Bio201 Exam 2 Master with Answers

Muscles (Comparisons or General Questions): !Which of the following is not an important functional difference between smooth and skeletal muscles ? a) actin and myosin are arranged differently - skeletal muscle => linear, sarcomere based structure, - smooth muscle => network based b) Ca++ from the sarcoplasmic reticulum is critical to contraction in skeletal but not in smooth muscle c) Neural stimulation (via synapses) fire each contraction in skeletal but not smooth muscle d) Kinases and phosphatases are the major mechanism of controlling myosin ATPase activity in smooth but not in skeletal muscle !Excitation-contraction coupling in smooth muscle differs from that in skeletal muscle in that: a) Cytosolic[Ca++] is elevated in smooth muscle. b) The activation signal reaches myosin rather than actin in smooth muscle. c) Calmodulin is important in skeletal muscle d) Myosin light chain kinase is important in smooth muscle. e) B and D are correct. !Compared to smooth muscle, skeletal muscle a) is slower to contract in response to a stimulus b) develops tension more rapidly and relaxes more rapidly c) sustains contractions longer without fatigue d) A and C e) A, B and C !Which one of the following proteins is important for skeletal muscle contraction but not for smooth muscle contraction? a) Actin b) Myosinc) Ca++ -ATPased) Myosin-adenosine triphosphatase (ATPase) e) Troponin !Which of the following is NOT involved in bringing about muscle relaxation? a) re-uptake of Ca++ by the sarcoplasmic reticulum b) removal of ACh at the endplate by acetylcholinesterase c) refractory membranes d) tropomyosin interference with myosin activity !Skeletal muscle is similar to smooth muscle in that both types: a) show sarcomeric organization of thick and thin filaments b) contract in response to hormonal stimulation c) contract in response to increases in cytoplasmic Ca++ d) have troponin-linked regulation of crossbridge cycling e) relax in response to ACh !

Skeletal muscle differs from cardiac muscle in that only skeletal muscle: a) has contraction initiated by binding of Ca++ to troponin b) regulates force of contraction by regulating release of intracellular Ca++

c) shows a length-active tension curve that depends on filament overlap d) regulates the speed of contraction by phosphorylation of myosin heads e) shows temporal summation !Cardiac muscle is similar to skeletal muscle in that a) both show temporal summation of contractions b) the contractions of both are initiated by ACh binding c) muscarinic cholinergic stimulation slows the contractions of both d) both are equally compliant(have similar passive elastic characteristics) e) contractions of both require action potentials !Cardiac muscle cells differ tom skeletal muscle cells in that only cardiac muscle cells: a) utilize an increase in myosin light chain kinase as a mechanism to regulate the strength of contraction b) contract in response to an increase in cytoplasmic [Ca++] c) utilize an increase in Ca++-calmodulin as a mechanism to regulate the strength of contraction d) propagate action potentials along their plasma membrane e) require “trigger Ca++” to release Ca++ from the sarcoplasmic reticulum (CICR) !!Skeletal Muscle Physiology: !At the neuromuscular junction, acetylcholine (ACh) directly causes the opening of a) Na+ channels and depolarization toward the Na+ equilibrium potential b) K+ channels and depolarization toward the K+ equilibrium potential c) Ca++ channels and depolarization toward the Ca++ equilibrium potential d) Na+ andK+ channels and depolarization to a value halfway between the Na+ and K+ equilibrium potentials

e) Na+ and K+ channels and hyperpolarization to a value halfway between the Na+ and K+ equilibrium potentials !A motor unit refers to a) a single motor neuron plus all of the muscle fibers it innervates. b) a single muscle fiber plus all of the motor neurons that innervate it. c) all of the motor neurons supplying a single muscle. d) a pair of antagonistic muscles. e) a sheet of smooth muscle cells connected by gap junctions. !In skeletal muscle, which of the following events occurs before depolarization of the T tubules in the mechanism of excitation–contraction coupling? a) Depolarization of the sarcolemmal membrane b) Opening of Ca++ release channels on the sarcoplasmic reticulum(SR) c) Uptake of Ca++ into the SR by Ca++ -adenosine triphosphatase(ATPase) d) Binding of Ca++ to troponin C e) Binding of actin and myosin

Which of the following temporal sequences is correct for excitation-contraction coupling in skeletal muscle? a) Increased intracellular [Ca++]; action potential in the muscle membrane; cross-bridge formation b) Action potential in the muscle membrane; depolarization of the T-tubules; release of Ca++ from the sarcoplasmic reticulum (SR) c) Action potential in the muscle membrane; splitting of adenosine triphosphate (ATP); binding of Ca++ to troponin C d) Release of Ca++ from the SR;depolarization of the T-tubules; binding of Ca++ to troponin C !One of the major differences among skeletal muscle fiber types is in their resistance to fatigue. The fibers with the most endurance rely on ____________ for energy. a) lactic acid accumulation b) ketone body degradation c) anaerobic glycolysis d) oxidative phosphorylation !Which of the following is NOT involved in bringing about skeletal muscle relaxation? a) re-uptake of Ca++ by the sarcoplasmic reticulum b) tropomyosin interference with myosin activity c) closure of ryanodine receptor Ca++ channels d) MLC phosphatase deactivation of myosin ATPase activity e) troponin conformational shifts. !Within a single skeletal muscle fiber, the tension developed during a twitch can vary because a) strength of contraction depends on the resting length of the sarcomere b) the motor neuron releases differing amounts of neurotransmitter into the synapse c) Calcium induced calcium release can vary with the strength of the stimulus d) stimuli vary in intensity e) all of the above !Suppose that you measure the velocity of contraction of a particular muscle as it lifts a certain mass. Adding additional mass would __________ the velocity of contraction a) increase b) decrease c) not affect !Which of the following is involved in the gradation of muscle contraction? a) variation in the number of motor units activated b) variation in the frequency of action potentials initiated in each muscle fiber c) variation in the size of the action potentials initiated in each muscle fiber d) Both A and B above. e) All of these answers. !Within a single fiber, the tension developed during a twitch can vary because a) the amount of overlap of thick and thin filaments must be sufficient to allow cross-bridge formation b) the motor neuron releases differing amounts of neurotransmitter into the synapse c) stimuli vary in intensity and duration

d) stimuli vary in intensity e) all of the above !Smooth Muscle Physiology: !Ca++ is important in the contraction of smooth muscle. Which of the following is not true about smooth muscle contraction? a) Ca++ binds to calmodulin. b) Ca++ enters the cytosol from the sarcoplasmic reticulum. c) Contraction is immediately triggered by calmodulin binding. d) MLCK (myosin light chain kinase) forms a complex to activate myosin. e) When MLCK activates myosin, ATPase activity is high and crossbridge formation is active. !Ca++ is important in the contraction of smooth muscle. Which of the following is not true about smooth muscle contraction? a) Ca++ binds to calmodulin. b) Ca++ enters the cytosol from the sarcoplasmic reticulum. c) MLCK (myosin light chain kinase) forms a complex to activate myosin. d) Ca++ dephosphorylates the myosin ATPase e) When MLCK activates myosin, ATPase activity is high and crossbridge formation is active. !The regulation of smooth muscle contraction is mediated by the phosphorylation of __________ in response to calcium binding to __________. a) myosin, calmodulin. b) actin, calmodulin. c) troponin, calmodulin. d) myosin, troponin. e) actin, troponin. !Which of the following pairings is correct for smooth muscle? a) multiunit smooth muscle—gut smooth muscle b) decreased contraction in response to NE—vascular smooth muscle c) phosphorylation of myosin—increased cAMP levels in smooth muscle d) maintenance of tone—latch bridges e) dense bodies—organize the array of thick filaments !Cardiovascular Physiology: !A particular drug acts on the pacemaker cells of the SA node to increase heart rate. Which of the following is a possible mechanism of action of this drug? a) binds to L-type Ca++ channels and inhibits their opening b) binds to and activates cholinergic muscarinic (M2) receptors c) binds to and activates β adrenergic receptors d) binds to and activates phosphodiesterase e) binds to Na+ pacemaker channels and inhibits their opening !!

In which of the following is a Ca++ channel correctly matched with its function? a) ryanodine receptor channel—formation of IPSP b) IP3 receptor—influx of “trigger Ca++” in cardiac muscle c) L-type Ca++ channel—plateau of ventricular action potential d) nAChR/channel—release of neurotransmitter e) receptor-mediated Ca++ channel—initiates contraction of skeletal muscle !Acetylcholine slows the heart rate by a) increasing ion influx thus increasing the rate of Phase 4 depolarization b) increasing the permeability to Ca++ via G protein gated channels c) increasing the permeability to K+ via G-protein gated channels d) decreasing the permeability to Ca++ by decreasing adenyl cyclase activity e) C and D !Which of the following is NOT a consequence of β-adrenergic stimulation of cardiac ventricular muscle? (All comparisons are made with reference to the absence of β adrenergic stimulation.) a) increased Ca++ concentration in the cytoplasm during contraction b) increased rate of crossbridge cycling c) faster clearing of Ca++ from cytoplasm d) significant lengthening of the duration of the action potential e) increased storage of Ca++ in the sarcoplasmic reticulum !In cardiac nodal (pacemaker) cells, the pacemaker potential (phase 4) is due to increased ___ conductance, the upstroke of the action potential (phase 0) is due to increased ___ conductance, and the depolarization phase of the action potential is due to increased ___ conductance. a) Ca++, Na+, K+ b) K+, Na+, Ca++ c) Na+, K+, Ca++ d) Na+, Ca++, K+ !In the sinoatrial (SA) node, phase 4 depolarization (pacemaker potential) is attributable to a)an increase in K+ conductance b)an increase in Na+ conductance c) a decrease in Cl- conductance d) a decrease in Ca++ conductance e) simultaneous increases in K+ and Cl- conductances !Differences between autorhythmic myocardial cells and contractile myocardial cells include a) autorhythmic myocardial cells lack the inwardly rectified K+ channel b) autorhythmic myocardial cells have If channels c) autorhythmic myocardial cell action potentials do not have a true plateau phase d) B and C e) A, B and C !!

Which statement(s) best describe(s) the regulation of contraction strength of myocardial cells? a) The higher the intracellular concentration of Ca++ , the stronger the force of contraction will be b) Catecholamines make voltage-gated Ca++ channels more likely to open, thus allowing higher concentrations of Ca++ inside the cell. c) A and B are true !If a drug increases cAMP in SA nodal cells, the most likely response is a) elevated systolic arterial pressure b) decreased systolic arterial pressure c) increased heart rate d) decreased heart rate e) nor-epinephrine release !Myocardial contractility is best correlated with the intracellular concentration of a) Na+ b) K+ c) Ca++ d) Cl- e) Mg++ !The physiologic function of the relatively slow conduction through the atrioventricular (AV) node is to allow sufficient time for!a) runoff of blood from the aorta to the arteries !b) venous return to the atria c) atrial contraction filling of the ventricles d) contraction of the ventricles!e) repolarization of the ventricles!!Phase 4 voltage in ventricular cells is stabilized by !a) funny channels!b) L-type Ca++ channels !c) inwardly rectified K+ channels !d) fast Na+ channels e) acetylcholine!!Increasing the preload of cardiac muscle a) reduces the ventricular end-diastolic pressure (VEDP) b) reduces the peak tension of the muscle c) decreases the initial velocity of shortening d) decreases the time it takes the muscle to reach peak tension!e) increases the ventricular wall tension!!Ventricular end diastolic volume (EDV) is determined directly by the!a) cardiac output!b) systemic blood pressure!c) venous pressure!d) diastolic blood pressure only!

The importance of the plateau phase of the action potential of myocardial cells is in a) preventing overstretching of the cells b) enhancing the efficiency of oxygen use by the cells c) preventing fibrillation d) preventing tetany e) regulating Ca++ availability to the cells !In cardiac muscle tissue, a) Ca++ release from the sarcoplasmic reticulum initiates contraction b) Ca++ enters the cell from the extracellular fluid, directly initiating contraction c) Ca++ enters the cell from the extracellular fluid, which causes more Ca++ to be released from the sarcoplasmic reticulum d) both A and C are correct !You can increase cardiac output by all of the following EXCEPT: a) increasing venous return b) increasing heart rate c) constricting the arterioles d) increasing stroke volume !If the HR is 72 bpm and the SV is 72 mL, the cardiac output would be approximately equal to a) 5.2 liters/minute b) 144 mL/minute c) neither of these choices are correct !The steep repolarization to rest potential phase of the action potentials of myocardial contractile cells occurs when conductance to which ion(s) decrease? a)Ca++ b)K+ c)Na+ d)A and B e)A and C !Important effects of events during the plateau phase of the action potential of myocardial cells include a) initiating calcium-induced calcium release b) enhancing the efficiency of oxygen use by the cells c) preventing tetany d) A and C e) all of the above !Factors affecting the strength of contraction (contractile work) in ventricular cells the following except a)amount of Ca++ released by the sarcoplasmic reticulum b) pre-load (LVEDP) c) Myosin light chain kinase activity stimulated by calmodulin d) opening of precapillary sphincters in the papillary muscles e) C and D

The pulmonary veins: a) return blood to the left atrium b) carry relatively deoxygenated blood c) BOTH a and b d) NEITHER a nor b !Manganese ions block the calcium channels in the cardiac muscle membrane. How would the presence of manganese in the ECF affect the contraction of the heart muscle? a) the plateau phase of contraction would be longer b) the refractory period would be shorter c) the heart would beat less forcefully d) the heart rate would increase e) the contraction phase would be prolonged !Parasympathetic activation slows heart rate by release of the neurotransmitter _______________ which then stimulates the opening of a ____ channel. The resulting ionic current slows the rise of the ______________ potential. a) NE, Na+, Resting Membrane b) NE, K+, Action c) NE, Na+, Pacemaker d) ACh, Na+, Action e) ACh, K+, Pacemaker !Ivabrandine selectively blocks If channels in the heart. Which statement would be true concerning a patient who is taking this drug? a) The drug would slow down this individual’s heart rate. b) This patient must have been suffering from bradycardia. c) This drug would decrease the contractility of the patient’s heart. d) This drug would raise the blood pressure of the patient. e) The amount of calcium entering the patient’s heart cells would increase. !The fibrous skeleton of the heart is important because it a) forces electrical activity to be conducted through the atrioventricular node b) transmits electrical activity from the atria to the ventricles c) helps guide the blood into the proper chambers in sequence d) directs the flow of blood into the arteries !The ventricles are completely depolarized during which isoelectric portion of the electrocardiogram (ECG)? a) PR interval b) QRS complex c) QT interval d) ST segment e) T wave !!!

The ventricles repolarize during which portion of the electrocardiogram (ECG)? a) PR interval b) QRS complex c) QT interval d) ST segment e) T wave !Atrial contraction starts during the: a)P wave of an EKG b)QRS complex of an EKG c) T-wave of an EKG d) None of the above !Ventricular contraction is most closely correlated with the: a)P wave of an EKG b)QRS complex of an EKG c) T-wave of an EKG d) None of the above !The bulk of ventricular filling is most closely associated with the: a) P wave and PR interval b) QRS complex c) BOTH a and b d) NEITHER a nor b !Filling of the atria with blood: a) occurs during the P wave of an EKG b) is called atrial diastole c) BOTH a and b d) NEITHER a nor b !Scenarios: !Short Scenarios: !Joe Average has just been frightened by a very loud noise as he was taking a very difficult physiology exam. In response, his adrenal glands have released a large amount of adrenaline into his circulation. !

As the adrenaline reaches the heart , which of the following effects would you expect to see in cardiac cells? a) increased phase 4 depolarization due to increased “funny channel” conductance b) hyperpolarization of pacemaker cells due to increased conductance of G protein activated K+ channels c) lower peak sarcoplasmic Ca++ concentrations due to lower ryanodine receptor opening d) A and B e) A and C

Among the organ level responses expected as the adrenaline has its effect are: a) decreased heart rate b) increased heart rate with shorter systolic periods c) increased stroke work at a given LVEDP (pre-load) d) B and C e) none of the above !

Joe flinches at the sound, jabs his pen into his thumb drawing blood. Joe hates blood and his parasympathetic nervous system responds by dumping a significant load of acetylcholine in the heart. !

As the acetylcholine affects the heart , which of the following effects would you expect to see in cardiac cells? a) increased phase 4 depolarization due to increased “funny channel” conductance b) hyperpolarization of pacemaker cells due to inc conductance of G protein activated K+ channels

c) lower peak sarcoplasmic Ca++ concentrations due to lower ryanodine receptor opening d) A and B e) A and C !Among the organ level responses expected as the acetylcholine has its effect are: a) decreased heart rate b) increased heart rate with shorter systolic periods c) increased stroke work at a given LVEDP (pre-load) d) B and C e) none of the above

!Long Scenarios: !Out of this World Scenario Mary has a bacterial infection of the lung (pneumonia) which is causing some respiratory problems but the immediate concern is that her blood pressure is dangerously low despite the fact that her heart is beating rapidly and strongly. Assuming that she had become dehydrated, you gave her IV fluids without any benefit. Confused, you measure her central venous blood pressure (pressure in the large veins, and found it normal to slightly low). More fluids don’t help either. Using a special catheter, you measure her cardiac output and find it to be quite high (12L/min instead of the expected 5L/min). !ACh Increases Bill is having a vaso-vagal episode which results in acetylcholine being released onto the atria from fibers running in the vagus nerve. ! Ed[Andy in Sp14] just fell and cut his forehead. The cut isn’t that bad, but like many head wounds, it bleeds fairly freely and gaudily, although not enough to affect cardiovascular function. Unfortunately Ed is one of those folks who gets weak at the sight of blood, particularly his own. He suffers a diffuse release of acetylcholine from the parasympathetic nervous system. He’s been spared any respiratory effects and is generally fairly healthy.

!NE Increases Carrie is one of those people who can’t eat certain chocolate based sweets because in her body some of the compounds are modified into norepinephrine analogues (chemicals that act like nor-epinephrine). Unfortunately she fell off the wagon and just ate some of those candies and the nor-epinephrine analogues are now reaching her blood stream. ! Angela is one of a minority of people in whom some chocolate based sweets are largely metabolized to norepinephrine analogues (chemicals that act like nor-epinephrine). She unwittingly just ate several of those confections. She is otherwise healthy. ! Tom has taken a dose of cocaine. One of the actions of cocaine is to block the re-uptake of norepinephrine (and related catecholamines) into the synaptic bulbs that released them. (Re- uptake is the normal mode of limiting the effect of nor-epinephrine at synapses.) Thus, the effect of any nor-epinephrine released is magnified. ! Frodo has been taking a new diet pill that acts in two ways. First, it mimics nor-epinephrine at most sympathetic post-ganglionic synapses, second it prevents the re-uptake of norepinephrine at the same synapses by competitively inhibiting there-uptake system. (Re-uptake is the normal mode of limiting the effect of nor-epinephrine at synapses.) Thus, the effect of any nor-epinephrine released is magnified. !Vt Decreases Mort has had a viral gut infection leading to substantial diarrhea and (because he hasn’t felt like eating or drinking) dehydration. In toto, his total body fluids are about 4 L below their usual levels, of which 1.5 L come from the extracellular fluid (~ 450 ml from the blood). Such diarrhea can sometimes be associated with significant changes in the concentrations of ions in body fluids (like Na+, K+, Ca+, HCO3- ), but that does not seem to be the case with Mort. ! Gimli has been working hard in a desert environment, but has neglected to drink any water to replace the 2L of fluid lost via sweat and respiratory losses (think 600 ml lost from the blood volume). He had to stop working because he felt weak, but still feels poorly after a few minutes of rest. ! Mary fell, experiencing a deep cut that lead to the loss of around 500 ml of blood. The bleeding has been stopped, but no fluids have been given to replace the lost blood. Bill[Sp14], is in the process of developing Acute Tubular Necrosis (ATN), a malfunction of the kidneys, in this case due to a viral infection. ATN can have several effects, but most of them have not yet developed. What is a problem for now is that, due to his disease, his kidneys have been producing a large amount of urine. Some of that volume has been drawn from the cardiovascular system and his vascular volume is down by about 700 ml. Before the viral infection, Bill was healthy. Curiously enough, the viral infection itself is largely resolved. !Histamine Released into Bloodstream Hank has just been stung by a bee to which he is highly allergic. Huge amounts of histamine are being released from a series of mast cells. Histamine causes (among other things) the relaxation of smooth muscles in the arterioles and veins.

! Steve is allergic to nuts and has just unknowingly ingested some in a piece of cake. Luckily he is spared the respiratory problems such folks often have, but large quantities of histamine are being released from his cells. Histamine has a large number of physiological effects, but the critical one is that it tends to cause the smooth muscles in the large veins to relax. Aside from his allergies, Steve is a healthy young man. !ATP Supply Decreases Joe is suffering from a spasm in his left main coronary artery impairing blood flow to the heart. This can cause considerable pain, but what concerns us here is that delivery of oxygen to most of the heart is impaired limiting myosin ATPase function and contraction of the ventricular muscle ! Gandalf is having an episode of “atypical angina” in which blood flow to the heart through the coronary arteries is reduced by constriction of the coronary arteries while he is at risk. The episode results in decreased supply of oxygen to the ventricles, impaired ATP production, and thus, reduced ATP availability at, and use by, the ventricular muscle. !Tension Increased Milly is a subject in a early phase clinical trial. She receives a drug that increases the tension developed by both cardiac muscle cells and by the smooth muscle cells in the large systemic veins. As required by the study design, Milly is healthy young woman. !Random Drugs Affecting Channels Chris has inadvertently taken a reasonably large dose of his roommate’s verapamide, a new slow calcium channel inhibitor. It impairs Ca++ movement across the plasma membrane in the heart and affects both heart rate and contractility. This new drug does not affect Ca++ transport in smooth muscles. Rich just made a mistake. He’s supposed to make an oral presentation today. To allay some of the nervous jitters he usually suffers from making presentations, he “borrowed” a few of his father’s Cardial (β1 adrenergic receptor blocker that acts quite specifically at the heart). He took three (instead of the one his father takes). Now the drug is kicking in. Aside from his nerves he’s healthy. ! A TV show that I saw this year posed an interesting problem. In this show, several athletes (we’ll use Bob as our example) are given an injection that causes most of their systemic arteries and arterioles to produce huge quantities of nitric oxide. As we discussed, nitric oxide interacts with guanyl cyclase to produce cGMP and cause local vascular muscle to relax. ! It was a bad morning, Fran mistakenly took her husband’s slow channel blocker instead of the multivitamin she was reaching for. Slow channel blockers reduce the Ca++ conductance of the long acting channels responsible for the entry of Ca++ across the plasma membrane in muscle cells. Fran’s husband’s medicine works almost exclusively at the heart, but affects all cardiac cells. Fran is otherwise healthy.