Exam 3 Review

Question 1

Contraction of muscle is characterized by

a. Lengthening of sarcomere
b. Shortening of the I band, while the A bands move closer together
c. Sliding of actin (thin) filaments toward the Z line (disc)
d. Inhibition of myosin actin interaction by tropomyosin

Answer 1

b. Shortening of the I band, while the A bands move closer together

Question 2

Motor neurons stimulate skeletal muscle contraction by releasing ______ at the _____.

a. Calcium ions, motor end plate
b. Sodium ions, transverse (T) tubules
c. Acetylcholine, motor end plate
d. Tropomyosin, Z line of the sarcomere

Answer 2

c. Acetylcholine, motor end plate

Question 3

Energizing (“cocking”) of the myosin head depends upon

a. ATPase activity of troponin
b. Removal of all sarcoplasmic calcium by the SERCA pump
c. Calcium binding to actin
d. Myosin-induced hydrolysis of ATP to ADP + Pi

Answer 3

d. Myosin-induced hydrolysis of ATP to ADP + Pi

Question 4

What is NOT the correct order of events during excitation-contraction coupling in skeletal muscle?

a. Activation of T tubule calcium channels (DHP receptors), opening of sarcoplasmic reticulum (s.r.) calcium channels (ryanodine receptors)
b. Release of acetylcholine, opening of ligand-gated sodium channels
c. Reuptake of calcium into the sarcoplasmic reticulum, binding of calcium to tropomyosin
d. Release of calcium into the sarcoplasm, binding of calcium to troponin

Answer 4

c. Reuptake of calcium into the sarcoplasmic reticulum, binding of calcium to tropomyosin

Question 5

As the load against which a muscle is contracting get larger

a. The velocity of shortening gets slower
b. The contraction approaches isometric
c. The strength of contraction must increase in order to lift the load
d. All of the above

Answer 5

d. All of the above

Question 6

Strength of contraction of a SINGLE muscle fiber can be increased by

a. Decreased frequency of electrical stimulation
b. Increased frequency of electrical stimulation, up to the point of tetany
c. Pre-stretching the fiber to over twice its resting length
d. Nothing – strength of contraction is all-or-none

Answer 6

d. Nothing – strength of contraction is all-or-none

Question 7

When a motor neuron fires

a. All the muscle fibers in that neuron’s motor unit will contract together
b. The entire muscle tissue (i.e. all that muscle’s myofibers) will contract together
c. Only extracellular calcium will be important
d. Only fast twitch fibers will respond

Answer 7

a. All the muscle fibers in that neuron’s motor unit will contract together

Question 8

At a low-medium intensity of exercise of long duration, the generation of most of the ATP support muscle contraction is mainly derived from

a. Muscle pools of ATP and phosphocreatine
b. Oxidation of fatty acids
c. Fermentation of glucose
d. Breakdown of muscle glycogen

Answer 8

b. Oxidation of fatty acids

Question 9

Blood is

a. Mostly water
b. Plasma and formed elements (cells and cell fragments)
c. A fluid which transports gases, nutrients and waste materials through the circulatory system
d. All of the above

Answer 9

d. All of the above

Question 10

Total blood volume in an adult human is about

a. 5.5 liters
b. 120 mmHg
c. 5.5 mg/liter
d. 55 liters

Answer 10

a. 5.5 liters

Question 11

Your friend goes to visit Denver (about a mile above sea level) for a month. His levels of erythropoietin and his hematocrit would be

a. Unaffected
b. Elevated
c. Decreased
d. Dependent on thrombin activity

Answer 11

b. Elevated

Question 12

In response to bleeding from a damaged blood vessel, the first event in clot formation is

a. Stimulation of nitric oxide release
b. Conversion of fibrinogen to fibrin
c. Recruitment and sticking of platelets
d. Breakdown of fibrin by plasminogen

Answer 12

c. Recruitment and sticking of platelets

Question 13

During ventricular contraction and ejection of blood,

a. Both atrioventricular (AV) and semilunar valves are open
b. AV valves are closed but the chordae tendenae are loosely flapping all around
c. AV valves are closed and semilunar valves are open
d. Left AV and semilunar valves are open, while right AV and semilunar valves are closed

Answer 13

c. AV valves are closed and semilunar valves are open

Question 14

During diastole

a. Ventricular filling is initially passive and rapid
b. Ventricular pressure exceeds aortic pressure
c. Ventricular volume starts out as zero, i.e. all blood from the previous cycle has been ejected
d. Ventricular pressure exceeds venous pressure

Answer 14

a. Ventricular filling is initially passive and rapid

Question 15

In a given cycle, cardiac electrical excitation begins in _____ and culminates in stimulation of _____ by signals from _____.

a. AV node, ventricular contraction, atrial pressure waves
b. SA node, ventricular contraction, Purkinje fibers
c. SA node, both atrial and ventricular contraction, both right and left bundle branches
d. SA node, P wave, the QRS complex

Answer 15

b. SA node, ventricular contraction, Purkinje fibers

Question 16

If venous return to the heart increases,

a. Ventricular and diastolic volume (EDV, or preload) is unaffected
b. Stretch of the ventricular muscle and therefore contractility are increased
c. Stroke volume decreases
d. End systolic volume increases

Answer 16

b. Stretch of the ventricular muscle and therefore contractility are increased

Question 17

Under normal conditions, what prevents cardiac muscle from being subject to tetany?

a. Duration of action potentials in contractile fibers is similar to duration of contraction
b. Action potentials are reversed by opening of potassium channels
c. Inhibition of calcium channels (ryanodine receptors) in the sarcoplasmic reticulum
d. The conduction delay through the atrioventricular (AV) node

Answer 17

a. Duration of action potentials in contractile fibers is similar to duration of contraction

Question 18

The pulmonary circulation

a. Is a low pressure, low flow system
b. Gets only about 40% of cardiac output
c. Is a low pressure, high flow system
d. None of the above

Answer 18

c. Is a low pressure, high flow system

Question 19

The difference between systolic and diastolic pressure in the aorta (i.e. the pule pressure) is significantly less than the difference between left ventricular systolic and diastolic pressures due to

a. Elastic recoil of the aorta during diastole
b. Fluid leakage out of capillaries with discontinuous endothelium
c. The pressure being dampened out of the more compliant veins
d. Backwards flow from the venous system

Answer 19

a. Elastic recoil of the aorta during diastole

Question 20

Filtration of fluid from capillaries is favored by _____, while reabsorption is favored by _____

a. High plasma oncotic pressure, high capillary hydrostatic pressure
b. Low capillary oncotic pressure, high capillary hydrostatic pressure
c. Very low plasma albumin concentration, low tissue (i.e. extra-vascular) hydrostatic pressure
d. High capillary hydrostatic pressure, high capillary oncotic pressure

Answer 20

d. High capillary hydrostatic pressure, high capillary oncotic pressure

Question 21

Under normal conditions, the MOST important factor opposing blood flow is

a. The driving pressure created by the contracting ventricles of the heart
b. Dilation of arterioles in response to sympathetic stimulation
c. Resistance to flow, mainly determined by arteriolar diameter
d. Variable length of blood vessels

Answer 21

c. Resistance to flow, mainly determined by arteriolar diameter

Question 22

Cardiac output is

a. The product of stroke volume and heart rate
b. Increased during exercise
c. Decreased by increasing peripheral resistance
d. All of the above

Answer 22

d. All of the above

Question 23

Increased venous return

a. Can increase stroke volume but not contractility
b. Will increase both end diastolic volume and stroke volume
c. Is not possible unless in a “fight or flight” situation
d. Results when right atrial pressure exceeds venous pressure

Answer 23

b. Will increase both end diastolic volume and stroke volume

Question 24

An immediate effect of severe blood loss would be

a. Increased venous return
b. Increased cardiac output
c. Decreased cardiac output
d. Increased blood pressure

Answer 24

c. Decreased cardiac output

Question 25

The largest pressure drop in the cardiovascular system occurs in the

a. Capillaries
b. Arterioles
c. Post-capillary venules
d. Right and left atria

Answer 25

b. Arterioles

Question 26

Under resting conditions, the predominant EXTRINSIC factor influencing resistance to flow in skeletal muscle arterioles is

a. Tonic release of norepinephrine by sympathetic nerves (i.e. so-called “sympathetic tone”)
b. Release of histamine by parasympathetic nerves
c. Release of acetylcholine by parasympathetic nerves
d. Release of epinephrine by the adrenal gland

Answer 26

a. Tonic release of norepinephrine by sympathetic nerves (i.e. so-called “sympathetic tone”)

Question 27

The major circulatory changes during exercise include

a. Decreased heart rate and stroke volume, and increased total peripheral resistance
b. Higher cardiac output, skeletal muscle vasodilation, and intestinal vasoconstriction
c. Higher cardiac output, decreased venous return, and increased clotting
d. Decreased sympathetic tone, decreased release of metabolic vasodilators in skeletal muscle

Answer 27

b. Higher cardiac output, skeletal muscle vasodilation, and intestinal vasoconstriction

Question 28

Although sympathetic activity (large release of norepinephrine, NE) during exercise is high, arterioles in skeletal muscle are significantly dilated. How can this be if NE’s major effect mediated by alpha-adrenergic receptors, is to vasoconstrict?

a. During exercise, all alpha-adrenergic receptors are switched off
b. During exercise, NE suddenly become vasodilatory
c. The higher pressure produced by the higher cardiac output forces constricted vessels open
d. In working skeletal muscle, sympathetic tone is countered, mainly by local metabolic vasodilation and to a lesser extend, through extrinsic vasodilation mediated by acetylcholine and epinephrine

Answer 28

d. In working skeletal muscle, sympathetic tone is countered, mainly by local metabolic vasodilation and to a lesser extend, through extrinsic vasodilation mediated by acetylcholine and epinephrine

Question 29

An increase in sympathetic signals will _____ cardiac output and _____ total peripheral resistance

a. Decrease, decrease
b. Increase, decrease
c. Increase, increase
d. Have no effect on, increase then decrease

Answer 29

c. Increase, increase

Question 30

Autonomic regulation of both cardiac function and the state of peripheral vasodilation/constriction

a. Activity of baroreceptors (pressure sensors) in the carotid sinus and aortic arch, which increase their firing rate as blood pressure increases
b. Signals from the SA node
c. Spontaneous pacemaker activity of motor neurons in the medulla oblongata
d. Metabolic activity in skeletal muscle

Answer 30

a. Activity of baroreceptors (pressure sensors) in the carotid sinus and aortic arch, which increase their firing rate as blood pressure increases

Question 31

You measure blood pressure of two individuals: person A’s systolic/diastolic pressure is 140/70. Person B’s is 140/110. From this information, what might you surmise?

a. B’s pulse pressure is higher than A’s
b. B’s stroke volume is likely significantly lower than A’s
c. A’s heart is having to work harder against a higher afterload
d. Person A may subject to pulmonary congestion

Answer 31

b. B’s stroke volume is likely significantly lower than A’s

Question 32

Diuretic drugs (which increase excretion of water in the urine) are sometimes used in individuals with hypertension. How might this help these patients?

a. With less water in the system, the resulting increase in plasma oncotic pressure is sensed by receptors in the carotid sinus, which act to decrease cardiac output
b. Diuretic drugs block alpha adrenergic receptors, thus decreasing sympathetic vasoconstriction
c. Diuretics stimulate cholinergic-mediated vasodilation
d. By increasing the volume of urine excreted, diuretics effectively lower total blood volume, which is an effective means of lowering blood pressure

Answer 32

d. By increasing the volume of urine excreted, diuretics effectively lower total blood volume, which is an effective means of lowering blood pressure

Question 33

Normal, involuntary ventilation (i.e. under resting conditions) depends upon

a. Rhythmic contraction and relaxation of breathing muscles, under control of signals from the brainstem respiratory center
b. Unobstructed airways through the conducting zone
c. High compliance and elasticity of the lungs
d. All of the above

Answer 33

d. All of the above

Question 34

Peripheral chemoreceptors in aorta and carotid arteries influence brainstem control of respiration by monitoring

a. Tissue pO2
b. Plasma CO2
c. CO2 in the medulla of the brainstem
d. pH in the medulla

Answer 34

b. Plasma CO2

Question 35

Lower pressure in the pleural space compared with intrapulmonary pressure (i.e. pressure in the lungs)

a. Keeps the lungs from over-inflating
b. Prevents leakage of pulmonary surfactant
c. Holds the lungs against the chest wall during both inspiration and expiration
d. Allows hypoxic vasoconstriction

Answer 35

c. Holds the lungs against the chest wall during both inspiration and expiration

Question 36

When CO2 in plasma rises

a. Plasma pH decreases
b. Plasma pH increases
c. The diffusion distance between Type I alveolar cells and alveolar capillaries increases
d. The diaphragm relaxes to prevent over-inflation of the lungs

Answer 36

a. Plasma pH decreases

Question 37

Hypoxia can result from

a. Decreasing atmospheric pressure, e.g. climbing to 25,000 feet in an unpressurized aircraft
b. Narcotic overdose
c. Obstruction of the bronchioles with mucus
d. All of the above

Answer 37

d. All of the above

Question 38

In hypoxic vasoconstriction,

a. High levels of alveolar oxygen elicit a decrease in blood flow to the capillaries near those alveoli
b. Blood flow through capillaries is diverted away from those alveoli that are hypoxic, and redirected to those which have a normal pO2
c. Blood leaving the lung has a pO2 that is too low to sustain life
d. A mismatch results between ventilation of the alveoli and pulmonary capillary perfusion

Answer 38

b. Blood flow through capillaries is diverted away from those alveoli that are hypoxic, and redirected to those which have a normal pO2

Question 39

Under normal circumstances, MOST oxygen in the blood is carried

a. Dissolved in the plasma
b. Bound to hemoglobin
c. In the red cell membrane
d. In the form of bicarbonate (HCO3-)

Answer 39

b. Bound to hemoglobin

Question 40

What factors tend to increase transfer of O2 from a red cell to a tissue?

a. Low pCO2 in the tissue
b. Low red cell levels of 2,3-diphosphoglycerate (2,3-DPG)
c. Lower pO2 in the tissue than in the red cell
d. All of the above

Answer 40

c. Lower pO2 in the tissue than in the red cell