Question 1

Receptors for neurotransmitters are of primary functional importance in assuring one-way synaptic transmission because they are mostly found on the
A)axonal membrane.
B)axon hillock.
C)dendritic membrane.
D)mitochondrial membrane.
E)presynaptic membrane.

Accepted Answer

Receptors for neurotransmitters are mostly found on the dendritic membrane, which is where the majority of synaptic contacts are made. This location allows the neurotransmitter to bind with the receptor and initiate a postsynaptic response, ensuring one-way communication between neurons.

Question 2

An example of the action of metabotropic receptors occurs when
A)voltage-gated ion channels open.
B)voltage-gated ion channels close.
C)acetylcholine-gated sodium channels open.
D)cAMP-linked ion channels open.
E)the undershoot/after-hyperpolarization occurs.

Accepted Answer

The answer of An example of the action of metabotropic...

Question 3

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.

Accepted Answer

An IPSP is an inhibitory signal that hyperpolarizes the postsynaptic membrane, making it less likely to fire an action potential. This is typically achieved by opening ion channels that allow an efflux of positively charged ions (such as potassium) or an influx of negatively charged ions (such as chloride). Option A is the best choice because an efflux of potassium ions would make the membrane more negative, making it more difficult to reach the threshold for firing an action potential.

Question 4

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.

Accepted Answer

The release of acetylcholine at the neuromuscular junction causes the opening of ion channels on the motor end plate of the skeletal muscle. These channels are ligand-gated sodium channels, meaning they open in response to a chemical (acetylcholine) binding to them. This allows sodium ions to flow into the muscle cell, generating an action potential that ultimately leads to muscle contraction.

Question 5

The major inhibitory neurotransmitter of the human brain is
A)acetylcholine.
B)epinephrine.
C)glutamate.
D)nitric oxide.
E)GABA.

Accepted Answer

GABA (gamma-aminobutyric acid) is the major inhibitory neurotransmitter of the human brain. It regulates neuronal activity by reducing the ability of neurons to fire action potentials, therefore reducing the overall excitability of the brain. Acetylcholine, epinephrine, glutamate, and nitric oxide are all neurotransmitters, but they have different functions within the brain.

Question 6

An example of ligand-gated ion channels is
A)the spreading of action potentials in the heart.
B)acetylcholine receptors at the neuromuscular junction.
C)cAMP-dependent protein kinases.
D)action potentials on the axon.
E)graded hyperpolarization.

Accepted Answer

Acetylcholine receptors at the neuromuscular junction are an example of ligand-gated ion channels. They open in response to the binding of acetylcholine and allow for the influx of cations such as sodium and calcium, which can depolarize the cell and lead to muscle contraction.

Question 7

Assume that a single IPSP has a negative magnitude of -0.5 mV at the axon hillock and that a single EPSP has a positive magnitude of +0.5 mV. For a neuron with an initial membrane potential of -70 mV, the net effect of the simultaneous arrival of six IPSPs and two EPSPs would be to move the membrane potential to
A)-72 mV.
B)-71 mV.
C)-70 mV.
D)-69 mV.
E)-68 mV.

Accepted Answer

The answer of Assume that a single IPSP has a...

Question 8

Functionally, which cellular location is the neuron's "decision-making site" as to whether or not an action potential will be initiated?
A)axonal membranes
B)axon hillocks
C)dendritic membranes
D)mitochondrial membranes
E)presynaptic membranes

Accepted Answer

The axon hillock is considered the neuron's "decision-making site" because it is where the summation of all excitatory and inhibitory signals from the dendrites is integrated. If the net depolarization reaches a certain threshold at the axon hillock, an action potential will be initiated. The other cellular locations listed do not play a direct role in this decision-making process.

Question 9

Botulinum toxin inhibits the presynaptic release of acetylcholine. If inhibition occurs at a neuromuscular junction, then
A)the synaptic cleft will close.
B)muscle contraction will cease.
C)the post-synaptic cell will die.
D)muscles will spasm.
E)receptor ion channels will remain open.

Accepted Answer

Botox works by inhibiting the release of acetylcholine, which is needed for muscle contraction. Therefore, if inhibition occurs at a neuromuscular junction, muscle contraction will cease.

Question 10

The primary neurotransmitter from the parasympathetic system that influences its autonomic targets is
A)acetylcholine.
B)adenosine.
C)norepinephrine.
D)adrenaline.
E)dopamine.

Accepted Answer

The parasympathetic system primarily uses acetylcholine as its neurotransmitter to influence its autonomic targets.

Question 11

When several EPSPs arrive at the axon hillock from different dendritic locations, depolarizing the postsynaptic cell to threshold for an action potential, this is an example of
A)temporal summation.
B)spatial summation.
C)tetanus.
D)the refractory state.
E)an action potential with an abnormally high peak of depolarization.

Accepted Answer

When several EPSPs arrive at the axon hillock from different dendritic locations, the process is referred to as spatial summation. The EPSPs are generated simultaneously and their effects add together, depolarizing the postsynaptic cell to threshold for an action potential. Temporal summation, on the other hand, refers to the accumulation of EPSPs from a single presynaptic input over time, rather than from multiple inputs simultaneously. Tetanus refers to a sustained contraction of a muscle due to high-frequency stimulation of its motor neurons. The refractory state refers to the period of time after an action potential when the neuron is unable to fire another action potential, due to the inactivation of sodium channels. An action potential with an abnormally high peak of depolarization is not a recognized term in neuroscience.

Question 12

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.

Accepted Answer

Acetylcholine is terminated in a synapse by its degradation by a hydrolytic enzyme, acetylcholinesterase, which is found on the postsynaptic membrane. This enzyme breaks down acetylcholine into acetate and choline, which can then be reuptaken by the presynaptic neuron and used again to synthesize new molecules of acetylcholine. Active transport across the membranes and diffusion across membranes do not play a significant role in terminating the activity of acetylcholine in a synapse.

Question 13

Neurotransmitters affect postsynaptic cells by
A)initiating signal transduction pathways in the cells.
B)causing molecular changes in the cells.
C)affecting ion-channel proteins.
D)altering the permeability of the cells.
E)All of these options are correct.

Accepted Answer

Neurotransmitters can affect postsynaptic cells in multiple ways, including initiating signal transduction pathways, causing molecular changes in the cells, affecting ion-channel proteins, and altering the permeability of the cells. Therefore, all of the options given are correct.

Question 14

The major excitatory neurotransmitter of the human brain is
A)acetylcholine.
B)epinephrine.
C)glutamate.
D)nitric oxide.
E)GABA.

Accepted Answer

Glutamate is the most abundant excitatory neurotransmitter in the human brain, playing a key role in learning and memory. Acetylcholine and epinephrine are primarily involved in the peripheral nervous system, while nitric oxide is a gas that acts as a signaling molecule in various physiological processes. GABA, on the other hand, is a major inhibitory neurotransmitter in the brain.

Question 15

Adjacent neurons with direct (non-neurotransmitter)action potential transfer are said to have electrical synapses, based on the presence of
A)tight junctions at their point of contact.
B)gap junctions at their point of contact.
C)leaky junctions at their point of contact.
D)anchoring junctions at their point of contact.
E)desmosomes at their point of contact.

Accepted Answer

Gap junctions are the type of junctions that allow direct transfer of action potential between adjacent neurons. These junctions create small pores or channels that connect the cytoplasm of the two cells, forming an electrical synapse. Tight junctions, leaky junctions, anchoring junctions, and desmosomes do not allow direct transfer of action potentials.

Question 16

Neurotransmitters categorized as inhibitory are expected to
A)act independently of their receptor proteins.
B)close potassium channels.
C)open sodium channels.
D)close chloride channels.
E)hyperpolarize the membrane.

Accepted Answer

Inhibitory neurotransmitters typically function by hyperpolarizing the membrane, making it more negative and thus less likely to fire an action potential. This is often achieved through mechanisms such as opening potassium channels (allowing K+ to exit the cell, making the inside more negative) or opening chloride channels (allowing Cl- to enter the cell, making the inside more negative), not by closing them.

Question 17

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

Accepted Answer

The correct sequence of events in transmission at a chemical synapse is as follows:

1) An action potential depolarizes the membrane of the axon terminal (3).
2) Calcium ions rush into the neuron's cytoplasm (2).
3) The synaptic vesicles release neurotransmitter into the synaptic cleft (5).
4) Neurotransmitter binds with receptors associated with the postsynaptic membrane (1).
5) The ligand-gated ion channels open (4).

Therefore, the correct sequence of events is option C, i.e. 3 → 2 → 5 → 1 → 4.

Question 18

A neuropeptide that might function as a natural analgesic is
A)acetylcholine.
B)epinephrine.
C)endorphin.
D)nitric oxide.
E)GABA.

Accepted Answer

Endorphins are neuropeptides that are known to act as natural painkillers by binding to opioid receptors in the brain and spinal cord, blocking the transmission of pain signals. Acetylcholine, epinephrine, nitric oxide, and GABA are neurotransmitters that have different functions in the body but are not primarily associated with pain relief.

Question 19

When several IPSPs arrive at the axon hillock rapidly in sequence from a single dendritic location, hyperpolarizing the postsynaptic cell more and more and thus preventing an action potential, this is an example of
A)temporal summation.
B)spatial summation.
C)tetanus.
D)the refractory state.
E)an action potential with an abnormally high peak of depolarization.

Accepted Answer

This is an example of temporal summation, where multiple inputs from a single presynaptic neuron arrive in rapid succession and summate to produce a larger overall effect on the postsynaptic neuron. The accumulated IPSPs hyperpolarize the membrane potential and prevent an action potential from being generated. Spatial summation involves summation of inputs from multiple presynaptic neurons arriving at different dendritic locations, and tetanus refers to a sustained, high-frequency series of stimuli that can cause a long-lasting contraction in muscles. The refractory state refers to the period after an action potential during which the neuron is temporarily unresponsive to further stimulation, and an abnormally high peak of depolarization would not be expected in this scenario of inhibitory inputs.

Question 20

Ionotropic receptors are found at synapses operated via
A)ligand-gated ion channels.
B)second-messenger-gated ion channels.
C)electrical synapses.
D)inhibitory, but not excitatory, synapses.
E)excitatory, but not inhibitory, synapses.

Accepted Answer

Ionotropic receptors are also known as ligand-gated ion channels, which means they are operated by the binding of a specific molecule (ligand) to the receptor, causing the channel to open and allow ions to pass through. This results in a rapid, direct response to neurotransmitter release at the synapse.

Quiz 48: Neurons, Synapses, and Signalling

Receptors for neurotransmitters are of primary functional importance in assuring one-way synaptic transmission because they are mostly found on the

An example of the action of metabotropic receptors occurs when

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

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 major inhibitory neurotransmitter of the human brain is

An example of ligand-gated ion channels is

Functionally, which cellular location is the neuron's "decision-making site" as to whether or not an action potential will be initiated?

Botulinum toxin inhibits the presynaptic release of acetylcholine. If inhibition occurs at a neuromuscular junction, then

The primary neurotransmitter from the parasympathetic system that influences its autonomic targets is

When several EPSPs arrive at the axon hillock from different dendritic locations, depolarizing the postsynaptic cell to threshold for an action potential, this is an example of

The activity of acetylcholine in a synapse is terminated by

Neurotransmitters affect postsynaptic cells by

The major excitatory neurotransmitter of the human brain is

Adjacent neurons with direct (non-neurotransmitter) action potential transfer are said to have electrical synapses, based on the presence of

Neurotransmitters categorized as inhibitory are expected to

A neuropeptide that might function as a natural analgesic is

When several IPSPs arrive at the axon hillock rapidly in sequence from a single dendritic location, hyperpolarizing the postsynaptic cell more and more and thus preventing an action potential, this is an example of

Ionotropic receptors are found at synapses operated via