3. The Heart3. The Heart

large musclelarge muscle size of your clenched size of your clenched

fistfist hollow with 4 chambershollow with 4 chambersCardiac Cycle:Cardiac Cycle: contracts – blood contracts – blood

rushes outrushes out relaxes – rushes inrelaxes – rushes in 0.8 s0.8 s

Parts of the HeartParts of the Heart

Atria (Atrium, sing.)Atria (Atrium, sing.) upper chambers, left & rightupper chambers, left & right smaller & thin walledsmaller & thin walled take in deoxygenated blood from body (lf take in deoxygenated blood from body (lf

atria) or oxygenated blood from lungs (rt)atria) or oxygenated blood from lungs (rt)VentriclesVentricles lower chamberslower chambers thick walls, muscularthick walls, muscular pumps oxygenated blood out of heart to pumps oxygenated blood out of heart to

body (rt) or deox. blood to lungs (lf)body (rt) or deox. blood to lungs (lf)

Blood FlowBlood Flow one way onlyone way only into R atrium from into R atrium from

inferior/superior vena cavainferior/superior vena cava R ventricleR ventricle pulmonary artery to lungs pulmonary artery to lungs

to be oxygenatedto be oxygenated pulmonary veins into L pulmonary veins into L

atriumatrium L ventricleL ventricle out aorta to bodyout aorta to body

ValvesValves

prevent blood flowing backwardsprevent blood flowing backwards atrioventricular valves – b/w atria & vent.atrioventricular valves – b/w atria & vent. pulmonary valve – b/w R vent & pul arterypulmonary valve – b/w R vent & pul artery aortic valve – b/w L vent & aortaaortic valve – b/w L vent & aorta heartbeat is sound of valves opening/closing “lub heartbeat is sound of valves opening/closing “lub

dub”dub” lub – atriovent. valve closinglub – atriovent. valve closing dub – pul. & aortic valves closingdub – pul. & aortic valves closing

Types of CirculationTypes of Circulation

1.1. Systemic CirculationSystemic Circulation heart to body and heart to body and

returnreturn ~ 90% of blood ~ 90% of blood

2. Pulmonary Circulation2. Pulmonary Circulation heart to lungs and heart to lungs and

returnreturn ~ 10%~ 10%

3. Cardiac Circulation3. Cardiac Circulation blood in heart at blood in heart at

any timeany time <1%<1%

Regulation of HeartbeatRegulation of Heartbeat avg teen HR (heart rate) 60-100 beats/min avg teen HR (heart rate) 60-100 beats/min

(bpm)(bpm) affected by age, fitness, stress…affected by age, fitness, stress… athletes have low HR, babies highathletes have low HR, babies high exercise, stress/fright inc. HRexercise, stress/fright inc. HR pacemaker in wall of R atrium regulates HRpacemaker in wall of R atrium regulates HR

PacemakerPacemaker sends electrical impulse over the atria to make sends electrical impulse over the atria to make

them contract (blood in)them contract (blood in) as atria contract, the impulse reaches the AV as atria contract, the impulse reaches the AV

node (atrioventricular) on the walls between the node (atrioventricular) on the walls between the ventricles and makes them contract (blood out)ventricles and makes them contract (blood out)

makes heart beat in rhythmic cyclemakes heart beat in rhythmic cycle BiologySourceBiologySource change in voltage is measured by an ECG change in voltage is measured by an ECG

(electrocardiogram)(electrocardiogram)

Measuring Blood Pressure Measuring Blood Pressure (BP)(BP)

sphygmomanometer – pressure cuff to measure BPsphygmomanometer – pressure cuff to measure BP uses mm Hg (standard liquid pressure unit)uses mm Hg (standard liquid pressure unit) 2 numbers ex. 120/702 numbers ex. 120/70 11stst # = systolic pressure # = systolic pressure

– pressure in artery when vent. contractpressure in artery when vent. contract 22ndnd # = diastolic press. # = diastolic press.

– pressure in art. when vent. relaxedpressure in art. when vent. relaxed

BPBP

depends on cardiac output & resistance of depends on cardiac output & resistance of arteries to blood flowarteries to blood flow

Cardiac Output – amt blood pumped/minCardiac Output – amt blood pumped/min– as volume inc, so does pressureas volume inc, so does pressure

Resistance due to elasticity of artery wallsResistance due to elasticity of artery walls– if walls don’t expand easily, press incif walls don’t expand easily, press inc

BP changes with age, fitness, weight…BP changes with age, fitness, weight… avg healthy teen BP 120/80avg healthy teen BP 120/80