Cardiovascular regulation

Question 1

Whats the role of the cardiovascular centre

Answer 1

• Maintain a stable MAP
• Ensure adequate blood flow to vital organs – especially the brain

Question 2

What happens when the baroreceptor reflex is triggered

Answer 2

1. Mean arterial pressure increases above normal level
2. Baroreceptors are stimulated & send more impulses to the medulla along afferent nerves
3. The medulla decreases the frequency of sympathetic impulses to the SAN of the heart
4. Fewer vasomotor impulses are sent to blood vessels, allowing for vasodilation
5. A decrease in CO₂ and resistance to flow decreases mean arterial pressure back to its normal level

Question 3

Describe baroreceptors

Answer 3

• Nerve endings in arteries in the carotid sinus and aortic arch
• Buffering of blood pressure
• Detect the stretch of the arterial wall as it indicates increasing pressure

Question 4

What is orthostasis

Answer 4

A decrease in systolic BP of 20 mmHg or in diastolic BP of 10 mmHg within 3 minutes of standing

Question 5

Whats orthostasis caused by and why does it occur

Answer 5

• Caused by gravity affecting distribution of venous blood
• Body requires more blood
• Decrease in cardiac filling pressure
• SV decreases by 30-40%
• The individual feints

Question 6

How to baroreceptors respond to preserve cerebral perfusion

Answer 6

• Baroreceptors are stimulated less
• Fewer impulses are sent to the medulla along afferent nerves
• Medulla increases frequency of sympathetic impulses to the SAN
• HR increases, limiting CO₂ fall
• Mean arterial pressure increases by 10-15 mmHg

Question 7

Whats the primary role of atrial and pulmonary stretch receptors

Answer 7

Regulate blood volume – determines CO₂

Question 8

What effect does venous blood pressure falling have on atrial and pulmonary stretch receptors

Answer 8

• Atrial pressure decreases
• Cardiopulmonary stretch receptors are less stimulated

Question 9

What does the decrease in venous blood pressure cause

Answer 9

• Release of ADH from hypothalamus
• Constriction of afferent renal arterioles
• Fluid loss is reduced
• ADH stimulates vasoconstriction in splanchnic circulation
• Mean arterial pressure is restored to normal levels

Question 10

What effect do chemoreceptors have on:
- Breathing
- Tidal volume
- CO₂
- TPR

Answer 10

• Stimulation causes respiratory centre to increase rate and depth of breathing
• Increase in tidal volume initiates lung inflation reflex – increases HR and vasodilation
• Increase in CO₂ and TPR, and therefore mean arterial pressure

Question 11

Adrenaline:
What does the release occur after?
How is CO₂ increased?

Answer 11

• Release occurs after stimulation of sympathetic preganglionic fibres
• Adrenaline increases CO₂ by an increase in HR and SV

Question 11

Whats the hormonal regulation of blood pressure

Answer 11

Many hormones exert an influence on arterial blood pressure

Question 12

Describe the effect of noradrenaline

Answer 12

• Causes vasoconstriction, raising TPR
• Raises mean atrial pressure

Question 13

Describe what the Renin-angiotensin-aldosterone system is, including the end goal

Answer 13

• Stimulated by a fall in blood volume or renal blood flow
• Detected by juxtaglomerular cells in the kidney
  The end result is:
  1. Vasoconstriction, raising TPR
  2. Increased Na+ reabsorption, raising blood volume, CO₂ and mean arterial pressure

Question 14

How does ADH effect mean arterial pressure

Answer 14

Raises mean arterial pressure

Question 15

How does ANP effect mean arterial pressure

Answer 15

Reduces mean arterial pressure

Question 16

How does nitric oxide effect mean arterial pressure

Answer 16

Little effect on mean arterial pressure