L10 Special Circulation

Question 1

Main ways blood flow is regulated

Answer 1

via auto regulation

• myogenic
• remodelling + angio

Question 2

explain myogenic regulation

Answer 2

o Pressure Stretches Smooth Muscle
o Vascular smooth muscle contracts in response to stretch
o Resistance increases
• Local metabolites also involved

Question 3

why does cerebral blood flow need to be regualted

Answer 3

o Cap pressure in brain inc > liquid leaks > swelling of brain > // needs to be able to reduce blood flow

Question 4

average parameters of cerebral blood flow and consequences if deviates

Answer 4

o Below 60 mmHg brain is ischemic and CIR starts

o Above 160 mmHg cerebral oedema occurs (frank starling)

Question 5

why is there little response of symp on cerebral blood flow

Answer 5

cant cross blood brain barrier)

Question 6

3 ways to skin blood flow with change in temp

Answer 6

1. Skin blood vessels dilate/constrict when warm/cold
2. Peripheral detect= activate reflex control of sympathetic fibres via hypothalamus
3. Core detect= Hypothalamus measures controls sympathetic nerves to skin.

Question 7

explain sweating when above 37

Answer 7

cholinergetic symp activate sweat glands

• release bradykinin (dilator)
• blood flow = inc

Question 8

inc in skin temp //= two actions

Answer 8

direct (local dilation)

reflex (core + peripheral receptors)

Question 9

explain heat exhaustion

Answer 9

• Sweating reduces blood volume and increases skin blood flow by vasodilation.
• Fall in TPR and BV reduces MAP
• Fall in BP stopped by baroreceptor reflex but cardiovascular system stressed.
• Heat exhaustion cardiovascular system unable to supply blood to both working muscle and skin.

Question 10

explain heat stroke

Answer 10

• Heat stroke unable to cool body core temperature rises until death.

Question 11

What is brain and heart dominated by in regualtion

Answer 11

brain= auto
heart= local metabolites