Download Heart Physiology part 1

Physiology of the Heart
Physiology of the heart
You should understand by now that the Physiology of the
Heart refers to the function of the heart
You need to be familiar with the conduction system of the
heart, the cardiac cycle, sounds of the heart, and cardiac out
put
Conduction System of the
Heart
Cardiac muscle is unique because it can contract
spontaneously and independently even if all nervous
connections to the heart are severed
These contractions however, are not erratic but regular and
steady in rhythm
Beats per minute
The atrial cells of the heart beat roughly 60 times per minute
The ventricular cells of the heart beat only 20-40 times per
minute
Without some unifying system to control them the heart
would be an uncoordinated and inefficient pump
Intrinsic Conduction
The Intrinsic Conduction
System (Nodal System) of
the heart is made of very
specialized cardiac tissue
that is a cross between
muscle and nervous tissue
Intrinsic Conduction
We see 2 large ovals which are
the nodes of the system
•The sinoatrial node (SA
Node) acts as the pace maker
of the heart
•The atrioventricular node
(AV Node) slows the impulse
before sending it to the
ventricles
Cardiac Cycle
Two most important terms in understanding cardiac cycle
are Systole and Diastole
Systole is heart contraction
Diastole is heart relaxation
5 Phases of Cardiac Cycle
Cardiac sounds
In a healthy heart you
should be able to hear a
steady “lub-dub” sound of
contraction
We have to understand
that there is a sequence to
the sounds
lub-dub, pause, lub-dub,
pause
“Lub” and “Dub” sounds
The “lub” sound we hear is
from the the closing of the
AV valves
This is then followed by a
pause
The “dub” sound we hear is
from the closing of the
semilunar valves
Blood flow
It is important to realize
that blood flows silently as
long as the flow is smooth
and un-interupted
If the flow becomes
irregular we can hear
murmurs