16 - Responses to CVS Stress

Question 1

NOTE: when measuring BP, it is always taken at the same horizontal level as the heart

Answer 1

this is because there is different BP at different areas of the body and in different positions

Question 2

Why is standing a problem when measuring BP?

How does this change when lying down?

Answer 2

gravity has an effect

when lying down, the effect of gravity is the same across the body

Question 3

Why is the pressure in the arteries above the heart lower than the pressure in the heart?

Answer 3

the blood above the heart experiences a greater force from gravity so would be forced back into the heart

Question 4

Is there greater pressure higher up or lower down in the body?

Answer 4

lower down

Question 5

How does gravity impact the the blood in individual types of blood vessels?

Answer 5

• arteries - little impact
  the thick musculature in arteries maintains the BP
• veins - causes venous distension
  less muscular
  blood in the veins lower down tries to return to the heart, but has to against the force of gravity
  the veins then stretch and blood pools in the veins in the lower legs
  this results in less blood in the arterial system and lower BP

Question 6

What are the actions of aldesterone and vasopressin in the kidney?

Answer 6

both act on the collecting duct

• aldesterone stimulates sodium reabsorption
• vasopressin stimulates water retention

Question 7

What are the control mechanisms that change when you exercise?

Answer 7

• SNS leads to constriction of blood vessels to counteract the fall in TPR (due to vasodilation of blood vessels to the heart, lungs and skeletal muscle)
• profound vasoconstriction in the abdominal regions
• decrease sympathetic response to the skin - vasodilation to allow radiation of heat from the skin
• NOTE: there is an overall decrease in TPR
• CO increases because of the increase in sympathetic activity and decreased parasympathetic activity, which increase SV and HR
• when you exercise, the skeletal muscle is in use, so it squeezes the veins and forces blood up the body (this increases venous return and therefore stroke volume)