PSC1002/L08 Blood Pressure

Question 1

What is required to drive blood pressure?

Answer 1

A pressure gradient within each circulation

Question 2

Define mean arterial blood pressure (MABP).

Answer 2

Product of the input to the arterial system and resistance to flow

Question 3

How is cardiac output calculated?

Answer 3

CO = SV x HR

Question 4

Define total peripheral resistance (TPR).

Answer 4

Sum of individual vessels resistance to flow

Question 5

How is mean arterial blood pressure calculated?

Answer 5

MABP = CO x TPR

Question 6

What is a typical stroke volume and cardiac output?

Answer 6

SV = 70ml
CO = 4.9L/min

Question 7

Describe how parasympathetic nerves affect the heart. (3)

Answer 7

ACh release
Activated muscarinic ACh receptors
Decreased heart rate

Question 8

Describe how sympathetic nerves affect the heart. (3)

Answer 8

NA release
Activated B1-adrenergic receptors
Increased heart rate and contractility

Question 9

Describe why sympathetic stimulation increases HR. (3)

Answer 9

Steeper ‘slope’ of pacemaker potential
RMP is less negative
Threshold is reached quicker

Question 10

Describe why parasympathetic stimulation decreases HR. (3)

Answer 10

Less steep ‘slope’
More negative RMP
Longer to reach threshold

Question 11

What occurs as a directly result of muscarinic receptor activation?

Answer 11

Opening out K+ channels (out of cell)

Question 12

What is a term for changes in heart rate?

Answer 12

Chronotropic effects

Question 13

What are the 2 basic mechanisms for regulation of stroke volume?

Answer 13

Intrinsic
Extrinsic

Question 14

What is another name for the intrinsic mechanism of stroke volume regulation?

Answer 14

Frank-Starling Mechanism

Question 15

Describe Starling’s Law of the heart.

Answer 15

The force of contraction is proportional to the initial (just before contraction) muscle fibre length in diastole

Question 16

What is a result of increased venous return to the heart? (2)

Answer 16

Stretching of muscle fibres
Directly affects subsequent force of contraction

Question 17

Describe the basis for Starling’s Law. (2)

Answer 17

Increased stretch increased sensitivity of contractile proteins to Ca2+
Intracellular [Ca2+] required to generate 50% maximal tension is lower than when muscle fibre is not stretched

Question 18

Give 2 reasons why Starling effects are important.

Answer 18

Helps in matching output of right and left sides of the heart
Enables heart to adapt to changes in pumping capacity when either venous return or arterial blood pressure changes

Question 19

Describe extrinsic effects on the heart. (6)

Answer 19

Increase in sympathetic activity
Enhances contractility of cardiac muscle
NA/Ad
Binding to B1-adrenergic receptors
Results in enhanced stroke volume
Smaller ESV at end of contraction

Question 20

Give another term for extrinsic effects on the heart.

Answer 20

Inotropic effects (contractility)

Question 21

How does NA affect the ventricular function curve?

Answer 21

Causes an upward shift

Question 22

How do catecholamines increase contractility? (2)

Answer 22

Through cAMP second messenger system
Increased [Ca2+] (trigger calcium)

Question 23

What is the role of phosphoLAMBA? (2)

Answer 23

Phosphorylated by pKA
Regulates activity of Calcium ATPase in SR (negative regulator)

Question 24

What is venous return maintained by? (4)

Answer 24

Venous to atrial pressure differences
Venous valves
Venomotor tone
Respiration

Question 25

What is venomotor tone?

Answer 25

Some veins have smooth muscle and receive sympathetic supply