Question 1

The junction between two neurons across which an impulse passes is the:

Accepted Answer

Synapse. A synapse is the junction between the axon terminal of one neuron and the dendrite of the next.

Question 2

At a chemical synapse, the impulse is transmitted by molecules called:

Accepted Answer

Neurotransmitters. Neurotransmitters (e.g. acetylcholine) diffuse across the synaptic cleft to relay the impulse.

Question 3

The arrival of an impulse at the axon terminal causes the entry of ______, triggering neurotransmitter release:

Accepted Answer

Ca²⁺ ions. Ca²⁺ influx at the terminal makes synaptic vesicles fuse and release neurotransmitter into the cleft.

Question 4

At an electrical synapse, impulse transmission is ______ than at a chemical synapse:

Accepted Answer

Faster (almost instant, via direct current flow). Electrical synapses allow direct, very fast current flow between cells; chemical synapses are slower (with a synaptic delay).

Question 5

Neurotransmitters are released from the pre-synaptic terminal by:

Accepted Answer

Exocytosis of synaptic vesicles into the synaptic cleft. Synaptic vesicles fuse with the pre-synaptic membrane and release neurotransmitter by exocytosis.

Question 6

The key difference between chemical and electrical synapses is that chemical synapses:

Accepted Answer

Use neurotransmitters and have a synaptic delay; electrical use direct ion flow with no delay. Chemical synapses transmit via neurotransmitters (with a brief delay); electrical synapses conduct current directly and rapidly.

Question 7

At a chemical synapse, the pre-synaptic and post-synaptic membranes are separated by a fluid-filled space called the:

Accepted Answer

Synaptic cleft. The synaptic cleft is the narrow gap between the pre-synaptic and post-synaptic membranes across which the neurotransmitter diffuses at a chemical synapse.

Question 8

The neurotransmitter that is released at cholinergic synapses and at the neuromuscular junction is:

Accepted Answer

Acetylcholine. Acetylcholine is the neurotransmitter released at cholinergic synapses and at the skeletal neuromuscular junction, where it binds receptors on the post-synaptic membrane.

Question 9

Transmission across a chemical synapse is unidirectional (one-way) mainly because:

Accepted Answer

Neurotransmitter is stored and released only from the pre-synaptic membrane, while receptors lie only on the post-synaptic membrane. Only the pre-synaptic terminal contains synaptic vesicles with neurotransmitter, and only the post-synaptic membrane bears the receptors. This asymmetry makes chemical transmission strictly one-way.

Question 10

At an electrical synapse, the impulse passes directly from one neuron to the next because the membranes are:

Accepted Answer

In very close apposition, allowing current to flow directly like along an axon. At electrical synapses the pre- and post-synaptic membranes lie extremely close, so current (ions) flows directly between them, making transmission faster than at chemical synapses but rarer in the human body.

Question 11

Arrange the following events of chemical synaptic transmission in the correct order: (1) neurotransmitter binds receptors on post-synaptic membrane; (2) Ca²⁺ enters the pre-synaptic terminal; (3) impulse reaches the axon terminal; (4) synaptic vesicles fuse and release neurotransmitter into the cleft.

Accepted Answer

3 → 2 → 4 → 1. The impulse reaches the terminal, opening Ca²⁺ channels; Ca²⁺ influx triggers vesicle fusion and neurotransmitter release into the cleft; the transmitter then binds post-synaptic receptors. Order: 3 → 2 → 4 → 1.

Question 12

Assertion (A): The influx of Ca²⁺ into the axon terminal is essential for neurotransmitter release. Reason (R): Ca²⁺ promotes the fusion of synaptic vesicles with the pre-synaptic membrane, causing exocytosis of the transmitter.

Accepted Answer

Both A and R are true and R is the correct explanation of A. Arrival of the impulse opens voltage-gated Ca²⁺ channels; Ca²⁺ entry causes synaptic vesicles to fuse with the membrane and release transmitter by exocytosis. R correctly explains why Ca²⁺ influx is needed for release.

Question 13

Binding of an excitatory neurotransmitter to receptors on the post-synaptic membrane most directly causes:

Accepted Answer

Opening of ion channels that depolarise the post-synaptic membrane. When an excitatory transmitter binds its receptor, ligand-gated ion channels open and produce a depolarising (excitatory post-synaptic) potential that may generate a new impulse in the post-synaptic neuron.

Question 14

Which of the following statements comparing electrical and chemical synapses is INCORRECT?

Accepted Answer

Chemical synapses transmit impulses faster than electrical synapses. Transmission across an electrical synapse is faster than across a chemical synapse because of the synaptic delay introduced by transmitter release and diffusion at chemical synapses. So saying chemical synapses are faster is incorrect.

Question 15

The brief delay (synaptic delay) that occurs during transmission across a chemical synapse but not at an electrical synapse is due to the time taken for:

Accepted Answer

Release, diffusion across the cleft, and receptor binding of the neurotransmitter. At a chemical synapse the transmitter must be released, diffuse across the cleft, and bind post-synaptic receptors, all of which take time and cause the synaptic delay. Electrical synapses transmit current directly and have essentially no delay.

Question 16

After acetylcholine has acted on the post-synaptic membrane at a cholinergic synapse, continuous stimulation is prevented because the transmitter is:

Accepted Answer

Rapidly broken down by the enzyme acetylcholinesterase in the cleft. Acetylcholinesterase hydrolyses acetylcholine in the synaptic cleft, ending its action so the post-synaptic membrane can return to rest. Without this breakdown the receptor would be continuously stimulated.

Question 17

Fill in the blanks. I. A nerve impulse is ...(a)... from one neuron to another through junctions called ...(b).... II. ...(c)... of an impulse across electrical synapses is very similar to impulse ...(d)... along a single axon.

Accepted Answer

a-Transmitted, b-Synapses, c-Transmission, d-Conduction. A nerve impulse is transmitted from one neuron to another through junctions called synapses; transmission across electrical synapses is very similar to impulse conduction along a single axon.

Question 18

Synapses are of

Accepted Answer

Two types-Electrical and chemical. Synapses are of two types: electrical synapses and chemical synapses.

Question 19

Read the following statements and find out the incorrect statements. a. A synapse is formed by the membranes of a pre-synaptic neuron and a post-synaptic neuron, which may or may not be separated by a gap called synaptic cleft. b. At electrical synapses, the membranes of pre- and post-synaptic neurons are in very close proximity. c. Electrical current can flow directly from one neuron into the other across chemical synapses. d. Impulse transmission across a chemical synapse is always faster than that across a electric synapse. e. Electrical synapses are rare in our system.

Accepted Answer

c and d. Electrical current flows across electrical (not chemical) synapses, and chemical synapse transmission is slower than electrical; so statements c and d are incorrect.

Question 20

During transmission of nerve impulse, the released neurotransmitter binds to their specific receptors, present on the

Accepted Answer

Post-synaptic membrane. The neurotransmitter binds to specific receptors present on the post-synaptic membrane.

Synapse & Transmission — NEET Biology MCQs with Solutions

Questions with solutions