Question

Q1. Which of the following is TRUE of the absolute refractory period?

Select one:
a) it establishes the maximum frequency with which a nerve cell can conduct action potentials
b) it does not end until the Na+/K+ pump has restored the ions to their original summate
c) two of the above are correct
d) a, b, and c are correct

Q2. In order for a neuron to move from the absolute to the relative refractory period, a majority of that neuron's sodium channels must have their:

Select one:

a) inactivation gates open
b) activation gates closed
c) inactivation gates closed
d) activation gates open and inactivation gates closed

Q3. Which of the following statements concerning propagation of action potentials is TRUE?

Select one:
a) saltatory conduction occurs only in myelinated fibers
b) during the propagation of action potentials, the action potential gets progressively smaller as it moves down the membrane
c) during contiguous conduction, localized current flow causes hyperpolarization of an adjacent portion of the membrane
d) the action potentials can undergo spatial and temporal summation
e) more than one of the above is correct

Q4. Which of the following is NOT true of graded potentials?

Select one:
a) They are produced after the binding of neurotransmitter to receptor
b) they will decrease in magnitude as the current flows away from the initial site
c) they are produced at chemically-gated ion channels
d) they are limited in duration by the refractory period of the membrane

Q5. Assume that a post-synaptic neuron has two pre-syanptic inputs: X and Y. When pre-synapitc neuron X is stimulated, the post-synaptic membrane becomes slightly

Select one:
a) excitatory
b) inhibitory
c) not enough info

Q6. assume that a post-synaptic neuron has two pre-syanptic inputs: X and Y. Given that pre-synaptic neuron X causes hyperpolarization of the post-synaptic membrane, what kind of permeability changes may have occurred in the post-synaptic neuron?

Select one:
a) increase permeability both Ca2+ and K+
b) increased permeability to K+ but not Na+
c) increased permeability to anionic proteins
d) increased permeability to Ca2+
e) increased permeability to both K+ and Na+

Q7. Which type of autonomic receptor is found in the synapse of the parasympathetic postganglionic fiber with the effector organ?

Select one:

a) alpha
b) nicotinic
c) beta-2
d) beta-1
e) muscarinic

Q8. With pre-marathon training, a runner's body adjusts by increasing the amount of acetylcholinesterase. What would be the physiological effect on skeletal muscle fibers?

Select one:

a) it would inhibit the release of Ach from the presynaptic cell
b) it would inhibit the attachment of Ach to muscarinic receptors
c) it would lead to a faster speed of contraction

Q9. Acetylcholine stimulates an action potential in the muscle cell membrane by:

Select one:
a) Opening channels in the neuromuscular junction which allow sodium to move out of the muscle cell
b) Opening channels in the neuromuscular junction which allow potassium to move into the muscle cell
c) Opening channels in the neuromuscular junction which allow sodium to move in and potassium to move out, though sodium moves faster than potassium because both chemical and electrical gradients drive sodium into the cell
e) Opening channels in the neuromuscular junction which allow sodium to move in and potassium to move out, though potassium moves faster than sodium because potassium is closer to equilibrium

Q10. As ATP binds to the myosin head,

Select one:
a) the myosin head detaches from actin
b) the myosin molecule lengthens
c) the myosin head attaches more tightly to actin
d) the myosin molecule shortens
e) the myosin head's actin binding site is physically blocked

Q11. Which type of autonomic receptor is found on the adrenal medullary cells?

Select one:
a) alpha
b) nicotinic
c) beta-2
d) beta-1
e) muscarinic

Q12. Compared to epinephrine, norepinephrine has a greater affinity for what type of receptor?

Select one:
a) alpha
b) nicotinic
c) beta-2
d) beta-1
e) muscarinic

Q13. Phosphocreatine

Select one:
a) provides the muscle cell with a quick energy source
b) removes Ach from the neuromuscular junction
c) blocks the myosin binding site in a relaxed muscle
d) responsible for the release of Ach
e) pumps Ca2+ back into the sarcoplasmic reticulum

Q14. In twitch summation,

Select one:
a) the muscle fiber is stimulated again before the filaments have completely returned to their resting position
b) stronger muscle contractions occur but stronger action potentials do not uoccur
c) a second action potential occurs in the muscle fiber, before the first action potential is finished
d) both a and b are correct
e) all of the above are correct

Q15. The force generated by a single muscle fiber:

Select one:
a) is always the same
b) can be increased by increasing the frequency of action potentials
c) can be increased by motor unit recruitment
d) more than one of the above is correct

Q16. an isometric(static) muscle contraction:

Select one:
a) muscle tissue shortens
b) muscle tension exceeds the force of the load
c) the load is moved
d) both b and c are correct
e) none of the above is correct

Q17. Which of the following statements concerning the characteristics of different muscle fiber types is FALSE?

Select one:
a) the higher the ATPase activity, faster the speed of contraction
b) muscle fibers containing large amounts of myoglobin have a dark red color in comparison to the paler fibers, which have little myoglobin
c) oxidative types of muscle fibers contain a lot of myoglobin
d) scientific studies have found that, with selective training of a muscle tissue, slow twitch fibers can transform into fast twitch fibers and vise versa
e) in response to weight training, fast twitch fibers increase protein synthesis

Answer 1

1. Refractory period is the time interval at which an excitable cell cannot produce another action potential in response to normal stimulus. Absolute refractory period is corresponds to depolarizing and repolarizing phase of action potential so that a nerve cell can conduct action potential at maximum frequency. In this period activation and inactivation of sodium channels occur and inactivated channels can not re open even every strong stimuli is applied to the membrane. Many potasium channels are open during this time.

Thus answer is a) it establishes the maximum frequency with which a nerve cell can conduct action potentials

2. Relative refractory period corresponds to hyperpolarization phase of action potential. In this phase voltage gated potassium channels are open and Inactivated sodium channels are closed.

Thus answer is d) activation gates open and inactivation gates closed

3. Saltatory conduction is the rapid propagation of action potential along the myelinated axons due to uneven distribution of voltage gated ion channels

Answer is a) saltatory conduction occurs only in myelinated fibers

4. Graded potential generated in dendrites or cell body of a postsynaptic neuron in response to opening of mechanically gated or ligand gated ion channels (example of ligand - neurotransmitters). Graded potential have more duration than action potential but does not have refractory period

Thus answer is d) they are limited in duration by the refractory period of the membrane