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How much blood does the heart pump? L/min
How long does it take for all the blood to be pumped through?
one minute
a thin layer of endothelium in the heart
muscle layer (cardiac muscle)
thin external layer covering the heart
Sinoatrial node
SA node or pacemaker;located within the posterior wall of the right atrium; rhythmic impulses originate in the SA node and spread through the atria
Atrioventricular node
AV node; located within the lower right interatrial septum; an impulse is delayed there for about 1/10 of a second to allow the atria to contract before ventricular contraction
Atrioventricular bundle
AV bundle or bundle of HIS; originiates in the AV node, dividing into two bundle branches which extend down the two sides of the interventricualr septum
Purkinje fibers
originate from the right and left branches, extending to the papillary muscles and lateral walls of the ventricles
Factors that may alter the heartbeat rate
sympathetic and parasympathetic impulses, hormones, body temp., exercise, and emotions
the phase of contraction
the phase of relaxation
4 steps of cardiac cycle
1)mid-diastole 2)Atrial systole 3)Ventricular systole 4)Early diastole
the atria and ventricles are relaxed, the tricuspid and mitral valves are open, and the aortic and pulmonary valves are closed. Blood flows passively from the atria into the ventricles, with 65% to 85% of ventricular filling occurring before the end of t
atrial systole
atria contract ad pump the additional 20-30% of the blood into the ventricles. As the atria contract, the vena cava and pulmonary veins narrow; there is some regurgitation. There is about 135 ml of blood in each ventricle.
ventricular systole
pressure changes and the AV valves close ¬タワlub¬タン. All 4 valves are closed (isovolumetric ventricular contraction phase). When the pressure on the right exceeds 10 mm Hg and the left exceeds 80 mm Hg the pulmonary and aortic valves open.
Isovolumetric ventricular contraction phase
the moment when all 4 valves are closed and no blood can enter or leave the ventricles.
Minimum diastolic pressure on both sides
10mm Hg and 80 mm Hg
Normal resting condition pressure
24 mm Hg and 120 mm Hg
Stroke volume
volume of blood ejected from either ventricle; 70 to 80 ml
End-systolic volume
Amount of blood remaining in either ventricle at the end of systole; 50 ml
Early diastole
as the ventricles relax, pressure drops; the pulmonary and aortic valves close, preventing backflow ¬タワdub¬タン. The tricuspid and mutral valves open, and blod flows from the atria into the ventricles
the mercury manometer to take blood pressure
Auscultatory method
method to take blood pressure using atrial sounds
Sounds of Korotkoff
the turbulent flow of the blood with each beat creates vibrations that are heard in the stethoscope when taking blood pressure using the auscultatory method
Pulse pressure
the difference between the systolic and diastolic pressures; this pressure difference is what drives blood along the arteries to the capillaries.
SA node rate
72-75 beats/min
AV node rate
50-60 beats/min
ventricles rate
30-40 beats/min
factors that increase heart rate
excitement, anger, pain, hypoxia, exercise, epinephrine, norepinephrine, thyroid hormones, fever, inspiration
less than 60 beats/min
more than 100 beats/min
factors that decrease heart rate
expiration, fear, grief
strength of contraction
franks starling's law of the heart
the greater the filling during diastole, the greater the force of contractin during systole
epinephrine and norepinephrin
caffeine, theophylline
drug used for cardiac failure
factors that have a positive inotropic effect
frank starling, catecholamines, xanthines, digitalis
rate of contraction
rate of conduction of impulse
two ways nerves contrals the heart
chronotropic and inotropic
sympathetic control of heart
increase rate and force of contraction, uses norepinephrine to increase permeability to Na and Ca
max sympathetic stimulation
250 beats/min
parasympathetic control of heart
decrease rate and force of contraction, S.A node-right vagus, A.V. node- left vagus, uses acetylcholine to increase permeability to K+
max parasympathetic stimulation
20-30 beats/min
stroke volume
60-80 ml; amount of blood pumped out of each ventricle per beat
cardiac output
CO= stroke volume X heart rate
caradiac output of average person
5.76 Liters/minute
factors causing an increase in cardiac output
axiety, eating, exercies, increased body temperture, pregnancy
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