Control and Coordination

One Marks Questions

Answer: Neuron

Answer: Forebrain.

Answer: Iodine stimulates the thyroid gland to produce the thyroxin hormone. Deficiency of this hormone results in the enlargement of the thyroid gland. This can lead to goitre.

(i) Gustatory receptors – these are sensitive to taste.
(ii) Olfactory receptors – these are sensitive to smell.

Answer: The cerebellum in the hind-brain controls the posture and balance of the body.

Involuntary action including blood pressure salivation vomiting is controlled by the medulla in the hindbrain.

Answer: The growth of the pollen tube toward the ovule.

Answer: The plant hormone that promotes growth is auxin.

Answer: The plant hormone that inhibits growth is Abscisic acid.

Answer: Testosterone in male. Oestrogen in female.

Answer: Spinal cord is enclosed in a bony cage called the vertebral column.

Two Marks Questions

Answer: A synapse is a gap between the two neurons. At synapse the electrical signals converted into chemicals, that can easily cross over the gap and pass on to the next neurons where it again converted into electrical signals.

An involuntary action by human body parts in response to a stimulus is called reflex action.
It helps us in protecting us from the sudden stimulus which may harm us.

CNS – Brain and Spinal cord
PNS - Cranial nerves and spinal nerves

When growing plants detect light auxin synthesized at the shoot tip, helps the cell to grow longer. When light is coming from one side of the plant auxin diffuses towards the shady side of the shoot. This concentration of auxin stimulates the cell to grow longer on the side of the shoot which is away from light. Thus the plant appears to bend towards the light.

Answer: When a tendril comes in contact with a support, auxin diffuses towards the opposite side of the shoot, auxin stimulates faster growth of the cells on the opposite side that's why the tendril forms a coil around the support.

When the sugar level in blood increases, it is detected by the a-cells of the pancreas which response by producing more insulin. As the blood sugar level falls, insulin secretion is reduced.

Three Marks Questions

1. End of the dendritic tip of a nerve cell.
2. Electrical impulses travel from the dendrites to the cell body, and then along the axon to its end.
3. Synapsis.

Phototropism: movement of the plant towards or away from the light.
Eg: Shoots respond by bending towards light while roots respond by bending away from light.

Geotropism: movement of plant parts towards the earth or away from it. Roots of the plant always grow downwards while shoots usually grow upward and away from the earth.

Hydrotropism: movement of plant parts towards or away from any source of water. Roots of the plant always grow towards the water while shoots usually grow upward and away from the water.

* Heart beats faster, resulting in the supply of more oxygen to our muscle.
* The blood to the digestive system and skin is reduced due to the contraction of muscles around small arteries in these organs. This diverts the blood to our skeletal muscles.
* The breathing rate also increases because of the concentration of the diaphragm and the rib muscle.

1. He is suffering from diabetes.
2. Deficiency of insulin causes diabetes.
3. Pancreas secret insulin.

a. Pituitary gland
b. Stimulates growth in all organs
c. Dwarfism


Four Marks Questions

Three endocrine glands with their function in the human body are as follows: 1. Thyroid gland: It secretes a hormone called thyroxine which regulates the metabolism of carbohydrates, fats and proteins in the body and so provides the best balance for nutrients and mental ability.

2. Adrenal gland: It secretes two hormones—adrenalin and corticoid hormones regulate blood pressure, heartbeat, breathing rate and carbohydrate metabolism.

3. Pancreas: It secretes two hormones—insulin and glucagon. Insulin hormone lowers the blood glucose level. Glucagon hormone increases the blood glucose level.

(a) Brain is covered by a three-layered membrane called meninges. In between the layers of meninges and brain, cavity fluid named Cerebro Spinal Fluid (CSF) is filled. The hard skull covers the meninges. Thus Meninges, CSF and Skull protect our brain to a certain extent.

(b) Two main parts of the hind-brain are — Medulla and Cerebellum. Their functions are
Medulla: Involuntary actions such as blood pressure, salivation and vomiting.
Cerebellum: It is responsible for the precision of voluntary actions and maintaining the posture and balance of the body.

A reflex arc is a neural pathway that controls reflex action.
1. Receptor organ perceives the stimulus and activates a sensory nerve impulse.
2. Sensory nerve carries a message in the form of the sensory impulse to the spinal cord.
3. The spinal cord acts as a modulator: The neurons of the spinal cord transmit the sensory nerve impulse to the motor neuron.
4. Motor never conducts these impulses to the effectors' muscles which respond to the stimulus.

Four different types of plant hormones are
Auxins, Gibberellins, Cytokinins, Abscisic acid.

1. Auxins: Helps the cell to grow longer. Promote the bending of the stem towards the light. Promote the growth of a tendril around support.
2. Gibberellins: Helps in the growth of the stem.
3. Cytokinins: Promote cell division, such as in fruits and seeds.
4. Abscisic acid inhibits the growth of the plant body including wilting of a leaf.

1. Goitre 2. Swollen neck 3. Thyroxine 4. Thyroid gland 5. Iodine