Transcript Heart Physiology

HEART PHYSIOLOGY
What a Job!

It pushes your
six liters of blood
through your
blood vessels
over 1000 times
a day!

Thousands of
cells function
as one unit!
Basic Heart Anatomy
Note: Right & left are named
based on position in the chest
& seem reversed in a diagram
 Superior chambers = atria
 Small,

limited muscle
Inferior chambers =
ventricles
 Large,
heavily muscled
 Pumping chambers

Septum divides ventricles
Valves


Prevent back-flow of blood
Two atrioventricular (AV) valves:
 Tricuspid
 Bicuspid/mitral

Two semilunar valves:
 Pulmonary
 Aortic
Purpose?

Pulmonary circuit
 Between
heart & lungs
Why?
What is the pump?

Systemic circuit
 Between
heart & rest of
body
Why?
What is the pump?
Right Atrium

Receives deoxygenated
blood from
 Superior
vena cava (from
body above diaphragm)
 Inferior vena cava (from
body below diaphragm)
 Coronary sinus (from heart)

Passes blood through
tricuspid valve to RV
Left Atrium

Receives oxygenated
blood from lungs through:
 Right
and left superior
pulmonary veins
 Right and left inferior
pulmonary veins

Passes blood through the
bicuspid/mitral valve to
the LV
Ventricles


RV pumps
deoxygenated blood to
lungs through
pulmonary semilunar
valve into pulmonary
trunk
LV pumps oxygenated
blood to body through
aortic semilunar
valve to aorta
Cardiac Cycle = one heartbeat



Systole – contraction of the ventricles
Diastole – relaxation of the ventricles
Events occur in 3 phases:
1: Mid-to-Late Diastole





Heart in complete relaxation
Low pressure
Blood flowing into atria and ventricles
Semi-lunar valves closed
A-V valves open
END – atria contract
and force remaining
blood into ventricles
2: Ventricular Systole



Ventricles contract, increasing
pressure
A-V valves close
Atria begin filling with blood
END –
 Ventricular pressure > artery
pressure
 Blood forced out semilunar valves
3. Early Diastole


Ventricles relax, dropping pressure
Semi-lunar valves close
END –
 Atrial pressure > ventricular
pressure
 Blood is forced through AV valves
Heart Rhythm
1.
2.
Intrinsic Conduction
System (ICS) –
“specialized” tissue sets
basic rhythm, ~75
beats/minute
Extrinsic Control –
nervous system can
increase or decrease
heart rate
Intrinsic Conduction System
Starts with autorhythmic cells:
1.
SA (sinoatrial) Node –
“Pacemaker” - causes the
atria to contract
2.
AV (atrioventricular)
Node – causes ventricles
to contract
Continues through rest of ICS:
3.
Bundle of His
4.
Bundle branches
5.
Purkinje fibers
Depolarization Sequence
1
2
3
4
5
Electrocardiogram [ECG/EKG]

Traces the flow of current through the heart
Cardiac Output


Stroke Volume (SV) – Blood pumped per
ventricle per heartbeat
Cardiac Output (CO) – Blood pumped per
ventricle per minute
= Heart Rate (HR) * Stroke Volume (SV)
Normal Adult HR is ~75 beats/minute
Average resting SV is ~70 ml/beat
What is the average adult CO?
Irregular Heartbeats

Tachycardia


Bradycardia



(>100 beats/min)
(<60 beats/min)
Ischemia – lack of
adequate blood supply
Fibrillation – rapid
uncoordinated
shuddering of heart
muscle (major
cause of heart
attack/death)