Physiology questions Physiology questions ...Mainly for medical students , are you up for the challenge Warqueen published on December 20, 20171 response 0 Questions in vertical order Which part of the heart’s conduction systemsends the impulse that begins the process ofconduction? Atrioventricular (AV) node Sinoatrial (SA) node Bundle of His Purkinje fibers An impulse travel through the heart’sconduction system in which of the followingsequences? Atrioventricular (AV) node, bundle of His,sinoatrial (SA) node, bundle branches, Purkinjefibers Bundle of His, sinoatrial (SA) node, bundlebranches, Purkinje fibers, atrioventricular (AV)node Purkinje fibers, bundle branches, bundle of His,sinoatrial (SA) node, atrioventricular (AV) node . Sinoatrial (SA) node, atrioventricular (AV) node,bundle of His, bundle branches, Purkinje fibers The function of coronary circulation is to: Regulate the cardiac cycle Deliver oxygenated blood from the lungs intosystemic circulation Supply cardiac muscle with oxygenated bloodand drain deoxygenated blood from it Drain excess blood from the ventricles The layer of the heart wall primarily responsiblefor the heart’s pumping action is the: Myocardium Endocardium Epicardium Pericardium Cardiac output is determined from which of thefollowing factors? Heart rate and blood pressure Oxygen consumption and carbon dioxidesecretion Stroke volume and heart rate Ventricular contraction and venous return The volume of blood, in liters, that each ventricleof the heart ejects every minute is known as: stroke volume cardiac output heart rate blood pressure Oxygenated blood flows from the heart throughsystemic circulation in which order? Arteries, veins, capillaries, arterioles, venules Veins, venules, capillaries, arterioles, arteries Arteries, arterioles, capillaries, venules, veins Capillaries, veins, venules, arterioles, arteries Arteries are structurally different from veins inwhich way? They have thicker and stretchier walls toaccommodate higher pressures They lack valves They have a tunica media a and b The purpose of valves is to: Filter debris from the bloodstream Ensure unidirectional blood flow Move blood through arteries All of the above In a resting state, the plasma membrane of aneuron is: Depolarized Polarized Hyperpolarized Impermeable Signals are passed through the nervous system: Electrically Chemically Mechanically a and b The wave of depolarization that is propagateddown an axon is known as the: Graded potential Resting potential Action potential Refractory period Which of the following statements aboutneurotransmitters is false? Excitatory neurotransmitters may generate anaction potential in the neuron they reach At a neuromuscular junction, acetylcholine hasinhibitory effects Dopamine helps regulate muscle tone Norepinephrine is found in both the centraland peripheral nervous systems . A signal moves through the parts of a singleneuron in what order? Dendrites, cell body, axon, axon terminals Axon terminals, axon, cell body, dendrites Cell body, dendrites, axon, axon terminals Axon, dendrites, axon terminals, cell body A myelinated axon transmits a signal................... anon-myelinated axon More slowly than More quickly than At the same rate as More accurately than When a neuron is not transmitting a signal, whichof the following is true? The cell membrane is depolarized The cell contains an action potential The cell cannot be stimulated byneurotransmitters The net charge inside the cell is negative Which type of cells phagocytize debris in thecentral nervous system? Ependymal cells Astrocytes Microglia Oligodendrocytes . If the nicotinic channels at the neuromuscular junction pass both Na+ and K+ why does stimulation of these channels cause depolarization of the skeletal muscle? The driving force for K+ is very large. The driving force for Na+ is very large. The K+ channels are not open. The Na+ ion is smaller and therefore passes more easily. The resting membrane potential is closer to the Na+ Nernstpotential. What effect will hypocalcemia have on theneuromuscular junction? Increased release of acetylcholine Increased muscle depolarization(Na overstimulation) C. Decreased activation of nicotinic receptors D. Inhibition of acetylcholine esterases E. Increased influx of Ca2+ into motor nerve terminal Most of the ATP generated in nerve cells is utilized to energize the: Na-Ca exchanger H-ATPase in the cell membrane Na-K ATPase synthesis of proteins Fast anterograde transport occurs at a rate of about: 40 mm/day 400 mm/day 1 mm/day 10 mm/day The largest known axons are found in: humans whales squids ostriches The normal resting cardiac muscle cell is most permeable to: Na K Ca Cl The membrane potential at which net flux of an ion across the membrane is zero is called resting membrane potential spike potential threshold potential electrotonic potential equilibrium potential of that ion The resting membrane potential of ventricular cardiomyocytes is closest to the equilibrium potential for: sodium chloride potassium calcium The Nernst potential (also called equilibrium potential) is positive for: Na and Cl Na and K Na and Ca K and Cl The equilibrium potential of chloride in mammalian spinal motor neurons is typically about + 20 mV minus 40 mV (inside negative) minus 70 mV (inside negative minus 90 mV (inside negative) The resting membrane potential of some neurons is equal to the equilibrium potential of: Na K Cl Ca If intracellular and extracellular potassium concentrations are approximately 140 mmol/L and 14 mmol/L respectively, the equilibrium potential for potassium is approximately: minus 30 mV inside negative minus 60 mV inside negative minus 90 mV inside negative minus 120 mV inside negative Which one of the following increases excitability of cardiac muscle? Increase in ECF [K+] from 5 to 10 mM Increase in ECF [K+] from 5 to 70 mM Decrease in ECF [K+] from 5 to 1.4 mM Hypokalemia would be expected to result in: increased neuronal excitability a more negative RMP no change in RMP a decrease in firing level of neurons The membrane potential of cardiac muscle cells is most affected by even a small change in plasma concentration of: Na K Cl Ca Which of the following would justify excluding sodium conductance from the equation for estimating resting membrane potential in skeletal muscle fibers? Extracellular [Na] is higher than ICF [Na] Na-K pump extrudes 3 Na for 2 K pumped in Negligible Na permeability of the resting membrane Unexcited cells are equally permeable to Na and K Excitability, in neurophysiology, is defined as: presence of a resting membrane potential use of more than 30% of ATP synthesized for powering the Na-K ATPase response to a threshold stimulus with a propagated action potential presence of voltage gated ion channels in a tissue Physiologically, the site of origin in motor neurons of conducted impulses is the: dendritic zone axon hillock terminal buttons node of Ranvier In motor neurons, the portion of the cell with the lowest threshold for the production of a fullfledged action potential is: initial segment soma dendritic zone node of Ranvier In the CNS, the membranes that wrap around myelinated neurons are those of: Schwann cells oligodendroglia endothelial cells astrocytes The number of Na channels per square micrometer of membrane in myelinated mammalian neurons is maximum in the: cell body dendritic zone initial segment node of Ranvier Which one of the following statements about electrotonic potentials is incorrect? They are graded responses. They are local (non-propagated) responses. They may be depolarizing or hyperpolarizing. They are produced by a threshold stimulus A stronger than normal stimulus can cause excitation of nerve or muscle during the absolute refractory period Relative refractory period pike potential Overshoot An excitable cell has an RMP of -70 mV and a firing level of - 50 mV. This cell would be inexcitable when its membrane potential is -30 mV - 55 mV - 70 mV - 90 mV For the same conditions (as in the above question), the cell would be most excitable when its membrane potential is: - 30 mV - 55 mV -70 mV - 90 mV Conduction speed is slowest in the: SA node atrial pathways bundle of His Purkinje system Ventricular myocardium . What is the effect of vagal stimulation on the membrane potential of the SA node? It increases an inward calcium current It increases the slope of the prepotential. It activates a hyperpolarizing potassium current. It increases intracellular cAMP. Activation of beta-adrenergic receptors in the heart is normally associated with which of the following? Decrease in the slope of phase 4 depolarization in SA nodal cells. Decrease in conduction speed through AV node. Inhibition of Ca induced Ca release following depolarization in ventricular myocytes. Accelerated sequestration of Ca in the sarcoplasmic reticulum by the Ca-ATPase Reduction in the rate of rise in ventricular pressure during isovolumic contraction Cardiac muscle cannot be tetanized because of: accommodation its slow rate of repolarization calcium influx during phase II Intrinsic heart rate is determined by: Intrinsic heart rate is determined by: vagotomy administration of atropine beta-adrenergic receptor blockade IV administration of atropine and atenolol The ability of the AV node to generate its own impulses when the sinus node is “sick” is due to: a constant phase 4 membrane potential slow calcium entry during phase zero spontaneous diastolic depolarization the absence of prepotentials T wave inversion occurs when ventricular repolarization occurs from: endocardium to epicardium epicardium to endocardium apex to base of the heart base to apex of the heart Which of the following is more likely to produce an S3 sound? Left ventricular hypertrophy Right ventricular hypertrophy Left atrial enlargement Left ventricular cardiomyopathy The inotropic state of cardiac muscle can be altered because: it has the ability to recruit or diminish the number of muscle cells activated during a contraction its intracellular calcium concentration can be altered force generation in cardiac muscle is modulated by Ca++/calmodulin interaction it functions on the ascending limb of its isometric length tension curve its multinucleated anatomical property When the vagus stimulates the sinoatrial node (SAN) the nodal cells respond quickly showing a higher minimum repolarization potential. Fast activation by acetylcholine of the following ionic channel is primarily responsible for this effect. A voltage sensitive Na+ channel The L-type calcium channel The T-type calcium channel A receptor activated K+ channel Our astronaut has returned to normal gravity after orbiting the earth at an altitude of 250 miles for three months. The instantaneous effect on the heart after arriving at a normal gravity environment would be: An increase in afterload A decrease in preload An increase in right atrial pressure A decreased parasympathetic stimulation of the heart Complete depolarization of the ventricles eliminates the electrical dipoles that were formed during this process and brings back the ECG to zero potential. When this occurs we enter into a portion of the ECG called: The PR interval ST segment QRS complex QT interval P wave A mother brings her 5 year old child into the pediatric ward complaining about the child being too tired during the day with little activity for a normal 5 year old. Your examination reveals that the child has a normal weight but she looks pale and there is a strange puffiness to her features. Blood tests come up with a very low Albumin level in plasma and confirm your initial thoughts about possible Kwashiorkor disease. The mother indicates that she only gives the child potato fries or chips since this is the only food that she will eat. As soon as a normal albumin level is restored in the child, the significant level of muscle wasting due to the malnutrition is revealed and the puffiness disappears as well as the normal weight. The puffiness was a result of: Increased capillary oncotic pressure Decreased capillary filtration pressure Decreased capillary oncotic pressure Too much fat from the fries As a result of one of the following you will observe a lower end systolic volume in the heart? Effect of norepinephrine Increased preload increased mean arterial pressure decreased end diastolic volume In the event of strong parasympathetic stimulation to the heart (Vagus Nerve) the rhythmicalexcitation can stop and also block transmission through the AV Node, the ventricles stop beatingfor 5-20 seconds, but then at some point the Purkinje Fibers develop rhythm of their own at arate of 15-40 beats per minute. The term that best describes this is: Vasovagal Reaction Wolf Parkinson White Syndrome Atrial Escape Ventricular Escape The dP/dt is an index of cardiac contractility that can be measured by relating the rise in ventricular pressure during systole with: Time ESV Stroke volume EDV Match the definition given to the correct term from the list: Diminished perfusion to tissues Hypoxia Anoxia Ischemia Shock Complete lack of oxygen Anoxia Hypoxia Shock Ischemia Match the definition given to the correct term from the list: Cardiac output decreases below the pressure required to deliver nutrients to the tissues Hypoxia Anoxia Shock Ischemia A skeletal muscle that is depleted of its ATP supply will gradually stiffen and fail to relax. This is because ATP is necessary to: provide the energy for relaxation maintain the separation of thick and thin filaments when the muscle is at rest. allow the thick and thin filaments to detach from each other during the cross-bridge cycle. promote the binding of calcium ions to the regulatory proteins and cause relaxation Calcium ions are required for the normal activation of all muscle types. Which statement below most closely describes the role of calcium ions in the control of skeletal muscle contraction? The binding of calcium ions to regulatory proteins on the thin filaments removes the inhibition of actin-myosin interaction The binding of calcium ions to the thick filament regulatory proteins activates the enzymatic activity of the myosin molecules Calcium ions serve as a direct chemical inhibitor of the interaction between actin and myosin. A high concentration of calcium ions in the myofilament space is required to maintain muscle in a relaxed state Synapses are communication points between two neurons or a neuron and effector such as a muscle. Not all synapses are equal, based on your current knowledge of synapses select the statement that best describes a chemical synapse: The chemical synapse mediates faster synaptic transmission compared to _the electrical synapse Since in the chemical synapse the pre-synaptic membrane is tightly connected to the post-synaptic cell via the connexons, the flow of ions between the neurons occurs bi directionally. The chemical synapse involves the Ca2+ dependent release of neurotransmitters into the synaptic cleft via exocytosis. Similar to the electrical synapse, gap junction channels are part of the chemical synapse. E. None of the above statements are correct In the face of insufficient oxygen to meet its current metabolic requirements, a contracting skeletal muscle: quickly loses its ability to contract and relaxes until oxygen is again available can maintain contraction by using metabolic pathways that do not require oxygen consumption maintains contraction by using a large internal store of ATP that is kept in reserve contracts more slowly at a given force, resulting in a saving of energy. A researcher studies membrane potential of isolated neurons. He reports two action potentials for the same neuron: the first one depolarizes the membrane to +50 mV, while the second one reaches +11 mV. Which of the following manipulations by the researcher best explains the lower magnitude of the second action potential? Decrease sodium concentration outside the cell Decreased sodium concentration inside the cell Decreased potassium concentration inside the cell Decreased potassium concentration outside the cellll Increased calcium concentration outside the ce The trigger zone that integrates incoming signals from other cells and initiates an action potential to send down the axon is rich in Na+ channels. This zone is best known as: Axon trunk Axon hillock Dendritic trunk Dendritic spines Joe is a 15-year-old who belongs to the school track team. After a recent competition he felt extremely weak, unable to walk and had to be carried out of the tack. Next morning his pediatrician tested Joe's blood K+ levels before and after he ran on a treadmill. Joe's serum K+ was very low (2.2 mEq/L) after the treadmill run. His pediatrician diagnosed him with primary hypokalemic periodic paralysis. Joe was put on K+ supplementation. Why did K+ supplementation improved Joe's condition: By normalizing serum K+ thus preventing further hyperpolarization of the membrane potential By normalizing serum K+ thus preventing further depolarization of the membrane potential By further decreasing K+ serum concentration thus causing depolarization of the membrane potential. . By further decreasing K+ serum concentration thus causing hyperpolarization of the membrane potential During an in vitro experiment, the membrane potential of a cell becomes hyperpolarized from - 75 to -120 mV. An inhibitory drug is applied to the bath resulting in depolarization of the membrane. Which of the following likely explains this effect? Sodium channels become inactivated The inhibitory drug is activating ligand gated potassium channels The inhibitory drug is activating voltage gated sodium channels. Inhibitory drugs normally depolarize the postsynaptic membrane. your recording that occur spontaneously. Base on your physiology knowledge about neuromuscular junction physiology, you conclude that you are recording: IPSPs in response to quantal glycine release EPSPs in response to quantal glutamate release mEPSPs in response to quantal acetylcholine release mEPSPs in response to quantal GABA release mEPSPs in response to neuropeptides release Wendy is a 23-year-old photographer for a local magazine. Over the last 9 months she has been experiencing severe eye strain, tiredness while brushing her hair and teeth, and extreme fatigue. Her head physician evaluated her and he requested an antibody test, which confirmed myasthenia gravis. Wendy is put on pyridostigmine, an acetylcholinesterase inhibitor and felt much better. Pyridostigmine most likely improved Wendy's symptoms by Decreasing synaptic concentration of Ach, thus decreasing its action Decreasing the likelihood of an action potential occurring thus decreasing muscle contraction Increasing synaptic concentration of Ach, thus prolonging its action Increasing the interaction of SNARE's thus increasing the release of Ach. If the nicotinic channels at the neuromuscular junction pass both Na+ and K+ why does stimulation of these channels cause depolarization of the skeletal muscle The driving force for K+ is very large. The driving force for Na+ is very large The K+ channels are not open. The Na+ ion is smaller and therefore passes more easily.The resting membrane potential is closer to the Na+ Nernst potential Botulinum toxin is used to treat certain eye disorders such as crossed eyes (strabismus) and uncontrolled blinking (blepharospasm), to treat muscle stiffness/spasms or movement disorders (such as cervical dystonia, torticollis), and to reduce the cosmetic appearance of wrinkles. The injection of botulinum toxin into skeletal muscle reduces the amplitude of minature end plate potentials. the frequency of minature end plate potentials. the end plate potentials. presynaptic Ca2+ influx. Both B and C are correct.