Quiz: Physiology

A medical student was working in a neurophysiology lab and was learning factors that determine the resting membrane potential of a neuron. Which of the following statements correctly explains how a change in concentration of an ion inside or outside of the neuron would change its resting membrane potential?

A A medical student was working in a neurophysiology lab and was learning factors that determine the resting membrane potential of a neuron. Which of the following statements correctly explains how a change in concentration of an ion inside or outside of the neuron would change its resting membrane potential? B A decrease in the extracellular K+ concentration increases the gradient for K+ to leak out of the neuron, making the cell more hyperpolarized. C An increase in the extracellular K+ concentration would move the resting membrane potential from a normal value of −90 mV to −70 mV. D A decrease in the extracellular Na+ concentration would reduce the size of the resting membrane potential.

The relative refractory period:

A Occurs during depolarization B It characterized by inability of any stimulus to generate an action potential. C It is due to in activation of all Na+ channels D It is due to in activation of some voltage gated Na+ channels.

The relative refractory period:

A Occurs during depolarization B It characterized by inability of any stimulus to generate an action potential. C It is due to in activation of all Na+ channels D It is due to in activation of some voltage gated Na+ channels.

The function of tropomyosin in skeletal muscle include:

A Binding to myosin during contraction B Acting as a relaxing protein at rest by covering the binding sites on actin C Sliding on actin to produce shortening. D Releasing Ca++ after propagation of action potential

During skeletal muscle contraction:

A ATP ase activity of myosin head is inhibited B Tropomyosin covers the active site of actin C Attachment, tilting and detachment occurs between myosinhead and actin D The initial length of muscle fiber increase

The processes where by the body generate heat Is

A Conduction B Evaporation C Convection D Muscular activity

The absolute refractory period of the nerve Is the period during which

A A strong stimulus will excite. B A weaker stimulus will excite. C Stimulus of eny type is completely in effectivث D It correspond to ascending limb of A.P and descending of limb of A.P

Regarding the action potential In nerve membrane all are true EXCEPTS

A It is all or none in characters B A threshold stimulus is required for its initiation C Hypcrpolarization occurs when the membrane potential overshoots more ti the negative side D The current is spread by decremental conduction

Excitation contraction coupling involves nil the following, except:

A Release of Ca-H- from troponin B Formation of cross bridges between actin and myosin. C Spread of depolarization along the transverse tubules. D Hydrolysis of ATP to ADP

Skeletal muscle membrane Na+ -K+ -ATPase is stimulated by:

A Insulin B Epinephrine C a and b D estrogen

An increase in sodium conductance is associated with which of the following?/

A The descending limb of the skeletal muscle action potential B The resting membrane of the nerve action potential C The refractory period of the nerve cell action potential D The end-plate potential of the skeletal muscle fiber

An increase in sodium conductance is associated with which of the following?/

A The descending limb of the skeletal muscle action potential B The resting membrane of the nerve action potential C The refractory period of the nerve cell action potential D The end-plate potential of the skeletal muscle fiber

As regard conduction of action potential in a nerve:

A In thick myelinated nerve fibers can reach up to 120 meter / second. B Can be increased by increase calcium C Can be increased by cooling D Is conducted with decrement

Contraction of skeletal muscles:

A Produces more work when the muscle contracts isometrically than when it contracts isotonically B Depends on external Ca++ C Decrease in magnitude with rapid repeated stimulation D Does not depend on action potential

During depolarization

A Voltage activated Na+ channels open B The membrane becomes impermeable to Na+ C When membrane potential reaches -55 m.v Na+ & K+ fluxes occur at the same time D K+ ions diffuse outside

During depolarization

A Voltage activated Na+ channels open B The membrane becomes impermeable to Na+ C When membrane potential reaches -55 m.v Na+ & K+ fluxes occur at the same time D K+ ions diffuse outside

During depolarization

A Voltage activated Na+ channels open B The membrane becomes impermeable to Na+ C When membrane potential reaches -55 m.v Na+ & K+ fluxes occur at the same time D K+ ions diffuse outside

During depolarization

A Voltage activated Na+ channels open B The membrane becomes impermeable to Na+ C When membrane potential reaches -55 m.v Na+ & K+ fluxes occur at the same time D K+ ions diffuse outside

Myelin sheath:

A Present in the myelinated and unmyelinated nerve fibers B Formed of lipoprotein complex and acts as electric insulator C It is formed of successive wrappings of the membrane of Schwann cells D t is the cause of decreased coniduction of nerve impulse

The contractile response in skeletal muscle

A Starts after the action potential is over B Does not last as long as the action potentia C Produces more tension when the muscle contracts isometrically than when it contracts isotonically D Produces more work when the muscle contracts isometrically than when it contracts isotonically

The function of tropomyosin in skeletal muscle include:

A Binding to myosin during contraction B Acting as a relaxing protein at rest by covering the binding sites on actin C Sliding on actin to produce shortening D Releasing Ca++ after propagation of action potential.

Which of the following is true for the excitation-contraction coupling of skeletal and smooth muscle?

A An action potential causes calcium levels in the cytosol to increase B Calcium binds to troponin C Thick and thin filaments slide past each other D Both a and c

Myotomes originate from:

A Extraembryonic mesoderm B Paraxial mesoderm C Intermediate mesoderm D Somatopleuric mesoderm

One of the following anomalies is NOT related to muscular system:

A Arthrogryposis multiplex B Duchenne dystrophy C Multiple sclerosis D Muscle agenesis

Aversion of the foot is produced by

A Tibialis anterior and posterior B Peroneus longus and brevis C Extensor digitorum D Extensor hallucis longus E All the above

Aversion of the foot is produced by

A Tibialis anterior and posterior B Peroneus longus and brevis C Extensor digitorum D Extensor hallucis longus E All the above

Which of the following tumors is chondroblastic origin

A Chondromyxoid fibroma B Ewing sarcoma C Multiple myeloma D Osteochondroma E Osteosarcoma

The sarcomere (the structural and functional unit of skeletal muscle) is:

A the distance between two Z-lines B the distance between two M-lines C the distance between two I- bands D the distance between two A- bands

About neurilemma:

A It acts as an electric insulator around the nerve fiber B It surrounds the axons of all neurons inside and outside the CNS C it is responsible for the color of the white matter of the spinal cord D It is essential for regeneration of the damaged verve fibers

Continuous conduction:

A Occurs in myelinated nerve fibers B Occurs by jumping of charges from one node of Ranvier to another C Is relatively slow 0.5-2.0 meter / second D Occurs in the neuro-muscular junction

Repolarization

A Occurs at first gradual then becomes fast B Results from closure of sodium gates and opening of potassium gates C Is represented by the ascending limb of the spike D Is followed by appearance of response

Repolarization

A Occurs at first gradual then becomes fast B Results from closure of sodium gates and opening of potassium gates C Is represented by the ascending limb of the spike D Is followed by appearance of response

Which of the following has the lowest conduction velocity?

A α fibers B β fibers C B fibers D C fibers

An increase in sodium conductance is associated with which of the following?

A The descending limb of the skeletal muscle action potential B The resting membrane of the nerve action potential C the refractory period of the nerve cell action potentia D The end-plate potential of the skeletal muscle fiber

As regard conduction of action potential in a nerve:

A in thick myelinated nerve fibers can reach up to 120 meter / second. B Can be increased by increase calcium C Can be increased by cooling D Is conducted with decrement

Myelin sheath:

A Present in the myelinated and unmyelinated nerve fibers B Formed of lipoprotein complex and acts as electric insulator C It is formed of successive wrappings of the membrane of Schwann cells D It is the cause of decreased conduction of nerve impulse

The function of tropomyosin in skeletal muscle include:

A Binding to myosin during contraction B Acting as a relaxing protein at rest by covering the binding sites on actin C Sliding on actin to produce shortening D Releasing Ca++ after propagation of action potential.

Action potential

A Is a graded potential B Is produced by sub-threshold stimulus C Starts with repolarization caused by outward movement-of Cl D Is conducted slower in thin nerve fibers E All the above

Which troponin binds to tropomyosin

A Troponin I B Troponin M C Troponin C D Troponin T

Action potential

A is a graded potential B Is produced by sub-threshold stimulus C Starts with repolarization caused by outward movement-of Cl D Is conducted slower in thin nerve fibers E All the above

On arrival of an excitation wave through the axon to M.E.P

A it leads to increase permeability of the membrane to Na B It leads to increase permeability of the membrane ++to Ca C it leads to increase permeability of the membrane +to k D All the above E None of the above

Salutatory conduction

A Occurs in unmyelinated nerve fibers B May reach up to 1 20 meter second C Occurs by jumping from one neuron to anothe D Decreases gradually with distance till it disappears E It is a slowest type of conduction

The resting membrane potential is caused by

A Na-K pump & selective membrane permeability B Diffusion of Na+ ions inside the nerve fibers C Opening of chemically activated ion channels D Opening of voltage activated ion channels E Both A and B are correct

Action potential:

A Is a graded potential B Is produced by sub-threshold stimulus C Starts with repolarization caused by outward movement of Cl D Is conducted slower in thin nerve fibers

The resting membrane potential is caused by:

A Na-K pump & selective membrane permeability B Diffusion of Na+ ions inside the nerve fibers C Opening of chemically activated ion channels D Opening of voltage activated ion channels E Both A and B are correct.

Salutatory conduction:

A Occurs in unmyelinated nerve fibers B May reach up to 120 meter / second C Occurs by jumping from one neuron to another D Decreases gradually with distance till it disappears E It is a slowest type of conduction

The force of muscle contraction affected by the following EXCEPT:

A Type of muscle fibers B The initial length of muscle fiber C Sympathetic stimulation D Fatigue E CL++ concentration

On arrival of an excitation wave through the axon to M.E.P.:

A It leads to increase permeability of the membrane to Na B It leads to increase permeability of the membrane to Ca++ C It leads to increase permeability of the membrane to k+ D All of the above. E None of the above

Sweeping self) nerve conduction

A Occurs in myelinated nerve .fibers B May reach up to 1 20 meter /.second C Occurs by jumping from one .neuron to another D action potential developed at the point of stimulation E It is fast type of conduct

The resting membrane potential of a cell

A Is dependent on the permeability of a cell membrane to K+ being +greater than to Na B Falls to zero if Na+/ K+ ATPase in membrane is .inhibited C Is equal to the equilibrium .+potential for K D Is equal to the equilibrium ,+potential for Na E Is dependent on the permeability of a cell membrane to Na+ being greater than to K+1

The resting membrane potential of a cell

A Is dependent on the permeability of a cell membrane to K+ being +greater than to Na B Falls to zero if Na+/ K+ ATPase in membrane is .inhibited C Is equal to the equilibrium .+potential for K D Is equal to the equilibrium ,+potential for Na E Is dependent on the permeability of a cell membrane to Na+ being greater than to K+1

The nerve action potentia

A It is rapid changes in the .membrane potentials B Begin by changing the positive resting potential to .negative potential C Once started it travels over the entire membrane D Both a and c are correct E None of the above

The relative refractory period

A Occurs during depolarization B It characterized by inability of any stimulus to generate an .action potentia C t is due to in activation of all Na+ channels o D It is due to in activation of some voltage gated Na+ channels E None of the above

As regard neuro-muscular transmission all are FALSE except

A There is no fatigue B Occurs from nerve to muscle J.e. one way conduction C It is blocked by Acetylcholine D It is increased by Curare E It is multi-directional

During skeletal muscle contraction

A The distance between the z- lines of the sarcomere decreases B The head of actin get charged with ATP. The charging with ATP disconnects them from the active sites on myosin C The Ca++ combined with troponin C is detached and recollected back into the sarcoplasmic reticulum D All of the above

During skeletal muscle contraction

A ATP ase activity of myosin head is inhibited B Tropomyosin covers the active site of actin C Attachment, tilting and detachment occurs between myosin head and actin D The initial length of muscle .fiber increase E Ca+ needed to start contraction come from ECF

Resting membrane potential in medium-sized nerve is normally about

A mv 50 - B mv 35 + C mv 70 - 0 D .mv 90 - E mv 55 -

The most important ion during resting membrane potential is

A +Na B +K C ++Ca D Cl E HCO3

During an action potential depolarization of nerve cell membrane is brought about by

A Increased sodium permeability B Increased calcium permeability C Increased chloride permeability D Increased potassium permeability E Both a and b are correct

Descending limb of the spike potential in the nerve

A Represents depolarization B Is caused by potassium inflow C Is caused by sodium inflow D Represents Repolarization E Is caused by calcium inflow

Concerning the RMP

A It is mainly due to K+ influx through leak channels B It is mainly due to Na+ efflux C It is usually of fixed value in all tissues D It is mainly due to K+ efflux through leak channels E It is more negative in nerve fibers than muscle fibers

The ascending limb of the spike potential in the nerve

A Is caused by K+ inflow B Represents depolarization C Is caused by Na+ inflow through leak channels D Represents Repolarization E Is associated with increased excitability

The local response

A is characterized by depressed excitability B Can not be summated Obeys the all or none law C Is followed by an absolute refractory period D None of the above

The excitability of the nerve is zero rduring

A Super normal phase of excitability B Relative refractory period C Sub normal phase of excitability D Local response E Absolute refractory period

Refractory period is longest in

A Skeletal muscle B Cardiac muscle C Multi-unit smooth muscle D Single unit smooth muscle E Both b and d are correct

The absolute refractory period

A Is a period during which .excitability is completely lost B Is a period during which stronger stimulus is needed to excite the muscle fiber C Is coincided with the .descending limb of the spike D Is a period during which the excitability is less than normal E None of the above

The absolute refractory period in the skeletal muscle

A Coincides with the descending limb of the spike B Coincides with after .depolarization C is short and ends before start .of contraction D is accompanied only with.decreased excitability E Is long and occupies the .duration of contraction

Relative refractory period

A Is an increase in excitability B Is a complete loss of excitability C Coincides with the second 2/3 of descending limb of spike D During it the nerve can't respond to any stimulus whatever its strength

Nerve excitability is increased by

A Cooling B Local anaesthetics C Acidosis D Alkalosis E Deep pressure

AlI or none law can be applied to

A Whole skeletal muscle B Nerve trunk C whole heart D Multi unit smooth muscle E Single unit smooth muscle

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