4- Physiology MCQ of Excitable Tissues PDF

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EXCITABLE TISSUE 1. The Resting Membrane Potential: a) Is a property of all cells b) Depends primarily on sodium influx c) Magnitude is the same in all excitable cells d) Is mostly due to Gibbs-Donnan effect e) Drops immediately to zero if sodium-potassium pump is blocked 2. Active transport differs from facilitated diffusion in that: a) It requires a carrier b) It moves substances from high to low concentration c) It requires energy d) It occurs through channels e) It is the only mechanism that moves sodium across cell membranes 3. The following substances may cross cell membranes by simple passive diffusion except: a) Potassium b) Sodium c) Protein d) Water e) Chloride 4. The action potential in skeletal muscles a) Usually starts in the end plate b) Causes the release of calcium from sacroplasmic reticulum c) Has no refractory period d) Is similar in shape to that of cardiac muscle, but takes less time e) Is due to auto-rhythmicity of skeletal muscles 5. Contraction of skeletal muscles does not require: a) Influx of extracellular Ca2+ b) Myosin c) Troponin d) An action potential e) Actin 6. In chemical synapses, the following are needed for proper function except: a) A neurotransmitter from the presynaptic neuron b) A receptor for the neurotransmitter in the postsynaptic neuron c) A mechanism for the removal of the transmitter d) Ca2+ channels in the synaptic knob e) Ca2+ channels in the post-synaptic neuron

7. Smooth muscle is similar to skeletal muscle in that: a) It forms latch bridges b) It has myosin c) It has troponin d) An action potential is essential for starting contraction e) Is the property of plasticity 8. When an axon is described with one of the following it means the speed of the transmission is slow except: a) Small in diameter b) Unmyelinated c) Demyelinated d) Type C e) In the peripheral nervous system not CNS 9. In order to initiate skeletal muscle contraction Ca2+ should bind to: a) Myosin b) Tropomyosin c) The Z-Line d) Actin e) Troponin 10. The resting membrane potential is generated by the following factors: a) Selective permeability of cell membrane to K+ b) The high concentration of Na+ in the ECF c) The high concentration of phosphates in the cell nucleus d) The low concentration of Ca2+ inside the cells e) Free movement of bicarbonate across the cell membrane 11. The following is not one of the functions of proteins in the cell membrane: a) Assists endocytosis b) Receptor for neurotransmitters c) Adhesion between cells d) Enzyme e) Hormone 12. The following is true about changes in cell membrane potential: a) The action potential occurs in all tissues b) Local potentials do not occur in excitable tissues c) Local potentials are all-or-none d) Active transport of Na+ is responsible for depolarization e) Repolarization takes longer than depolarization 13. The following is true about the action potential: a) An external stimulus is needed for its initiation in the SA node b) The depolarization phase is due to Ca2+ influx in cardiac muscle property c) Its duration in cardiac muscle is similar to skeletal muscle d) It is essential for initiation of contraction in all types of muscles e) K+ efflux is always the primary cause of repolarization

14. Which of the following is not essential for a muscle twitch in a skeletal muscle? a) ATP b) Myosin c) Ca2+ d) Myoglobin e) Troponin 15. Which of the following does not apply to chemical synapses: a) More than one neurotransmitter may be released b) Neurotransmitter that opens Cl channels are stimulatory to postsynaptic neurons c) The transmitter may be inhibitory d) Ca2+ is needed for the release of transmitter from presynaptic neurons e) Activity of postsynaptic neuron is determined by many presynaptic neurons 16. Contraction of a cell: a) Is due to phospholipids interacting with myosin b) Requires Ca2+ c) Only muscle cells can contact d) Is always associated with an action potential e) Muscle contraction is an "all or none" response 17. Skeletal muscle cells: a) Depends on extracellular calcium for contraction b) Have muscarinic cholinergic receptors c) Have calmodulin instead of troponin d) Act as a syneytium e) Can be tetanized 18. The excitability of neurons is increased by: a) Hypocalcemia b) Hyponatraemia c) Hypokalaemia d) Hypermagnesaemia e) Hypercalcaemia 19. Myelin: a) Is important in the peripheral nerves but not the CNS b) Is formed by microglial cells c) Is an insulator d) Decreases the speed of transmission of action potentials e) Is a carbohydrate in nature

20. The following is not a feature of chemical synapses: a) Convergence b) Divergence c) Synaptic Delay d) Transmission of impulse in both directions e) Postsynaptic inhibitory potential 21. The functions of the proteins of the cell membrane include: a) Active transport of K+ from inside the cell to outside b) Facilitated diffusion of proteins from inside the cell to outside c) Channels for influx of Na+ d) Antibodies e) Neurotransmitters 22. Components of the reflex arc always include the following except: a) A receptor b) An afferent pathway c) An efferent d) Contact center e) The brain 23. The factor that generates the resting membrane potential include: a) The voltage-gated K+ channels b) The ligand-gates K+ channels c) Leak channels d) Active transport of K+ from the ICF to ECF e) Diffusion of Cl- from the ICF to ECF 24. The features of an action potential include all the following except: a) Depolarization b) Repolarization c) A refractory period d) A threshold stimulus e) Is preceeded by hyperpolarization 25. Myelination of the neurons may be abonormal if there is deficiency of: a) Vitamin B12 b) Folic acid c) Iron d) Erythrope e) Interleukin-4 26. The function of lipids in the cell membrane is a) Makes channels for fatty acids b) Acts as receptors c) Facilitated Diffusion d) A barrier to water-soluble substances e) Adhesion between cells

27. The functions of the proteins of the cell membrane include except: a) Active transport b) Ion channels c) Water channels d) Enzymes e) Hormones 28. The resting membrane potential is mainly due to: a) Na+ influx b) Cl- influx c) K+ influx d) K+ efflux e) Ca2+ efflux 29. The Na-K pump: a) Is the main generator of the resting membrane potential b) Is the main regulator of cell volume c) Is found only in nerve and muscle cells d) Action can be described as facilitated diffusion e) Action can be described as secondary active transport 30. The following is true about receptors in the cell membrane except: a) Chemical messangers may have more than one receptor b) Different receptors explain different effects of chemical messangers c) Receptors are always on cell membrane d) Receptors are proteins e) The chemical messangers cannot work if there are no receptors 31. The most important factor in generating the resting membrane potential is: a) Ca2+ b) Na- gated channels c) K- gated channels d) Aquaponins e) Leak channels 32. The most important factor in generating an action potential is: a) Leak channels b) Electrically gated channels c) Chemically gated channels d) The phospholipids of the cell membrane e) The Na-K pump 33. The following is true about a skeletal muscle cell: a) At rest it has an endplate potential but not a resting membrane potential b) It depends on extracellular Ca2+ for its contraction c) Is often voluntary d) Needs ATP for contraction but not relaxation e) Contains creatine phosphate

34. The following is needed for the normal functioning of a chemical synapse except: a) A neurotransmitter b) Gap junctions between pre-synaptic and post-synaptic neurons c) Ca2+ channels in the synaptic knobs d) A receptor for the neurotransmitter on the post-synaptic neuron e) A removal mechanism for the neurotransmitter 35. An action potential can be induced much easier in cases of: a) Hypocalcemia b) Hypernatraemia c) Hypermagnesaemia d) Hypoxia e) Hypokalemia 36. Facilitated Diffusion: a) Requires energy expenditure b) Active transport c) Transported by a protein carrier down its concentration gradient d) Diffusion down concentration gradient e) Faster than primary active transport 37. The resting membrane potential will increase (hyperpolarization) when there is: a) Hyponatremia b) Hypercalcemia c) Hypermagnesimia d) Hypokalaemia e) Hypoglycemia 38. Divergence means: a) The neurotransmitter released by a synaptic knob diffuses to act on many neurons b) The presynaptic neuron has dendrites c) The axon of the presynaptic neuron divides to make synapses d) Many synaptic knobs are found on the postsynaptic neuron e) Neurons have different shapes 39. The speed of conduction of an impulse (action potential) is faster when the axon of the neuron is: a) Small in diameter b) Has a low resting membrane potential c) Is type C not type A d) Is myelinated e) Has many Na-K pumps

40. The action potential in skeletal muscles: a) Is similar in shape to that of cardiac muscle but takes less time b) Is due to autorythmicity of skeletal muscles c) Usually starts in the endplate d) Causes the release of calcium from the sacroplasmic reticulum e) Has no refractory period 41. An excitatory post-synaptic potential would develop if the neurotransmitter: a) Opens chloride channels b) Opens potassium channels c) Closes sodium channels d) Opens calcium channels e) Enters the postsynaptic cell 42. Which of the following has the slowest conduction velocity: a) A-alpha fibers b) A-beta fibers c) A-gamma fibers d) C fibers e) B fibers 43. Hypocalcemia causes tetany because: a) Ion channels become unstable and open easily b) It generates a concentration gradient that favors efflux of calcium from excitable tissue cells c) It reduces the resting membrane potential d) It inhibits blood clotting leading to bleeding into muscles with reflex muscle contraction e) It stimulates release of neurotransmitters 44. Which of the following is not essential for a muscle twitch in a skeletal muscle? a) ATP b) Myosin c) Ca2+ d) Myoglobin e) Troponin 45. Which of the following does not apply to chemical synapses? a) More than one neurotransmitter may be released b) Neurotransmitter that opens Cl- channels are stimulatory to postsynaptic neurons c) The transmitter may be inhibitory d) Ca2+ is needed for the release of the transmitter from the presynaptic neurons e) The activity of the post-synaptic neuron is determined by many pre-synaptic neurons

46. The following can diffuse through the lipid bilayer of the cell membrane: a) Proteins b) Phosphates c) Ca2+ d) Water e) DNA 47. Functions of cell membrane proteins include being: a) Transporters b) Antigens c) Contraction proteins d) Relaxation proteins e) Transcription factors 48. The resting membrane potential: a) It is a characteristic of excitable tissues b) It is usually +35 mV c) It is increased by hypercalcaemia d) It is increased by hypokalaemia e) Has the same value in all cells 49. The action potential: a) Is a graded change in the membrane potential b) Is a feature of the neuromuscular junction c) Is a feature of any synapse d) Is characterized by a refractory period e) Is a prominent feature of vascular smooth muscle 50. The transmission of impulses across chemical synapses may occur without the need for: a) Ca2+ b) Receptors c) A neurotransmitter d) Na-K pump e) An action potential 51. Contraction of a muscle fiber may occur in the absence of: a) Ca2+ b) Actin c) Myosin d) ATP e) An action potential 52. Which feature is unique to cells of excitable tissues: a) Their membrane contains sodium potassium ATPase b) Their membranes contain voltage-gated channels c) A Na+ gradient exists across their membrane d) They have a non-zero resting membrane potential e) Their membranes are selectively permeable to some ions

53. During an isotonic muscle contraction the following is true: a) The Z-lines move closer together and the A-band remains constant b) The I-band increases and the A-band remains constant c) The A-band decreases and the I-band decreases d) The A-band remains constant and the H-zone increases e) The Z-lines disappear and the I-band increases 54. The function of calcium during the cross bridge cycle is: a) To cause detachment of the myosin head and actin complex b) To induce a conformoational change in the myosin molecule, so it can perform a power stroke c) To bind to the thick filament and release the inhibition between myosin and actin d) To prevent rigor mortis from occuring e) To bind troponin and release the inhibition ofmyosin binding sites on actin 55. Which physical property of a substance would increase the rate of its free diffusion across a pure lipid bilayer? a) It must be charged b) It must have a high partitioning coefficient c) It must be water soluble d) It must have a high molecular weight e) It must be polar 56. The Sodium-Potassium Pump: a) Transports potassium against chemical and electrical gradients b) Transports sodium against electrical gradient c) Transports sodium against both chemical and electrical gradient d) Is the main generator of the resting membrane potential e) Is a form of secondary active transport 57. Which of the following would not affect the rate of diffusion of a substance across the capillary wall? a) The pore size of the capillary b) The concentration difference across the capillary wall c) The hydrostatic pressure of the interstitial space d) The surface area of diffusion e) The molecular size of the diffusing substance 58. When the action potential arrives at the terminal buttons it releases the neurotransmitter by increasing intracellular: a) Sodium b) Potassium c) Calcium d) Chloride e) Magnesium

59. Synaptic transmission: a) Is facilitated by chloride b) Is birectional c) Is mainly electrical in humans d) Is inhibited by calcium e) None of the above 60. The resting membrane potential: a) Is all or none b) Only occurs in excitable tissues c) Is due to sodium leaving the cells d) Is mainly due to anions inside the cell e) Is a potassium diffusion potential 61. Transmission in nerve fibers: a) Is slow in type A fibers b) Is salutatory in non-myelinated fibers c) Is enhanced in nerve fibers with large diameters d) Is the same in all fibers e) Is blocked by atropine 62. Neuromuscular junction transmission: a) Is chloride dependent b) Is facilitated by influx of calcium in muscle c) Is blocked by beta blockers d) Is blocked by atropine in striated muscle e) Is blocked by Botulinum toxin 63. The excitatory postsynaptic potential: a) Is due to neurotransmitter release from pre-synaptic neurons b) Is potassium dependent c) Is calcium dependent d) Does not summate e) Is all or none 64. Concerning skeletal muscle contraction: a) Actin binding sites are covered during contraction b) ATPase is found in the head of the cross bridge c) Calcium binds to myosin d) Isometric muscle contraction is caused by change in the length of the muscle fiber e) Tropomyosin covers the binding sites during muscle contraction 65. Repolarization: a) Is due to active transport K+ out of the cell b) Is partly due to influx of Clc) Is usually much quicker than depolarization d) Coincides with the relaxation phase of the muscle twitch in skeletal muscles e) Is due to Ca2+ influx in cardiac muscle

66. The excitatory postsynaptic potential: a) May be due to efflux of Clb) Can be summated to generate an action potential in the dendrites c) Is usually due to Na+ influx d) Necessarily leads to generation of an action potential e) Is also known as the prepotential 67. The speed of transmission of an impulse along an unmyelinated axon becomes quicker if: a) The axon becomes shorter b) The diameter of the axon decreases c) The number of Na+ channels is doubled d) The number of K+ channels is reduced e) The number of mitochondria is increased 68. Red muscle fibers: a) Are suitable for quick movements b) Fatigue easily c) Can store oxygen d) Are rich in creatinine e) Have no troponin 69. The receptor potential: a) Is all or none b) Is decreased by increasing the frequency of stimulation c) Is not threshold dependent d) Is propagated e) Is influenced by changing the intensity of stimulation 70. The following substances move through the cell membrane through channels: a) Bicarbonate b) Urea c) Oxygen d) Water e) Glucose 71. Active transport is of great importance in: a) Repolarization b) Transport of fatty acids across cell membranes c) Movement of water caused by ADH d) Movement of glucose between the ECF and ICF e) Osmotic diuresis

72. It is correct to describe a chemical synapse with the following except: a) Allows impulses to pass in both directions between the presynaptic and postsynaptic neurons b) Can have more than one transmitter released together c) Increases speed of transmission of action potentials along neural pathways d) It is enveloped by myelin to isolate it from its surroundings e) The presynaptic neuron can switch between neurotransmitter to cause either excitation or inhibition of the postsynaptic neuron 73. When a cell is depolarized it is due to: a) Opening of Cl- channels b) Opening of K+ channels c) Opening of Ca2+ channels d) Activation of the Na-K pump e) Absence of aquaproteins 74. During a muscle twitch of a skeletal muscle fiber the following takes place: a) The action potential that started the muscle twitch continues throughout the duration of the twitch b) Ca2+ must enter the cell from the ECF c) Ca2+ must bind to actin d) Relaxation will only occur when Ca2+ is actively pumped back to the sacroplasmic reticulum e) The high energy molecules creatine phosphate is of critical importance for the beginning of the twitch 75. Which of the following does not happen at the endplate of a skeletal muscle cell: a) Binding of acetylcholine to nicotinic receptors b) Opening of Na+ channels c) Depolarization d) An action potential e) Destruction of acetylcholine by choline esterase...