Review Sheet Exercise 31 Conduction System of the Heart and Electrocardiography

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Review Sheet

Exercise 31

Conduction System of the Heart and Electrocardiography


Lab Time/Date

The Intrinsic Conduction System

1. List the elements of the intrinsic conduction system in order, starting from the SA node.

SA node AV node             AV bundle (bundle of His)  

left and right bundle branches        subendocardial conducting network
(Purkinje fibers)  

At what structure in the transmission sequence is the impulse temporarily delayed? AV node

Why? Allows completion of atrial contraction before initiation of ventricular systole

2. Even though cardiac muscle has an inherent ability to beat, the nodal system plays a critical role in heart physiology.

What is that role? Ensures that depolarization proceeds in an orderly manner from atria to ventricles; accelerates and coordinates heart activity to effectively pump blood


3. Define ECG. Recording of electrical changes occurring during heart activity.

4. Draw an ECG wave form representing one heartbeat. Label the P, QRS, and T waves; the P-R interval; the S-T segment, and the Q-T interval.

5. Why does heart rate increase during running? Heart rate increases during running secondary to action of the sympathetic nervous system. Norepinephrine, released by sympathetic axons on the heart, and the hormone epinephrine released during a sympathetic

discharge stimulate pacemaker cells to fire more rapidly.

6. Describe what happens in the cardiac cycle in the following situations.

1. immediately before the P wave: The heart is in diastole.

2. during the P wave: Depolarization of the atria

3. immediately after the P wave: Contraction of the atria

4. during the QRS wave: Depolarization of the ventricles

5. immediately after the QRS wave (S-T segment): Contraction of the ventricles

6. during the T wave: Repolarization of the ventricles

7. Define the following terms.

1. tachycardia: Heart rate over 100 beats/min.                            

2. bradycardia: Heart rate below 60 beats/min.                             

3. fibrillation: Very rapid uncoordinated myocardial activity                   

8. Which would be more serious, atrial or ventricular fibrillation? Ventricular fibrillation

Why? The ventricles bear major responsibility for pumping blood from the heart to the lungs and all other body organs.

9. Abnormalities of heart valves can be detected more accurately by auscultation than by electrocardiography. Why is this so? Most often serious valve problems cause turbulennt blood flow, which can be detected (heard) with a stethoscope. Since the valves do not have electrical activity (they are not part of the conduction system) no electrical signals can be recorded from them on the ECG.

Review Sheet

Exercise 32


Lab Time/Date

Anatomy of Blood Vessels

Microscopic Structure of the Blood Vessels

1. Cross-sectional views of an artery and of a vein are shown here. Identify each; on the lines to the sides, note the structural details that enabled you to make these identifications:

Now describe each tunic more fully by selecting its characteristics from the key below and placing the appropriate key letters on the answer lines.

Tunica intima a, c, f     Tunica media d, e     Tunica externa b                  


a. innermost tunic

b. most superficial tunic

c. thin tunic of capillaries

d. especially thick in elastic arteries

e. contains smooth muscle and elastin

f. has a smooth surface to decrease resistance to blood flow

2. Why are valves present in veins but not in arteries? The high blood pressure in arteries propels the blood through them. The blood pressure in veins is low and often the blood is flowing against gravity. Valves prevent backflow.

3. Name two events occurring within the body that aid in venous return.

Skeletal muscle “milking action”              and changes in thoracic cavity pressure during breathing

4. Why are the walls of arteries proportionately thicker than those of the corresponding veins? Arteries must withstand high pressure and pressure fluctuations. Veins are low-pressure vessels.

Major Systemic Arteries and Veins of the Body

5. Use the key on the right to identify the arteries or veins described on the left. Some terms are used more than once.


d        1. the arterial system has one of these; the venous
system has two

a. anterior tibial

i        2. these arteries supply the myocardium

b. basilic

r       , z        3. two paired arteries serving the brain

c. brachial

o        4. longest vein in the lower limb

d. brachiocephalic

k        5. artery on the dorsum of the foot checked after leg surgery

e. celiac trunk

j        6. serves the posterior thigh

f. cephalic

t        7. supplies the diaphragm

g. common carotid

c        8. formed by the union of the radial and ulnar veins

h. common iliac

b       , f        9. two superficial veins of the arm

i. coronary

w        10. artery serving the kidney

j. deep artery of the thigh

p        11. veins draining the liver

k. dorsalis pedis

q        12. artery that supplies the distal half of the large intestine

l. external carotid

s        13. drains the pelvic organs

m. femoral

m        14. what the external iliac artery becomes on entry into the thigh

n. fibular

C        15. artery that branches into radial and ulnar arteries

o. great saphenous

y        16. supplies most of the small intestine

p. hepatic

h        17. join to form the inferior vena cava

q. inferior mesenteric

e        18. an arterial trunk that has three major branches, which run to the liver, spleen, and stomach

r. internal carotid

l        19. major artery serving the tissues external to the skull

s. internal iliac

a       , n       , o       , u        20. four veins serving the leg

t. phrenic

v        21. artery generally used to take the pulse at the wrist

u. posterior tibial

v. radial

w. renal

x. subclavian

y. superior mesenteric

z. vertebral

6. What is the function of the cerebral arterial circle?

Provides an alternate set of pathways for blood to reach brain tissue in case of impaired blood flow anywhere in the system

7. The anterior and middle cerebral arteries arise from the internal carotid artery.

They serve the cerebral hemispheres     of the brain.

8. Trace the pathway of a drop of blood from the aorta to the left occipital lobe of the brain, noting all structures through which it flows. Aorta subclavian artery vertebral artery basilar artery posterior cerebral artery occipital brain tissue.

9. The human arterial and venous systems are diagrammed on this page and the next. Identify all indicated blood vessels.

10. Trace the blood flow for each of the following situations.

a. from the capillary beds of the left thumb to the capillary beds of the right thumb: Digital vein, L radial vein, L brachial vein, L axillary vein, L subclavian vein, L brachiocephalic vein, superior vena cava, R atrium, R ventricle, pulmonary trunk, pulmonary artery, lobar artery, pulmonary capillaries of the lung, lobar veins, pulmonary veins, L atrium, L ventricle, aortic arch, brachiocephalic artery, R subclavian artery, R axillary artery, R brachial artery, R radial artery, digital artery

b. from the mitral valve to the tricuspid valve by way of the great toe: Through mitral valve into left ventricle, aorta, common iliac artery, external iliac artery, femoral artery, posterior tibial artery, medial plantar artery, digital artery, capillary beds, digital vein, plantar arch, plantar vein, posterior tibial vein, femoral vein, external iliac vein, common iliac vein, inferior vena cava, right atrium, then through tricuspid valve

Pulmonary Circulation

11. Trace the pathway of a carbon dioxide gas molecule in the blood from the inferior vena cava until it leaves the bloodstream. Name all structures (vessels, heart chambers, and others) passed through en route.

Inferior vena cava right atrium tricuspid valve right ventricle pulmonary (semilunar) valve pulmonary trunk right or left pulmonary artery lobar artery pulmonary capillary beds in lungs air sacs (alveoli) of lungs

12. Trace the pathway of oxygen gas molecules from an alveolus of the lung to the right ventricle of the heart. Name all structures through which it passes. Circle the areas of gas exchange. Alvelous alveolar/capillary walls pulmonary vein left atrium mitral valve left ventricle aortic (semilunar) valve aorta systemic arteries capillary beds of tissues systemic veins superior or inferior vena cava right atrium tricuspid valve right ventricle

13. Most arteries of the adult body carry oxygen-rich blood, and the veins carry oxygen-poor blood.

How does this differ in the pulmonary arteries and veins? The pulmonary arteries carry oxygen-poor blood to the lungs, whereas the pulmonary veins carry oxygen-rich blood from the lungs to the left heart.

14. How do the arteries of the pulmonary circulation differ structurally from the systemic arteries? What condition is indicated by this anatomical difference? The pulmonary arteries are more like veins anatomically. They have relatively thin walls, reflecting the fact that the pulmonary circulation is a low-pressure bed.

Fetal Circulation

15. For each of the following structures, first indicate its function in the fetus; and then notes its face (what happens to it or what it is converted to after birth). Circle the blood vessel that carries the most oxygen-rich blood.


Function in fetus


Umbilical artery

Carries O2-poor blood from the fetus to the placenta.

Obliterated. Becomes the medial umbilical ligament.

Umbilical vein

Carries O2-rich blood from the placenta to the fetus.

Obliterated. Becomes the round ligament of the liver (ligamentum teres).

Ductus venosus

Shunts blood through the fetal liver, bypassing the bulk of its tissue.

Becomes the fibrous ligamentum venosum.

Ductus arteriosus

Bypasses the fetal lungs by shunting blood from the pulmonary trunk to the aorta.

Occludes. Becomes the ligamentum arteriosum.

Foramen ovale

Bypasses the lungs by shunting blood from the right atrium to the left atrium.

Closes. Becomes the fossa ovalis.

16. What organ serves as a respiratory/digestive/excretory organ for the fetus? Placenta

Hepatic Portal Circulation

17. What is the source of blood in the hepatic portal system? Blood drained from the digestive viscera.

18. Why is this blood carried to the liver before it enters the systemic circulation? This blood is rich in nutrients. The liver is the key body organ responsible for maintaining proper blood concentrations of glucose, proteins, etc. Its phagocytes also cleanse the blood of debris.

19. The hepatic portal vein is formed by the union of (a) splenic vein         , which drains the spleen,     , pancreas     , greater curvature of the
        , distal large intestine via the inferior mesenteric vein ,

and (b) superior mesenteric   , which drains the small intestine     and

ascending colon .

The gastric         vein, which drains the lesser curvature of the stomach, empties directly into the hepatic portal vein.

20. Trace the flow of a drop of blood from the small intestine to the right atrium of the heart, noting all structures encountered or passed through on the way. Capillaries of small intestine superior mesenteric vein hepatic portal vein liver sinusoids hepatic vein inferior vena cava right atrium of heart

Review Sheet

Exercise 33

Human Cardiovascular Physiology: Blood Pressure and Pulse Determinations


Lab Time/Date

Cardiac Cycle

1. Using the grouped sets of terms to the right of the diagram, correctly identify each trace, valve closings and openings, and each time period of the cardiac cycle.

i   1. aortic pressure

k   2. atrial pressure

n   3. ECG

o   4. first heart sound

p   5. second heart sound

g   6. ventricular pressure

m   7. ventricular volume

h   8. aortic (semilunar)
valve closes

f   9. aortic (semilunar)
valve opens

b, d  10. AV and semilunar
valves closed (2 letters)

j  11. AV valve closes

l  12. AV valve opens

a, e  13. ventricular diastole
(2 letters)

c  14. ventricular systole

2. Define the following terms.

systole: Contraction of the ventricles (general usage)

diastole: Ventricular relaxation (general usage)

cardiac cycle: One complete heartbeat including atrial and ventricular contraction

3. Answer the following questions concerning events of the cardiac cycle.

When are the AV valves closed? During ventricular systole

What event within the heart causes the AV valves to open? Atrial pressure greater than

ventricular pressure

When are the semilunar valves closed? During the period of relaxation of the heart as a

whole and during atrial contraction

What event causes the semilunar valves to open? Ventricular pressure greater than pressure in great arteries

Are both sets of valves closed during any part of the cycle? Yes              

If so, when? Momentarily after atrial contraction and ventricular systole.         

Are both sets of valves open during any part of the cycle? No

At what point in the cardiac cycle is the pressure in the heart highest? Ventricular systole

Lowest? Ventricular diastole

What event results in the pressure deflection called the dicrotic notch? The momentary increase in aortic pressure that occurs when its semilunar valves snap shut

4. Using the key below, indicate the time interval occupied by the following events of the cardiac cycle.

Key: a. 0.8 sec b. 0.4 sec c. 0.3 sec d. 0.1 sec

a 1. the length of the normal cardiac cycle b    3. the quiescent period

d 2. the time interval of atrial systole c      4. the ventricular
contraction period
5. If an individual’s heart rate is 80 beats/min, what is the length of the cardiac cycle?
0.75 sec What portion of the cardiac cycle decreases with a more rapid heart rate? Quiescent period (ventricular relaxation period)

6. What two factors promote the movement of blood through the heart? Alternate contraction and relaxation of the myocardium

and opening and closing of the heart valves

Heart Sounds

7. Complete the following statements.

The monosyllables describing the heart sounds are 1 . The first heart sound is a result of closure of the 2 valves, whereas the second is a result of closure of the 3 valves.
The heart chambers that have just been filled when you hear the first heart sound are the 4 , and the chambers that have just emptied are the 5 . Immediately after the second heart sound, both the 6 and 7 are filling with blood.

1. lub-dup

2. atrioventricular

3. aortic and pulmonary (semilunar)

4. ventricles

5. atria

6. atria

7. ventricles

8. As you listened to the heart sounds during the laboratory session, what differences in pitch, length, and amplitude (loudness) of the two sounds did you observe? First heart sound is longer, louder, and lower in pitch than the second heart sound, which is short, sharp, and high-pitched.

9. In order to auscultate most accurately, indicate where you would place your stethoscope for the following sounds:closure of the tricuspid valve: Left or right sternal border of the 5th intercostal space

closure of the aortic valve: Right sternal border of the 2nd intercostal space
apical heartbeat: 5th intercostal space in line with the middle of the left clavicle

Which valve is heard most clearly when the apical heartbeat is auscultated? Mitral

10. No one expects you to be a full-fledged physician on such short notice, but on the basis of what you have learned about heart sounds, how might abnormal sounds be used to diagnose heart problems?

Abnormal sounds such as swishing sounds after valvular closure or high-pitched sounds arising when blood is forced through constricted (valve) openings might indicate valvular problems.

The Pulse

11. Define pulse. Pressure surges in an artery occurring during each contraction and relaxation of the left ventricle

12. Describe the procedure used to take the pulse. Place the first 2–3 fingertips of one hand over an arterial pressure point. Compress firmly and then release the pressure slightly to palpate the pulse.

13. Identify the artery palpated at each of the pressure points listed.

at the wrist: Radial on the dorsum of the foot: Dorsalis pedis

in front of the ear: Temporal at the side of the neck: Carotid

14. When you were palpating the various pulse or pressure points, which appeared to have the greatest amplitude or tension?

Carotid artery Why do you think this was so? The carotid arteries are the major arteries that deliver blood to the brain and they are closest to the heart.

15. Assume someone has been injured in an auto accident and is hemorrhaging badly. What pressure point would you compress to help stop bleeding from each of the following areas?

the thigh: Femoral artery the calf: Popliteal artery

the forearm: Brachial artery the thumb: Radial artery

16. How could you tell by simple observation whether bleeding is arterial or venous? If it spurts, it is arterial. It will flow evenly if it is venous blood.

17. You may sometimes observe a slight difference between the value obtained from an
apical pulse (beats/min) and that from an arterial pulse taken elsewhere on the body. What is this difference called?

Pulse deficit

Blood Pressure Determinations

18. Define blood pressure. Pressure exerted by blood against the walls of the blood vessels

19. Identify the phase of the cardiac cycle to which each of the following applies.

systolic pressure: Systole (ventricular contraction)

diastolic pressure: Diastole (relaxation)

20. What is the name of the instrument used to compress the artery and record pressures in the auscultatory method of determining blood pressure? Sphygmomanometer

21. What are the sounds of Korotkoff? Sounds that can be auscultated over a partially
occluded artery

What causes the systolic sound? Sound of turbulent blood flow as it first begins to move
through the constricted artery

What causes the disappearance of the sound? Blood is flowing freely; the artery is no

longer constricted

22. Interpret the pressure reading for each of the three numbers listed: 145/85/82. 145=systolic pressure; 85=diastolic pressure reported as the point where the sound muffles; 82=diastolic pressure reported as the point at which sound disappears

23. Assume the following BP measurement was recorded for an elderly patient with severe arteriosclerosis: 170/110/–. Explain the inability to obtain the third reading.
The patient’s arteries are so narrowed by arteriosclerosis that blood flow is always
partially occluded. Hence, the sound.

24. Define pulse pressure. Systolic pressure minus diastolic pressure

Why is this measurement important? It indicates the actual working pressure (actual amount of blood forced out of the heart during systole).

25. How do venous pressures compare to arterial pressures? Venous pressures are lower.

Why? Veins are far removed from the pumping action of the heart.

26. What maneuver to increase the thoracic pressure illustrates the effect of external factors on venous pressure? Valsalva maneuver

How is it performed? A person takes a deep breath, and mimics the motions of exhaling forcibly, but without actually exhaling. The glottis will close and the intrathoracic pressure will increase.

27. What might an abnormal increase in venous pressure indicate? (Think!) Heart failure. With the heart unable to adequately pump blood, it pools in the lower extremities and increases venous pressure.

Observing the Effect of Various Factors on Blood Pressure and Heart Rate

28. What effect do the following have on blood pressure? (Indicate increase by ↑ and decrease by ↓.)

1. increased diameter of the arterioles 4. hemorrhage

2. increased blood viscosity 5. arteriosclerosis

3. increased cardiac output 6. increased pulse rate

29. In which position (sitting, reclining, or standing) is the blood pressure normally the highest?

Standing The lowest? Reclining

What immediate changes in blood pressure did you observe when the subject stood up after being in the sitting or reclining position? It decreased initially and then increased.

What changes in the blood vessels might account for the change? Upon standing, gravitational pull caused blood pooling in the lower part of the body, but then vasoconstriction initiated by the vasomotor center caused blood pressure to rise.

After the subject stood for 3 minutes, what changes in blood pressure were observed? It
decreased once again.

How do you account for this change? Decreased activity of the sympathetic nervous system.

30. What was the effect of exercise on blood pressure? It increased the blood pressure

On pulse rate? It increased the pulse rate. Do you think these effects reflect changes in cardiac output or in peripheral resistance? Both; cardiac output increases, but peripheral resistance also changes (it decreases as vessels to skeletal muscles and the heart dilate, and increases as vessels to other organs, e.g., GI tract and kidneys, constrict). Overall, peripheral resistance often decreases during exercise, but it decreases less than cardiac output increases. Therefore, blood pressure rises.

Why are there normally no significant increases in diastolic pressure after exercise? Since diastolic pressure reflects the heart in relaxation, it would not be expected to

increase in healthy individuals.

31. What effects of the following did you observe on blood pressure in the laboratory?

cold temperature: Increased BP

What do you think the effect of heat would be? Decreased BP

Why? Vasodilation would occur.

32. Differentiate between a hypo- and a hyperreactor relative to the cold pressor test. Hyperreactors exhibit a rise of 23 mm Hg or more in BP during the test. Hyporeactors exhibit a smaller increase or a decrease in BP.

Skin Color as an Indicator of Local Circulatory Dynamics

33. Describe normal skin color and the appearance of the veins in the subject’s forearm
before any testing was conducted.

Skin pink; veins flat and difficult to see.

34. What changes occurred when the subject emptied the forearm of blood (by raising the arm and making a fist) and the flow was occluded with the cuff? Skin becomes pale (cyanotic in some cases) and cool.

What changes occurred during venous congestion? Skin becomes pink (red) and warm, and veins are congested and very visible.

35. What is the importance of collateral blood supplies? Can maintain the blood supply to
an organ or body part in case the major nutrient artery is occluded

36. Explain the mechanism by which mechanical stimulation of the skin produced a flare. Local inflammatory response produced by the chemical mediators released by injured tissue cells
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