The Cardiovascular System 3 Flashcards
is systole contraction or relaxation
contraction
is diastole contraction or relaxation
relaxation
is pressure higher during systole or diastole
systole (contraction)
what is happening during diastole
all four chambers are relaxed
blood is flowing into the atria then ventricles
what is happening during atrial diastole
atria relax, their pressure is low
AV valves start off closed
as atria fill, ventricle pressure becomes lower than atrial pressure
AV valves open allowing blood to flow passively into ventricles (80% of what’s in the ventricles)
what is happening during atrial systole
atria depolarize because of SA node
atria contract, their pressure gets higher
blood is forced from atria into ventricles (20-30% of what’s in the ventricles)
what is happening during ventricular diastole
ventricles are relaxed, their pressure is low
ventricles being filled passively
AV valves open once ventricular pressure is below atrial pressure
what is happening during ventricular systole
ventricles contract, their pressure rises
AV valves close
semilunar valves open when ventricular pressure gets above arterial pressure
blood is ejected from ventricles into pulmonary and systemic circulation
define end-diastolic volume (EDV)
volume of blood in each ventricle at end of ventricular diastole (relaxation)
aka: how much blood fills the ventricle before it contracts
what is happening during the isovolumetric ventricular contraction phase
ventricles begin to contract after depolarization
AV valves close
ventricular pressure is still less than arterial pressure so semilunar valves are still closed
all valves are closed
blood volume doesn’t change
what is happening during the ventricular ejection phase
semilunar valves open
ventricles continue to contract and push blood out the trunks
define stroke volume (SV)
amount of blood ejected by ventricles
define end systolic volume (ESV) and give its equation
amount of blood remaining in ventricle after contraction
ESV = EDV - SV
what is happening during the isovolumetric ventricular relaxation phase
ventricles relax and their pressure drops
semi-lunar valves close
AV valves still closed
all valves closed, no movement of blood
what happens if ejected blood volumes between both ventricles are not equal
edema or swelling
define cardiac output (CO) and give its equation
amount of blood pumped by a single ventricle in one minute
liters/min
CO = HR x SV
define cardiac reserve
difference between cardiac output during exercise and at rest
ex. athletes have higher cardiac reserves
define chronotropic agents
substances that change heart rate by altering the activity of SA and/or AV nodal cells
what does a positive chronotropic agent do
increase heart rate
what does a negative chronotropic agent do
decrease heart rate
explain how sympathetic nerve stimulation influences heart rate
sympathetic nerves release norepinephrine onto heart
at the time same, sympathetic simulation causes Arenal gland to release epinephrine and NE
epinephrine and norepinephrine bind to beta-one adrenergic receptors on the AV and SA node
bind activates G-coupled protein pathway ultimately causing phosphorylated calcium channels to enhance calcium influx so the cell fires sooner
increases heart rate
how does thyroid hormone influence heart rate
increases amount of beta-one adrenergic receptors
more binding, more firing
increase in heart rate
how does caffeine influence heart rate
inhibits breakdown of cAMP
more activated protein kinase, more phosphorylation
increase in heart rate
how does nicotine influence heart rate
increases release of norepinephrine
more stimulus, more firing
increase in heart rate
