MCAT Biology : Other Circulatory Physiology

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #1 : Other Circulatory Physiology

Which of the following statements about thermoregulation is incorrect?

Possible Answers:

When someone is cold, they may eventually shiver to increase their heat production.

Sweat can cool someone down on a hot day, since sweat releases energy from the body to evaporate into the environment.

When someone is cold, they will experience vasodilation in their hands, allowing more blood flow to the hands to maintain uniform temperature through the whole body.

One form of insulation used by the body is subcutaneous fat.

Correct answer:

When someone is cold, they will experience vasodilation in their hands, allowing more blood flow to the hands to maintain uniform temperature through the whole body.

Explanation:

When someone is cold they, will experience vasoconstriction in their hands, allowing less blood to flow to the hands. Their hands will feel colder, since less blood is reaching their hands. When the body is cold, it concentrates blood flow to the core. This maintains a constant, warm blood supply to the vital organs, as well as reduces the blood flow to extremities that have a greater surface area for heat loss to the environment.

Example Question #2 : Other Circulatory Physiology

During heavy exercise, what happens to the circulatory system vessels?

Possible Answers:

Vasoconstrict

Vasodilate

Produce more hemoglobin

Pump less blood

None of these

Correct answer:

Vasodilate

Explanation:

During heavy exercise, the body temperature increases. Heat must leave as efficiently as possible, and thus the body's blood vessels will vasodilate. Vasodilation leads to the vessels being closer to the skin, thus allowing quicker heat transfer to the environment. This effect is accomplished, in part, by stimulation from the sympathetic nervous system.

Example Question #3 : Other Circulatory Physiology

On a cold day, which of the following changes will occur in the circulatory system?

Possible Answers:

Vasodilation

Decrease blood pressure

Vasoconstriction

Increase blood flow

None of these

Correct answer:

Vasoconstriction

Explanation:

On a cold day, it is vital to keep body at a steady temperature through homeostatic processes. The body will compensate for heat loss by having the blood vessels vasoconstrict. This leads to the vessels being farther from the skin, allowing less heat loss due to blood flow. This also explains why conditions like frostbite generally start at the extremities, where surface area is greatest. These regions have the greatest amount of vasoconstriction, and thus contain the smallest amount of warm blood, leaving them prone to the cold environment due to a lack of internal heating.

Example Question #4 : Other Circulatory Physiology

The collection of fluids in the interstitium of the legs and feet is known as peripheral edema, and is closely linked to defects in the circulatory system and blood composition. Which of the following would be least likely to cause this condition?

Possible Answers:

Congestive heart failure

Diabetes

Sickle cell anemia

Kidney failure

Correct answer:

Diabetes

Explanation:

The body strives to maintain the levels of fluid within the body. Several systems, including the circulatory system, lymphatic system, and renal system, are all responsible for keeping the blood flowing throughout the body and removing unnecessary fluid.

Circulatory defects, such as congestive heart failure and sickle cell anemia, and defects of the kidneys can result in peripheral edema. Diabetes itself does not cause peripheral edema, however, complications of diabetes (such as heart disease) may result in some swelling of the limbs.

Example Question #5 : Other Circulatory Physiology

Name the valve that separates the right atrium from the right ventricle.

Possible Answers:

Ventricular valve

Tricuspid valve

Pulmonary valve

Bicuspid valve

Aortic valve

Correct answer:

Tricuspid valve

Explanation:

The tricuspid and bicuspid valves constitute the atrioventricular valves, which separate the heart's atria from its ventricles. The tricuspid valve separates the right atrium from the right ventricle. The bicuspid valve separates the left atrium from the left ventricle.

The pulmonary and aortic valves constitute the semilunar valves, which separate the heart's ventricles from major arteries. The pulmonary valve separates the right ventricle and the pulmonary artery. The aortic valve separates the left ventricle and the aorta.

There is no such thing as a ventricular valve.

Example Question #6 : Other Circulatory Physiology

Which of the following structures is one cell layer thick and functions as the site of gas and nutrient exchange in the circulatory system?

Possible Answers:

Venules

Capillaries

Veins

Arterioles

Arteries

Correct answer:

Capillaries

Explanation:

Each capillary consists of a single layer of epithelium, known as simple squamous epithelium. Substances pass between and through these cells, allowing nutrients to pass from the capillary lumen into the interstitium and allowing wastes to pass from the interstitium to the capillary lumen. Red blood cells flow through the capillaries in single file due to the small circumference of the vessel.

Venules are small veins leading away from the capillary network. Arterioles are small terminal arteries leading into the capillary network. Veins are blood vessels carrying blood toward the heart, while arteries carry blood away from the heart.

Example Question #7 : Other Circulatory Physiology

The transporation of deoxygenated blood from the heart to the lungs is accomplished by which of the following?

Possible Answers:

Inferior vena cava

Thoracic aorta

Pulmonary veins

Axillary vein

Pulmonary arteries

Correct answer:

Pulmonary arteries

Explanation:

The pulmonary arteries bring deoxygenated blood from the body into the lungs, where carbon dioxide is exchanged for oxygen. The oxygen-rich blood leaves the lungs to return to the heart through the pulmonary veins. This is the only occurrence in which arteries carry oxygen-poor blood and veins carry oxygen-rich blood.

The thoracic aorta supplies the bronchi, esophagus, pericardium, chest wall, and diaphragm with oxygenated blood. The inferior vena cava collects deoxygenated blood from the lower extremities and transports it to the heart. In the upper limbs, superficial veins merge to form the axillary vein. These empty into the superior vena cava, and then into the heart. 

Example Question #8 : Other Circulatory Physiology

In what form is carbon dioxide usually circulated in human blood?

Possible Answers:

Carbonic acid

Bicarbonate ion

Carbon monoxide gas

Carbon dioxide gas

Carbonate ion

Correct answer:

Bicarbonate ion

Explanation:

Carbon dioxide is usually circulated in human blood in the form of , or bicarbonate. This is an important part of the blood buffering system, as the bicarbonate ion is the conjugate base of carbonic acid.

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