MCAT Biology Circulatory system

Question 1

The flow of blood through a tissue is known as ___

Answer 1

perfusion

Question 2

Inadequate blood flow is known as __

Answer 2

ischemia

Question 3

___have smooth muscle in their walls that can act as a control valve to restrict or increase the flow of blood into the capillaries of tissues

Answer 3

Arterioles

Question 4

After passing through capillaries, blood collects in small veins called ___

Answer 4

venules

Question 5

Except for the largest vesssels near the heart, veins lack a __

Answer 5

muscular wall

Question 6

What are the 4 major roles of endothelial cells lining blood vessels

Answer 6

Vasodilation and vasoconstriction
Inflammation
Angiogenesis
Thrombosis

Question 7

Why have mammals evolved a separate circulation for lungs?

Answer 7

Blood is pumped away from the heart at high pressure in arteries to pass through the capillaries. If the blood is to pass through one bed of capillaries, and then through another bed of capillaries, the pressure must be very high in the first set of capillaries or blood will not have enough pressure to pass through the second set of capillaries. Having two separate circulations solves this problem

Question 8

In the ___ blood passes first through capillaries in the intestine, then collects in veins to travel to the liver, where the vessels branch and the blood passes again through capillaries

Answer 8

Hepatic portal system

Question 9

___is another portal system where blood passes through capillaries in the hypothalamus to the portal veins, then to capillaries in the pituitary

Answer 9

Hypothalamic-hypophysial portal system

Question 10

The __ evolved as direct transport systems, to transport nutrients directly from the intestine to the liver or hormones from the hypothalamus to the pituitary, without passing through the whole body

Answer 10

Portal systems

Question 11

The very first branch from the aorta are ___ which branch to supply blood to the wall of the heart

Answer 11

Coronary arteries

Question 12

Deoxygenated blood from the heart collects in __

Answer 12

coronary veins

Question 13

Coronary veins merge to form ___ located beneath a layer of fat on the outer wall of the heart

Answer 13

Coronary sinus

Question 14

Blood in the __ is the only deoxygenated blood that does not end up in the inferior vena cava or superior vena cava, it drains directly into the right atrium

Answer 14

Coronary sinus

Question 15

Ventricular pressure is very ___ and atrial pressure is __

Answer 15

Ventricular pressure is very high and atrial pressure is lower

Question 16

During diastole ___

Answer 16

ventricles are relaxed, blood is able to flow into them from the atria

Question 17

At the end of diastole, ____initiating systole

Answer 17

Ventricles contract

Question 18

During systole pressure in the atria __

Answer 18

is low and thus the atria fills with blood from the vena cava and pulmonary veins

Question 19

The equation for cardiac output (L/min) =

Answer 19

Stroke volume (L/beat) X Heart rate (beats/min)
CO = SV x HR

Question 20

Two principle ways to increase venous blood return

Answer 20

1. increase total volume of blood in circulatory system (retain more water)
2. Contraction of large veins can propel blood towards the heart
   - this is why presence of valves throughout the venous system is essential here

Question 21

Propagation of action potentials requires____

Answer 21

voltage-gated ion channels

Question 22

Difference between neurons and cardiac muscle cells is that cardiac muscle is a ___ the cytoplasm of different cells can communicate via gap junctions

Answer 22

Functional syncytium

Question 23

The two voltage-gated ion channels involved in cardiac muscle are

Answer 23

Voltage-gated sodium channels (fast sodium channels)

Slow calcium channels

Question 24

Why are slow calcium channels in the heart called that?

Answer 24

They stay open longer than the fast sodium channels do, causing the membrane depolarization to last longer in cardiac muscle than in neurons producing a plateau phase

Question 25

The action potentials of cardiac muscle travel down along ___

Answer 25

T tubules, allow the entry of calcium from the extracellular environment and also induce the sarcoplasmic reticulum to release calcium

Question 26

The combination of intracellular and extracellular calcium causes the contraction of ___

Answer 26

actin-myosin fibers

Question 27

Why does the SA node reach threshold faster than any other region of the heart does?

Answer 27

Because it has the most Na+ leak channels

Question 28

The resting membrane potential of cardiac muscles is about __

Answer 28

-90 mV

Question 29

The constant level of inhibtiion provided by the vagus nerve releasing acetylcholine that synapse near the SA node bringing the norm heart rate down to 60-80 from its intrinsic 120 bpm is called___

Answer 29

vagal tone

Question 30

The role of the parasympathetic system in controlling the heart is to __

Answer 30

modulate the rate by inhibiting rapid automaticity

Question 31

During "fight-or-flight" the sympathetic postganglionic neurons innervate the heart by releasing__

Answer 31

norepinephrine

Question 32

The second way the sympathetic nervous system influences the heart is by the adrenal medulla__

Answer 32

releasing epinephrine which binds to receptors on cardiac muscle cells

Question 33

The driving force for blood flow is __

Answer 33

a difference in pressure from arteries to veins

Question 34

Ohms law summarizes the pressure of blood flow into the formula

Answer 34

``` P= Q x R Q = blood flow or cardiac output (L/min) R = resistance ```

Question 35

How would an increase in stroke volume change blood pressure?

Answer 35

Since CO=SV x HR, an increase in stroke volume would increase cardiac output. Since blood pressure and cardiac output are directly proportional, an increase would increase blood pressure as well

Question 36

The principle determinant of resistance of blood flow is __

Answer 36

the degree of constriction of arteriolar smooth muscle known as precapillary sphincters

Question 37

A basa level of pressure privded by constant level of norepinephrine released by millions of sympathetic postganglionic axons innervating precapillary sphincters of arteriolar smooth muscle is termed__

Answer 37

adrenergic tone

Question 38

The pulse pressure is the difference between __

Answer 38

systolic and diastolic pressure

Question 39

The hormone ___ made in the kidneys stimulates RBC production in the bone marrow.

Answer 39

Erythropoietin

Question 40

RBC have no organelles or nucleus and rely on __for ATP synthesis

Answer 40

Glycolysis

Question 41

When none of the four subunits of hemoglobin have oxygen bound they assume a ___ which has a relatively low affinity for oxygen

Answer 41

tense conformation

Question 42

The ___of hemoglobin has a higher affinity for oxygen

Answer 42

Relaxed conformation

Question 43

What three factors stabilize the tense configuration of hemoglobin (low O2 affinity)

Answer 43

1. Decreased pH 2. Increased pCO2 (level of CO2) in the blood 3. Increased temperature

Question 44

At a given pO2 which has a higher % saturation: tense or relaxed hemoglobin?

Answer 44

Relaxed since it has a higher affinity. This just means that at any O2 level, relaxed hemoglobin will bind more O2 than tense hemoglobin will

Question 45

What are the three ways that Carbon dioxide is transported in the blood

Answer 45

70% is transported by the conversion of CO2 to Carbonic acid 20% binds to a site on hemoglobin (not the binding site of oxygen) this helps stabilize the tense Hb 3. CO2 is somewhat water-soluble can dissolve in blood, unlike O2 NO O2 can dissolve in blood

Question 46

Amino acids and glucose are absorbed from the digestive tract and carried by a special vein called ___

Answer 46

hepatic portal vein to the liver

Question 47

Fats are absorbed from the intestine and packaged into chylomicrons which enter into tiny lymphatic vessles in the intestinal wall called __

Answer 47

lacteals

Question 48

Lacteals empty into larger lymphatics which eventually drain into a large vein near the neck

Answer 48

Not a card just know this

Question 49

Two white blood cells can squeeze through the intercellular clefts, the spaces between capillaries, they aere

Answer 49

Neutrophils and macrophages because they are capable of amoeboid motility

Question 50

Two reasons water has a tendency to flow out of capillaries.

Answer 50

1. Hydrostatic pressure created by the heart simply tends to squeeze water out of the capillaries 2. High osmolarity of the tissues tends to draw water out of the bloodstream