Vascular system and Special circulation

Question 1

What kind of pressure do arteries carry blood at?

Answer 1

Arteries carry blood at high pressure

Question 2

Why must arteries have an elastic component?

Answer 2

Gives them ability to recoil

Question 2

Why must arteries have an elastic component?

Answer 2

Gives them ability to recoil

Question 3

Why must arteries be thick walled?

Answer 3

thick smooth muscle allows the artery to withstand high systemic pressure

Question 4

What are the differences between arterioles and arteries?

Answer 4

Arterioles are smaller
With higher resistance
And better at controlling blood flow into capillaries

Question 5

What are some of the major properties of capillaries?

Answer 5

They have a flattened endothelial wall with high permeability and allows gases/ nutrients to be exchanged
They make up a large nextwork that connects arterioles to venules

Question 6

What are some of the major properties of veins?

Answer 6

Thin wall as venous blood flows at a low pressure
A lot of sympathetic innervation (sympathetic vasoconstriction)

during vasoconstriction they supply most of venous return

Question 7

What is one adaptation of the Circle of Willis

Answer 7

Allows perfusion of all brain parts even if one vessel is blocked

Question 8

What is the metabolic theory of blood flow?

Answer 8

Increase in BP leads to an increase in blood flow and metabolites such as CO2 that cause vasodilation
The increased blood flow washes these metabolites away
therefore as there are fewer vasodilators the blood flow does not increase

Question 9

What kind of vessels are especially sensitive to CO2?

Answer 9

Cerebral vessels

Question 10

What is the myogenic theory of blood flow?

Answer 10

Increasing blood pressure increases the stretch of the vascular smooth muscle, this causes reflex vasoconstrictio so blood flow does not increase

Question 11

What are some mediators that may cause vasodilation in cerebral blood flow?

Answer 11

K+/ Potassium
Nitrous oxide
Adenosine

Question 12

What stimulates the release of nitrous oxide?

Answer 12

Low pH or hypoxia

It is produced in the vascular endothelium

Question 13

Describe the CNS Ischaemic response

Answer 13

when MAP builds up during a haemorrage in the brain, hypoxia occurs
this causes metabolites to build up which stimulates the medullary cardiovascular centre
symapthetic activity then increases the BP

Question 14

What does a rise in ICP do to the vessels in the brain?

Answer 14

It compresses them

Question 15

What is the cushings reflex?

Answer 15

When the vessels in the brain are compressed the Ischaemic response occurs
This means that there will be vasoconstriction of the systemic vessels leading to an increase in blood pressure
Therefore CBF is maintained as increase in BP leads to an increase in Perfusion

Question 16

In terms of the vessels

How would you describe the coronary circulation?

Answer 16

Blood flows from the occluded to the non-occluded vessels

Question 17

What is the consequence of the LV contracting during systole

Answer 17

The contraction of the LV means that the coronary vessels become occluded, meaning that during this time there is actually no blood/oxygen flow to the ventricle

Question 18

What is the systolic pressure in the LV?

Answer 18

120 mmHg

Question 19

What percentage of oxygen does the heart take from its vessels?

Answer 19

The heart takes around 75% in comparison to other tissues which only take around 25%- this is because the heart only has a short exposure to oxygen

Question 20

What are some of the sources of oxygen of the heart?

Answer 20

glucose, fatty acids, amino acids, ketones

Question 21

What are the receptors for symapthetic coronary innervation?

Answer 21

alpha 1 and beta 1 adrenoreceptors

Question 22

What does an increase in cardiac work lead to?

In terms of metabolites

Answer 22

Increased metabolites which act as vasodilators

Question 23

What is the portal system responsible for?

Answer 23

For directing blood from parts of the GIT to the liver

Question 24

What occurs to the vessels of the GIT during sympathetic innervation?

Answer 24

vasoconstriction, as blood is diverted to the cardiac and skeletal muscle

Question 25

What are some examples of hypoxic damage that occurs to the liver during prolonged vasoconstriction?

Answer 25

microvilli are damaged in the GIT
Necrosis of hepatocytes in the liver
reduced GR in the liver