Chapter 20 - The Heart - The Cardiac Cycle Flashcards
What are the 2 phases of the cardiac cycle
systole
diastole
What is happening during diastole
When the heart muscles are RELAXED and fill with blood
What is happening during systole
a CONTRACTION pumps blood out of the heart
In which phase are the semilunar valves open?
systole
What is the FIRST STEP of the cardiac cycle
atrial systole
atrial contraction forces blood into the ventricles
What happens after atrial systole?
atrial diastole
(atria relax)
What happens after atrial diastol?
1st phase of ventricular systole
(ventricular contraction pushes the AV valves closed but does not create enough pressure to open the semilunar valves
what happens after the 1st phase of ventricular systole?
2nd phase of ventricular systole
(ventricular pressure rises and exceeds pressure in the arteries. SEMILUNAR VALVES OPEN AND BLOOD IS EJECTED)
What happens after the 2nd phase of ventricular systole?
ventricular diastole (early)
semilunar valves close and blood flows into the relaxed atria
what happens in ventricular diastole (late)
all chambers are relaxed and the ventricles fill passively
in which phase is blood from the atria ejected into the ventricles
when the atria contract (systole)
what is the “stroke volume” (SV)
the volume of blood ejected per beat (each ventricular ejects 70-80mL of blood)
what is the “end diastolic volume”
the maximum amount of blood that each ventricle will hold in this cycle
what does it mean when the ventricles are in “isovolumetric contraction”
the first phase of ventricular systole
ventricular pressures are not yet high enough to open the semilunar valves and force blood out, but tension and pressures are rising
ISOMETRIC CONTRACTIONS ARE OCCURRING
in ventricular ejection, what term can you use to describe their ejection
isotonic. the muscle cells shorten and tension production remains constant
What is the ESV?
END SYSTOLIC VOLUME
explain what end systolic volume means
the amount of blood remaining in a ventricle after the semilunar valve closes
when ventricular pressures fall below those of the atria, what happens?
the atrial pressures force the AV valves ope
what is “isovolumetric relaxation”
occurs during ventricular diastole
all the heart valves are closed. ventricular pressure drops rapidly over this period because of the elasticity of the connective tissues of the heart and cardiac skeleton helps “re expand” the ventricles to their resting dimensions
when the heart rate increases, all the phases of the cardiac cycle are,,,
shortened
what is the term for “listening to the heart”
auscultation
what is used to listen to heart sounds
a stethoscope
do the 2 ventricles eject equal volumes of blood?
yes
what does EDV stand for and what does it mean
end diastolic volume
the amount of blood in each ventricle at the end of ventricular diastole (the start of ventricular systole)
what does ESV stand for and what does it mean
end systolic volume
the amount of blood remaining in each ventricle at the end of ventricular systole
What does SV stand for and what does it mean
stroke volume
the amount of blood pumped out of each ventricle during a single beat
how can the stroke volume (SV) be calculated?
SV= EDV-ESV
what is the “ejection fraction”
the percentage of the EDV represented by the SV
what is the most important factor in an examination of a single cardiac cycle?
stroke volume
what does CO stand for and what does it mean
cardiac output
the amount of blood pumped by the left ventricle in one minute
CO=
SV * HR
NAME 2 FACTORS AFFECTING HEART RATE
autonomic innervation(parasympathetic decreases heart rate)
hormones (epinephrine, norepenephrine, thyroid hormone all increase heart rate)
name 2 factors affecting stroke volume
EDV ESV
What is the “autonomic headquarters” for cardiac control?
the cardiac centers of the medulla oblongata
acetylcholine ____ heart rate
decreases
acetylcholine is released by ___ neurons
parasympathetic
“filling time” is the duration of the……
ventricular diastole
what is the “venous return”
the amount of blood returning to the heart through the veins
what ADJUSTS the heart rate in response to the venous return
the atrial reflex
what ADJUSTS the heart rate in response to the venous return
the atrial reflex
what ADJUSTS the heart rate in response to the venous return
the atrial reflex
filling time depends entirely on…..
the heart rate
what is the preload?
the degree of stretching in ventricular muscle cells during ventriculr diastole
what is the “afterload”
the amount of tension that the contracting ventricle must produce to force open the semilunar valve to eject blood
the greater the EDV, the ____ the preload
larger
what is the term for the amount of force produced by a singular contraction?
contractility
what is the cardiac reserve?
the difference between resting and maximal output
