CVS Physiology Flashcards
What is the normal range of arterial blood pressure?
85-100mmhg
What are the anatomical locations of the arterial baroreceptors and what are their afferent fibres?
Carotid baroreceptors are found in the carotid sinuses at the birfurcation of the common carotid arteries (C4).
Aortic baroreceptors are found in the aortic arch.
The afferent nerve for the carotid baroreceptors is the glossopharangeal nerve (IX) and for the aortic baroreceptors it is the vagus nerve (X)
What is postural hypotension?
Postural hypertension is a drop in blood pressure due to a change in body position. This typically happens when moving from a supine position to a standing position. It is most common in older people.
What class of drugs is most likely to cause postural hypotension and why?
Alpha 1 receptor antagonists as they stop the effects of the sympathetic NS and cause peripheral vasodilation. This prevents the baroreceptor reflex from working so when the blood pressure falls when standing up then this cannot be corrected for.
What are the main effects of alpha 1 adrenoceptors and what agonist effects them most?
Mainly acted on by Noradrenaline
Causes contraction of smooth muscle (intestinal sphincters), peripheral and abdominal viscera vasoconstriction
What are the main effects of alpha 2 adrenoceptors and what agonist effects them most?
Mainly acted on by Adrenaline
Causes mixed effects on smooth muscle, inhibits release of noradrenaline and platelet activation.
What are the main effects of beta 1 adrenoceptors and what agonist effects them most?
Mainly acted on by adrenaline
Causes positive chronotropic (Increases HR) and inotropic (enhancing contractility) effects.
Increased renin secretion from juxtaglomerular cells of the kidney.
What are the main effects of beta 2 adrenoceptors and what agonist effects them most?
Mainly acted on by adrenaline
Causes smooth muscle relaxation (E.g. Bronchodilation), vasodilation of vessels to muscles etc.
What are the main effects of beta 3 adrenoceptors and what agonist effects them most?
Mainly acted on by noradrenaline
Causes enhancement of lipolysis in adipose tissue.
How do Sympathomimetics work and what are their side effects?
They are stimulant compounds that mimic the effects of agonists on the sympathetic nervous system. They have the side effects of causing cardiac arrhythmias and can also cause pharmacological tolerance reulting in greater concentrations of the drug being required in order to produce the same effects.
Why would sympathomimetics not be appropriate for treating poisoning or septicaemia?
For poisoning they would reduce blood flow to the liver and kidneys through vasoconstriction. this would reduce the bodies ability to detoxify and excrete the poisons through use of these organs.
For septicaemia the bacteria in the blood would cause inflammation due to inflammatory mediator release for mast cells. This would require very large doses of sympathomimetics to overcome this vasodilation and cause the vessels to constrict.
Why does the use of beta blockers increase the patients susceptibility to lidocaine toxicity?
They cause reduce cardiac output through blocking adrenoreceptors in cardiac tissue. this results in reduced blood flow to the liver and kidneys which reduces the metabolism and excretion of lidocaine.
