Lesson: Control and Coordination

Question 1

Which of the following is a plant hormone?

(a) Insulin

(b) Thyroxin

(c) Oestrogen

(d) Cytokinin



Question 2

The gap between two neurons is called a

(a) Dendrite

(b) Synapse

(c) Axon

(d) Impulse



Question 3

The brain is responsible for

(a) Thinking

(b) Regulating the heartbeat

(c) Balancing the body

(d) All of the above



Question 4

What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?


Functions of receptor in our body:

·         They sense external stimuli such as heat or pain and pass on the information to the brain. The brain, in turn, instructs related organ to take necessary action.

·         They also trigger an impulse in the sensory neuron which sends message to the spinal cord.

When receptors do not function properly, the brain does not get signals regarding external stimuli. This may lead to accident or bodily damage. For example, if we accidentally touch any hot object, then our hands might get burnt as non-functional receptors cannot perceive external stimuli of heat and pain.

Question 5

Draw the structure of a neuron and explain its function.


Neurons are also known as nerve cells. They are the structural and functional units of our nervous system. A neuron is the largest cell in a body that carries messages across large distances in a body. The messages are in the form of electrical signals called electrical impulses or nerve impulses.

The structure of a neuron is shown below:

The components of a neuron are:

·         Dendrites: Dendrites are tree-like extensions which receive information from a body part or other neurons and transmit electric signals to a cell body.

·         Cell body: Cell body (also known as soma) is the place where all the dendrites are joined. It produces all necessary proteins for other parts of a neuron.

·         Nucleus: Nucleus is the most important organelle which contains genes that consist of DNA.

·         Axon hillock: Axon hillock is part of a cell body that receives signals from all dendrites and creates the electric impulse which travels down the axon.

·         Axon: Axon is a long tube which carries electric signals away from a cell body towards the terminal button and transmits them to other neurons.

·         Myelin sheath: Myelin sheath is made up of proteins and fats and is responsible for protection and insulation of neurons.

·         Synaptic terminals: Synaptic terminals are terminal buttons that are located at the end of a neuron and are responsible for sending signals on to other neurons

·         Synapse: Synapse is a small gap at the end of a neuron that allows information to pass from one neuron to the next muscle or gland.

Question 6

How does phototropism occur in plants?


Growth movement in plants in response to light stimulus is called phototropism. In plants, shoots bend towards a source of light and roots bend away from the light source. Therefore, shoots show positive phototropism whereas roots show negative phototropism.

Question 7

Which signals will get disrupted in case of a spinal cord injury?


The nerves from all over the body meet in a bundle inside the spinal cord. In case of spinal cord injury, there will be total shutdown of signal transmission from rest of the body to the brain.  Therefore, messages from the brain too will not be conducted to any organ.

Question 8

How does chemical coordination occur in plants?


Chemical coordination occurs in plants through plant hormones. Different plant hormones help to coordinate growth, development and responses to the environment.


·         Auxin promotes cell growth.

·         Gibberellin promotes stem growth.

·         Cytokinins promote cell division.

·         Abscisic acid inhibits growth, wilting and shedding of leaves etc.

·         Ethylene helps fruits ripen by making them softer and sweeter.

Question 9

What is the need for a system of control and coordination in an organism?


There are various organs in an organism. For survival of an organism, these organs must work together in a proper manner. In human beings, the nervous system and the endocrine system work together for control and coordination. Hormones are responsible for overall growth and development of an organism, and the central nervous system is responsible for daily decision that includes voluntary and involuntary actions.

Question 10

How are involuntary actions and reflex actions different from each other?


Involuntary actions: These actions are part of routine activities. They happen in involuntary organs. They are directly under the control of brain.

Reflex actions: These actions are in response to a sudden danger or action and happen in voluntary organs. They are not under the control of brain.

Question 11

Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.


Nervous System Mechanism:

·         It is fast

·         It is facilitated by neuro transmitters

·         The information is transmitted in the form of electric impulses

Hormone System Mechanism:

·         It is slow

·         It facilitates hormonal control

·         The information is transmitted in the form of chemical messengers

Question 12

What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?


The movement in a sensitive plant is facilitated by chemical control and the movement in our legs is facilitated by nervous control.