CVS: Regulation of BP, Capillary Exchange Flashcards
(26 cards)
what determines the MAP
volume of blood in the arterial system
what determines the rate of bloof flow out of the arteries
peripheral resistance in the arterioles
T/F: Mean arterial pressure increases when blood flow into the arteries exceeds blood flow out
True
When inflow > outflow, pressure builds up in the arterial system
resistance to blodo flow is greatest in what blood vessels & why
greatest in arterioles & capillaries due to narrow diameter
what is total peripheral resistance (TPR)
the resistance to blood flow through the entire arteriole system
3 ways that MAP can be altered
MAP can be modulated by altering:
1. stroke volume
2. heart rate
3. total peripheral resistance
how does body detect changes in BP
- stretch sensitive baroreceptors in walls of carotid artery & aortic arch
- increase in BP cause walls of blood vessels to stretch
- baroreceptors more active in response
barorecptors activate sensory nerves that return to where
cardiovascular control centre in medulla oblongata
T/F: Flow through the circulatory system is inversely proportional to resistance.
True
→ According to Ohm’s Law (F ∝ 1/R), when resistance increases, flow decreases
what is resistance regulated by
degree of contraction of smooth muscle in arterioles
how does body counteract reduction to BP
increased sympathetic nerve activity will:
* increase cardiac output by increasing cardiac rate & stroke volume
* contract venous SM promoting venous return (more blood to heart )
* stimulates contraction of arterial SM, increases peripheral resistance
* vasoconstriction of kidney arterioles minimises urine (prevents further decrease in pressure by retaining body fluid)
affect vagus nerve has on heart
vagus nerve slows down heart
how does body counteract elevation of BP
Stimulation of vagus nerve activity will:
* reduce cardiac output by slowing heart rate
Inhibition of sympathetic nerve activity will:
* reduce cardiac output by slowing heart rate & stroke volume
* relaxation of arterial SM to decrease peripheral resistance
kidneys stimulated to produce more urine, reducing total blood volume
T/F: A decrease in arterial stretch increases baroreceptor firing to lower blood pressure.
False
→ Decreased stretch reduces baroreceptor firing, which increases sympathetic tone to raise blood pressure
T/F: During high blood pressure, reduced sympathetic output leads to vasodilation and decreased resistance.
True
→ This helps lower MAP by allowing greater blood flow out of the arteries
T/F: Arterial smooth muscle relaxes when sympathetic activity increases.
False
→ Sympathetic stimulation contracts arterial smooth muscle, leading to vasoconstriction, not relaxation
T/F: Blood pressure is unaffected by changes in total blood volume.
False
→ An increase in blood volume raises pressure, and a decrease lowers it. Volume and pressure are closely linked
T/F: Reduced salt and water reabsorption by the kidneys leads to a decrease in blood volume.
True
→ Less reabsorption means more urine output, lowering blood volume and reducing pressure
T/F: The heart muscle becomes weaker in hypertension due to reduced workload.
.
False
→ The heart must work harder, especially the ventricles, which can lead to hypertrophy and failure, not reduced workload
T/F: Hydrostatic pressure is higher at the venous end of a capillary than at the arterial end.
False
→ Hydrostatic pressure is highest at the arterial end (about 38 mmHg) and drops to ~16 mmHg at the venous end
what side of the capillaries does net filtration occur at
net filtration occurs at the arterial side due to the higher BP (closer to heart)
what side of the capillaries does net reabsorption occur at
venous end
due to decreased blood pressure, driven by colloid osmotic pressure
T/F: Reabsorption of interstitial fluid back into capillaries is driven by the fall in hydrostatic pressure and sustained colloid osmotic pressure at the venous end.
True
→ At the venous end, lower hydrostatic pressure and constant colloid osmotic pressure promote net reabsorption
T/F: The net direction of fluid movement across a capillary wall is determined by the balance between hydrostatic and colloid osmotic pressures.
True
→ These opposing forces are known as Starling forces, and they dictate whether fluid is filtered or absorbed
