What is heart rate?

A

the number of heart beats per minute

41
Q

What determines heart rate?

A

the rate of spontaneous depolarization at the sinoatrial node

42
Q

How is the heart controlled through the parasympathetic system?

A

vagus nerve acts on muscarinic receptors to slow the heart

negative chronotrpic effect

43
Q

How is the heart controlled through the sympathetic system?

A

cardiac sympathetic fibers stimulate beta-adrenergic receptors and increases heart rate
positive chronotropic effect

44
Q

What is stroke volume?

A

the amount of blood pumped out by a ventricle with each beat

determined by contractility, preload, and afterload

45
Q

What is contractility?

A

the force of the ventricular contraction

depends on the preload

46
Q

How does sympathetic stimulation affect contractility? Parasympathetic?

A

sympathetic stimulation increases the contractility of the myocardium (positive inotropic effect)
parasympathetic has the opposite effect

47
Q

What is the preload?

A

the ventricular volume at the end of diastole

48
Q

What is preload mainly dependent on?

A

the return of venous blood from the body

49
Q

What can influence venous return in preload?

A

changes in position
intra-thoracic pressure
total blood volume and muscle tone in the venous wall

50
Q

What is Sterling’s law of the heart?

A

the force of the ventricular contraction is proportional to the stretching of the fibers during diastole
an increased preload results in an increased stroke volume

51
Q

What is the afterload?

A

the resistance to ventricular ejection

52
Q

What causes the afterload and what is that known as?

A

resistance to flow in the systemic circulation

systemic vascular resistance

53
Q

What determines the resistance in the afterload?

A

the diameter of the arterioles and pre-capillary sphincters

the narrower they are, the higher the resistance

54
Q

What controls the level of systemic vascular resistance?

A

the sympathetic system

in turn, controls the tone of the muscle in the wall of the arterioles and hence the diameter

BIO 232 Anatomy OIT (10 decks)

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