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HN320 Lecture Notes - Pulmonary Valve, Mitral Valve, Aortic Stenosis

Health Sciences
Course Code
Michael Wilkie

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BI217 Lecture: The Anatomy and Physiology of the Human Heart
Why Do We Need a Circulatory System?
With multicellular organisms oxygen could not longer diffuse through to all the cells
of the body, insufficient for the inner cells
Because of this, it was essential to produce a circulatory system
In Harvey’s equation r squared is the radius
As animals got bigger, the amount of oxygen necessary at the surface increases to
ensure that the innermost cells receive sufficient oxygen
Functions of the Cardiovascular System
The typical resting heart beat is roughly 60 beats per minute
In a typical year 5.26x105 min/year
3.2x107 beats per year for the average heart x 70 years = 2.2 2.6 billion times in a
Volume: average cardiac output (sum of the heart rate x the volume of blood pumped
per beat) = about 5L of blood per minute
5L x 5.26x105 minutes/year = 2.6 -3.0 million liters of blood pumped per year
2.6 3.0 million x 70 years = 184 210 million liters of blood per lifetime
Anatomy of the Heart
Arteries carry oxygenated blood except for the pulmonary artery (these leave from the
Veins take blood to the heart
The right and left atria contract simultaneously as do the right and left ventricles
The amount pumped from the left and right ventricle should be equal if not there can
be a back up of blood pulmonary edema, multi-organ failure, and the tissues will be
starved of blood (this is often the cause of death for those in high altitudes)
Gas exchange takes place at the level of the capillaries
Left side = systemic circuit
Right side = pulmonary circuit
Coronary arteries and veins are very prominent on the surface of the heart
Left ventricle is much more muscular greater distance to pump the blood, faces much
more resistance to blood flow (must generate a greater force)
Left ventricular hypertrophy
Veins are more floppy looking they only have a thin layer of muscle surrounding them
Aortic (aneurisms) rupture = instant death (this can increase with cocaine use because of
increased blood pressure)
Aorta has a thicker layer of muscle has many branches (carotid arteries, brachial
artery, femoral artery blood under extreme pressure)
Pericarditis can be caused by streptococci inflammation of the pericardium can lead to
friction rub, where the heart has less room surrounding it
Electrical coupling allows the heart to beat in a coordinated fashion (myocardial
infarction would disrupt this electrical pathways would have to be diverted)
Auto-rhythmic fibers much smaller, constitute the electrical wiring of the heart, find in
the pacemaker of the heart (sino-atrial node)
Contractile fibers they do all the work, these can get bigger, these are signaled by the
auto-rhythmic cells to contract

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Gap junctions electrically coupled because they allow for ions to flow between
adjacent cells (or chemical messengers) therefore electrical currents can move back
and forth between adjacent cells
Cardiac muscle allows pumps from the apex to the base (where the aorta and the
pulmonary artery leave the heart)
Endocardium lines the internal surface of the heart it is also what the valves are
constructed of (connective tissue)
AV Valves: Tricuspid separates the right atrium and ventricle and bicuspid (mitral)
which separates the left atrium from the left ventricle
AV node delays the electrical signaling
Papillary muscles also contract when the ventricles contact to stop the valves from
blowing back (act as anchors)
Purpose of valves is to prevent the backflow of blood to maintain cardiac output
Semilunar Valves: Pulmonary and aortic valves
Diseases of the Heart
Streptococcal infection can cause rheumatic fever which can lead to tissue damage and
Leaking could be from calcium deposits or scarring, this can lead to turbulence (aka.
Heart murmurs)
Mitral Valve Stenosis (bicuspid valve stenosis)
The left AV valve does not open as much as it should when the valves are suppose to
spring open
Narrowing of left AV valve
Can be caused by rheumatic fever which damages tissues throughout the body
Mitral Valve Regurgitation
Blood is going the wrong way you get a backflow of blood due to leakage in the valve
Can be detected as a heart murmur with a stethoscope
ECG, chest X-rays, and ultrasounds (echocardiogram)
Treatment = valve repair using catheters, or replacement of the valve
Mitral Valve Prolapse
The leaflets or lobes of the valve bulge into the left atrium leading to some leakage or
back flow
Difficult to diagnose, probably drops in blood pressure, chest pain, migraines
Signs clicking sound when listening with a stethoscope, there may also be murmurs as
well due to turbulence when the ventricles contract
Could take drugs to slow the heart rate for example, beta blockers (decrease the work
load on the heart)
Aortic Valve Stenosis
Narrowing of the valve decrease in blood flow through the systemic circuit
May be caused by scar tissue, possibly due to an infection, or build ups of calcium
Diagnosis = echocardiogram, preceded by the detection of a heart murmur, may do
cardiac catheterization
Typically seen in the elderly
Aortic Valve Regurgitation
Could be caused by rheumatic fever, or could be congenital
Detected in routine medical exams as a heart murmur

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Echocardiogram to confirm the diagnosis
Signs chest pains, palpitations (noticeable feelings of heart racing)
Treatment antibiotics if it is due to rheumatic fever, drugs that decrease BP/Digoxin
which decreases the strength at which the heart contracts
Membrane Transport
Review toolbox on page 100, chapter 4 pages 95-101
Key Definitions Solute, Solvent (ECF or ICF/cytosol)
If solute concentrations are different between the ICF and ECF the cell will either
swell or shrink
Calcium is incredibly low in the intracellular fluid (this is stored in the sarcoplasmic or
endoplasmic reticulum) important for triggering muscle contraction, and is critically
important as a second messenger
Focus of potassium, sodium, calcium, and chloride when looking at the electrochemical
properties of cells
Membrane potential is always inside relative to outside this is pretty much constant
across cells because there is a build up of excess anions right next to the plasma
This does not refer to the entire cell cations must be equal to the number of anions
the charge separation can only occur at the level of the plasma membrane
The driving force (combination of the electrical and chemical gradients) using the
Nernst equation
Primary active transport examples ATPase, Calcium ATPase, Proton pump (H+
ATPase), Sodium-Potassium ATPase
Secondary active transport antiporter or symporter
Active transport moves substances from low to high energy
Law of electroneutrality positive and negative charges have to balance each other (but
negative charges tend to collect on the inside of the membrane and positive on the
outside due to differences in permeability when the cell is at rest)
Can use the Nernst potential to predict which way an ion is going to move (in the
direction that moves their membrane potential towards the Nernst potential)
Net Driving Force (Fion) = Em Eion
Negative Fion indicates inward movement, positive Fion indicates outward movement
Note: membrane must be permeable to that ion
Fig 4-5 a) some potassium would be leaking out (through potassium leak channels)
and at the same time the electrical gradient is drawing some potassium back in no net
gain or loss
Fion = -94 (-94) = 0
If membrane potential is equal to the Nernst potential, you are not getting any net gain
or loss
B) The membrane potential is more positive the potassium will not be as attracted into
the cell so the potassium would move in the direction to drive its Vm in the direction of
its Ek
C) The Nernst potential is less than the membrane potential, the potassium will move
into the cell to bring the values closer
Against the electrical OR chemical gradients = active transport
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