Integration of cardiovascular mechanisms Flashcards
Resistance to blood flow
direct proportions/inverse proportions etc
Directly proportional to blood viscosity
Directly proportional to length of blood vessel
Inversely proportional to radius of blood vessel ^4
Vasomotor tone
Caused by a tonic discharge of sympathetic nerves (continuous release of noradrenaline) which causes VSM to be partially constricted at rest.
Extrinsic control of VSM
Involves nerves and hormones
Extrinsic control of VSM: NERVES
VSM are supplied by sympathetic nerves.
Neurotransmitter: noradrenaline acting on alpha receptors
Extrinsic control of VSM: HORMONES
Adrenaline:
- acting on alpha receptrors (mainly in skin, gut, kidney); vasoconstriction
- acting on beta receptors (mainly in cardiac and skeletal muscle arterioles); vasodilation
Angiotensin II (from RAAS): - causes vasoconstriction
ADH:
- causes vasoconstriction
Intrinsic control of VSM
Can over-ride extrinsic control mechanisms.
Matches blood flow of tissues to their metabolic needs.
Includes local chemical and physical factors.
Intrinsic control of VSM: CHEMICALS
Metabolites
Humoral agents
- Released in response to tissue injury or inflammation
Intrinsic control of VSM: PHYSICAL FACTORS
Cold - causes vasoconstriction
Warmth - causes vasodilation
Endothelium
Inner lining of blood vessels, important in maintenance of vascular health.
Damage causes: Increased BP, increased cholesterol, diabetes etc.
Factors which increase venous return
Increased blood volume
Increased venomotor tone
Increased skeletal muscle pump
Increased resp pump
Acute CVS response to exercise
Exercise
Increased sympathetic activity - Increased HR, SV, CO.
= Increased SBP
Increased blood flow - Vasodilation in skeletal & cardiac muscle
= Decreased DBP
Post exercise hypotensive response
Chronic CVS response to exercise
Regular aerobic exercise Decreased BP Decreased sympathetic tone Increased parasympathetic tone to heart Increase in vasodilators Decrease in vasoconstrictors
