Exam 2 (B)

A  It activates an autoimmune disease that destroys myelin.

B  It will cause persistent twitches with short periods of rest in between.

C  It will cause flaccid paralysis (no muscle contraction possible).

D  Muscle function is fine, but it will cause a loss of voluntary control.

E  It will cause spastic paralysis (sustained, unwanted muscle contraction).

A  They are able to summate.

B  They depolarize postsynaptic cell membranes.

C  They are produced by the opening of ligand-gated sodium channels.

D  They transmit signals over relatively short distances.

E  They are always the same amplitude.

A  They act as non-conducting voltage sensors that mediate excitation-contraction coupling.

B  They cause the absolute refractory period to be very brief.

C  They are responsible for preventing tetanic contractions.

D  They are directly responsible for making cardiac muscle fatigue-resistant.

E  They function exactly the same in cardiac muscle cells as they do in skeletal muscle.

A  In skeletal muscle, calcium initiates contraction by binding to myosin light-chain kinase, while in smooth muscle calcium initiates contraction by binding directly to tropomyosin.

B  In skeletal muscle, calcium initiates contraction by binding to troponin, while in smooth muscle calcium initiates contraction by binding directly to myosin.

C  In skeletal muscle, calcium ions bind to a regulatory protein on thin filaments; in smooth muscle, calcium ions bind to a regulatory protein on thick filaments.

D  In skeletal muscle, calcium initiates contraction by binding to troponin, while in smooth muscle calcium initiates contraction by binding to calmodulin.

E  All of the choices are true.

A  Skeletal muscle cells generate the most force when the contraction occurs at an intermediate length.

B  The longer a skeletal muscle cell is when it begins to contract, the stronger the force generation will be.

C  The shorter a skeletal muscle cell is when it begins to contract, the stronger the force generation will be.

D  The tension in a skeletal muscle cell is greatest when contractions occur at either very short or very long lengths.

E  Skeletal muscle cells generate the same amount of force, regardless of their length.

A  inside the muscle cell sarcoplasm.

B  bound to receptors on the sarcoplasmic reticulum.

C  bound to acetylcholinesterase in the end plate membrane.

D  bound to muscarinic receptors at the end plate.

E  bound to Ca2+ ions.

A  Multiple action potentials in the motor neuron cause a sustained contraction.

B  Repeated action potentials from the motor neuron summate into a sustained depolarization of the motor end plate, causing a sustained contraction.

C  A single action potential in the motor neuron causes a sustained contraction.

D  A very large amplitude action potential in the motor neuron causes a very strong contraction in the skeletal muscle cell.

E  The action potential in the muscle cell is prolonged to last as long as the contraction.

A  By the size of action potentials

B  By the duration of action potentials

C  By whether the action potential peak is positive or negative

D  By the frequency of action potentials

A  actin; detachment

B  ATP; detachment

C  ATP; attachment

D  calcium; attachment

E  calcium; detachment

A  tetanus occurs.

B  sarcomeres do not significantly shorten.

C  tension generated by the muscle always exceeds the load on the muscle.

D  H zones shorten.

E  the whole muscle shortens.

A  lower concentrations of glycolytic enzymes in her leg muscles.

B  leg muscles with a larger diameter.

C  a higher density of capillaries in her leg muscles.

D  leg muscles with a smaller diameter.

E  hypertrophy of type I muscle fibers.

A  The order of motor unit recruitment is independent of the size of the alpha motor neuron that innervates them.

B  The order of recruitment of motor units in a muscle is such that the first units recruited generate the most tension.

C  Motor units whose motor neurons have large-diameter cell bodies are recruited first, while motor units with smaller-diameter motor neurons are only activated as the level of activation in the spinal cord increases.

D  Recruitment of one fast-glycolytic motor unit provides a smaller increment in whole-muscle tension than recruitment of one slow-oxidative motor unit.

E  The order of recruitment of motor units in a muscle is such that the last units recruited are those that fatigue most readily.

A  Muscle relaxation

B  Drowsiness

C  None of the answer choices are correct

D  Muscle cell twitches (contractions)

E  Muscle paralysis

A  Z is excitatory and Y is inhibitory.

B  They are both inhibitory.

C  Y is excitatory and Z is inhibitory.

D  They are both excitatory.

A  activation and inactivation of voltage-dependent Na+ channels.

B  increased K+ flux into the cell.

C  Increased Na+ flux through K+ channels.

D  increased K+ permeability of the cell.

E  Na+ permeability that is greater than that during the depolarization phase.

A  K+ flows rapidly into the cell.

B  PK+ becomes much greater than PNa+.

C  Na+ efflux (flow out of the cell) occurs.

D  PK+ is the same as PNa+.

E  PNa+ becomes much greater than PK+.

A  dyenin proteins.

B  lysosomal proteins.

C  kinesin proteins.

D  smooth endoplasmic reticulum.

E  proteins associated with synaptic vesicles.

A  Actin dissociates from myosin.

B  Ca2+ is released from the sarcoplasmic reticulum.

C  Actin binds to myosin.

D  Cross-bridges rotate, sliding past the thin filament.

E  Cross-bridge heads are cocked into an “energized” state.

A  The depolarization phase of the action potential

B  The exocytosis of neurotransmitter

C  The graded potential

D  All of these will not occur

E  The repolarization phase of the action potential

A  A nicotinic acetylcholine receptor antagonist

B  A drug that inhibits release of acetylcholine

C  A drug that inhibits acetylcholinesterase

D  Atropine (a muscarinic acetylcholine receptor antagonist)

E  Curare

A  Actin and myosin attach, thin filaments slide toward the middle of sarcomeres, calcium release into cytosol

B  Calcium release into cytosol, calcium ion influx through sarcolemma, actin and myosin attach, thin filaments slide toward the middle of sarcomeres

C  Calcium release into cytosol, actin and myosin attach, calcium ion influx through sarcolemma, thin myofilaments slide toward the middle of sarcomeres

D  Calcium release into cytosol, actin and myosin attach, thin filaments slide toward the middle of sarcomeres, calcium ion influx through sarcolemma

E  Calcium ion influx through sarcolemma, calcium release into cytosol, actin and myosin attach, thin myofilaments slide toward the middle of sarcomeres

A  The plasma membrane is completely impermeable to potassium ions.

B  The plasma membrane is most permeable to sodium ions.

C  The permeability of the plasma membrane to potassium ions is much greater than its permeability to sodium ions.

D  The concentration of sodium ion is greater inside the cell than outside.

E  The plasma membrane is completely impermeable to sodium ions.

A  Dopamine

B  Gamma-aminobutyric acid (GABA)

C  Norepinephrine

D  Glutamate

E  Endorphin

A  Changes in cytosolic calcium do not regulate cross-bridge activity in smooth muscle.

B  Smooth muscle does not use troponin-tropomyosin to regulate cross-bridge activity.

C  Smooth muscle does not have thick and thin filaments.

D  Smooth muscle is striated.

E  The myosin in smooth muscle requires phosphorylation before it can bind to ATP.

A  All muscles of the body might present a tense, fully contracted state.

B  All muscles of the body might present a limp, relaxed state known as flaccid paralysis.

C  All muscles of the body might exhibit frequent small twitches.

D  All muscles of the body will be completely normal in function.

A  No effects on her running

B  All muscle contractions after Sarah reaches her maximum heart rate (about 10 minutes into her run)

C  Every moment of Sarah’s runs

D  All muscle contractions after Sarah reaches fatigue (about an hour into her run)

E  Just the first few seconds of exercise

A  The voltage-gated Na+ channels are in the inactivated state.

B  There is equal permeability to Na+ and K+.

C  Most of the voltage-gated Na+ channels are in the closed state.

D  All of the K+ channels in the membrane are open.

E  The permeability to Na+ is much greater than the permeability to K+.

A  They form the Z lines that mark the end of each sarcomere.

B  They store the calcium ions that are the main source of activation for the cross-bridge cycle.

C  They allow action potentials to propagate deep into the center of skeletal muscle cells.

D  They manufacture and store ATP.

E  They run in parallel with the myofibrils, and have abundant Ca2+-ATPase proteins for pumping Ca2+ back into the sarcoplasmic reticulum.

A  The rate of ATP hydrolysis by myosin is the same in all types of skeletal muscle.

B  Myosin cross-bridge heads contain two binding sites, one for actin and one for tropomyosin.

C  Troponin covers the binding site on myosin molecules until Ca2+ binds to troponin to remove it from its blocking position.

D  Myosin is an ATPase.

E  All of the myosin cross-bridge heads in a thick filament are oriented and rotate in the same direction.

A  It always brings a postsynaptic cell to threshold.

B  It only refers to addition of EPSPs.

C  The size of an EPSP depends on the size of the stimulus.

D  A synapse is stimulated a second time before the effect of a first stimulus at the synapse has terminated.

E  Two synapses on different regions of a cell are stimulated at the same time.

A  Skeletal muscle usually exhibits spontaneous activity, while smooth muscle cannot contract spontaneously. 

B  Myosin is the main regulatory protein in smooth muscle.

C  Only skeletal muscle has both actin and myosin.

D  Myosin is the main regulatory protein in skeletal muscle.

E  Only skeletal muscle requires increased calcium ion concentration in the cytosol for contraction.

A  In smooth muscle cells, it must be preceded by an action potential in the cell membrane.

B  In skeletal muscle cells, it requires the influx of extracellular calcium ion.

C  In skeletal muscle cells, excitation-contraction coupling begins when an action potential propagates along the sarcoplasmic reticulum membrane.

D  Calcium-induced calcium release plays a role in cardiac muscle cells, as well as in some smooth muscle cells.

E  In all kinds of muscle it requires the entry of calcium from the extracellular fluid.

A  The relative refractory period refers to the period of time during which another action potential can be initiated in that part of the membrane that has just undergone an action potential if a stronger than normal stimulus is applied

B  The refractory period prevents the action potential from spreading back over the part of the membrane that just underwent an action potential.
The relative refractory period refers to the period of time during which another action potential can be initiated in that part of the membrane that has just undergone an action potential if a stronger than normal stimulus is applied.
The refractory period places an upper limit on the frequency with which a nerve cell can conduct action potentials.
The absolute refractory period refers to the period of time during which another action potential cannot be initiated in that part of the membrane that is undergoing an action potential, no matter how great the strength of the stimulus.

C  The refractory period places an upper limit on the frequency with which a nerve cell can conduct action potentials.

D  The absolute refractory period refers to the period of time during which another action potential cannot be initiated in that part of the membrane that is undergoing an action potential, no matter how great the strength of the stimulus.
The refractory period prevents the action potential from spreading back over the part of the membrane that just underwent an action potential.

A  Contraction will occur, but the muscle will be stuck in the contracted state and unable to relax.

B  Only one cross-bridge cycle will occur but no second cycle. 

C  Tropomyosin will continue to cover the myosin binding sites on actin and no cross-bridges will form.

D  A single twitch in skeletal muscle but no sustained contraction.

E  Binding of myosin to actin will take place.

A  Voltage-gated Na+ channels are opened.

B  ATPase destroys the energy supply that was maintaining the action potential at its peak.

C  The permeability to Na+ increases greatly.

D  The Na+, K+ pump restores the ions to their original locations inside and outside of the cell.

E  The permeability to K+ increases greatly while that to Na+ decreases.

A  actin.

B  myosin.

C  tropomyosin.

D  troponin.

E  the thick filament.

A  Type 2X fibers are smaller in diameter.

B  Type 2X motor units contain fewer fibers per alpha motor neuron

C  Type 2X fibers fatigue more readily.

D  Type 2X fibers have more abundant mitochondria.

E  Type 2X fibers have more abundant myoglobin.

A  depolarize a dendrite.

B  cause a change in membrane potential.

C  trigger an excitatory postsynaptic potential.

D  be conducted to the axon hillock.

E  trigger an action potential.

A  Ca2+ that activates contraction of smooth muscles can come from either the ECF or from the sarcoplasmic reticulum.

B  A single smooth muscle cell may be innervated by both a sympathetic neuron and a parasympathetic neuron.

C  In the absence of any neural input, skeletal muscle cannot generate tension.

D  Synaptic input onto skeletal muscle cells is always excitatory, whereas inputs to smooth muscle cells may be either excitatory or inhibitory.

E  Contractile activity of smooth muscle cells does not normally require Ca2+.

A  All of the motor neurons supplying a single muscle

B  A single motor neuron plus all the muscle fibers it innervates

C  A pair of antagonistic muscles

D  All of the muscles that affect the movement of any given joint

E  A single muscle fiber plus all of the motor neurons that innervate it

A  Beta-endorphin

B  Gamma-aminobutyric acid (GABA)

C  Dopamine

D  Glutamate

E  Norepinephrine

A  There will be no change to the membrane potential in the postsynaptic cell.

B  The postsynaptic cell will undergo an IPSP.

C  The postsynaptic cell will immediately undergo an action potential.

D  The postsynaptic cell will undergo an EPSP.

A  an action potential requires the opening of Ca2+ channels, whereas a graded potential does not.

B  action potentials vary in size with the size of a stimulus, while graded potentials do not.

C  an action potential is propagated without decrement, whereas a graded potential decrements with distance.

D  an action potential has a threshold, whereas a graded potential is an all-or-none phenomenon.

E  movement of Na+ and K+ across cell membranes mediate action potentials, while graded potentials do not involve movement of Na+ and K+.

A  agonist to epinephrine receptors.

B  Any of these are possible

C  agonist to serotonin receptors.

D  agonist to glycine receptors.

E  agonist to the endogenous opioid receptors.