regulation of the cardiovascular system 2 Flashcards
what is the term for persistent high pressure
hypertension
what is the term for persistent low pressure
hypotension
is there still pressure in the arteries when it is in diastole
There is still a residual pressure in the arteries when the left ventricle is filling during diastole
Systolic arterial pressure (SAP)
○ This is when the pressure of the arterial is at its greatest
○ This occurs when the left ventricle is ejecting blood during systole
where does pressure decreases the most at
arterioles due to their radius
hence arteriolar radius controls the total peripheral pressure
equation to calculate mean arterial pressure
mean arterial pressure = cardiac output x total peripheral pressure
short term regulation of blood pressure
baroreceptor regulation
- autonomic nervous system
long term regulation of blood pressure
- Control of fluid volume
○ ADH (hormone) (aka vasopressin)
- Renin-angiotensin-aldosterone system
where are the baroreceptors located at
- aortic arch
- carotid anus
baroreceptors are nerve fibre endings
what happens when blood pressure increases
- the firing rate of the baroreceptor nerve fibres increases
- goes to brain stem in the medulla oblongata
- increased vagal output, - decreasing heart rate
- decreasing sympathetic output
- decreasing heart rate
- decreasing contractility
- decreasing TPR (arteriolar tone) (e.g. vasodilation) - lowers blood pressure
how often do baroreceptors reset
- Baroreceptor reflex is very fast acting
- Changes occurs in seconds, providing blood pressure buffering
When pressure is altered for many minutes, the baroreceptors will reset and think of it as the new normal pressure
RASS system process (what happens when there is low blood pressure)
Process:
- When we have low blood pressure, the renal perfusion will reduce
- This will trigger sympathetic stimulation, causing the release of renin
- Renin acts to convert angiotensinogen into angiotensin I
- Enzyme ACE will then convert angiotensin I into angiotensin II
- angiotensin II:
a. Some of it will be broken down into inactive state
b. Some will act on arterioles and venules which causes vasoconstriction, hence increasing the TPR
c. Some will act on the posterior pituitary gland to release ADH (vasopressin)
d. Some will act on adrenal cortex to release aldosterone - Aldosterone and ADH then acts on the kidney to retain sodium and water, hence increasing plasma volume
Increasing circulating volume -> increases preload -> increases cardiac output (starling’s law) -> mean arterial pressure increase
where is ADH released from
posterior pituitary glands
where is aldosterone released from
adrenal cortex
what is the quicker regulation in the RASS system
(constriction)
what is the slower regulation in the RASS system
(hormonal control of aldosterone and ADH)
what is another long term volume control mechanism
volume receptors
how does volume receptors work when there is an increase in blood volume
When atrial volume receptors are stimulated, two process occurs:
1. Inhibition of sympathetic system a. Reduce vasoconstriction pathways to kidneys leading to diuresis i. This causes reduce in blood volume, reduce in central venous pressure, reduce in stroke volume, reduce in cardiac output, reduce in arterial pressure 2. Inhibition of ADH secretion from posterior pituitary gland This causes reduce in blood volume, reduce in central venous pressure, reduce in stroke volume, reduce in cardiac output, reduce in arterial pressure
what is one volume receptor and what is it
atrial receptor - low pressure stretch receptors
