Chapter 22: Chemical Coordination and Integration

Q1Written answer

A milkman is very upset one morning as his cow refuses to give any milk. The milkman’s wife gets the calf from the shed. On fondling by the calf, the cow gave sufficient milk. Describe the role of endocrine gland and pathway associated with this response?

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Worked solution

Oxytocin hormone is the hormone which stimulates the release of milk from the mammary gland by causing surrounding cells to contract. When the infant starts feeding breast stimulates the posterior pituitary to produce the oxytocin hormone and oxytocin hormone stimulates the milk secretion. It also contracts the smooth muscles of the uterus to expel the foetus outside the body of the mother.

Q2Written answer

A sample of urine was diagnosed to contain a high content of glucose and ketone bodies. Based on this observation, answer the following:

a. Which endocrine gland and hormone is related to this condition?

b. Name the cells on which this hormone acts.

c. What is the condition called and how can it be rectified?

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Worked solution

a. The pancreas is the gland and hormone is Insulin which is responsible for this condition.

b. Hepatocytes and adipocytes cells are the main cells on which insulin act. Insulin allows muscles, liver and fat cells to take up this glucose.

c. This condition causes diabetes mellitus. Diabetes mellitus is a condition in which the body does not produce enough insulin hormone which results in a high level of sugar in the blood. It can be controlled by maintaining cholesterol, glucose level and blood pressure to the normal level.

Q3Written answer

Calcium plays a very important role in the formation of bones. Write on the role of endocrine glands and hormones responsible for maintaining Calcium homeostasis.

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Worked solution

Thyroid gland and the parathyroid gland that is an antagonist with each other are responsible for maintaining calcium homeostasis. Calcitonin is responsible for the high calcium level in the blood.

It also decreases plasma calcium concentration by decreasing mobilization of calcium from bones. Parathyroid hormone increases the calcium level in blood which is secreted by the parathyroid gland. It increases the reabsorption of calcium by renal tubules of the kidney.

Q4Written answer

Illustrate the differences between the mechanism of action of a protein and a steroid hormone.

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Worked solution

Protein hormone:

Protein hormones are insulin, glucagon, prolactin etc. They have to bind their receptors which are present on the plasma membrane. They form their hormone receptor complex on the membrane. They are water-soluble hormone so they can’t diffuse to lipid layer plasma membrane and bind to a receptor on membrane.

Steroid hormone:

Steroid hormone is an androgen, estrogen etc. which don’t have their receptor on plasma membrane they directly diffuse to their target site. They don’t produce a secondary messenger.

Q5Written answer

Hypothalamus is a super master endocrine gland. Elaborate.

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Worked solution

Hypothalamus is a super master endocrine gland as it secretes hormones that regulate the synthesis and secretion of the pituitary gland which is the master gland. It is connected to the anterior lobe of the pituitary gland by hypo physical portal veins. The hormones which are secreted by hypothalamus are:

1. Adrenocorticoicotropic releasing hormone (ARH) or corticotrophin

2. Growth hormone-releasing hormone (GHRH)

3. Thyrotropin-releasing hormone (TRH)

4. Growth hormone inhibitory hormone (GHIH)

5. Gonadotropin-releasing hormone (GnRH)

6. Prolactin inhibitory hormone (PIH)

7. Prolactinrelasing hormone (PRH

8. MSH releasing hormone (MSHRH)

9. MSH Inhibitory hormone (MSHIH)

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