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Phase 1 of the Cardiac Cycle

Ventricular filling (diastole)
1. Ventricles expand & AV valves open
2. Blood flows into ventricles quickly!, then
3. P-wave occurs
4. Atria contracts, sends last 1/3 of blood to
* At end of Phase 1:
each ventricle contains an end-diastolic
volume (EDV) of about 130mL

Phase 2 of the Cardiac Cycle

Isovolumetric Contraction (stystole)
1. QRS wave occurs
2. Atria repolarize & relax
3. Ventricles begin contracting
4. AV valves close
5. heart sound S1 occurs
6. Semilunar valves remain closed
7. No blood is expelled

Phase 3 of the Coronary Cycle

Ventricular Ejection
1. Semilunar Valves open
2. blood is ejected rapidly!, then slowly
3. each ventricle ejects a stroke volume of
about 70mL, which is an ejection fraction
of 54% of the EDV
4. blood remaining behind (60mL) is end-
systolic volume (ESV)
** T-wave begins @ middle of this phase

Phase 4 of the Cardiac Cycle

Isovolumetric Relaxation (diastole)
1. Ventricles repolarize & relax
2. Semilunar valves close
3. heart sound S2 occurs
4. AV valves remain closed
5. no blood enters ventricles until next
phase 1
** each ventricle ejects same amount of

Pacemaker Physiology

Pacemaker Physiology (PP)
1. Starts @ -60mV - showing depolarization
* caused by slow inflow of Na+ without out-
flow of K+
2. When Pacemaker Potential reaches
threshold of -40mV . . .
3. Voltage-regulated fast calcium channels
4. Ca2+ flows in from ECF - this produces
rising (depolarizing) phase of action
potential. (peaks slightly above 0 mV)
5. K+ gates open & K+ leaves cell (repolor-
ization occurs)
6. K+ gates close & PP starts over again
** each depolarizaiton of SA node sets off
1 heartbeat

Electrocardiogram - P wave

P wave is produced when a:
* signal from the SA node spreads
through the atria and depolarizes them
** P wave indicates atrial depolarization

Electrocardiogram - QRS complex

QRS complex:
* signal from the AV node spreads
through the ventricular myodardium
** QRS complex indicates ventricular
depolarization, BUT atrial repolarization
occurs at same time

Electrocardiogram - ST segment

ST segment:
* corresponds to the plateau in the myo-
cardial action potential & represents
the time when ventricles contract and
eject blood into the Aorta & Pulmonary
** Ventricular systole begins @ ST seg.

Electrocardiogram - T wave

T wave is:
* indicates ventricular repolarization and
is followed by ventricular diastole.

Cardiac Output

The amount of blood ejected by each
ventricle in 1 minute

Cardiac Output formula

Heart rate (HR) x Stoke volume (SV) =
Cardiac Output (CO)


Pressure sensors found in the Aorta & internal Carotid Arteries.
* monitors blood pressure


Tension in the Ventricular Myocardium
immediately before it begins to contract.
** Amount of blood in left ventricle at end
of diastole = end-diastolic volume


Blood pressure in the Aorta & Pulmonary
Trunk immediately distal to the semilunar
* Amount of pressure left ventricle needs to open aortic valve

What are the 2 centers that con-
stitute the cardiac center?

1. Cardioacceleratory center
2. Cardioinhibitory center

Cardioaccelatory Center

Cardioaccelatory Center:
* raises heart rate through sympathetic
cardiac nerves.

Cardioinhibitory Center

Cardioinhibitory Center:
* reduces heart rate through the para-
sympathetic fibers in the vagus nerve.

What does the Sympathetic and
Parasympatheic do to the heart?

They modify heart rate & contraction

An electrocardiogram is a graph-
ical representation of

Atrial & Ventricular de- and repolarization

An elongagted P wave suggests

a problem with Atrial depolarization

The first heart sound heard is the result of

Closure of the AV valves

Atrial pressure is at its highest

The AV valves are open

If the time of Ventricular filling were
increased in duration

The end diastolic volume (EDV) would
be greater

An artery is defined as

a vessel that carries oxygenated blood AWAY from the heart.

The valve that lies between the right atrium & the right ventricle is the

tricuspid valve

A sudden drop in blood pressure will cause

a reflexive increase in the heart rate

What valve keeps blood from backing up into the Left Ventricle?

Aortic Valve

When the Ventricles relax blood in
the Aorta flows ______

flows back toward the heart filling the
coronary arteries.

The small patch of heart tissue that depolorizes spontaneously to
begin each heartbeat is the

Sinoatrial Node

An EKG is a composite recording of _______

All of the action potentials produced by the heart

During a normal cardiac cycle which phase has the longest duration?

Quiescent period

What chamber has to work harder than the others, so it has the thick-
est myocardium?

Left Ventricle

The vessel just before the circum-
flex artery in normal circulation is
the _______

Anterior Interventricular artery

Myocardial ischemia can lead to

tissue death


refers to the cardiac muscle tissue


Connective tissue layer that covers the external surface of the heart

What chambers of the heart is at the base of the heart?


The chordae tendineae are connect-
ed to the walls of the ventricle via

the papillary muscles

Cardiac muscle depends almost
entirely on _______ to make ATP.

aerobic respiration

When the Atria begins depolarizing
the _______ is filling.

Atrial is filling.

Which wave on an EKG represents
ventricular depolarization?

QRS complex


pump blood


1. carries deoxygenated blood to heart


receive blood

The Pulmonary circulation is made up of what side of the heart/


Great Vessels

Arteries & Veins entering & leaving the
* Superior and inferior vena cava, pulmonary artery and vein, and aorta.

The systemic circulation is made up of what side of the heart?


What side of the heart contains
oxygenated blood?


Papillary muscles

The 3 cone-shaped muscle projections
inside the right ventricle

Trabeculae carneae

Irregular muscular ridges on the inner wall
of each ventricle

What side of the heart contains
deoxygenated blood?


Aortic semilunar valve

The end of the left ventricle & the beginning
of the aorta


Atria contraction


Ventricle relaxation

When the pacemaker potential
reaches threshold, what type of
channels open to allow Calcium and
Sodium to flow in from the ECF?

Voltage-regulated fast calcium-sodium

A pacemaker potential results from

A slow inflow of Na+ without a compensating
outflow of K+

Pacemaker Potential

The result of the cells of the SA node ex-
hibiting a potential in which the membrane
voltage starts at -60 mV and drifts spontan-
eously toward a threshold of -40 mV.


Rapid heartbeat

Atrial flutter

abnormally rapid rate of atrial depolarization

Purkinje fibers

Fibers that relay the signal from the AV node to the ventricles, telling them to contract


Slow heartbeat

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