Q4. Assertion: at the site of an action potential, the inner side of the axonal membrane becomes positively charged. Reason: threshold depolarisation opens voltage-gated Na channels, allowing Na influx. Are both true, and does the reason explain the assertion?
Both are true, and the reason explains the assertion (NCERT page 233).
Q5. What do the synaptic knobs of an axon contain?
Synaptic vesicles containing chemicals called neurotransmitters (NCERT page 232).
Q6. Is the new potential produced in a post-synaptic neuron always excitatory?
No. It may be either excitatory or inhibitory (NCERT page 235).
Q7. Which type of neuron has one axon and two or more dendrites, and where is it found?
A multipolar neuron, found in the cerebral cortex (NCERT page 232).
Q8. Does every excitatory postsynaptic potential produce an action potential?
No. An excitatory postsynaptic potential increases the likelihood of firing, but it is a graded response. The neuron integrates excitatory and inhibitory inputs; an action potential is generated only when the trigger region reaches threshold (see Synapse above).