Question

Compare and contrast the physiological (nervous, endocrine, vascular, metabolic) responses triggered by hyperthermia & hypothermia, and how each response helps to maintain Homeothermy.

Answer 1

Physiological response by hyperthermia-

1)Nervous system-

Hypothalamus is the centre for responses for rising temperature(hyperthermia).

-Stimulation of hypothalamus results in anorexia, cutaneous vasodilatation, sweating and increases in respiration via autonomic nervous system.

Anorexia(decreased food intake) decreases sympathetic discharge which results in decreased heat production.

2)Endocrine system-

-Decreased thyroid stimulating hormone (TSH) secretion from anterior pituitary gland, which results in decreased thyroid hormones secretion.

Decreased thyroid hormones secretion results in decreased heat production.

-Decreased catecholamines(epinephrine and nor-epinephrine) secretion from adrenal medulla results in decreased heat production.

3)vascular response-

-cutaneous vasodilatation occurs which results in increased heat loss.

4)Metabolic response-

-Increased sympathetic discharge causes sweating, which results in increased heat loss and cools the body.

-Decreased skeletal muscle contraction causes decreased muscle metabolism results in decreased heat production.

Physiological responses by hypothermia-

1)Nervous system-

Stimulation of hypothalamus results in hunger, increased heart rate, increased blood pressure, cutaneous vasoconstriction and shivering.

Hunger increase food intake and thereby increases sympathetic discharge, which results in increased heat production.

2)Endocrine system -

-Increased TSH secretion from anterior pituitary gland causes increased thyroid hormones secretion which results in increased heat production.

-Increased catecholamines secretion from adrenal medulla,which results in increased heat production.

3)vascular response -

Cutaneous vasoconstriction, which results in decreased heat loss.

4)Metabolic response -

-Increased skeletal muscle contraction and increases the muscle metabolism causing shivering, which results in increased heat production.

-Increased basal metabolic rate results in increased heat production.