61 terms

Circulatory System: The Heart - Saladin

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