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
how does cocaine influence heart rate
inhibits reuptake of norepinephrine
more opportunities for it to bind
increase in heart rate
how does increased parasympathetic activity influence heart rate
parasympathetic outflow is sent from cardiac inhibitory center to SA and AV node using vagus nerve
parasympathetic axons release acetylcholine onto muscarinic receptors on SA and AV node
ACh binds and opens the potassium channels
potassium flows out of cell making it more negative
takes conducting cell longer to reach threshold
lowers heart rate
how do beta-blocker drugs influence heart rate
interfere with EPI and NE binding to beta receptors
used to treat high blood pressure
how do autonomic reflexes influence heart rate
baroreceptors, chemoreceptors, and proprioceptors send signals to cardiovascular control center in medulla oblongata
how does the atrial reflex influence heart rate
aka bainbridge reflex
stops heart from overfilling
increases heart rate if baroreceptors detect too much stretch
what are the three factors that influence stroke volume
venous return, inotropic agents, and afterload
how does venous return affect stroke volume
directly related to stroke volume
determines preload
define venous return
volume of blood returned to the heart
define preload
pressure stretching the heart wall before shortening
what is the frank-sterling law
as EDV increase, SV increase
more blood in ventricle, more stretch, more overlap of thick and thin filaments, more forceful contraction, more SV
what causes venous return rate to decrease
low blood volume
high heart rate
how do inotropic agents influence stroke volume
alter contractility
positive: more calcium, higher contractility, increase in stroke volume
negative: less calcium, lower contractility, decrease in stroke volume
how does afterload influence stroke volume
afterload and stroke volume are inversely related
can be caused by atherosclerosis
define afterload
resistance in arteries to eject blood in ventricles
