Vascular system and Special circulation Flashcards
What kind of pressure do arteries carry blood at?
Arteries carry blood at high pressure
Why must arteries have an elastic component?
Gives them ability to recoil
Why must arteries have an elastic component?
Gives them ability to recoil
Why must arteries be thick walled?
thick smooth muscle allows the artery to withstand high systemic pressure
What are the differences between arterioles and arteries?
Arterioles are smaller
With higher resistance
And better at controlling blood flow into capillaries
What are some of the major properties of capillaries?
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
What are some of the major properties of veins?
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
What is one adaptation of the Circle of Willis
Allows perfusion of all brain parts even if one vessel is blocked
What is the metabolic theory of blood flow?
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
What kind of vessels are especially sensitive to CO2?
Cerebral vessels
What is the myogenic theory of blood flow?
Increasing blood pressure increases the stretch of the vascular smooth muscle, this causes reflex vasoconstrictio so blood flow does not increase
What are some mediators that may cause vasodilation in cerebral blood flow?
K+/ Potassium
Nitrous oxide
Adenosine
What stimulates the release of nitrous oxide?
Low pH or hypoxia
It is produced in the vascular endothelium
Describe the CNS Ischaemic response
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
What does a rise in ICP do to the vessels in the brain?
It compresses them
What is the cushings reflex?
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
In terms of the vessels
How would you describe the coronary circulation?
Blood flows from the occluded to the non-occluded vessels
What is the consequence of the LV contracting during systole
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
What is the systolic pressure in the LV?
120 mmHg
What percentage of oxygen does the heart take from its vessels?
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
What are some of the sources of oxygen of the heart?
glucose, fatty acids, amino acids, ketones
What are the receptors for symapthetic coronary innervation?
alpha 1 and beta 1 adrenoreceptors
What does an increase in cardiac work lead to?
In terms of metabolites
Increased metabolites which act as vasodilators
What is the portal system responsible for?
For directing blood from parts of the GIT to the liver
