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BELLE MCAT Biology > Circulatory System > Flashcards

Circulatory System Flashcards

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1
Q

True or False: All blood cells in the adult are initially produced in the bone marrow.

A

True

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2
Q

What primary function do platelets serve?

A

Platelets are cellular fragments derived from megakaryocytes; they are responsible for clotting, or coagulation.

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3
Q 
Place the following in order from highest BP to lowest BP: 
Vena Cava 
Aorta
Arterioles 
Veins
Arteries
Venules
Capillaries
A 
Arota
Arteries
Arterrioles
Capillaries
Venules
Veins
Inferior Vena Cava
The aortic pressure (1) is about 95 mmHg in a normal adult. The mean blood pressure does not fall very much as the blood follows down the aorta and through large distributing arteries, such as the femoral artery (2). It is not until the small arteries and arterioles, such as the renal arteriole (3), that there is a significant decrease in blood pressure. Approximately 50-70% of the BP drop occurs within the smaller arteries and arterioles. By the time blood reaches the capillaries (4), the mean BP may be 25-30 mmHg, depending upon the organ. The pressure falls further as blood travels into the venules (5) and veins (6), and back to the heart via the vena cavae (7).
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4
Q

Carries deoxygenated blood away from the heart

A

Pulmonary artery

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5
Q

Carries recently oxygenated blood toward the heart

A

Pulmonary vein

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6
Q

Directly receives blood from the vena cava

A

Right atrium

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7
Q

Pumps blood toward the lungs

A

Right ventricle

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8
Q

The heart can contract without a neural input because of impulse initiation from what?

A

Pacemaker cells in the sinoatrial (SA) node initiate and regulate the rhythmic contractions of the heart.

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9
Q

In a typical oxygen-dissociation curve of hemoglobin, what type of shift does fetal hemoglobin represent?

A

Left Shift. Pressure is typically on the x-axis of an oxygen dissociation curve. Fetal hemoglobin has a greater affinity for oxygen than adult hemoglobin; therefore it takes less pressure for oxygen to bind, causing a shift to the left.

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10
Q

Blood’s greatest component by volume is what?

A

Plasma

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11
Q

Platelets are derived from

A

Platelets are cellular fragments derived from megakaryocytes. Platelets are responsible for blood coagulation or clotting in the circulatory system. An interesting fact about platelets is that they contain ribosomes and do synthesize some proteins, yet have no nucleus in which to produce mRNA.

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12
Q 
Which of the following proteins has the most integral role in blood clotting?
Actin
Myosin 
Collagen
Fibrin
A

Fibrin
During the formation of a blood clot, fibrinogen is converted by thrombin into fibrin, an insoluble protein that combines with platelets to form a blood clot.

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13
Q

From what organ is erythropoietin released, and what is this hormone’s primary function?

A

Erythropoietin is a hormone secreted by the kidneys in response to cellular hypoxia. It increases the production of red blood cells (erythrocytes) in bone marrow.

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14
Q

Whta stimulates the release of erythropoietin?

A

Hypoxia

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15
Q

On what type of cell is the Rh factor most likely expressed?

A

The Rh factor is a type of protein on the surface of red blood cells.

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16
Q

Describe resistance to blood flow in the circulatory system

A

Resistance to blood flow within a vascular network is determined by the size of individual vessels and the organization of the vascular network. Changes in vessel diameter as the blood flows through the various vessel types are important for regulating blood flow within an organ, as well as for regulating arterial pressure. Thus, we expect that the greater the decrease in vessel diameter experienced, the greater the resistance. However, total area in blood flow, or total cross-sectional area, will influence the resistance in a given blood vessel type as well. The total cross sectional area of the body’s capillary beds is far greater than any other type of vessel. Thus, even though the diameter of an individual capillary is smaller than the diameter of an arteriole, due to the vast amount of capillaries found in the body, arterioles are the site of greatest resistance in the body’s blood vessels. Among the larger arteries and veins, veins have a larger diameter than arteries, thus providing a lower resistance to blood flow. Therefore, vascular resistance decreases in the order of arterioles, capillaries, arteries, and finally venules and veins.

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17
Q

Arrange the following items in order of decreasing vascular resistance.

Capillaries
Venules and veins
Arteries
Arterioles

A

Arterioles

Capillaries

Arteries

Venules and veins

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18
Q

True or False Urea and CO2 diffuse into blood via capillaries

A

true

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19
Q

True or False Plasma is often forced into spaces between cells and is ultimately picked up by the lymphatic system to be returned to general circulation

A

true

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20
Q

True or False Gas, nutrient, and waste exchange occurs in capillary beds.

A

true

21
Q

Which artery does NOT contain oxygenated blood?

A

pulmonary artery

22
Q

Why does backflow of blood in the heart occur when valves are absent?

A

There is higher pressure in the ventricles. The ventricles are larger and more muscular than the atria and therefore can create more pressure. A fundamental concept involving fluids is that they flow from areas of high pressure to low pressure. Valves are neat structures which prevent blood from reentering the lower pressure atria.

23
Q 
Which of the following initiates systole?
Contraction of Ventricles
Relaxation of Atria 
Relaxation of Ventricles 
Contraction of Atria
A

Contraction of ventricles. When the ventricles contract, the pressure increases above pressures in the atria. The mitral and tricuspid valves close, while the semilunar valves open, allowing blood to flow into the arteries.

24
Q

How are ventricular muscle cells connected?

A

Cardiac muscle consists of individual cells connected by intercalated discs to work as a single functional organ. Note that the prefix “inter-“ means “between.”

25
Q

How would a high oxygen environment impact R/T state?

A

High oxygen environments will shift the hemoglobin into a predominantly R state, which has a high affinity for oxygen.

26
Q

True or false: The four hemoglobin subunits are connected together in part by peptide bonds.

A

This statement is false. Quaternary structure is maintained by the association between hydrophobic domains on adjacent subunits. Ionic interactions (salt bridges) confer structural specificity and additional attractive force. Peptide bonds are the basic bond of primary structure, holding together adjacent amino acids.

27
Q

High Affinity state of hemoglobin

A

R state. When you are Relaxed, you are AFFable. High affinity for oxygen corresponds to the R state, and low affinity corresponds to the T state. Whenever oxygen is bound, hemoglobin exists in the R (relaxed) state, and oxygen affinity is high. In contrast, the T (taut) state is marked by low oxygen affinity.

28
Q

Low Affinity state of hemoglobin

A

T state. When you are Tense, you are NOT affable. High affinity for oxygen corresponds to the R state, and low affinity corresponds to the T state. Whenever oxygen is bound, hemoglobin exists in the R (relaxed) state, and oxygen affinity is high. In contrast, the T (taut) state is marked by low oxygen affinity.

29
Q

Why, when at lower partial pressures of O2, does hemoglobin have less affinity for oxygen compared to myoglobin?

A

Within tissues that are metabolically active, the partial pressure of oxygen is relatively low. Under these conditions, hemoglobin exhibits a low affinity for oxygen, which facilitates its release into the tissues. Myoglobin, a monomeric protein, does not exhibit cooperativity. Its affinity for oxygen is similarly high regardless of its surrounding environment.

30
Q

Where will the curve shift: high pH

A

High pH corresponds with a left shift

31
Q

Where will the curve shift: High temperature

A

high temperature and high CO2 correspond with a right shift.

32
Q

Where will the curve shift: high CO2

A

high temperature and high CO2 correspond with a right shift.

33
Q

How will Fetal Hemoglobin’s affinity for 2,3-BPG differ from regular hemoglobin?

A

Fetal hemoglobin must draw its oxygen from maternal hemoglobin, which necessitates a slightly higher oxygen affinity. This is accomplished, in part, by a reduction in the binding of 2,3-BPG. Since 2,3-BPG normally decreases oxygen affinity, a reduction in the binding of this compound ultimately increases fetal hemoglobin’s affinity for oxygen.

34
Q

How does 2,3-BPG impact affinity?

A

Decreases oxygen affinity

35
Q

Prosthetic group in myoglobin

A

Heme

36
Q

How is CO2 converted to carbonic acid?

A

Carbon dioxide is converted to carbonic acid by carbonic anhydrase within erythrocytes.

37
Q

How would the affinity for oxygen and binding curve compare for someone who has lived on the base of everest for a month compare to someone at the base of the grand canyon?

A

They would have a lower O2 affinity and a right shift curve. 2,3-BPG reduces the affinity of hemoglobin for oxygen, which facilitates more effective oxygen delivery to the tissues. This corresponds to a rightward shift in the dissociation curve. In the presence of this compound, at a given partial pressure of oxygen, a comparatively low percentage of hemoglobin will be saturated with oxygen.

38
Q

Select all correct answers. Sickle cell crisis is characterized by intense pain, which occurs as a result of the formation of “sickled” erythrocytes within the microvasculature. Erythrocytes are more vulnerable to sickling when concentrations of T-state hemoglobin are high. Sickle-cell crisis is likely induced by…

A

acidosis, hypoxia, intense exercise

39
Q

True or False: RBC’s are likely to contain mitochondria

A

false, they dont really have membrane bound organelles

40
Q

RhoGAM is an anti Rh-isoimmunization drug that prevents a mother’s immune system from attacking her fetus.

A

B+ and B-

41
Q

True or false: atherosclerosis is the build up fatty deposits in any circulatory vessel, resulting in reduced blood flow to target tissues.

A

This statement is false. It is important to watch out for subtleties on the MCAT. It’s not any vessel that atherosclerosis affects - it’s the arterial circulatory system, most commonly the coronary arteries. Blockage of these vessels causes reduced blood flow to the heart, resulting in ischemia (hypoxia) and possibly even infarction (cell death).

42
Q

Describe the process of heart contraction in terms of the nervous system

A

The SA node fires and sends the signal to the atria to fully contract. It also propagates a signal to the AV node, which then relays this signal to the bundle of His, and that signal then is passed through Purkinje fibers. The spreading of the impulse from the AV node is what triggers the ventricles to contract.

43
Q

Describe the structure of arteries

A

The arteries are composed of three layers. The innermost layer is comprised of endothelial cells and is known as the tunica intima.The middle layer is made up of smooth muscle and is called the tunica media.The outermost is the tunica externa which is primarily made up of collagen.

44
Q

Endothelial lining is a characteristic of what part of arteries?

A

Tunica intima

45
Q

Where will smooth muscle be found in the arteries?

A

The middle layer is made up of smooth muscle and is called the tunica media.

46
Q

Where will collagen be found in the arteries?

A

The outermost is the tunica externa which is primarily made up of collagen.

47
Q

True or False: Vessel length is proportional to resistance in blood flow

A

true

48
Q

True or False: Vessel radius is proportional to resistance in blood flow

A

False, it is inversely proportional

BELLE MCAT Biology (20 decks)

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