Thermoregulation

Question 1

• What is ecophysiology?

Answer 1

The study of thermoregulation

Question 2

• Define the following terms: Endotherm, homeotherm, ectoderm, polikotherm

Answer 2

Endotherm – heat generated by heat production from body
Homeotherm – temperature maintained within narrow limits
Ectotherm – heat from external sources
Poikilotherm – body temperature across wide range

Question 3

• What is it called when no active control of body temperature is taking place?

Answer 3

Thermoneutral zone

Question 4

• What are the three components of the thermoregulatory system?

Answer 4

A sensory component, an integrating centre (hypothalamus), a motor component

Question 5

• What two types of command signals may be signalled by the hypothalamus?

Answer 5

Somatic motor system – affect heat production in skeletal muscle
Sympathetic nerve fibres – blood flow to the skin, activity of sweat glands, activity of smooth muscles that regulate the thickness of fur or plumage

Question 6

• When the animal is too cold, what does SNS stimulation lead to?

Answer 6

Piloerection, increased BMR, skin vasoconstriction, brown adipose tissue

Question 7

• What is brown adipose tissue?

Answer 7

Specialised adipose tissue which is abundantly rich in mitochondria endowed with respiratory chain enzymes

Question 8

• How does BAT make heat?

Answer 8

Contains a unique protein – uncoupling protein 1, UCP1 uncouples mitochondrial energy production – uncouple cellular respiration uses H+ ions from the electron transport chain to generate heat

Question 9

• What are the main stimulatory factors of UCP1?

Answer 9

Cortisol, SNS, cold temperature, leptin, prolactin, thyroid hormones

Question 10

• What are neonates more susceptible to cold than adults?

Answer 10

Higher ratio of body surface to blood volume, higher proportional surface area of the head, lack of musculature, poor thermal insulation, inability to move away from cool areas

Question 11

• What is the main difference between precocial and atricial young with regards to heat production?

Answer 11

Altricial – immature HPA axis at birth, precocial – mature HPA axis at birth

Question 12

• What are the main responses to an animal being too hot?

Answer 12

Adrenergic inhibition, cholinergic stimulation & voluntary responses

Question 13

• What are diurnal changes?

Answer 13

The normal changes in body temperature that occur each day

Question 14

• What is the effect of exposure to pyrogens?

Answer 14

Increase the hypothalamic set-point