Integrated cardiovascular function Flashcards
How is CO regulated?
Sympathetic activity to veins: increased venous compliance = increased CVP = increased venous return = increased CO; blood volume: increased CVP = increased venous return = increased CO; skeletal muscle pump: increased CVP = increased venous return = increased CO; inspiration movements: increased venous pressure = increased CO
How is total peripheral resistance (TPR) regulated?
Hematocrit; local controls; neural controls; hormonal controls
How does hematocrit affect TPR?
Increased hematocrit = increased blood viscosity = increased TPR; doesn’t normally change unless training in high altitude to increase oxygen carrying capacity
How do local controls increase TPR?
Vasoconstrictors increase peripheral resistance: internal blood pressure from myogenic response; Endothelin-1
How do local controls decrease TPR?
Vasodilators decrease peripheral resistance: decreased O2; increased K+; increased CO2; increased H+; increased osmolality; adenosine; eicosanoids; NO
How do neural controls increase TPR?
Increased sympathetic stimulation = vasoconstriction
How do neural controls decrease TPR?
Decreased sympathetic stimulation + neurons releasing NO = vasodilation
How do hormonal controls increase TPR?
Epi (on alpha adrenergic on tissues not directly involved in exercise) + angiotensin II + vasopressin = vasoconstriction
How do hormonal controls decrease TPR?
Epi (on beta-2 adrenergic on skeletal muscles) + atrial natriuretic peptide = vasodilation
What detects changes in blood pressure?
Baroreceptors in the carotid bodies and aortic arch
How do baroreceptors detect changes in blood pressure?
Are stretch-sensitive
How do baroreceptors normalise blood pressure?
Affect HR directly, and SV indirectly, to affect CO ad thus MAP
What is the control centre for CV?
Medulla oblongata; is connected to baroreceptors by vagus (to aortic) and glossopharangeal (to carotid) nerves
How does the medulla oblongata interpret impulses from baroreceptors?
Rate of impulses in afferent nerves related to pressure (increased impulses = increased MAP)
How does the medulla oblongata regulate MAP?
Increased MAP: decreased sympathetic to heart, arterioles, veins; increased parasympathetic to heart; = decreased HR + decreased SV = decreased CO = decrease MAP to normal
How does the CV system compensate for increased blood volume/pressure?
Vasodilation and decreased CO
How do the kidneys compensate for increased blood volume/pressure?
Excretion of fluid in urine to decrease blood volume
How do the kidneys compensate for decreased blood volume/pressure?
Baroreceptors in kidneys detect; increase secretion of renin; angiotensin II is released: aldosterone released by adrenal cortex ( = increased water absorption at kidneys) + vasoconstricts vessels
How does the CV system compensate for decreased blood volume/pressure?
Baroreceptors in carotid bodies and aortic arch detect; pituitary gland releases ADH: vasoconstriction + increased water absorption at kidneys; sympathetic output decreased: Epi released from adrenal medulla = vasoconstriction + increased HR
What occurs during the orthostatic baroreceptor reflex?
In tilt position w/ no muscular contraction in legs: HR increases to maintain CO as blood pressure decreases transiently; SV decreases w/ influence of sympathetic as blood pools in legs from gravity; TPR increased due to increased sympathetic stimulation; blood pressure has transient drop
What is the valsalva maneouvre?
Forced expiration with closed glottis
What are examples of when the valsalva maneouvre might occur?
When coughing, lifting heavy weights, and playing brass
What occurs during the valsalva maneouvre?
Intrathoracic pressure increases dramatically; heart mechanically squeezed; blood pressure increases; HR plummets to compensate for high blood pressure; blood pressure decreases again; HR peaks to increase CO. Release of pressure around heart mechanically releases heart; blood pressure decreases transiently
During exercise, where does blood flow increase?
Skeletal muscle, skin, heart
During exercise, where does blood flow decrease?
Kidneys, digestive tracts, all other parts of body not directly involved in exercise
During exercise, where does blood flow remain constant?
Brain, due to autoregulation and the fixed volume of the cranial cavity being unable to accommodate large increases in blood flow
During exercise, where does peripheral resistance decrease?
Muscle, heart, and skin
During exercise, where does peripheral resistance increase?
Everywhere that isn’t directly involved in PA
What is the net effect on TPR during exercise?
Decreased TPR (vasodilation > vasoconstriction)
How does CO differ between trained and untrained individuals?
CO greater in trained
How does HRmax differ between trained and untrained individuals?
Little difference - HRmax mainly determined by age; trained people have a lower HR for a given workload
How does SV differ between trained and untrained individuals?
SV greater in trained
