The activity of acetylcholine in a synapse is terminated by

The activity of acetylcholine in a synapse is terminated by 

A) its active transport across the presynaptic membrane.
B) its diffusion across the presynaptic membrane.
C) its active transport across the postsynaptic membrane.
D) its diffusion across the postsynaptic membrane.
E) its degradation by a hydrolytic enzyme on the postsynaptic membrane.







Answer: E

The following steps refer to various stages in transmission at a chemical synapse. 1. Neurotransmitter binds with receptors associated with the postsynaptic membrane. 2. Calcium ions rush into neuron's cytoplasm. 3. An action potential depolarizes the membrane of the axon terminal. 4. The ligand-gated ion channels open. 5. The synaptic vesicles release neurotransmitter into the synaptic cleft. Which sequence of events is correct?

The following steps refer to various stages in transmission at a chemical synapse.
1. Neurotransmitter binds with receptors associated with the postsynaptic membrane.
2. Calcium ions rush into neuron's cytoplasm.
3. An action potential depolarizes the membrane of the axon terminal.
4. The ligand-gated ion channels open.
5. The synaptic vesicles release neurotransmitter into the synaptic cleft.
Which sequence of events is correct? 

A) 1 ? 2 ? 3 ? 4 ? 5
B) 2 ? 3 ? 5 ? 4 ? 1
C) 3 ? 2 ? 5 ? 1 ? 4
D) 4 ? 3 ? 1 ? 2 ? 5
E) 5 ? 1 ? 2 ? 4 ? 3





Answer: C

An inhibitory postsynaptic potential (IPSP) occurs in a membrane made more permeable to

An inhibitory postsynaptic potential (IPSP) occurs in a membrane made more permeable to 

A) potassium ions.
B) sodium ions.
C) calcium ions.
D) ATP.
E) all neurotransmitter molecules.






Answer: A

The observation that the acetylcholine released into the junction between a motor neuron and a skeletal muscle binds to a sodium channel and opens it is an example of

The observation that the acetylcholine released into the junction between a motor neuron and a skeletal muscle binds to a sodium channel and opens it is an example of 

A) a voltage-gated sodium channel.
B) a voltage-gated potassium channel.
C) a ligand-gated sodium channel.
D) a second-messenger-gated sodium channel.
E) a chemical that inhibits action potentials.






Answer: C

The release of acetylcholine from the terminal of a motor neuron is most directly linked to

The release of acetylcholine from the terminal of a motor neuron is most directly linked to 

A) the entry of potassium into the axon terminal.
B) the exit of potassium from the axon terminal.
C) the entry of sodium into the axon terminal.
D) the exit of sodium from the axon terminal.
E) the entry of calcium into the axon terminal.






Answer: E

One possible disadvantage to a nerve net is that it might conduct impulses in two directions from the point of the stimulus. Most of the synapses in vertebrates conduct information in only one direction

One possible disadvantage to a nerve net is that it might conduct impulses in two directions from the point of the stimulus. Most of the synapses in vertebrates conduct information in only one direction 

A) as a result of the nodes of Ranvier.
B) as a result of voltage-gated sodium channels found only in the vertebrate system.
C) because vertebrate nerve cells have dendrites.
D) because only the postsynaptic cells can bind and respond to neurotransmitters.
E) because the sodium-potassium pump moves ions in one direction.





Answer: D

Neural transmission across a mammalian synaptic gap is accomplished by

Neural transmission across a mammalian synaptic gap is accomplished by 

A) the movement of sodium and potassium ions from the presynaptic neuron into the postsynaptic neuron.
B) impulses traveling as electrical currents across the gap.
C) impulses causing the release of a chemical signal and its diffusion across the gap.
D) impulses ricocheting back and forth across the gap.
E) the movement of calcium ions from the presynaptic into the postsynaptic neuron.






Answer: C