Control and Coordination Test - 3

In touch-me-not plant, the leaves move in response to touch and retain their original position when the touch stimulus is removed. So, the movement is reversible and does not involve growth. Growth is irreversible and occurs in the other three cases.

The motor neuron receives the impulse from the association neuron in the spinal cord and passes the impulse further to the effector organ.

Reflex actions are controlled by the spinal cord. Most involuntary actions like beating of heart are controlled by the mid brain and hind-brain and not spinal cord. So, beating of heart is not a reflex action.

When the light comes from one side of a plant, auxin diffuses towards the shady side of the shoot to promote elongation of cells on the side away from light. This causes the shoot to bend towards the light.

Oestrogen is secreted by ovaries in female.

The function of the olfactory receptors is to detect smell.

Cytokinins promote cell division, so they are present in greater concentration in areas of rapid cell division.

A reflex is an action in response to an urgent situation which requires quick action. Therefore, reflex arc connections between the input and output nerves are made at the spinal cord where they first meet each other so that the process of detecting a signal and responding to it is completed quickly.

Unlike animal muscle cells which change shape due to specialised proteins found in them, plant cells change shape by changing the amount of water in them, resulting in swelling or shrinkage, and hence change in shape.

The stimulus of touch is conveyed in a sensitive plant by electro-chemical means.