Question

The diagram given below is a representation of a certain phenomenon pertaining to the nervous system. Study the diagram and answer the following questions.

1. Name the phenomenon being depicted.
2. Give the technical term for the point of contact between the two nerve cells.
3. Name parts 1,2,3 and 4.
4. Write the functions of parts 5 and 6.

Answer 1

1. The phenomenon depicted in the image

1. The given image depicts a reflex action.
2. It is an unplanned, automatic, instantaneous response to a stimulus.

2. The technical term for the point of contact between nerve cells

1. Two nerve cells are placed next to each other closely and the point of contact is called the synapse.
2. It is a gap where the electrical impulses are transmitted from one nerve cell to the next nerve cell by the release of neurotransmitters.

3. Labelling of the parts

1. Sensory neuron carries impulses from the sensory receptors toward the central nervous system (CNS).
2. The cell body of the sensory neuron is housed in the dorsal root ganglion houses the cell bodies of sensory neurons. It transmits the incoming impulses towards the CNS for a response to be generated.
3. Based on the appearance of the color, the CNS is considered to be made of two substances- grey matter and white matter.
4. The grey matter comprises the neuronal cell body whereas the white matter comprises the nerve fibers (axons and dendrites). The white color is due to the myelination of the axonal fibers of the neurons.
5. In the spinal cord, these substances are arranged in a reverse fashion compared to the brain.
6. The grey matter surrounds the central canal of the spinal cord, whereas the white matter is present on the outer side of the spinal cord.

4. Functions of parts 5 and 6

1. Label 5 denotes the intermediate or relay neuron. These neurons have a high number of dendrites making multiple interconnections with the brain and spinal cord neurons.
2. Label 6 denotes a spinal nerve. Spinal nerves arise from the spinal cord. They are mixed nerves. It carries both sensory and motor impulses.