Thermoregulation

Question 1

Define poikilotherm

Answer 1

Cold blooded animal. Body temperature fluctuates with that of the environment and activity levels are related to environmental temperature.

Question 2

Define homeotherm

Answer 2

Maintain a steady body temperature and can increase or decrease it depending on enviromental conditions. Remain active at all environmental temperatures

Question 3

Define endotherm

Answer 3

Produce heat internally and can change their metabolic rate

Question 4

Define ectotherm

Answer 4

Rely on external sources for heat and they have low metabolic rates

Question 5

Define core body temperature

Answer 5

Temperature of the internal organs of the cranium and thoracic and abdominal cavities

Question 6

Define shell temperature

Answer 6

Temperature of the skin. Shows a greater degree of variation

Question 7

How can heat be transfered?

Answer 7

Evaporation, radiation, conduction

Question 8

How is thermogenesis controlled?

Answer 8

By the preoptic area in the hypothalamus. Detects changes in body temp and then stimulates the appropriate response. (heat promoting centre in posterior hypothalamus and heat losing centre in anterior hypothalamus)

Question 9

What behavioural changes decrease heat loss?

Answer 9

Huddling together, shivering, closed posture

Question 10

What are the physiological changes that occur to decrease heat loss?

Answer 10

1. Cutaneous vasoconstriction
2. Counter current exchange system
3. Piloerection/horripilation
4. Shivering thermogenesis
5. Non-shivering thermogenesis

Question 11

What are the physiological changes that occur to increase heat loss?

Answer 11

1. Peripheral vasodilation/altered conductance
2. Evaporative heat loss

Question 12

Describe 5 thermoregulatory disorders

Answer 12

1. Pyrexia - neutrophils and macrophages secrete pyrogen IL-1 which causes anterior hypothalamus to secrete PGE. PGE raises set temperature. Shivering and peripheral vasoconstriction increases temp. Liver and spleen hoard Zn and Fe, depriving bacteria. Once infection has gone, pyrogen secretion decreases and heat loss mechanisms are activated
2. Heat cramps - electrolyte depletion
3. Heat exhaustion - severe dehydration and electrolyte loss
4. Heat stroke - gain heat by radiation and conduction, can’t lose by evaporation
5. Hypothermia - 35-37, shivering, vasoconstriction, muscles less responsive. 33-35, intense shivering, blue extremities, muscle miscoordination and mild confusion. Less than 32, no shivering, cognitive impairment, metabolism shuts down, v poor muscle coordination, terminal burrowing, tachycardia (ventricular tachycardia, atrial fibrillation)