BIO 2232 Exam 3 Review Sheet Conduction to Thermoregulation AU 14
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Course
BIO 2232
Institution
Columbus State Community College
BIO 2232 Exam 3 Review Sheet
Cardiovascular Physiology
Cardiac Cycle
1) Define terms systole and diastole.
- Systole – contraction of the heart
- Diastole – the relaxation phase of a heart chamber
2) What is happening in the both the atria and the ventricles during atrial systole?
- The ...
bio 2232 exam 3 review sheet conduction to thermoregulation au 14
exam 3 review sheet conduction to thermoregulation au 14
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BIO 2232 Exam 3 Review Sheet Conduction to Thermoregulation AU 14
BIO 2232 Exam 3 Review Sheet
Cardiovascular Physiology
Cardiac Cycle
1) Define terms systole and diastole.
- Systole – contraction of the heart
- Diastole – the relaxation phase of a heart chamber
2) What is happening in the both the atria and the ventricles during atrial systole?
- The atria contracts during atrial systole
- The ventricles relax during atrial systole. Blood goes into the ventricles.
3) What are the phases of ventricular systole?
- Ventricular systole begins when the AV valves (tricuspid and mitral) close. (this is when the first
heart sound occurs)
- 1. ISOVOLUMETRIC CONTRACTION is the 1st phase of ventricular systole or early phase. The ventricles are
contracting but all valves in the heart are closed (no blood ejected). The ventricular pressure builds while the
volume is constant (remember the valves are closed).
- 2. Once the pressure exceeds that found in the aorta or pulmonary trunk then aortic and pulmonary
semilunar valves OPEN and EJECTION occurs. The blood now leaves the ventricles and enters the elastic
arteries - pulmonary artery and aorta. This is now the 2nd phase ventricular systole or late phase. (This
volume of blood ejected from each ventricle during systole is called stroke volume
4) What are the phases of ventricular diastole?
- Early/phase 1 – isovolumetric relaxtion. All valves closed. No blood entering or leaving at this time.
- Late/phase 2 – passive filling. AV valves now open. The blood is continuing to return to the heart
and so once enough pressure builds up against the closed AV valves (during isovolumetric
relaxation) then the AV valves open and blood begins to enter the ventricles. (The semilulnar valves
still remain closed during this time.)The ventricles fill with blood throughout passive filling. (The
ventricles receive blood throughout most of diastole NOT just when atria contract!) Interestingly
enough, about 80% of filling occurs before atrial contraction/systole.
5) How do active and passive filling differ? And when does the majority of ventricular filling occur?
- Active filling – the atria contracts
o Atrial systole occurs after passive filling or late ventricular diastole and is called active filling
- Passive filling – the atria relaxes
o Passive Filling is the 2nd phase which occurs as soon as the AV valves open. The blood is
continuing to return to the heart and so once enough pressure builds up against the closed
AV valves (during isovolumetric relaxation) then the AV valves open and blood begins to
enter the ventricles. (The semilulnar valves still remain closed during this time.)The
ventricles fill with blood throughout passive filling.
- The majority of ventricular filling occurs before atrial contraction/systole. Both the atria and
ventricles are in diastole.
6) What creates the first 2 heart sounds?
- The first sound is the lub and occurs when the AV valves close at the onset of isovolumetric
contraction (phase one of ventricular systole) and blood rushes against them. Note the sound is
from valves closing and causing the blood backing up behind them and the actual closure of the
valves themselves.
- The second sound is the dub. This occurs when the semilunar valves close and blood rushes against
them at the onset of isovolumetric relaxation or the beginning of ventricular diastole.
7) What causes a murmur?
, - Murmurs occur when there is no longer a smooth, laminar flow of blood through the valves. (This
means the flow is more turbulent or rough).
- Abnormal heart sounds produced by abnormal blood flow through heart.
- Many caused by defective heart valves.
Electrical Activity
1) Explain the function of the following anatomical structures: SA node, AV node, AV bundle/bundle of
His, left and right bundle branches, and Purkinje fibers.
- Heart’s conduction system
1. Excitation begins in the SINOATRIAL (SA) NODE (the normal pacemaker of the heart) and both
atria contract.
2. Then the signal travels to the ATRIOVENTRICULAR (AV) NODE. The AV node slows down the
action potential to allow the atria to empty blood into ventricles (active filling).
3. Now the signal travels to the ATRIOVENTRICULAR (AV) BUNDLE which is also called the bundle
of His. This is the only site where the action potential is conducted from atria to ventricles.
4. Next is the RIGHT AND LEFT BUNDLE BRANCHES. This brings the action potential down to
ventricles and out to right and left ventricular walls.
5. It then goes to the PURKINJE FIBERS. They move the action potential from the bottom of the
ventricles upward to the remainder of the ventricular myocardium. After this final event
happens the ventricles contract (only a fraction of a second after the first step causing atrial
contraction).
2) Which nodal cell is considered the pacemaker?
- SA node
3) What does the term autorhythmic mean? What anatomical structure in the heart makes this
possible?
- Autorhythmic – cardiac muscle doesn’t need motor neuron to contract. It can contract on its own
- Nodal cells or “pacemaker cells” make this possible
4) When does the signal transfer from the atria to the ventricles? Why is the fibrous skeleton
important?
- After the SA node becomes excited and atria contract, but before the signal travels to the AV bundle
- The atria and ventricles are separated electrically by the fibrous skeleton.
o Allows atria to contract then ventricles.
5) How do the action potentials rapidly distribute throughout the ventricles?
- Gap junctions within intercalated discs allow calcium to flow across to adjacent cardiac muscle cells,
thereby propagating the Action potential
6) Why is there a delay at the AV node? What is it allowing to happen?
- The AV node slows down the action potential to allow the atria to empty blood into ventricles
(active filling).
7) What does sinus rhythm mean? What happens if the stimulus originates somewhere other than the
“pacemaker”? What type of rhythm would this be?
- A normal rhythm of the heart or EKG that begins at the SA node at a rate of 60 to 100 beats per
minute is called a sinus rhythm.
- The AV node can take over as the pacemaker if the SA node is damaged but will be slower (about
50bpm). The AV bundle can also take over for the AV node, if needed, now but the heart would
only beat about 25-30 times a minute, giving inadequate blood supply to the brain if such a heart
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