cardiovascular homestasis Flashcards
what is cardiac output
the volume of blood pumped out per ventricle
factors affecting heart rate
postitive chronotropic caffeine epinephrine negative chronotropic sedative beta blockers
what causes pressure changes
hypotension
hamorrhage
bainbridge reflex
when there is an increase in the blood volume HR increases
factors affecting stroke volume
preload
amount of the ventricles are stretched by the EDV
contractibility
ability of cardiac muscle to increase the strength of pumping
after load
force placed on the ventricle wall during ejection
precise stroke volume
end diastole vol -end systolic vol
preload
amount that the ventricles are stretched by the EDV
contractibility
ability of cardiac muscle to increase the strength of pumping
afterload
force placed on the ventricle wall during ejection
frank starling law
automatic reflex
volume of blood ejected by the ventricle depends on the volume present in the ventricle at the end of diastole
how does preload affect SV
increased venous return would increase SV
decreased venous return decreases SV
effects on blood volume
hypovolemic shock caused by:
blood loss
dehydration
what does the body do to compensate after hypovolemic shock
increases HR
vasoconstriction
Renin- angiotensin- aldosterone system
RAAS
renin released from the kidney
converts ANG to ANG
Angiotension converting enzyme to ANGII
ANGII is a vasoconstrictor (increases BP) and causes adrenal glands to release aldosterone (increases water reabsorption)
what inhibits angiotensin covertering enzyme
ACE inhibitors
what affects the strength of contraction
inotropic agents
increase in contractile strength
increase in sympathetic stimuli
thyroxin
Ca2+
decrease in contractile strength
increased extracellular K+
Ca2+ channel blockers
blood pressure
systolic force heart pumps diastolic resistance of blood vessels normal 90/60 to 120/80
what innervates the smooth muscle of blood vessels
sympathetic nerve fibres
from vasomotor centre
skeletal muscle pump
movement compresses intramuscular veins
pushes blood to heart
respiratory muscle pump
ventilation assist in venous return
during inspiration:
lower pressure, lower atrial pressure
promotes filling and increases preload
Diaphragm presses downwards - higher abdominal pressure
- squeezes vena cava, encourages movement towards thoracic cavity
explain muscle and respiratory pumps to exercise
increased venous return (pump from skeletal muscle)
increased SV
explain sympathetic stimuli to exercise
increased HR
increased contractibility
increased in SV and CO
explain chemoreceptor response to exercise
increases muscle respiration
decrease in pO2
increased lactic acid
decrease in pH
what happens to BP ect when lying supine
blood evenly distributed
increased central venous pressure
increased EDV
increased SV
explain syncope/fainting
temporary reduction in blood flow to the brain
what syncope due to decrease in HR and BP
vasovagal
what syncope occurs due to heart problems
cardiac syncope
what occurs when BP lowers upon standing up
orthostatic hypotension
