Thermoregulation

Question 1

Define thermoregulation

Answer 1

Ability or an organism to maintain a pretty constant temperature despite environmental fluctuations. Dynamic stability between an animal’s internal environment and its external environment

Question 2

What is a homeotherm?

Answer 2

Temperature is maintained within narrow limits

Question 3

What is a poikilotherm?

Answer 3

Body temperature varies widely

Question 4

What does a thermoregulatory system consist of?

Answer 4

• Sensory component (nerves with thermoreceptors)
• Integrating centre (hypothalamus)
• Motor components (neurons that send commands to alter heat production/ loss)

Question 5

What do the command signals for thermoregulation travel along?

Answer 5

-Somatic motor system (may travel via sympathetic system)

Question 6

Where are the cooling and heating centres located?

Answer 6

Heating centre= posterior hypothalamus

Cooling centre= anterior hypothalamus

Question 7

Describe the response to cold temperatures

Answer 7

• Skin thermoreceptors detect change in temp and cooled blood reached the hypothalamus.
• Cerebral cortex and hypothalamic thermostat communicate
• Results in SNS stimulation, TRH release and shivering

Question 8

What affect does TRH release have on the control of temperature?

Answer 8

TRH release acts on the anterior pituitary to increase TSH secretion. TSH causes the thyroid gland to secrete more T3 and T4
INCREASES BASAL METABOLIC RATE

Question 9

What affect does SNS stimulation have on controlling a too cold temperature?

Answer 9

• triggers piloerection
• acts on adrenal medulla to increase adrenaline which increases BMR
• Noradrenaline causes skin vasoconstriction
• Simulate brown adipose tissue

Question 10

Where is brown adipose tissue located?

Answer 10

• Perirenal
• Interscapular
• Abdominal

Question 11

Which type of animal don’t have any brown fat?

Answer 11

Birds

Question 12

Describe brown adipose tissue

Answer 12

-Mitochondria rich
-Very vascularised
-Multilobulated
Contains uncoupling protein 1 in the inner mitochondrial membrane-> movement of H+ ions across the membrane creates heat

Question 13

What stimulates uncoupling protein?

Answer 13

• Cortisol
• Sympathetic NS
• Cold temperature
• Leptin

Question 14

What are the factors that make neonates more susceptible to cold than adults?

Answer 14

• Larger surface area to body volume
• Bigger surface area of head to body
• Poor thermal insulation (lack of subcut fat)

Question 15

Compare the differences between altricial and precocial young

Answer 15

Altricial= immobile, lack of hair. eyes are closed, IMMATURE HPA AXIS AT BIRTH
Precocial= mobile after bitch, have hair, eyes are open, MATURE HPA AXIS AT BIRTH

Question 16

Describe the response to hot temperatures

Answer 16

• Skin thermoreceptors detect hot temp and hot blood reaches hypothalamus
• Leads to adrenergic inhibition and cholinergic nervous system stimulation

Question 17

What does the adrenergic inhibition result in? (thermoregulation)

Answer 17

-Decreases BMR

Triggers skin vasodilation

Question 18

What result does the stimulation of the cholinergic NS? (thermoregulation)

Answer 18

Sweating

Question 19

Describe normal changes of body temperatures INDEPENDANT of environmental temp

Answer 19

• Core temperature changes naturally in diurnal period

- Fever response- exposure to pyrogens increase hypothalamic set point

Question 20

Describe the fever response

Answer 20

• It is a defence mechanism
• Aim is to increase T cell and immune function
• May limit invading organisms growth