Short Answer Type Questions
Q 1. Why is it advised to use iodised salt in our diet? [CBSE2015]
Ans: Iodised salt contains iodine which is necessary for the thyroid gland to synthesise thyroxine hormone. Thyroxine regulates carbohydrate, protein and fat metabolism in the body to provide growth balance. Its deficiency causes goitre.
Q 2. Label the parts (a), (A), (c) and (d) and show the direction of flow of electrical signals in the given figure.
(a) Sensory neuron
(b) Spinal cord (CNS)
(c) Motor neuron
(d) Effector (Muscle in arm)
The direction of flow of electrical signals will be
(i) Receptor (hand) to spinal cord through sensory neuron.
(ii) Sensory neuron to motor neuron through relay neuron.
(iii) Spinal cord to effector through motor neuron.
Q 3. Label the endocrine glands in the given figure.
(a) Pineal gland
(b) Pituitary gland
(c) Thyroid gland
(d) Thymus gland
Q 4. Answer the following:
(a) Which hormone is responsible for the changes noticed in females at puberty?
(b) Dwarfism results due to deficiency of which hormone?
(c) Blood sugar level rises due to deficiency of which hormone?
(d) Iodine is necessary for the synthesis o f which hormone?
(b) Growth hormone
Q 5. Answer the following:
(a) Name the endocrine gland associated with brain.
(b) Which gland secretes digestive enzymes as well as hormones?
(c) Name the endocrine gland associated with kidneys.
(d) Which endocrine gland is present in males but not in females?
(a) Pituitary gland
(c) Adrenal glands
Long Answer Type Questions
Q 6. What are the major parts of the brain? Mention the functions of different parts.
Ans. The major parts of the brain are:
(i) Forebrain including cerebrum and olfactory lobes.
(ii) Hindbrain including cerebellum, pons and medulla oblongata.
Functions of different parts are as follows:
(i) Forebrain: There are specific regions in cerebrum for each kind of stimulus and response.
(ii) Midbrain: It controls reflex movements of the head, neck and trunk in response to visual and auditory stimuli.
(a) Cerebellum controls the coordination of body movements and posture.
(b) Pons take part in regulating respiration.
(c) Medulla oblongata is the regulating centre for swallowing, coughing, sneezing and vomiting.
Q 7. Name various plant hormones. Also give their physiological effects on plant growth and development.
Ans: The various plant hormones are auxin, gibberellin, cytokinin and abscisic acid.
Their physiological effects on plant growth and development are as follows :
Auxin - It is a growth hormone which helps in cell enlargement and cell differentiation. Auxin also promote fruit growth.
Gibberellin - It also helps in the growth of the stem.
Cytokinin - It promotes the cell division. It is present in high concentrations in the areas of rapid cell division such as fruits and seeds.
Abscisic acid (ABA) — They are responsible for inhibiting or checking the growth. It also causes wilting of the leaves.
Q 8. Why is the flow of signals in a synapse from asexual end of one neuron to dendrite end of another neuron but not the reverse?
Ans. A chemical substance is released when the electrical signal reaches the axonal end of a neuron and this chemical diffuses to the dendrite end of another neuron, which generates electrical signal. Thus, at the axonal end, the electrical signals converted into chemical signals but at the dendrite end of neurons these chemicals are not present thus the reverse action is not possible.