CVPR Week 2: Cardiac Muscle Physiology II

Question 1

Question

Answer 1

Question 2

Extrinsic regulation of vascular resistance

Answer 2

• Neural / Hormonal control

Question 3

Intrinsic regulation of vascular resistance

Answer 3

Regulation by local factors and mechanisms inherent to cells of the vascular wall

Question 4

Regulation of vascular resistance

Answer 4

Question 5

Question

Answer 5

Question 6

Extrinsic regulation of Cardiac output

Answer 6

• Neural/Hormonal control

Question 7

Intrinsic regulation of Cardiac output

Answer 7

Starling’s Law of the heart

Question 8

Objectives

Answer 8

Question 9

How is Heart Rate determined?

Answer 9

HR is determined by pacemaker activity

• Principle control of HR is by the ANS (extrinsic)

Question 10

How is stroke volume determined?

Answer 10

Both intrinsic (Starling’s Law) and extrinsic (ANS) mechanisms regulate SV

Question 11

Question

Answer 11

Sympathetic β1 receptors by Norepinephrine to speed up

Sympathetic α1 receptors vascular constriction

M2 by acetylcholine to inhibit adenylate cyclase???

Question 12

Sympathetic pathway and parasympathetic pathways

Answer 12

Question 13

What phase of an action potential and what type of action potential is important in determining HR?

Answer 13

Phase 4 of slow-response action potentials in the SA node

Question 14

How HR is increased?

Answer 14

Ne increases the slope of SA nodal pacemaker potentials to quicken the ‘pace’ resulting in a decreased interval between action potentials thus increasing HR

Question 15

How HR is decreased?

Answer 15

ACh decreases the slope of the pacemaker potential by hyperpolarizing the SA nodal cells

Question 16

Identify the effect on HR

Answer 16

Question 17

Identify the effect on HR

Answer 17

Question 18

β1 receptor signal transduction mechanism

Answer 18

• NE stimulation of β1 receptor
• Gs-coupled activating Adenylate cyclase creating cAMP and activating PKA

Leads to

1. leads to greater Ca²⁺ influx
2. greater CICR from the SR
3. greater contraction
4. PKa can phosphorylate Ryanodine receptors and can increase sensitivity to Ca²⁺ so leads to more CICR and therefore greater contraction

Question 19

Cardiac Muscarininic receptor signal transduction mechanisms

Answer 19

Question 20

Autonomic tone predominating normal resting individuals

Answer 20

Question 21

During sympathetic stimulation, not only is contractility increased but cardiac myocytes are receiving action potentials more frequently, so how do cardiomyocytes quickly relax

Answer 21

• PKA phosphorylates PL (Phospho Lambda), which regulates (inhibitory) SERCA pump Ca²⁺ pump and when phosphorylated by PKA, PL disinhibits SERCA.
• so PKA inhibits PLs inhibition of SERCA
• ACh would have the opposite effect

Question 22

Parasympathetic effect on contractility

Answer 22

can influence atrial contractility but not really in the ventricles

Question 23

Effects of NE and ACh on SV

Answer 23

Question 24

Effects of NE on ventricular myocyte contractility

Answer 24

Question 25

Effects of ACh on ventricular myocyte contractility

Answer 25

Question 26

Signal transduction mechanisms associated with β1 receptor and muscarinic receptor stimulation

Answer 26

Question 27

Summary of autonomic control of the heart: HR regulation

Answer 27

Question 28

Summary of autonomic control of the heart: Contractility regulation

Answer 28

Question 29

Starling's Law of the Heart description

Answer 29

Question 30

Starling's Law of the Heart diagram

Answer 30

* ventricular pressure is a function of ventricular end-diastolic volume * when the volume is really high starling's law no longer applies and force of contraction is reduced

Question 31

Thick and thin filament overlap

Answer 31

Question 32

Starling's Law of the Heart: Mechanism

Answer 32

Question 33

Longer fiber lengths ________ spacing between thick and thin filaments.

Answer 33

reduces

Question 34

Starlings law explanation

Answer 34

greater end diastolic volume stretching the heart = greater stroke volume

Question 35

Longer fiber lengths increase the affinity of?

Answer 35

Troponin C for Ca²⁺

Question 36

Starling Curves altered by stimuli

Answer 36

Question 37

Starling's Law of the heart: Physiological significance

Answer 37

Question 38

Starling's Law of the heart: Physiological significance diagram

Answer 38

sympathetic venous pressure get increased venous return get increased end-diastolic volume get an increased stroke volume

Question 39

What mechanisms lead to increased CO?

Answer 39

* ↑ sympathetic activity to the heart increases HR and contractility * ↑ sympathetic to venous indirectly increase venous constriction and venous return increasing end-diastolic volume (α1 receptors) and thereby increasing cardiac output by starlings law * parasympathetic is the opposite effect on HR and contractility

Question 40

Myocardial response to afterload stress

Answer 40

like lifting a heavyweight, increased BP or afterload impairs myocardial performance contraction velocity and cardiac output

Question 41

What is afterload stress?

Answer 41

the load that cardiac muscle must overcome in order to shorten

Question 42

Afterload is?

Answer 42

Aortic pressure (MABP)

Question 43

Myocardial responses to afterload stress results in?

Answer 43

↑ Arterial pressure and decreased myocardial performance

Question 44

Question

Answer 44

Question 45

Effects of increasing HR on CO

Answer 45

Question 46

Decreased SV associated with high HR (tachycardia) can limit?

Answer 46

CO

Question 47

Decreased SV associated with high HR (tachycardia) can limit? Then what happens with exercise?

Answer 47

so the increased sympathetic tone and venous return helps to mitigate this

Question 48

Summary of intrinsic mechanisms of cardiac regulation

Answer 48

Question 49

Summary of physiologic regulation of myocardial performance

Answer 49

Question 50

Question

Answer 50

Question 51

Question

Answer 51

Question 52

Question

Answer 52

Question 53

chronotropic effects means

Answer 53

time effects in this case HR

Question 54

Cardiac Function Curve AKA

Answer 54

Starling curve

Question 55

typical systole time

Answer 55

300 msec

Question 56

Typical diastole time

Answer 56

500 msec

Question 57

Cardiac cycle typical time

Answer 57

800 msec

Question 58

an increase in HR takes time from?

Answer 58

diastole which will decrease cardiac output

Question 59

Atrial pacing increase reduces

Answer 59

stroke volume

Question 60

Cardiac output to atrial pacing

Answer 60

Question 61

Tachycardia can _______ filling time and thereby can reduce _________ and \_\_\_\_\_\_\_\_\_.

Answer 61

* stroke volume * limit cardiac output

Question 62

What is the principal control mechanism of HR?

Answer 62

Autonomic nervous system (extrinsic)