Exam 2

A  myosin.

B  tropomyosin.

C  the thick filament.

D  actin.

E  troponin.

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

B  Myosin is an ATPase.

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

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

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

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

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

C  It only refers to addition of EPSPs.

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

E  It always brings a postsynaptic cell to threshold.

A  leg muscles with a larger diameter.

B  a higher density of capillaries in her leg muscles.

C  leg muscles with a smaller diameter.

D  hypertrophy of type I muscle fibers.

E  lower concentrations of glycolytic enzymes in her leg muscles.

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

B  The permeability to Na+ increases greatly.

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

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

E  Voltage-gated Na+ channels are opened.

A  PK+ is the same as PNa+.

B  K+ flows rapidly into the cell.

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

D  PNa+ becomes much greater than PK+.

E  PK+ becomes much greater than PNa+.

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

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

C  No effects on her running

D  Just the first few seconds of exercise

E  Every moment of Sarah’s runs

A  They are responsible for preventing tetanic contractions.

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

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

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

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

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

B  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.

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

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

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  cause a change in membrane potential.

B  be conducted to the axon hillock.

C  trigger an excitatory postsynaptic potential.

D  trigger an action potential.

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

B  Actin dissociates from myosin.

C  Ca2+ is released from the sarcoplasmic reticulum.

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

E  Actin binds to myosin.

A  A drug that inhibits acetylcholinesterase

B  Curare

C  Atropine (a muscarinic acetylcholine receptor antagonist)

D  A nicotinic acetylcholine receptor antagonist

E  A drug that inhibits release of acetylcholine

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

B  The postsynaptic cell will immediately undergo an action potential.

C  The postsynaptic cell will undergo an EPSP.

D  The postsynaptic cell will undergo an IPSP.

A  They are able to summate.

B  They transmit signals over relatively short distances.

C  They depolarize postsynaptic cell membranes.

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

E  They are always the same amplitude.

A  bound to receptors on the sarcoplasmic reticulum.

B  bound to Ca2+ ions.

C  bound to acetylcholinesterase in the end plate membrane.

D  bound to muscarinic receptors at the end plate.

E  inside the muscle cell sarcoplasm.

A  sarcomeres do not significantly shorten.

B  H zones shorten.

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

D  tetanus occurs.

E  the whole muscle shortens.

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

B  It activates an autoimmune disease that destroys myelin.

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

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

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

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

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

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

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

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

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

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

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

A  ATP; attachment

B  calcium; attachment

C  ATP; detachment

D  actin; detachment

E  calcium; detachment

A  Type 2X fibers have more abundant mitochondria.

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

C  Type 2X fibers are smaller in diameter.

D  Type 2X fibers have more abundant myoglobin.

E  Type 2X fibers fatigue more readily.

A  Y is excitatory and Z is inhibitory.

B  They are both excitatory.

C  Z is excitatory and Y is inhibitory.

D  They are both inhibitory.

A  A pair of antagonistic muscles

B  All of the motor neurons supplying a single muscle

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

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

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

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

B  increased K+ flux into the cell.

C  increased K+ permeability of the cell.

D  Increased Na+ flux through K+ channels.

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

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

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

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

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

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

A  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.

B  The refractory period prevents the action potential from spreading back over the part of the membrane that just underwent an action potential.

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

D  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.

E  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.

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

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

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

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

E  Binding of myosin to actin will take place.

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

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

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

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

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

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

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

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

A  Dopamine

B  Norepinephrine

C  Gamma-aminobutyric acid (GABA)

D  Glutamate

E  Endorphin

A  agonist to serotonin receptors.

B  agonist to glycine receptors.

C  agonist to epinephrine receptors.

D  Any of these are possible

E  agonist to the endogenous opioid receptors.

A  They manufacture and store ATP.

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

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

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

E    

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

A  The plasma membrane is completely impermeable to sodium ions.

B  The plasma membrane is completely impermeable to potassium ions.

C  The plasma membrane is most permeable to sodium ions.

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

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

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

A  Norepinephrine

B  Dopamine

C  Glutamate

D  Beta-endorphin

E  Gamma-aminobutyric acid (GABA)

A  By the frequency of action potentials

B  By the duration of action potentials

C  By whether the action potential peak is positive or negative

D  By the size of action potentials

A  You will experience the visual sensation before the pain sensation.

B  It depends on the magnitude of the pain sensation, it may reach the brain first or second.

C  You will feel the pain sensation before the visual sensation.

D  Both sensations will occur at the same time.

A    

B  Muscle cell twitches (contractions)

C  None of the answer choices are correct

D  Drowsiness

E  Muscle paralysis

F  Muscle relaxation

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

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

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

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

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

B  Smooth muscle is striated.

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

D  Smooth muscle does not have thick and thin filaments.

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

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

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

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

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

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

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

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

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

D    

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

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

A  Only skeletal muscle has both actin and myosin.

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

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

D  Myosin is the main regulatory protein in smooth muscle.

E  Myosin is the main regulatory protein in skeletal muscle.

A  The exocytosis of neurotransmitter

B  All of these will not occur

C  The depolarization phase of the action potential

D  The graded potential

E  The repolarization phase of the action potential