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20 Cards in this Set
- Front
- Back
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what are the main determinants of blood flow? (4)
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blood pressure = Q x TPR
heart suction - diastole - filling pressure drops in ventricles - systole - ventricular contraction pulls atria down, atria expand and increases VR breathing - causes a pumping action skeletal muscle pump - stimulates Frank-Starling Mechanism |
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Determinants of blood flow - Poiseuille's equation? (4)
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pressure - increase driving force
radius - flow varies to the 4th power of radius viscosity - depends on Hct siphon - pressure differences between two points, can overcome gravity |
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what are the main controls of tissue circulation?
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internal pressure of circulation - high at major arteries, low in capillary beds
arterioles and precapillary sphincters - act as valves no precapillary sphincters in muscle capillary beds - determined by terminal arterioles and sphincters in major arteries |
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how is the CVS regulated?
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Intrinsically - tissue metabolism
extrinsically - blood pressure |
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what is the neural control of the heart?
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sympathetic nerves increase heart rate and contractility and parasympathetic nerves do the opposite by innervating the SA and AV nodes
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neural control of the cardiovascular system?
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cerebral cortex contain cardiovascular control centre which receives information from peripheral afferents
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when is the hypothalamus particularly influential?
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during temperature challenges from environment or exercise
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how do baroreceptors work as a control mechanism?
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there are stretch receptors in the heart and major arteries
a BP set point is established and this is increased with exercise inhibit CVC pressor area - vasodilate muscle circulation |
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how do chemoreceptors work as a control mechanism?
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in aortic and carotid bodies
respond to decreased PO2, increased PCO2, decreased pH, also send impulses to pressor area of CVC |
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how do muscle afferents work as a control mechanism?
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respond to mechanical, thermal and chemical stimuli
send signal to CVC to increase BP by increase HR, cardiac contractility and vasoconstriction type III-activated by muscle contraction type IV to chemical stimuli |
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how do hormonal mechanisms work to control the CV and how is it affected by training?
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catecholamines enhance the effect of sympathetic stimulation
epinephrine and norepinephrine stimulates alpha adrenergic receptors - vasoconstriction epinephrine alone stimulates beta andrenergic receptors to induce vasodilation training reduces the catecholamine response to allow more BF to other tissues |
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what counteracts the catecholamine response?
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AcH and adenosine decrease HR and cardiac contractility to protect the heart
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what is the function of vasopressin?
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most potent vasoconstrictor to combat CV drift - drop in BP and increase HR during exercise
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how do Renin and angiotensin II react to a fall in blood pressure?
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renin is released from the kidney which leads to the production of angiontensin II, a potent vasoconstrictor
this causes the kidney to retain fluid and salt which increases blood volume it also causes aldosterone secretion which has the same effects |
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what is the skeletal BF determined by?
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need to balance BP and the muscle metabolic needs
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what are vasodilators (5)?
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adenosine, lowering of PO2, high PCO2, low pH and La
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what makes vascular smooth muscle relax (3)?
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NO, prostacyclin, EDHF
NO is most potent vasodilator - released by RBCs and promoted by catecholamines |
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what regulates Brain blood flow?
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Cerebral blood flow is stimulated by carbon dioxide and can increase by 25% during exercise
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what regulates coronary artery blood flow and how much does it increase during exercise?
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NO release by endothelial cells
no flow during systole, only during diastole increases from 260ml/min to 900ml/min during max exercise |
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what regulates skeletal muscle blood flow to isolated muscle and how much does it increase?
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heart limits blood flow to maintain cardiac output and isolated muscles can increase to 300ml/100g/min from 60-100ml/100g/min
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