Transcript Heart Beat and Blood Pressure

Heart Beat and
Blood Pressure
Heart Beat Animation
• http://www.nhlbi.nih.gov/health/dci/Disease
s/hhw/hhw_pumping.html
• http://www.nhlbi.nih.gov/health/dci/Disease
s/hhw/hhw_electrical.html
What makes a heart beat?
• Heart muscle contraction is due to the presence
of nodal tissue in two regions of the heart
• SA node and AV node
SA Node
• The heart beat is set by the sinoatrial node
(SA node)
• The SA node is a bundle of specialized
nerves
• The SA node is located in the right atrium
• The SA node stimulates the contraction of
both left and right atrium
• The SA node acts as a pacemaker setting
a rhythm of about 70 beats/min.
AV Node
• AV node is located farther down in the
right atrium
• It receives the signals from the SA node
and acts as a conductor spreading the
nerve signals down special tracts toward
the ventricles causing them both to
contract
Coordination of the Beating
• If there was no
coordination, the heart cells
would all beat randomly
(fibrillation)
• Coordinated beating
occurs because of the SA
node (the pacemaker cells)
send nerve impulses to the
other cells stimulating them
to beat at the right time
Coordination of the Beating(2)
• Contraction of ventricles
– Take blood in from the
atria
– Pump blood out to the
body
• Contraction of atria
– Take blood in from body
– Pump blood into the
ventricles
• Coordinated beating of
one then the other
The Cardiac Cycle
• The heart beats or contracts 70 times per minute. The
human heart will undergo over 3 billion contraction cycles
during a normal lifetime.
• The cardiac cycle consists of two parts:
1. systole (contraction of the heart muscle)
The contraction of the ventricles that opens the
valves and forces blood into the
arteries
2. diastole (relaxation of the heart muscle)
When the ventricle fills with blood.
• Atria contract while ventricles relax.
• Normal cardiac cycles (at rest) take 0.8 seconds.
Blood Pressure
• Blood pressure is a measure of the force
exerted by the blood on the wall of the
arteries
– An example is 120/80 (systolic
pressure/diastolic pressure)
• Systolic pressure is the result of the contraction of
the ventricles (normal 110-140)
• Diastolic pressure is during the ventricle relaxation
(normal 70-90)
Electrocardiogram (ECG)
• An electrocardiogram (ECG) measures changes
in electrical potential across the heart, and can
detect the contraction pulses that pass over the
surface of the heart.
• There are three slow, negative changes, known
as P, R, and T.
• Positive deflections are the Q and S waves. The
P wave represents the contraction impulse of the
atria, the T wave the ventricular contraction.
• ECGs are useful in diagnosing heart
abnormalities.
“Clear!!!”
http://sln.fi.edu/biosci/healthy/openheart.html
http://www.hhmi.org/biointeractive/cardiovascular/