Lecture 2

Question 1

What are the 3 types of cardiac muscle within the heart?

Answer 1

Atrial, ventricular, and specialized excitatory and conductive

Question 2

What are some characteristics of cardiac muscle?

Answer 2

• involuntary
• found only in heart
• striated
• self stimulating
• acts as a syncytium
• under nervous, endocrine, and other chemical control

Question 3

What are characteristics of skeletal muscle?

Answer 3

• voluntary
• most skeletal fibers extend entire length of the muscle and striated
• not self stimulating
• have motor units
• contract/relax rapidly
• under nervous system control

Question 4

What are characteristics of smooth muscle?

Answer 4

• involuntary
• contraction is prolonged tonic contraction (may last hours or day)
• has slow cycling of the myosin cross bridges that cause prolonged contraction
• located in nurtures, blood vessels, intestines
• low energy requirement to sustain contraction
• maximum force of contraction is often great than in skeletal muscle

Question 5

What are components of cardiac output?

Answer 5

CO(L/min)=HR(beats/min)xSV (L)

heart rate x stroke volume

Question 6

What is normal resting cardiac output?

Answer 6

4-8 L/min

Question 7

What are the normal parameters for HR and SV to determine normal CO?

Answer 7

HR: 70 b/m
SV: 71 mL/b

Question 8

What is normal HR at rest?

Answer 8

-60-100 bpm

Question 9

What does normal HR indicate?

Answer 9

• healthy myocardial cells

- healthy SA node

Question 10

What is the significance of chronotropic effects?

Answer 10

they are mechanisms that alter cardiac rate

Question 11

What are examples of positive chronotropic effect and effect on HR?

Answer 11

• epinephrine (adrenal)
• norepinephrine (sympathetic)
• increases HR

Question 12

What are examples of negative chronotropic effect and effect on HR?

Answer 12

• achetylcholine (vagus)
• parasympathetic
• decreases HR

Question 13

What are the effects of the sympathetic NS on cardiovascular system?

Answer 13

• increases HR
• vasodialtes coronary aa to increase blood flow to the heart
• increases myocardial contraction

Question 14

What are the effects of the parasympathetic NS on cardiovascular system?

Answer 14

• decreases HR
• vasoconstricts coronary aa
• depresses myocardial contraction

Question 15

What effect does aerobic exercise have on HR?

Answer 15

-increase in HR with increase intensity due to a decrease in the vagus nerve inhibition and increase sympathetic nervous system stimulation

Question 16

What happens to HR in a well trained athlete?

Answer 16

low resting HR may be due to enhanced parasympathetic input to the heart

Question 17

What effect does β-blockers have on HR and why?

Answer 17

• have a blunted HR response during exercise

- β receptors on the myocardial wall are unable to respond to sympathetic stimulation which causes HR to increase

Question 18

how should you monitor someone during exercise if they are on β-blockers?

Answer 18

Borg RPE scale

Question 19

how is stroke volume regulated?

Answer 19

• preload (sometimes referred to as end diastolic volume)
• contractility
• afterload

Question 20

What is EDV?

Answer 20

the max blood in the ventricles immediately prior to contraction

Question 21

What equals what in a normal healthy heart?

Answer 21

EDV=SV

Question 22

what does EDV=SV mean?

Answer 22

That the volume of blood that enters the ventricles completely leaves with the contraction of the heart.

Question 23

what is preload in a normal healthy heart?

Answer 23

the amount of stretch on the myocardial wall prior to contraction

Question 24

What is the Frank-Starling Mechanism?

Answer 24

an intrinsic property of heart muscle to increase SV based on the pre contractile myocardial cell length

Question 25

what happens in a non healthy heart in terms of preload/EDV?

Answer 25

the heart does not react to the stretch and the pt might have to take digitalis in order to increase the contraction of the heart

Question 26

normally the force of the contraction _____ as the blood volume ______ in a healthy heart?

Answer 26

increases, increases

Question 27

what happens in a diseased heart with force of contraction and what is the result?

Answer 27

- don't get increase force of contraction with diseased heart - you get backup of blood either in lungs of RV

Question 28

what is related to EDV in terms of contractibility?

Answer 28

the intrinsic control of contraction strength

Question 29

what does extrinsic control of contraction depend on?

Answer 29

on the activity of the sypathooadrenal system

Question 30

what produces a positive ionotropic effect?

Answer 30

Epinephrine from the adrenal and norepi from the sympathetic nerve ending which causes an increase in myocardial contractility which causes an increase in HR

Question 31

what happens when there is a reduction of sympathetic stimulation?

Answer 31

reduces HR and reduces myocardial contractility

Question 32

what is MVo2?

Answer 32

- myocardial oxygen consumption | - the amount of oxygen the myocardium is using

Question 33

how is MVo2 calculated?

Answer 33

-by rate pressure product (RPP)

Question 34

how is rate pressure produce (RPP) calculated?

Answer 34

HRx systolic BP=RPP

Question 35

what will increase MVo2?

Answer 35

any increase in HR or BP will increase MVo2

Question 36

Normal there is a linear relationship between MVo2 and what?

Answer 36

Coronary blood flow (CBF) | -not the case in diseased heart states

Question 37

what does myocardial oxygen supply depend on?

Answer 37

- delivery of oxygenated blood through coronary aa - the oxygen carrying capacity of arterial blood - the ability of the myocardial cells to extract oxygen from the atrial blood

Question 38

What are factors that influence a positive inotropic effect?

Answer 38

- increase sympathetic tone - increase in endogenous catecholamine - digitalis - sympathetic amine - increase HR - glucagon - angiotensin - aldactone - corticosteriords - hyperthyroidism - serotonin

Question 39

What are factors that influence a negative inotropic effect?

Answer 39

- β-blockers - calcium antagonist - barbiturates - acidosis - hypoxia - general anestesia - antiarrhythmic agents - heart failure - decrease function ventricular muscle mass - decrease myocardial o2 supply demand - circulating myocardial depressant factors

Question 40

What is after load?

Answer 40

pressure against which the ventricle must work in order to eject blood=pressure resisting the ejection of blood during systole

Question 41

If you have an increase in after load what is stroke volume?

Answer 41

decreased

Question 42

what causes an increase in after load?

Answer 42

systemic HTN or aortic valve stenosis

Question 43

If you have a decrease in after load what is stroke volume?

Answer 43

increased

Question 44

what causes a decrease in after load?

Answer 44

during aerobic exercise or vasodilators (beta-blocks)

Question 45

What is ejection fraction? (EF)

Answer 45

% of ventricular filling that is ejected with each heart beat (EF=SV/EDV)

Question 46

what is normal EF?

Answer 46

60-70%

Question 47

what is EF widely used as?

Answer 47

an index of contractility

Question 48

what is end systolic volume (ESV)?

Answer 48

- the amount of blood that remains in the heart following contraction - there must be a volume of blood that remains in the heart to maintain a certain degree of stretch within the muscle fibers of the myocardial cells

Question 49

what can then EF be as low as in pt's with heart failure?

Answer 49

40% which is really low

Question 50

What is ventricular compliance?

Answer 50

ease to which the ventricle descends when filled with blood?

Question 51

what happens if you have decreased compliance?

Answer 51

- caused by ventricles stiffer (LV hypertrophy) | - a given volume of filling will result in higher end diastolic pressure

Question 52

what happens if you have increased compliance?

Answer 52

- caused by LV dilation | - a given volume will effect a lower end diastolic pressure