Download Chapter 12: Checkpoint Questions - Burlington

Name: _____________________________________ Date: __________ Period: ____
Chapter 12: Checkpoint Questions
Cardiovascular System—The Heart
1. Describe the basic function of the cardiovascular system.
The cardiovascular system provides an internal transport system for blood, nutrients,
and waste products.
2. Compare and contrast the structure and functions of arteries, capillaries, and
veins.
Arteries, capillaries and veins are all blood vessels within the body.
Arteries are efferent vessels that carry blood (usually oxygenated) away from the
heart. Veins are afferent vessels that carry blood (usually deoxygenated) toward the
heart. Capillaries are the smallest, thin walled blood vessels that carry out nutrient
exchange via diffusion across the membranes. They create a network between arteries
and veins.
3. Compare and contrast the pulmonary and systemic circuits of the cardiovascular
system.
The pulmonary circuit pumps blood from the heart, to the lungs, and back, in order to
oxygenate the blood.
The systemic circuit carries (oxygenated) blood from the heart, to the rest of the
body/organs, and back, in order to deliver the oxygen and nutrients to the body.
It is therefore imperative that blood alternates between the two circuits.
4. List the four chambers of the heart and describe the major differences between
the atria and ventricles.
The four chambers of the heart are the right and left atrium, and the right and left
ventricles. Both of the atria collect blood (RA from the pulmonary circuit, and LA from
systemic circuit) Both of the ventricles pump blood out of the heart (RV pumps blood to
pulmonary circuit, and LV pumps blood to systemic circuit).
5. Describe the structure and function of the pericardium.
The pericardium consists of dense, fibrous tissue that surrounds and stabilizes the
heart. It consists of a parietal layer and visceral layer that holds pericardial fluid. This
fluid acts like a lubricant to reduce friction as the heart beats.
6. Compare and contrast the three layers of the heart wall.
The epicardium is the outer layer of the heart. It consists of epithelium and connective
tissue and is the visceral peridardium. The epicardium connects to the middle layer, the
myocardium, which contains all of the cardiac muscle tissue organized into concentric
layers. The myocardium allows the heart to “squeeze and twist” during contractions to
force blood out of the heart. The myocardium is attached to the inner-most layer, the
endocardium, which is composed of simple squamous epithelium. This layer lines the
inside of the heart and makes up the heart valves.
7. Describe the pathway that a blood cell would follow through the heart beginning in
the right atrium…and ending back in the right atrium.
The pathway would go as follows:
1. Right atrium
2. Through the right AV valve (tricuspid)
3. Right ventricle
4. Through the pulmonary semilunar valve
5. Pulmonary trunk (left and right pulmonary arteries)
6. Capillaries in lungs
7. Left and right pulmonary veins
8. Left atrium
9. Through the left AV valve (bicuspid)
10. Left ventricle
11. Through the aortic semilunar valve
12. Aorta (ascending, aortic arch, descending)
13. Systemic circuit
14. Capillaries in body
15. Veins
16. Vena cava (superior and inferior)
17. Right atrium
8. Identify and explain ONE similarity and ONE difference between the left and right
atria.
Both atria collect blood and are similar in structure.
The right atrium collects blood from systemic circuit (deoxygenated blood)
The left atrium collects blood from the pulmonary circuit (oxygenated blood)
9. Identify and explain ONE similarity and ONE difference between the left and right
ventricles.
Both ventricles pump blood. The right ventricle pumps (deoxygenated) blood to the
pulmonary circuit (pouch shaped, and thinner walls). The left ventricle pumps
(oxygenated) blood to the systemic circuit (cylindrically shaped with thicker walls).
10. Compare and contrast the atrioventricular valves to the semilunar valves in the
heart. In your explanation, be sure to include: a) location of valve(s); b) function of
valve(s).
The atrioventricular valves (AV) are located between the atria and ventricles. The right
is a tricuspid, and the left is a bicuspid valve. They both are connected to chordae
tendinae (heart strings) and papillary muscles. Their function is to prevent the back flow
of blood into the atria from the ventricles when they contract.
The semilunar valves are located in the pulmonary trunk and aorta. They are both
tricuspids but are not connected to chordae tendinae. Their functions are to prevent
the back flow of blood from the arteries back into the ventricles.
11. Damage to the semilunar valves on the right side of the heart would affect blood
flow to which vessel? Why might this cause a problem?
The semilunar valve on the right side prevents blood from re-entering the right ventricle
from the pulmonary trunk. If this didn’t work correctly blood deoxygenated blood would
not be able to reach the lungs.
12. What prevents the AV valves from swinging into the atria?
The AV valves are connected to papillary muscles by chordae tendinae (heart strings)
which prevent the valves from swinging into the atria.
13. What prevents the semilunar valves from allowing backflow?
The shape of the semilunar valves prevent blood from flowing back into the heart. The
semilunar valves have a concave shape which collects the blood flowing backwards,
causing the valve to close.
14. Why is the left ventricle more muscular than the right ventricle?
The right ventricle is only responsible for pumping blood to the lungs and back (short
distance); the left ventricle must pump blood throughout the entire body which requires
more pressure = thicker, more muscular walls.
15. What is the function of the coronary arteries?
The coronary arteries carry oxygenated blood from the left ventricle to the actual
tissue of the heart. They supply the cardiac tissue with oxygen and nutrients so that
the heart can function properly.
16. Describe the difference between diastole and systole with regards to heart
contractions.
Systole refers to either atria or ventricles while they are contracting (which increases
pressure and pumps blood out of chambers). Diastole refers to either atria or ventricles
while they are relaxing (which decreases pressure and allows chambers to fill with blood).
17. Summarize the steps of the “cardiac cycle”:
a. Step 1: Atrial systole begins: atrial contraction forces blood into the relaxed
ventricles.
b. Step 2: Atrial systole ends, atrial diastole begins
c. Step 3: Ventricular systole—1st phase: ventricular contraction pushes the AV
valves closed, but does not create enough pressure to open semilunar
valves.
nd
d. Step 4: Ventricular systole—2 phase: As ventricular pressure rises and
exceeds pressure in the arteries, the semilunar valves open and blood
is pushed into the aorta and pulmonary trunk.
e. Step 5: Ventricular diastole: As ventricles relax, pressure drops; blood flows
back against cusps of semilunar valves and forces them closed. Blood
flows into the relaxed atria. All chambers are relaxed before the new
cardiac cycle begins.
18. Is the heart always pumping blood when pressure in the left ventricle is rising?
Explain your answer.
No. When pressure in the left ventricle first rises, the heart is contracting but no blood
is leaving the heart. During the initial phase of contraction, both the AV and semilunar
valves are closed. The increase in pressure results from increased tension as the cardiac
muscle contracts. When ventricular pressure exceeds the pressure in the aorta, the
aortic semilunar valves are forced open, and blood is rapidly ejected from the ventricle.
19. What events causes the “lubb-dupp” heart sounds as heard with a stethoscope?
(HINT: There are 4 different heart functions that produce the sound)
The “lubb” is produced by the simultaneous closing of the AV valves and the opening of
the semilunar valves; the “dupp” is produced when the semilunar valves close.
20. If the cardioinhibitory center of the medulla oblongata were damaged, which part
of the autonomic nervous system would be affected, and how would the heart be
influenced? Explain your answer.
Damage to the cardioinhibitory center of the medulla oblongata—a part of the
parasympathetic division of the ANS—would result in fewer parasympathetic action
potentials to the heart and an increase in heart rate due to sympathetic dominance.
21. If the cardioacceleratory center of the medulla oblongata were damaged, which
part of the autonomic nervous system would be affected, and how would the heart
be influenced? Explain your answer.
Damage to the cardioacceleratory center of the medulla oblongata—a part of the
sympathetic division of the ANS—would result in fewer sympathetic action potentials to
the heart and a decrease in heart rate due to parasympathetic dominance.
22. Why is it a potential problem if the heart beats too rapidly?
If the heart beats too rapidly, it has too little time to fill completely between beats.
The heart pumps in proportion to the amount of blood that enters: The less blood that
enters, the less the heart can pump. If it beats too fast, very little blood will enter the
blood stream; tissues will suffer damage from the lack of blood supply.
23. Describe the three steps of ventricular contraction:
a. Step 1:
Rapid Depolarization: Caused by sodium ion entry.
It lasts 3-5 msec, and ends with the closure of
voltage-gated sodium channels.
b. Step 2:
The Plateau: Caused by calcium ion entry. It lasts
~175 msec, and ends with the closure of calcium
channels.
c. Step 3:
Repolarization: Caused by potassium ion loss. It
lasts 75 msec, and ends with the closure of
potassium channels.
24. If the cells of the SA node were not functioning normally, how would the heart rate
be affected? Explain your answer.
If cells of the SA node were not functioning, cells of the AV node would become the
pacemaker cells, so the heart would continue to beat but at a slower rate (40-60
beats/minute as compared to the SA node sending signals = 70-80 beats/minute)
25. Why is it important for the impulses from the atria to be delayed at the AV node
before passing into the ventricles? Explain your answer.
If impulses from the atria were not delayed at the AV node, they would be conducted
through the ventricles so quickly by the bundle branches and Purkinje fibers that the
ventricles would begin contracting immediately, before the atria had finished
contracting. As a result, the ventricles would not be as full of blood as they could be,
and the pumping of the heart would not be as efficient, especially during activity.