Bio 251 Exam Questions and Answers Correctly Approved 2025

Bio 251 Exam Questions and Answers Correctly Approved 2025 A muscle fiber can be innervated by multiple motor neurons. a) True b) False - Correct Ans-f The contraction time of a skeletal muscle is the time between initiation of stimulation and peak contraction of the muscle. a) True b) False - Correct Ans-f During contraction of all types of muscle cells, Ca++ initiates contraction by entering the cytoplasm of the muscle cell by the process of facilitated diffusion. a) True b) False - Correct Ans-t The plateau phase of the contractile cell action potential is caused by Na+ entering the cell. a) True b) False - Correct Ans-f The radii of arterioles can be adjusted independently to variably distribute cardiac output among organs. a) True b) False - Correct Ans-t Platelets contain actin and myosin. a) True b) False - Correct Ans-t Ischemic heart disease is a) Rapid but regular depolarizations and contractions b) Rapid irregular uncoordinated depolarizations contractions c) Action potentials not conducted between atria and ventricles d) Over excitation of non-SA node autorhythmic regions of heart e) Reduced blood supply to heart - Correct Ans-e The steps of synaptic transmission at a neuromuscular junction are listed below, out of order. Choose the correct order. 1. Acetylcholine binds to receptors on muscle cell. 2. Acetylcholine is released. BIO 251 BIO 251 3. A graded potential is produced on the motor end plate. 4. An action potential is produced on the muscle cell membrane. 5. Channels for both sodium and potassium are opened. 6. Voltage-gated calcium channels on the plasma membrane open. 7. An action potential arrives at the axon terminal. - Correct Ans-7621534 The parasympathetic nervous system can act as a stimulus to which types of muscle cells? a) Single-unit smooth b) Cardiac autorhythmic c) Cardiac contractile d) All the above e) a and b only - Correct Ans-e . In Fig 1, the muscle length that gives maximum contraction is a) 60 to 80 b) 80 to 100 c) 100 to 120 d) 120 to 140 e) 140 to 160 - Correct Ans-c The rapid depolarization of cardiac contractile cell membranes when threshold is reached is caused by Ca++ entering the cell. a) True b) False - Correct Ans-f Increased venous return will result in a decreased cardiac output. a) True b) False - Correct Ans-b Indicate which is the proper sequence of blood flow though the circulatory system: 1. right atrium 6. pulmonary vein 2. left atrium 7. lungs 3. right ventricle 8. systemic tissues 4. left ventricle 9. aorta 5. pulmonary artery 10. venae cavae - Correct Ans-10-1-3-5-7-6-2-4-9-8 Place the sequence of a skeletal muscle contraction in order: 1. Ca++ binds to troponin 2. End Plate Potential becomes Action Potential on surface of membrane 3. Tropomyosin moves aside 4. Actin binds to myosin 5. Action potential moves into T tubules 6 Ca++ released from SR 7. Cross-bridge cycling occurs BIO 251 BIO 251 8. Ca++ pumped into SR - Correct Ans-2-5-6-1-3-4-7-8 Asynchronous recruitment of skeletal muscle fibers can occur during tetanus. a) True b) False - Correct Ans-b . Myogenic activity can occur in a) Single-unit smooth b) Cardiac autorhythmic c) Multi-unit smooth d) a and b only e) a and c only - Correct Ans-d Reducing the radius of blood vessels by half will increase blood pressure by a factor of 16. a) True b) False - Correct Ans-a . Your hematocrit level is a) The percent of whole blood that is red blood cells b) The percent of whole blood that is plasma c) The percent of your ECF that is plasma d) The percent of your ECF that is interstitial fluid e) The percent of your total body fluids that are ECF - Correct Ans-a End Diastolic Volume is 150 ml/beat, End Systolic Volume is 80 ml/beat, and heart rate is 60 beats/min. What is the stroke volume? What is the cardiac output? a) 230 ml/beat; 290 ml/min b) 70 ml/beat; 1300 ml/min c) 20 ml/beat; 120 ml/min d) 70 ml/beat; 4200 ml/min e) 70 ml/beat; 4900 ml/min - Correct Ans-d Fast oxidative fibers contain more mitochondria than fast glycolytic fibers a) True b) False - Correct Ans-t Which type(s) of muscle cell are connected by gap junctions? a) Cardiac contractile b) Single-unit smooth c) Multi-unit smooth d) All the above e) a and b only - Correct Ans-e Place the sequence of cross-bridge cycling in order: BIO 251 BIO 251 1. Ca++ released from SR 2."Power stroke" as myosin pulls actin forward 3. ATP split into ADP and Phosphate on myosin 4. Myosin binding site on actin exposed 5. ADP released by myosin 6. ATP binds myosin 7. Actin releases myosin - Correct Ans-1-4-2-5-6-7-3 On entry into a smooth muscle cell, Ca++ binds calmodulin to initiate the sequence of events that result in cross bridge cycling. a) True b) False - Correct Ans-t Increased metabolic demands of a tissue usually leads to vasoconstriction of arterioles leading to that tissue. a) True b) False - Correct Ans-b . In a healthy person, the AV node functions as the pacemaker of the heart. a) True b) False - Correct Ans-b When energy is needed for muscle contraction at the onset of exercise, creatine phosphate is produced from ATP and creatine and is used as energy by the muscle a) True b) False - Correct Ans-b The leading cause of death in Western nations is a) Heart block b) Ectopic focus c) Atrial flutter d) Atrial fibrillation e) Ischemic heart disease - Correct Ans-e Ventricular fibrillation is a) Rapid but regular depolarizations and contractions of ventricles b) Rapid irregular uncoordinated depolarizations contractions of ventricles c) Action potentials not conducted between atria and ventricles d) Over excitation of non-SA node autorhythmic regions of heart e) Reduced blood supply to heart - Correct Ans-b . The binding of epi and/or norepi to ______ receptors on contractile cells in the ventricles will BIO 251 BIO 251 increase contractile strength of ventricles by _______ the Ca++ permeability of the cells, ______ Ca++ movement out of the SR, _______ the rate of myosin ATPase activity and _____ the rate of pumping Ca++ back into the SR. - Correct Ans-Beta-1; increasing; increasing; increasing; increasing . The velocity of blood through the capillaries is very slow in order to a) Increase the surface area for capillary exchange b) Minimize the distance over which capillary exchange occurs c) Maximize time for capillary exchange d) Decrease the flow rate of the blood e) Both c and d are correct - Correct Ans-c Atria and ventricles have separate cycles of systole and diastol