Physiology Unit 1

Anatomy

100

The outer layer and inner layer of the pericardium are called?

What iare parietal (outer fibrous) and visceral (inner serous- also called the epicardium) layers

200

(1) Which way is the heart positioned in the chest? (2) Which valve has two names?

(1) What is atria more to the right than ventricles; RA/RV more anterior than the LA/LV. (2) Mitral/bicuspid valve is the only valve to have two leaflets/cusps.

300

(1) The connection point between the valve cusps and the valve skeleton and the wall of the heart or artery is the? (2) What is the purpose of the papillary muscles and chordae tendineae?

(1) What is the commissure? (2) During ventricular contraction the papillary muscles also contract to pull tight the chords to prevent prolapse of the AV valves during systole. They do not close or open the valves - this occurs passively due to pressure changes above and below the valve.

400

(1) What is the shape of the RV and LV? (2) How does each chamber contract? (3) What is the purpose of the multiple layers of myocardial muscles all going in different directions?

(1) What is "C" shape for RV and cone shape for LV. (2) RV contracts by shortening and moving towards the IV septum. RV does NOT include the interventricular septum. LV contracts by shortening lengthwise as well as constricting inwards from all sides. LV includes the muscle of the interventricular septum. (3) Multiple muscles layers going different directions so that the heart chamber can both constrict and shorten lengthwise at the same time.

Cardiac cycle

100

What is happening during the A wave? C wave? V wave?

A wave - atrial contraction pressure; C wave - atrial pressure rise caused by isometric ventricular contraction; V wave - atrial filling pressure.

200

(1) What are atrial pressures during ventricular systole? diastole? (2) What are RV pressures in the cardiac cycle? (3) LV pressures?

(1) During ventricular systole RA 2 mmHg and LA 3 mmHg. During ventricular diastole atria contract raising RA to 10 mmHg and LA to 15 mmHg. (2) RV= 30/8 mmHg (3) LV = 100-140/3-12

300

What are the two pressures rises in the aortic pressure wave?

What is during ventricular ejection aortic pressure rises and falls alongside the ventricular pressure. In IVR the aortic pressure rises again but ventricular pressure falls at that time.

400

What causes the AV valves to close?

AV valves close the moment ventricular pressure is greater than atrial pressure. Just before closure the atria start to repolarize and relax, causing their pressure to drop quickly. Simultaneously, ventricles begin depolarization and contraction causing their pressure to rise quickly. This reversal of pressures cause the AV valves to close.

500

What causes the SL valves to close?

SL valves close the moment ventricular pressure drops below arterial pressure. Ventricles begin to repolarize and suddenly relax and drop their pressure quickly. At the same time arterial pressure does NOT drop due to elastic recoil of the arteries. Arterial pressure stays but venticular pressure drops creating a vacuum in the ventricles pulling back on arterial blood which flows towards the ventricles filling the cusps and closing the valve. AFTER THIS MOMENT the arterial blood continues to flow toward the closed valve causing a momentary rise in arterial pressure - in the aorta this sudden rise in aortic pressure AFTER the valve closes is called the "dicrotic notch" in the aortic pressure wave form.

Muscle

100

Define/explain the terms: sarcomere, sarcolemma, sarcoplasmic reticulum, T tubules, Troponin, Tropomyosin, Actin, Myosin, Crossbridge, power stroke.

Sarcomere - smallest working unit; sarcolemma - membrane; SR - stores calcium; T tubules - part of the sarcolemma conducts electricity; T & T cover active site on actin to prevent contraction; Actin - thin filament; Myosin - thick filament - which contracts its "head" after connecting to actin (power stroke); crossbridge-connection between actin and mysin; power stroke - contraction of myosin head tugs on actin shortening the sarcomere. Each power stroke requires an ATP molecule for each myosin molecule.

200

List the order of events of contraction

1. Pacer cell initiates an impulse "spark" or action potential. (2) AP travels across sarcolemma and down T tubules (3) electric gates open in SR releasing calcium. (4) T & T lift off exposing active site on actin. (5) myosin binds with actin and power stroke results. (6) new ATP molecule attaches to myosin head which causes it to detach/release from the previous actin and move to the next actin for another contraction.

300

How does filling affect heart contraction?

Heart has the most powerful contraction when it is filled completely. The more stretch, the more crossbridges form (within physiological limits).

Electricity

100

What is meant by the terms action potential, polarized state, threshold?

Action potential is the electrical change in the cell that takes from negative to positive and back again. Polarized state is the state of unequal charges on either side of the cell membrane. Threshold is the electronegativity level in which a full depolarization will occur. Below this level, depolarization will not occur.

200

What is meant by depolarization, plateau, repolarization?

Depolarization - sodium ions enter causing cell to become positive. Plateau is in the cardiac muscle cell and it is where Calcium enters the cell and maintains a positive charge of the membrane PREVENTING repolarization from continuing. It's like a "pause" in the action potential. Without this calcium flooding in the cell would have immediately gone to and through the repolarization phase. Repolarization potassium leaves the cell returning it to a negative level.

300

What are the electrical phases of the pacer cell?

Phase 4 slow depol - slow entry of Na; Phase 0 fast depol with fast entry of Ca; Phase 3 repol K exits.

400

What are the electrical phases of heart muscle electricity?

0= fast depol Na in; 1=Na doors close; 2 = Ca entry plateau - contraction begins here and rises through phase 3; 3 = repol with K exit; 4 = polarized state

500

The QRS of the EKG would be represented in a single heart muscle cell by what phase of the action potential?

What is Phase 0

Misc

100

The ST segment of the EKG is related to what phase of the muscle cell action potential? What ion is responsible for causing the positive voltage during this phase? What would the action potential be doing during this phase of this ion were not present?

What is the Plateau phase (phase 2). What is Calcium. What is repolarization.

200

What phase of the action potential coincides with the T wave? What ion movement is causing this electrical change during this time?

What is Phase 3. What is potassium exiting the cell.

300

Describe how the cardiac muscle cell phase 2 and 3 are related to contractile force? Why is this?

Contractile force begins to build during phase 2, peaks at the end of phase 2 and falls during phase 3. In other words, there is a delay from when phase 2 begins and contractile power peaks. This is because contractile force is directly related to the amount of calcium released into the interstitial fluid surrounding the actin/myosin filaments.

400

How does the sympathetic system affect the action potential of a cardiac pacer cell?

Sodium leaks into the cell more quickly. So the upslope of phase 4 is more vertical (takes less time to depolarize). Calcium is also released more quickly so the upslope of phase 0 also takes less time. Potassium exits more rapidly so repolarization of the pacer cell occurs more quickly as well. All of this allows the SA nodal cells to depolarize more frequently = faster heart rate.

500

What happens in the heart to cause a PVC, PJC, or PAC to occur?

In an abnormal area of the cardiac muscle, a cell that is NOT SUPPOSED TO BE permeable to sodium somehow allows sodium into the cell - thereby causing depolarization of that cell, which spreads through the whole heart.