Controlling vascular diameter Flashcards
We can control vascular diameter to control resistance extrinsically and intrinsically. What are two extrinsic controls of diameter? Give examples of each of these
Nervous control:
- sympathetic nerves
- NO from postganglionic nerves
Hormonal control
- adrenaline, angiotensin II, vasopressin
- adrenaline, ANP
What is a neural control that can we use to cause vasoconstriction of vasculature?
sympathetic nerves
What is a neuronal control that we use to cause vasodilation of vasculature?
NO
Describe the process of sympathetic stimulation on the vasculature. What is the effect of this?
This is to cause vasoconstriction
- the sympathetic nervous system releases noradrenaline which binds to the α1-adrenergic receptors which causes vasodilation and increased resistance
Is there a greater proportion of α1-adrenergic receptors in the brain or skin and why?
there is a greater number in the skin because we can restrict blood flow to the skin but we can’t really change blood flow to the brain
Describe the process of NO stimulation on the vasculature. What is the effect of this?
This is to cause vasodilation.
Postganglionic autonomic nerves release NO which relaxes smooth muscle cells and causes vasodilation, decreased resistance and increased blood flow
What are three hormones that are examples of extrinsic vasoconstrictors
Adrenaline, vasopressin, angiotensin II
What are two hormones that we can use to extrinsically vasodilate?
adrenaline, ANP
How can adrenaline cause both vasoconstriction and vasodilation?
Blood vessels have both α1-adrenergic receptors and β2-adrenergic receptors. If adrenaline binds to the α1-adrenergic receptors, it causes vasoconstriction but if it binds to the β2-adrenergic receptors, it causes vasodilation
As well as causing vasoconstriction, what is the effect of vasopressin/ADH?
it increases h2o reabsorption to increase CO
As well as causing vasocontriction, what is the effect of angiotensin II?
it stimulates Na+ reabsorption to increase CO
As well as causing vasodilation, what does ANP do?
it decreases h2o reabsorption which decreases CO
Flow auto-regulation does what?
it acts to control blood flow to maintain flow despite changes in perfusion pressure
How does flow regulation help is there is an increase in pressure?
Flow autoregulation means that the smooth muscles will be stretched due to an increase in pressure and this stimulates the to contract, causing vasoconstriction (this is going to decrease flow again)
How does flow regulation help if there is a decrease in pressure?
If there is a decrease in pressure, flow will decrease so there will be vasodilation to reduce resistance to increase flow again
