Regulation of CVS 10

Question 1

Stoke Volume Equation:

Answer 1

SV = End-diastolic volume - end-sytolic volume

Question 2

Cardian Output equation:

Answer 2

CO = HR x SV

Question 3

Mean systemic arterial pressure equation:

Answer 3

Mean BP = CO x TPR

Question 4

What are the two parts of the CVS?

Answer 4

Systemic and pulmonary

Question 5

What is venous volume distribution affected by?

Answer 5

• peripheral venous tone
• gravity
• skeletal muscle pump
• breathing

Question 6

What mainly controls flow comtrol?

Answer 6

Arterioles

Constriction of arterioles =

• blood flow to the organs they serve
• mean arterial blood flow
• pattern of distribution if blood to organs

Number of adrenoreceptos will affect the blood flow to an organ

Question 7

How is flow altered?

Answer 7

Affecting vessel radius

Question 8

Methods of regulating flow:

Answer 8

• local mechanisms ( intrinsic to smooth muscle or close to it)
• hormonal
• autonomic nervous system

Question 9

What is autoregulation?

Answer 9

The intrinsic capacity to compensate for perfusion pressure by changing vascular resistance

Question 10

What are the two theories for autoregulation?

Answer 10

Myogenic: smooth muscle fibres respond to stretch so as pressure rises, contraction occurs to kepp flow the same

Metabolic: IF flow to a bed decreases, more metabolites are produced which cause vasodilation and increased flow which in turn washes away the produced metabolites

Question 11

What endothelial substances regulate blood flow?

Answer 11

Endothelin 1
Nitric Oxide
Thromboxane A2
Prostacyclin

Question 12

Which hormones affect systemic circulation blood flow?

Answer 12

Kinins and ANP (vasodilators)

Vasopressin, A2 and noradrenaline (vasoconstrictors)

Question 13

Generalisation of ANS:

Answer 13

Sympathetic controls flow

Parasympathetic controls heart rate

Question 14

Which vessels do sympathetic fibres not innervate?

Answer 14

Capillaries. Distribution of innervated vessels is not equal. More supply kidney, gut, spleen and skin than skeletal muscle and the brain

Question 15

What does circulating noradrenaline preferably bind to?

Answer 15

Alpha-1-adrenoreceptors for smooth muscle contraction and vasoconstriction

Question 16

What does circulating adrenaline preferably bind to?

Answer 16

Beta-2-adrenoreceptors to cause vasodilation to some organs

Question 17

Where is the vasomotor centre located?

Answer 17

Bilaterally in the reticular substance of the medulla and lower third of the pons

Question 18

What does the VMC comprise of?

Answer 18

• Vasoconstrictor area
• Vasodilator area
• Cardioregulatory Inhibitory area

Question 19

What do lateral portions of the VMC control?

Answer 19

Heart rate and contractility

Question 20

What do medial portions of the VMC control?

Answer 20

Signals to Vagus nerves to the decrease heart rate

Question 21

How can cardiac force of contraction be increased?

Answer 21

Starlings Law

Question 22

Describe cascade post noradrenaline binding to beta-1-adrenoreceptors:

Answer 22

Activated Adenylate cylase which converts ATP to cAMP. This activate PKA which phosphorylates L-type Calcium channels/ SR release channels and SERCA increasing intracellular Ca2+ concentration. This increases contraction of heart

Question 23

How can stroke volume be increased?

Answer 23

Increased plasma adrenaline

Increased sympathetic activity

Question 24

Where do baroreceptors feedback to?

Answer 24

VMC via glossopharyngeal nerve if carotid sinus

via vagus if aortic arch

Question 25

When is baroreceptors most sensitive?

Answer 25

90-100mmHg

Question 26

What does increased baroreceptor firing lead to?

Answer 26

Increased parasympathetic activity and decrease in sympathetic