PHIL 1000X Study Guide - Final Guide: Superior Vena Cava, Heart Valve, Venae Cavae
13 May 2018
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BLOCK YA
MODULE Y2 - CARDIOVASCULAR PHYSIOLOGY
UNIT 2
The Heart
Unit Objectives
When you have finished this unit, you should be able to:
1. Describe the anatomy of the heart, and know the names, location, and one-way-flow
function of the valves.
a. Aorta - directs blood to tissues
b. and pulmonary trunk - lungs (artery)
c. Vanae cavae and pulmonary veins return back to heart
d. Coronary arteries and veins supply the heart with blood
e. Venae cavae - right ventricle - right atrium - lungs
f. Left atrium - pulmonary veins - left ventricle - left atrium - body (but not lungs)
g. Blood leaves heart via pulmonary trunk from RIGHT ventricle and via aorta from
LEFT ventricle
h. TWO SETS OF HEART VALVES: Atrioventricular (between atria and ventricles)
and semilunar (between ventricles and arteries)
i. CHORDAE TENDINEAE?? PAPILLARY MUSCLES?
i. If it isn’t part of the objectives, don’t worry about it
j. Tricuspid (three flaps) valve - separates RIGHT atrium and RIGHT ventricle
(RST)
k. Bicuspid (two flaps - MITRAL valve) separates LEFT atrium and LEFT ventricle
l. Semilunar separates ventricles from major arteries
i. Aortic between left ventricle and aorta
ii. Pulmonary between right ventricle and pulmonary trunk
m. BLOOD FLOW:
n.
o. Superior vena cava → right atrium → tricuspid (right AV) valve → right ventricle
→ pulmonary (right semilunar) valve → pulmonary trunk → pulmonary vein → left
atrium → mitral (bicuspid, left AV) valve → left ventricle → aortic (left semilunar)
valve → aorta
2. Describe action potentials in pacemaker cells and contractile cells. Compare these with
skeletal muscle.
a. Myocardio autorhythmic cells can spontaneously generate action potential
because of their unstable membrane potential (starts at -60) - PACEMAKER
POTENTIAL
b.
3. Know that pacemaker cells in the sinoatrial (SA) node produce spontaneous action
potentials in a rhythmic fashion, and that this results in the propagation of action
potentials throughout the heart (SA node → atria → AV node → bundle of His → bundle
branches → Purkinje fibres → ventricular muscle walls).
a. Pacemaker cell = “If” (funny current), this is a slow influx of Na+ that gradually
depolarizes the cell. That will eventually bring it to threshold. When it gets to
threshold, the upwards swing of the action potential will happen → but that
happens using Ca2+, not Na+ (v.g. Ca2+ channel opening). Peak of action
potential is reached. K+ channels open, and there is efflux of K+. That brings the
membrane potential back down. Then it restarts - once the cell is back at resting
potential, the “funny current” starts again, and brings the cell back to
depolarization. It’s essentially depolarizing on its own after every action potential.
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b.
c. Basically what happens to increase or decrease heart rate is a modification of the
funny channel current. This means that Na+ influx is somehow altered.
4. Describe how at any given time during heart electrical activity, some parts of the heart
are depolarized and other parts are not, and that these differences can be recorded from
the body surface as electrocardiograms (ECG's).
a.
5. Describe the ECG as a useful diagnostic tool, identify its features (P wave, QRS
complex, T wave) that serve to mark the timing and quality of particular cardiac electrical
events and explain what the P, QRS and T-waves represent.
a. The ECG is an extracellular recording that represents the sum of multiple action
potentials taking place in many heart muscle cells.
b. There are two major components of an ECG: waves and segments. Waves
are
the parts of the trace that go above or below the baseline. Segments
are sections
of baseline between two waves.
6. Major waves recorded from lead I
a. P wave - depolarization of atria
b. QRS complex - progressive wave of ventricular depolarization (Q sometimes
absent)
c. T wave - repolarization of ventricles
7. Describe excitation contraction coupling and relaxation in cardiac muscle.
a. Because depolarization initiates muscle contraction, the electrical events
(waves)
of an ECG can be associated with contraction or relaxation (collectively referred
to as the mechanical events
in the heart).
b. CARDIAC CYCLE
