Write notes on the following :

i. Hypothyroidism
ii. Melatonin


i. Hypothyroidism - It is the secretion of thyroid hormone is lesser amount than the normal. The deficiency in iodine in the diet leads to hypothyroidism. 
The effects of hypothyroidism are:
a. Goitre that is enlargement of tyhrois glands.
b. Hypothyroidiem during pregnancy causes defective developement and maturation of the baby. It may lead to stunted growth that is cretinism. mental retardation, low intelligence quotient, abnormal skin, deaf-mutism etc.
c. In adult women , it leads to irregularity in menstrual cycle. 

ii. Melatonin - It is a hormone secreted by the pineal gland. It has the following role:
a. It regulates the 24 hour cycle or the diurnal rhythm of the body. 
b. It regulates the normal rhythm of the sleep-wake cycle.
c. It maintains the body temperature.
d. It regulates the skin pigmentation, influences the metabolism, menstrual cycle and the defense capability of the body. 
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Discuss about functions of aldosterone and  Cortisol 

1. Aldosterone - 

Functions :

a. Regulates the balance of water in the body. 

b. It stimulates the reabsorption of Na+, water and excretion of K+.

b. It It helps in the maintenance of electrolytes, body fluid volume, osmotic pressure and blood pressure. 


2. Cortisol : 

Functions : 

a. Maintains the cardio-vascular system as well as kidney functions.

b. Produce anti-inflammatory reactions and suppresses the immune response.

c. It stimulates the producion of RBCs. 

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Explain the following :

(a) Insulin lowers the blood sugar level.

(b) Hypothalamus and pituitary function as an integrated and coordinated system.

(c)Body growth is greatly accelerated at puberty in the male.

(d) Adrenal medulla and the sympathetic nervous system function as a closely integrated system.

(e) Pituitary gland regulates the reproductive system.

 


(a) Insulin is reponsible for lowering the blood sugar level by converting excess of glucose to gylcogen which is stored in muscles and liver. 

(b) The hormones released by the hypothalamus controls all the secretions of hormones of pituitary gland. The hypothalamus hormones regulate the secretion and production of the pituitart hormones.  Pituitary gland regulates the activities of other glands. Thus, pituitary gland and hypothalamus function as an integrated and coordinated system.

(c) At puberty there is an increase in the testosterone secretion by Leydig’s cells. The testosterone hormone plays a major role in body growthand accelerates body growth during puberty.  

(d) Adrenal medulla and the sympathetic nervous system are closely integrated systems as the emergency hormones like adrenaline and noradrenaline are secreted during danger when nerve impulse reaches adrenal medulla via sympathetic nerves.

(e) Gonadotrophic hormone secreted by pituitary gland controls the male and the female gonads. The gonadotrophins released by the pituitary regulates the reproductive system. 

 

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Describe parathyroid gland and give its functions.

Parathyroid glands : These are four in number and located just at the back of thyroid gland, one pair each in the two lobes of the thyroid glands. These are of pink colour.

Hormones : These glands secrete parathyroid hormone (PTH) , which is a peptide hormone.

Functions of the hormones :

1. It increases the amount of calcium. It stimulates the resorption of Ca2+  from the digested food and and Ca2+ resorption in the renal tubules. It also the process of demineralization in bones. 

2. It decreases the amount of phosphorous in blood.

3. It plays a significant role in maintaining the calcium balance in the body. 

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Briefly explain the structure of adrenal gland and hormones secreted by its different parts.

Adrenal gland :

The adrenal glands are present in pairs, one at the anterior part of each kidney. The adrenal gland is made of two kinds of tissues namely 
i. Adrenal medulla. 
ii Adrenal cortex. 

Parts of Adrenal gland :

1. Adrenal cortex : It is the outer part of the adrenal gland. It is further differentiated into three parts :

(a) Zona glomerulosa (Outer zone)

(b) Zona fasciculata (Middle zone)

(c) Zona reticulosa (Inner zone outer to adrenal medulla).

Hormones secreted - Adrenal cortex secretes the following three hormones derived from steroids :

(i) Aldosterone or mineralocorticoids.

(ii) Cortisol or glucocorticoids.

(iii) Sexcorticoids or androgens.

2. Adrenal medulla : It lies inner to cortex.

Hormones secreted- It secretes two hormones namely:

(a) Epinephrine

(b) Norepinephrine.

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