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Endocrine System
1. Differentiate between :
(i) Nervous control and Hormonal control
(ii) Endocrine gland and Exocrine gland
(iii) Hormone and Enzyme
(iv) Simple goitre and Exopthalmic goitre
(v) Diabetes mellitus and Diabetes insipidus
(vi) Cretinism and Myxodema
(vii) Gigantism and Acromegaly
Ans. (i)
Nervous Control
(a) The information is sent in the
form of electric signals.
(b) The signals travel through nerve
fibres to specific target cells like
muscle fibres and glands.
(c) The nervous system causes
muscles to contract or relax,
glands to secrete more or less.
But it cannot bring about growth.
(d) Action is immediate (within few
milliseconds).
(e) Effect lasts for a short time.
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Hormonal Control
The information is sent in the form of
chemical signals.
The signals travel through
bloodstream to cells in different
organs.
Endocrine system brings about
changes in metabolic activities of all
body tissues. It affects growth.
Action is slow (can take hours or
days to produce response).
Effect is more lasting and permanent.
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(ii)
Endocrine Glands
(a) These are ductless glands.
(b) They pour secretion directly into the
blood.
(c) They secrete hormones.
(d) They control long-term activities of
target organs, e.g., thyroid glands.
Exocrine Glands
They may or may not have ducts.
The secretion is poured directly at
the site of action.
They secrete enzymes.
They control short-term activity,
e.g., gastric gland.
(iii)
Hormone
(a) They are produced by endocrine
glands.
(b) Chemically they may be proteins,
steroids or their derivatives.
(c) They are secreted at one site and
act at another.
Enzyme
They are produced by exocrine
glands.
All enzymes are proteins.
They act at their site of secretion or
pass through ducts to their site of
action.
Enzyme-mediated reactions are
reversible.
They act in low concentration.
An increase or decrease in their
concentration affects the rate of the
process.
They act quickly.
(d) Hormone-regulated processes are
not reversible.
(e) They are effective in low
concentration. Their undersecretion or over-secretion affects
body metabolism and growth.,
(f) They act either slowly or rapidly.
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(iv)
Simple Goitre
(a) Caused due to the enlargement of
thyroid gland because of
deficiency of iodine.
(b) Eyes do not bulge out.
(c) Less thyroxine is produced, hence
low metabolic rate.
(d) It may cause decrease in body
temperature, heartbeat and lack
of alertness.
(e) Increased intake of iodine can
prevent and cure this disorder.
Exopthalmic Goitre
Caused due to the enlargement
of thyroid gland because of
hypersecretion of thyroxine.
Eyes bulge out.
Excessive thyroxine produced,
hence increased metabolic rate.
It causes rise in blood pressure
and body temperature,
nervousness, irritability and
loss of body weight.
This can be rectified by
surgical removal of a part of
thyroid gland.
(v)
Diabetes insipidus
(a) This is due to under-secretion of
anti-diuretic hormone.
(b) It is marked by loss of excess
water in urine.
(c) Osmotic balance of the body is
disturbed.
(d) Healing power is not affected.
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Diabetes mellitus
This is due to failure of secretion of
insulin.
It is marked by loss of excess glucose
in urine.
Total metabolism of the body is
disturbed.
Body’s healing capacity is impaired.
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(vi)
Cretinism
(a) Caused by hyposecretion of
thyroxine in infants.
(b) It is characterised by stunted
growth, pot belly, protruding
tongue and pigeon chest.
(c) Mental and sexual retardation
takes place.
Myxoedema
Caused by hyposecretion of thyroxine in
adults.
It is characterised by puffy appearance,
due to accumulation of fat in the subcutaneous tissue and oedema
(accumulation of water in tissue space).
Mental and sexual development is not
affected but patients lack alertness.
(vii)
Gigantism
(a) Caused by oversecretion of
somatotropin in childhood.
(b) Due to abnormal elongation of bones
and muscles, person is of abnormally
large height.
Acromegaly
Caused by oversecretion of somatotropin
after adolescence.
Abnormal increase of bones of hands and
legs, and the lower jaw, person has
gorilla-like appearance but is not a giant.
2. Give general characterstics of hormones.
Ans. (i) Hormones are produced by endocrine glands and are distributed all through
the body by blood.
(ii) They are information molecules or chemical regulators secreted in response
to environmental changes in or outside the body.
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(iii) Chemically they may be large proteins (anterior pituitary hormone)
or small peptides (posterior pituitary hormone) or modified amino
acids (thyroid hormones) or amines (adrenal medulla hormones) or
steroids (adrenal-cortical hormones).
(iv) They have low molecular weight and diffuse readily through the cell
membrane.
(v) They regulate body functions along with nerves.
(vi) They don’t catalyse specific reactions but instead help in synthesis,
activation or inhibition of some enzymes in their target organs.
(vii) Abnormal production (more or less production) of hormones severely
affects body metabolism and growth.
3.
Explain :
(i) Why some women develop beard and some men develop breasts?
(ii) Effects of sex hormones at puberty.
(iii) People of hilly region usually develop goitre.
(iv) High stature of male body than the female body.
(v) Older people tend to feel more cold.
(vi) Pituitary gland is called the ‘master gland’.
(vii) Adrenaline is known as an ‘emergency hormone’.
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Ans. (i) The cause of the development of beard in females and breasts in males
with normal karyotype is due to excessive secretion of sex corticoids.
(ii) The sex hormones are secreted by the gonads. In males the hormones
secreted are testosterone and androsterone. They are responsible for
(a) normal maturation of sperms, (b) stimulation of secondary sex characters
i.e. facial hair (beard), pattern of body hair, low pitch of voice
(c) broadening of shoulders, (d) influence sex instinct and reflexes.
In females, the hormone oestrogen stimulates the development of
secondary sexual characterstics at puberty, i.e., development of hair in
pubic region and in the armpits, development of breast, fat deposits in
hips and high pitch of voice.
(iii) People in the hilly region usually develop goitre because of the enlargement
of thyroid gland. Deficiency of iodine in diet causes the thyroid to enlarge to
produce inadequate amount to thyroxine.
(iv) Male sex hormone stimulates the development of external male characters.
It also promotes the growth of many parts of the body tissues, including
bones and muscles. Since females do not have these hormones (androgens),
they do not grow as tall and or have strong statue.
(v) The thyroid gland regulates the body metabolism, including causing an
increase in basal metabolic rate which raises the body temperature.
With advancing age, the activity of thyroid gland slows down and body
heat production is lowered. That is why older people tend to feel colder
than youngsters.
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(vi) The pituitary gland is referred to as the ‘master gland, because the activities
and growth of the endocrine glands and somatic cells are under the influence
of secretions of the pituitary gland. Nearly 50,000 nerves fibres enter this
fragment of tissue, and an enormously rich blood supply carries its hormones
to the rest of the body.
(viii) Adrenaline is a hormone which prepares the body to meet any emergency
situation to ‘fight’, i.e., to face the danger of for ‘flight’, to run away from it,
and extra energy and strength are provided to the body for the situation. Extra
hormone is released into the blood at the time of emotional stress. The gland
itself is stimulated by the nerve endings of the autonomic nervous systems.
4. Match the items in Column A with those in Column B.
Column A
(i) Diabetes mellitus
(ii) Myxoedema
(iii) Demineralisation of bones
(iv) Addison’s disease
(v) Dwarfism
(vi) Cretinism
(vii) Tetany
(viii) Exopthalmic goitre
(ix) Darkening of skin
(x) Diabetes insipidus
Column B
(a) Hyposecretion of thyroxine in adults.
(b) Hyposecretion of human growth hormone.
(c) Hyposecretion of thyroxine in children.
(d) Hyposecretion of parathormone.
(e) Hypersecretion of Thyroxine.
(f) Hyposecretion of Insulin
(g) Hypersecretion of MSH.
(h) Hyposecretion of vasopressin.
(i) Hyposecretion of glucocorticoid.
(j) Hypersecretion of parathormone.
Ans. (i) (f) (ii) (a) (iii) (j) (iv) (i) (v) (b) (vi) (c) (vii) (d) (viii) (e) (ix) (g)
(x) (h).
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5. Given below is an outline diagram of human body showing position of certain
organs.
Ans.
6.
Complete the following table by filling in the blank spaces numbered 1 to 10.
Gland
1. ___________
Alpha cells of Pancreas
5. ___________
Lachrymal
9.___________
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Secretions
Oestrogen
3. ___________
6. ___________
7. ___________
10. ___________
8
Effect on body
2. ___________
4. ___________
Protruding eyes
8. ___________
Gigantism
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Ans.
Gland
1.Ovary
Secretions
Oestrogen
Alpha cells of Pancreas
5.Thyroid
Lachrymal
9.Pituitary
Effect on body
2. Controls secondary sexual
characters
3. Glucagon
4. Raises blood sugar level by
stimulating conversion of
glycogen to glucose.
6. Thyroxin
Protruding eyes
7. Lachrymal fluid (tears) 8. Serves as lubricants and
washes away dust particles.
10. STH or GH (somato Gigantism
trophic or growth
hormone)
7. The hormone that releases glucose into the blood.
Ans. Glucagon.
8. (a) Name the hormone produced by the thyroid gland and state its function in
the body.
(b) What would a child suffer from if there was hyposecretion from the thyroid?
(c) (i) The three hormones produced by the pancreas.
(ii) The hormones produced by adrenal medulla.
(iii) The condition caused by oversecretion of insulin.
Ans. (a) Thyroid gland secretes thyroxin and calcitonin.
Thyroxin promotes tissue metabolism, growth and differentiation.
Calcitonin promotes movement of calcium ions from blood to bones.
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(b) Hyposecretion of thyroid leads to simple goitre, cretinism in children and
myxodema in adults.
(c) (i) Three hormones produced by pancreas are insulin, glucagon and
somatostatin.
(ii) The hormone produced by adrenal medulla is adrenalin. It causes
stimulation of sympathetic nervous system.
(iii) The condition caused by oversecretion of insulin is diabetes mellitus.
9. Name the following:
(a) The hormone secreted by β -cells of islets of Langerhans.
(b) Hormone which increases blood sugar.
(c) Hormone which causes secretion of more urine.
(d) The hormone which stimulates the entire sympathetic nervous system.
Ans. (a) Insulin (b) Glucagon (c) Insulin (d) Adrenalin
10. Complete the following table by filling in blank space 1 to 8:
Name of gland
Islets of Langerhans
3..................
5..................
7..................
Ans. 1. Insulin.
Substance produced
1 .................
Adrenaline
Thyroxine
LH
One important function
2.................
4..................
6..................
8..................
2. Regulates blood sugar level. Stimulates deposition of extra glucose in
liver as glycogen.
3. Adrenal gland.
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4. Prepares the body for ‘fight’ or ‘flight’ actions by stimulating
sympathetic nervous systems.
5. Thyroid gland.
6. Promotes tissue metabolism, growth and differentiation.
7. Anterior Pituitary gland.
8. Stimulates ovulation, maintenance of corpus luteum and secretion of
progesterone in female and secretion of testosterone in males.
11. Why is iodine important for our body?
Ans. Iodine is the active ingredient in the production of thyroxin. And thyroxin,
in turn promotes tissue metabolism, growth and differentiation. Thus, it is
important.
12. If you stand to make your maiden speech before a large audience, your
mouth dries up and heart rate increases. What brings about these
changes?
Ans. The hormone responsible for this is adrenalin. It is a hormone, which prepares
the body to meet any emergency situation, for “Fight” i.e. to face danger or for
“flight”, i.e. to run away from it. Extra hormone is released into the blood at the
time of emotional stress.
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13. Compare the hormonal response with the nervous response with respect
to speed.
Ans. Hormonal response is slow, whereas, nervous response is immediate/
spontaneous.
14. How do endocrine glands differ from other glands?
Ans.
Apart from endocrine glands, there are exocrine glands. Unlike, exocrine
glands, endocrine glands “secrete internally”, also called ductless glands
because their secretions are poured directly into the blood and not through
any special duct. These glands activate each other and work as a system of
organs called endocrine system.
15. Mention any two differences between a hormone and an enzyme.
Ans. (i) Hormones are secreted by glands. Enzymes are not secreted by any gland.
(ii) Hormones have a direct effect on the target organs.
Enzymes only catalyse the reaction, they are not used up during the reaction.
16. Do you agree with the statement — “All hormones are chemical signals”?
Yes/No. Justify your answer.
Ans. Yes. Hormones are transmitted chemically through blood. They can bring about
specific chemical changes and regulate metabolism. They activate each other
and work in a coordinated manner. As for example, the hormone insulin acts on
liver and muscle cells and deposit extra glucose in the form of glycogen.
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17. If one adrenal gland is removed, the other one gets enlarged to some extent.
How do you explain this change.
Ans. The one remaining adrenal gland performs the function of two glands.
Therefore it gets slightly enlarged for enhanced secretion of hormones.
18. Given alongside is a portion from the human body showing some
important structure in ventral view.
(a) Where is this portion located in the body?
(b) Name the structures numbered 1 – 3.
(c) State one main function of each of the structures named above.
Ans. (a) In the neck
(b) 1 – Larynx
2 – Thyroid gland
3 – Trachea
(c) 1 – Production of sound
2 – Production of thyroxine
3 – Breathing
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19. Given below are two diagrams (one is correct, the other is somewhat incorrect)
showing the transport of a hormone from its source gland/cell to the target
organ/cell.
(a) Which one has the error – A or B? _________
(b) What is the error? _______________________
[Hint : Look at all the arrows indicating the direction of flow of hormone
inside blood stream.]
Ans. (a) B has error.
(b) Trap between gland and blood vessel. The hormone molecules are absorbed
directly into the blood stream.
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