Thermoregulation

Question 1

Define thermoregulation

Answer 1

The ability of an organism to maintain a relatively constant body temperature despite fluctuations in temperature in the external environment

Question 2

Define endotherm

Answer 2

Heat generated by heat production from body

Question 3

Define homeotherm

Answer 3

Temperature maintained within narrow limits

Question 4

Define ectotherm

Answer 4

Heat from external sources

Question 5

Define Poikilotherm

Answer 5

Body temperature across wide range (of environmental temperatures)

Question 6

What are the three components of a thermoregulatory system?

Answer 6

A sensory component: neurons that possess nerve endings with thermoreceptors continuously monitor body tempeature

An integrating centre: the hypothalamus functions as the control centre in the brain that compares the temperature information with an internal reference or set-point

A motor component: neurons that send command signals to alter heat production or heat loss

Question 7

The anterior hypothalamus is responsible for…

Answer 7

The thermoregulation ‘cooling centre’

Question 8

The posterior hypothalamus is responsible for…

Answer 8

The thermoregulation ‘heating centre’

Question 9

If the animal is too cold what happens?

Answer 9

Skin thermoreceptors and cooled blood reaches the hypothalamus. The cerebral cortex and the hypothalamus causes SNS stimulation, TRH release and shivering

Question 10

How does TRH raise the body temperature?

Answer 10

TRH release will stimulate the anterior pituitary to release TSH, this causes increased T3 and T4 which increase BMR

Question 11

How does SNS stimulation raise body temperature?

Answer 11

1. Piloerection
2. Stimulates the adrenal medulla to produce adrenaline which increases BMR
3. Noradrenaline is released which causes vasoconstriction in the skin
4. Stimulates brown adipose tissue

Question 12

Where is brown adipose tissue located?

Answer 12

Perirenal
Interscapular
Abdominal

Question 13

What does brown fat consist of?

Answer 13

It consists of small cells with a central nucleus and multilocular triglyceride droplets.
There are abundant mitochondria richly endowed with respiratory chain enzymes
It has a high degree of vascularisation

Question 14

What is Non-shivering thermogenesis (NST)?

Answer 14

In lambs, calves and humans UCP1 abundance peaks around the time of birth, this allows them to stay warm without shivering all the time.

Question 15

Brown fat contains a unique protein, uncoupling protein 1. Where is this protein and what is its function?

Answer 15

UCP1 exists in the inner mitochondrial membrane and uncouples mitochondrial energy production (allows the ATPsynthase to work without H+ ions)

Question 16

Once the triglyceride is broken down by the brown adipose tissue it leaves as ……………….

Answer 16

NEFA (non-esterified fatty acids)

Question 17

What is the difference between altricial and precocial young?

Answer 17

Altricial: immobile, closed eyes, lack hair or down, immature HPA axis at birth

Precocial: opposite

Question 18

What happens if the animal is too hot?

Answer 18

Skin thermoreceptors and warm blood reaching the hypothalamus tell the cerebral cortex and hypothalamus that the animal is hot and the hypothalamus provides adrenergic inhibition and stimulates the cholinergic nervous system

Question 19

How does adrenergic inhibition cool the animal down?

Answer 19

It decreases BMR and vasodilates the skin

Question 20

How does stimulation of the cholinergic nervous system cool the animal down?

Answer 20

It initiates sweating

Question 21

The body tends to be cooler at what time of day?

Answer 21

Night and warmer as it wakes up

Question 22

How does inducing a fever help the body’s defence mechanisms?

Answer 22

Inducing a fever is a defence mechanism that improves T-cell function and it may limit the pyrogens growth (although Some invading organisms evolved to adapt and benefit from fever)