Q5 of 44 Page 113

What is a synapse? How is it useful in transfer information? (AS1)

Axon is a single, usually very long process of uniform thickness. The most sensitive part of the neuron is axon hillock. The axon contains neurofibrils & microtubules but does not have Nissl's granules, Golgi complex, ribosomes, pigment granules, fat globules, etc. The axon ends in a group of branches, the terminal arborizations. When the terminal arborizations of the axon meet the dendrites of another neuron to form a synapse they form synaptic knobs. The synaptic knobs contain mitochondria and secretory vesicles.

Synapse is the point of contact between the terminal branches of the axon of a neuron with the dendrites of another neuron separated by a fine gap. Here, the nerve impulse jumps into the next neuron. This is a chemical process. As the impulse, reaches the terminal end of an axon, a chemical acetylcholine is released. This chemical sets a new impulse in the dendrites of another neuron. The chemical is soon broken down by enzymes to make the synapse ready for the next transmission.


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3

Give an example of coordination in your body where both hormonal and nervous control function together. (AS1)

 4

Consider that you are passing by a garbage disposal area and you immediately cover your nose. Arrange the events below in a logical order by marking them from 1 to 5 to trace the events that happen in the nervous system from detection of foul smell (stimulus generation) to covering your nose (response). (AS1)

A. At the end of the axon, electrical impulse releases chemicals


B. Stimulus received by the dendrites of a neuron sets off a chemical reaction that creates an electrical impulse.


C. Electrical impulse transmitted through cell body and axon


D. The chemicals cross the synapse and reach the next neuron. Similarly, the electrical impulse crosses several neurons


E. Finally, the impulse is delivered from neuron to the gland that helps in recognition of the foul smell and muscle cells that help in covering the nose

 6

Distinguish between (AS1)

Stimulus and Response

 6

Distinguish between (AS1)

Afferent and Efferent nerves