The chemicals released when the electrical impulse reaches the axon ending is called ‘X’. These ‘X’ are present in ‘Y’ located in the ‘Z’. Identify X, Y and Z.

Q. As the impulse reaches the end of an axon, a chemical called ______ is released.

Q. Question 21
Which of the following statements about transmission of nerve impulse is incorrect?

(a) Nerve impulse travels from dendritic end towards axonal end.
(b) At the dendritic end electrical impulses bring about the release of some chemicals which generate an electrical impulse at the axonal end of another neuron.
(c) The chemicals released from the axonal end of one neuron cross the synapse and generate a similar electrical impulse in a dendrite of another neuron.
(d) A neuron transmits electrical impulses not only to another neuron but also to muscle and gland cells.

Q. The substance that is released at axonal endings to propagate a nervous impulse are called _______ .

Q. Electrical impulse travels in a neuron from :
(a) dendrite → axon → axon end → cell body
(b) cell body → dendrite → axon → axon end
(c) dendrite → cell body → axon → axon end
(d) axon end → axon → cell body → dendrite

Q. Which of the following statements are incorrect?
(i) When an impulse travels along a myelinated neuron, it leaps over the myelin sheath from one node to the next.
(ii) At chemical synapse there is continuity between the presynaptic and postsynaptic neurons provided by the gap junctions.
(iii) Neurotransmitters are chemicals that are released from postsynaptic neuron which interact with specific receptors of presynaptic neuron.
(iv) Neurons releasing acetylcholine are described as cholinergic neurons and those releasing noradrenaline are described as adrenergic neurons.
(v) Refractory period is the period after the transmission of an impulse in a nerve fibre in which membrane of the axon regains its ability to transit impulses.