BIO 392 Exam #2 Study Guide Verified Study
Questions And Answers
In a graded potential, what is the effect of cytoplasmic resistance and current leak? ANS The strength of
the signal inside the cell decreases over a distance.
In most cells, the concentration of ions contributing to the membrane potential are __________ in the
intracellular fluid compared to the extracellular fluid, with the exception of __________ ions. ANS lower;
potassium
Which of the following would NOT cause the membrane potential to change from -70 mV to +30 mV? ANS
potassium ions leaving the cell. Because potassium ions are positively charged ions, if they leave the cell,
the cell will actually become more negative.
Neurotransmitters are usually released into synapses by __________. ANS exocytosis
A neuron has a resting potential of -70 mV and a threshold voltage of -50 mV. There are currently three active
synapses on the neuron's dendrites, each located the same distance from the axon. The potential changes are +
40 mV at synapse 1, + 20 mV at synapse 2, and -10 mV at synapse 3. These synaptic potentials diminish by
50% by the time they reach the trigger zone. Will this neuron produce an action potential at this time? Explain.
(Hint: Draw a graph of the voltage changes.) ANS Yes. At the trigger zone, all potentials have halved and
will sum as follows: +20mV (originated at synapse 1), + 10mV (originated at synapse 2), -5mV (originated at
synapse 3) sum to produce a total potential change of +25mV. The neuron required a minimum change of +20
mV (-70 mV + 20 mV = -50 mV), so it will produce an action potential.
Whether or not a neuron produces an action potential at a given moment depends on ________. ANS the
total potential change reaching threshold voltage at the trigger zone
Which type of receptor would bind acetylcholine and be found in skeletal muscle? ANS Nicotinic
cholinergic
A stronger stimulus to a neuron results in ________. ANS larger voltage changes in graded potentials and
greater frequency of action potentials produced in response
Somatic motor neurons secrete the neurotransmitter ________ onto ________ receptors at the target tissue.
ANS acetylcholine; nicotinic
, The neurotransmitter that controls skeletal muscle causes which of the following? ANS muscle contraction
Which type of receptor is found in the neuromuscular junction? ANS nicotinic
What is the trigger for ACh release into the synaptic cleft of a neuromuscular junction? ANS An action
potential at the axon terminal opens voltage-gated Ca2+ channels.
What is an appropriate classification for the ACh receptor found in the neuromuscular junction? ANS
ligand-gated, nonspecific, cation channel
How many molecules of ACh are necessary to completely activate the cholinergic nicotinic receptor? ANS
Two
What would be the effect of ACh binding to its receptor on the postsynaptic muscle cell? ANS Na+ would
flow into the cell and K+ would flow out of the cell.
Acetylcholinesterase (AChE) inhibitor administration is a common treatment for myasthenia gravis. Why does
this help alleviate some of the symptoms of this autoimmune disease? ANS AChE inhibition increases
ACh in the synaptic cleft to bind remaining ACh receptors.
Most skeletal muscles move bones. They do this by _____ on the bone, to _____ the joint angle. ANS
pulling; increase or decrease
The calcium-binding protein in muscle contractile units is _____. ANS troponin
The inward extensions of the sarcolemma are called _____, and they conduct _____ into the interior of the
muscle cell. ANS t-tubules; the action potential
Which is the smallest structure in terms of muscle? ANS Myosin
Which of these structures would not change size during a muscle contraction? ANS A band
Questions And Answers
In a graded potential, what is the effect of cytoplasmic resistance and current leak? ANS The strength of
the signal inside the cell decreases over a distance.
In most cells, the concentration of ions contributing to the membrane potential are __________ in the
intracellular fluid compared to the extracellular fluid, with the exception of __________ ions. ANS lower;
potassium
Which of the following would NOT cause the membrane potential to change from -70 mV to +30 mV? ANS
potassium ions leaving the cell. Because potassium ions are positively charged ions, if they leave the cell,
the cell will actually become more negative.
Neurotransmitters are usually released into synapses by __________. ANS exocytosis
A neuron has a resting potential of -70 mV and a threshold voltage of -50 mV. There are currently three active
synapses on the neuron's dendrites, each located the same distance from the axon. The potential changes are +
40 mV at synapse 1, + 20 mV at synapse 2, and -10 mV at synapse 3. These synaptic potentials diminish by
50% by the time they reach the trigger zone. Will this neuron produce an action potential at this time? Explain.
(Hint: Draw a graph of the voltage changes.) ANS Yes. At the trigger zone, all potentials have halved and
will sum as follows: +20mV (originated at synapse 1), + 10mV (originated at synapse 2), -5mV (originated at
synapse 3) sum to produce a total potential change of +25mV. The neuron required a minimum change of +20
mV (-70 mV + 20 mV = -50 mV), so it will produce an action potential.
Whether or not a neuron produces an action potential at a given moment depends on ________. ANS the
total potential change reaching threshold voltage at the trigger zone
Which type of receptor would bind acetylcholine and be found in skeletal muscle? ANS Nicotinic
cholinergic
A stronger stimulus to a neuron results in ________. ANS larger voltage changes in graded potentials and
greater frequency of action potentials produced in response
Somatic motor neurons secrete the neurotransmitter ________ onto ________ receptors at the target tissue.
ANS acetylcholine; nicotinic
, The neurotransmitter that controls skeletal muscle causes which of the following? ANS muscle contraction
Which type of receptor is found in the neuromuscular junction? ANS nicotinic
What is the trigger for ACh release into the synaptic cleft of a neuromuscular junction? ANS An action
potential at the axon terminal opens voltage-gated Ca2+ channels.
What is an appropriate classification for the ACh receptor found in the neuromuscular junction? ANS
ligand-gated, nonspecific, cation channel
How many molecules of ACh are necessary to completely activate the cholinergic nicotinic receptor? ANS
Two
What would be the effect of ACh binding to its receptor on the postsynaptic muscle cell? ANS Na+ would
flow into the cell and K+ would flow out of the cell.
Acetylcholinesterase (AChE) inhibitor administration is a common treatment for myasthenia gravis. Why does
this help alleviate some of the symptoms of this autoimmune disease? ANS AChE inhibition increases
ACh in the synaptic cleft to bind remaining ACh receptors.
Most skeletal muscles move bones. They do this by _____ on the bone, to _____ the joint angle. ANS
pulling; increase or decrease
The calcium-binding protein in muscle contractile units is _____. ANS troponin
The inward extensions of the sarcolemma are called _____, and they conduct _____ into the interior of the
muscle cell. ANS t-tubules; the action potential
Which is the smallest structure in terms of muscle? ANS Myosin
Which of these structures would not change size during a muscle contraction? ANS A band
