Exam 3 Review Flashcards by Bethany Smart

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

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

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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

c. Acetylcholine, motor end plate

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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

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

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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

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

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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

d. All of the above

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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

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

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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

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

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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

b. Oxidation of fatty acids

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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

d. All of the above

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Total blood volume in an adult human is about

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

a. 5.5 liters

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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

b. Elevated

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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

c. Recruitment and sticking of platelets

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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

c. AV valves are closed and semilunar valves are open

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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

a. Ventricular filling is initially passive and rapid

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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

b. SA node, ventricular contraction, Purkinje fibers

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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

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

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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

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

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

c. Is a low pressure, high flow system

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

a. Elastic recoil of the aorta during diastole

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

d. High capillary hydrostatic pressure, high capillary oncotic pressure

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

c. Resistance to flow, mainly determined by arteriolar diameter

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

d. All of the above

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

b. Will increase both end diastolic volume and stroke volume

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

c. Decreased cardiac output

The largest pressure drop in the cardiovascular system occurs in the a. Capillaries b. Arterioles c. Post-capillary venules d. Right and left atria

b. Arterioles

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

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

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

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

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

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

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

c. Increase, increase

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

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

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

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

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

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

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

d. All of the above

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

b. Plasma CO2

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

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

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

a. Plasma pH decreases

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

d. All of the above

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

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

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-)

b. Bound to hemoglobin

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

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