1: Cardiac Physiology and Neural Control

Question 1

Describe myogenic rhythm

Answer 1

Each myocyte depolarized at a set rate unless altered by the CNS, does not need neural input to fire

Question 2

With the SA node in control, what is typical HR?

Answer 2

60-100 bpm

Question 3

With the AV node in control, what is typical HR?

Answer 3

40-60 bpm

Question 4

With the Purkinje system in charge, what is typical HR?

Answer 4

20-40 bpm

Question 5

What mediates the strength and rate of heart innervation?

Answer 5

Instrinsic: ANS
Extrinsic: toxin, heart, etc

Question 6

What is a positive inotropic effect?

Answer 6

Increase strength of contraction

Question 7

What is a positive chronotropic effect?

Answer 7

Increase HR

Question 8

What effects does the sympathetic nervous system have on the heart?

Answer 8

Increase strength of contraction and HR

Question 9

What does the sympathetic nervous system have the most influence over in terms of cardiac function?

Answer 9

On the speed and response to exercise/maximum output

Question 10

What type of receptors allow there to be a sympathetic effect on the cardiovascular system?

Answer 10

Beta receptors

Question 11

Where do you find beta 1 receptors?

Answer 11

Cardiac and renal tissue

Question 12

Where do you find beta 2 receptors?

Answer 12

Smooth muscles of vascular beds

Question 13

Where do you find beta 3 receptors?

Answer 13

Adipocytes

Question 14

What is the role of the vagal nerve?

Answer 14

Keep HR lower at rest and to speed recovery after exercise

Question 15

What three effects does the parasympathetic nervous system have on the cardiac system?

Answer 15

1. Decrease strength of atrial contraction
2. Decrease HR
3. Slow conduction at AV node

Question 16

What receptors are responsible for parasympathetic control?

Answer 16

Alpha receptors

Question 17

Where are alpha 1 receptors found?

Answer 17

Smooth muscles

Question 18

Where are alpha 2 receptors found?

Answer 18

Adrenergic synapses to regulate release of norepinephrine

Question 19

What catecholamines are circulating and where are they produced?

Answer 19

Epinephrine and norepinephrine - produced in adrenal gland to increase strength of blood

Question 20

Describe free floating catecholamines

Answer 20

In blood stream waiting to bind to beta receptors to trigger sympathetic response. Will be replenished by sympathetic nervous system

Question 21

What are baroreceptors?

Answer 21

Stretch receptors in large arteries to induce vagal response and decrease pressure

Question 22

At what pressure are baroreceptors stimulated?

Answer 22

Arterial pressures of > 60 mmHg

Question 23

What happens once baroreceptors are stimulated?

Answer 23

Vasodilation or decreased HR, decreased strength of contraction

Question 24

What is the Starling effect?

Answer 24

Increased venous return causes increase strength of contraction

Question 25

What is the Anrep effect?

Answer 25

Increased aortic pressure causes increase strength of contraction

Question 26

What is the Bowdich effect?

Answer 26

Starling or Anrep causes increase in HR

Question 27

Describe the resting potential for myocardial cells

Answer 27

Slightly negative

Question 28

What two mechanisms assist with letting Na enter the cell?

Answer 28

1. Sodium-potassium pump
2. Sodium-calcium pump

Question 29

Describe the cells permeability to Na with depolarization?

Answer 29

Greater permeability

Question 30

Describe the cells permeability to Na with repolarization?

Answer 30

Less permeability

Question 31

What is the effect of high concentrations of Ca2+

Answer 31

Influences actin myosin attraction increasing the strength of the contraction and increase permeability of cell wall to Na