Coordinated responses of the CVS Flashcards
(17 cards)
What happens on standing up (orthostasis)?
- Blood pressure falls - postural hypotension
- Quick recovery - homestatic reflex
Baroreflex
Why is it difficult for blood to reach lower body
Flows from area of low concentration to high
95mmHg to 180mmHg
What is bernoulli’s law?
Blood flow = pressure energy + potential energy + kinetic energy
What creates high pressure in venous system at the feet?
hydrostatic pressure
What can make postural hypotension worse?
alpha adrenergic blockade or other drugs like calcium channel blockers
varicose veins - impede venous return
Lack of skeletal muscle activity
Reduced blood volume
Increased core temperature
What is microgravity
gravity in space
What happens to blood distribution under microgravity?
Fluid shift towards head / heart
Blood does pool in lower body (as it does under normal gravity)
What happens to blood volume under microgravity
Blood volume decreases by about 20%
Heart size decreases
stress on heart decreases
What happens after a return to gravity
Postural hypotension
Two types of exercise?
Dynamic and static
Anticipation of exercise causes change in the brain
Affects sympathetic activity and vagus inhibition
What changes does exercise cause ?
Increased lung oxygen uptake
Control of bp (bp rises slightly initially)
Co-ordinated dilation/constriction of vascular beds (targets areas where oxygen is delivered)
By how much can oxygen uptake by pulmonary circulation increase ?
10 -15 times
How can this increase in O2 be brought about?
Increase in heart rate
Increase in stroke volume
Increase in arteriovenous O2 difference
What happens to blood pressure in static exercise?
Increase to provide blood to stationary muscles
How does the CVS direct the increased O2 supply to muscle?
Lower vascular resistance
metabolic vasodilation
How is BP stabilised during dynamic exercise?
Vasoconstriction in non-exercising and non required tissues
