Cardiovascular regulation Flashcards
What is cardiodynamics?
movements and forces generated during cardiac contraction
What is EDV?
End diastolic volume - amount of blood in each ventricle at the end of ventricular distole
What is ESV?
End systolic volume - amount of blood remaining in each ventricle at end of ventricular systole
What is SV?
Stroke volume - amount of blood pump out of each ventricle during a single heart beat
What is Ejaction fraction?
Percentage of EDV represented by SV
What is preload of HR?
degree of stretching in ventricle muscles during diastole, proportional to EDV greater preload larger EDV
What is afterload of HR?
Amount of tension that the contracting ventricle must produce to force open SV and eject blood
What factors affect stroke volume?
Autonomic innervation
hormones
EDV
ESV
How does preload influence EDV?
Increase energy of myocyte contraction
degree of stretch on myocyte
venous return and filling time infleunce
What factors effect ESV?
Preload (force produced for contraction)
Contractibility of ventricle
Afterload
What is contractility?
Amount of force produced during contraction at preload.
increase contractility = positive inotropic agents
Decrease contractility - negative inotropic agents
What positive inotropic agents are there?
Neurotransmitters
b-adrenergic agonists
What negative inotropic agents are there?
ACh Ca channel blockers (verapamil) muscarinic agonist anoxia acidosis
What is afterload?
Tenstion the contracting ventricle produce to eject blood
pressures are 80mm and 20mm for SV
if afterload increases preload is constant Stroke volume decrease more blood remain
Afterload increase as narrow arteries and hypertension
What does the cardiac centre in medulla?
Cardioaccelaratory centre increase HR via sympathetic
Cardioinhibitory slows heart
both cardiac centres monitor changes in BP o2 and PH
What is the atrial reflex?
adjustments in HR in response to increase in venous return
Homeostatis mechanisms in CV centre ensure efficient blood flow for ?
appropiate Tissue perfusion
Tissue perfusion influenced by?
CO
BP
PR
Tissue perfusion mechanisms are?
Autoregulation
Neural mechanisms
Endocrine response
What does localised vasoconstriction and vasodilation of blood flow where?
Precapillary spincter muscles
What are local vasodilators?
low O2 Lactic acid NO low PH Histamine agents Increase temp
What are local vasoconstrictors?
Thromboxanes (released by platelet)
Endothelins (damaged endothelial cells)
When are endocrine factors activated?
autoregulation of BF fails to normalise conditions
What is the Vasomotive centre?
2 populations of cells in medulla associate lots with vasoconstriction and small with vasodilation
What does control of vasoconstriction include?
neurons innervate peripheral blood vessles in tissues are adrenergic
Release NA stimulates a1 adrenoreceptors in PM of SMC
What controls vasodilation?
neurons in skeletal muscle in brain relax smc in arterioles
Mainly cholinergic ACH triggers NO
Nitroxidergic release NO
Where are baroreceptors located?
In carotid sinus, aortic sinus and wall of right atrium
Where are aortic and carotid baroreceptors?
Aortic in ascending aorta monitor stretch and BF
Carotid monitor BP in carotid arteries blood supply
Increase in BP detected by baroreceptors regulate what?
Inhibition of cardio-accelaratory centre
Inhibition of vasomotor cells with vasoconstriction
What is atrial reflex/bainbridge?
regulatory feedback to increase HR
What are chemoreceptors sensitive to?
Changes in blood oxygen, CO2 and PH
What long term hormonal mechanisms to control BP?
ADH
Angiotensin II
EPO
ANP/BNP
What does ADH do?
posterior lobe of pituitary
increase peripheral constriction
due to low blood volume
what converts angiotension I to angiotensin II?
By ACE
What are 4 important functions of angiotensin II?
Stimulates secretion of adrenal aldosterone
Stimulates secretion of ADH
Stimulates thirst
Stimulates CO and vasoconstriction
What does EPO do?
Causes vasoconstriction in Blood vessels, produces RBC improve O2
What does natriuetic peptides do?
Released from atrial myocytes for excessive strethcing act on kidney increase urine production
