chapter 19 electrocardiogram, pressure/flow, cardiac cycle

the circulatory system: heart

P wave

represents atrial systole

PQ segment

represents time required for signals to pass SA node to AV node

QRS complex

represents ventricular repolarization

ST segment

represents ventricular systole

T wave

represents ventricular repolarization and relaxation

cardiac cycle

one complete contraction and relaxation of all 4 heart chambers

first heart sound (S1)

closure of AV valves (lubb)

Second heart sound (S2)

closure of semilunar valves (dubb)

cardiac cycle

1) Ventricular filling (diastole)

2) Isovolumetric contraction (systole)

3) Ventricular ejection (systole)

4) Isovolumetric relaxation (diastole)

ventricular filling phases

1) Rapid ventricular filling

2) Diastasis

3) Atrial systole

stroke volume

amount of blood ejected (70 mL at rest)

end-systolic volume

amount of blood left in heart

congestive heart failure

failure of a ventricle to eject blood effectively

cardiac output (CO)

amount ejected by each ventricle in 1 minute

normal (4-6 L)

cardiac output equation

heart rate X stroke volume = mL

pulse

surge of pressure produced by heart beat

felt by palpating superficial artery (radial or carotid)

tachycardia

resting adult HR above 100 bpm

bradycardia

resting adult HR below 60 bpm

sympathetic nervous system

cardioacceleratory center

parasympathetic nervous system

cardioinhibitory center stimulates vagus nerves

baroreceptors

signal cardiac center

pressure up/down, heart rate down/up

chemoreceptors

changes in blood pH, CO2, O2