Thermoregulation

Question 1

Do homeotherms regulate their own internal body temperature?

Answer 1

Yes.

Question 2

What four ways does heat transfer and how?

Answer 2

1. Conduction (contact with a solid surface).
2. Convection (via air or liquid).
3. Radiation (IR energy transfer to/from the environment).
4. Evaporation (sweat and fluid from airways).

Question 3

What are the two types of thermoreceptors?

Answer 3

Skin and body core.

Question 4

What determines the set point of the body?

Answer 4

The hypothalamus.

Question 5

What are the three main effectors in the thermoregulatory system?

Answer 5

1. Smooth muscle.
2. Sweat glands.
3. Skeletal muscle.

Question 6

What two ways can Basal Metabolic Rate (BMR) be measured in? What are their processes?

Answer 6

1. Direct calorimetry - In a sealed, insulated box. Heat is extracted to keep box constant is measured.
2. Indirect calorimetry - Uses spirometry to measure oxygen and convert it to an “energy equivalent”.

Question 7

What factors affect BMR?

Answer 7

Age, gender, climate, sleep, malnutrition, sympathetic stimulation, fever, hormonal effects and muscle activity.

Question 8

Is BMR higher in males or women and by how much?

Answer 8

10% to 15% due to male sex hormones.

Question 9

How do you calculate actual metabolic rate?

Answer 9

BMR + Metabolic rate of activity

Question 10

Follicles are the functional units of the thyroid gland. What three things do they consist of?

Answer 10

1. Follicular cells.
2. Colloid.
3. Dense capillary network.

Question 11

What store thyroid hormones?

Answer 11

Colloid.

Question 12

What are follicular cells composed of and what do they synthesise?

Answer 12

They are composed of cuboidal epithelial cells and synthesise thyroid hormones.

Question 13

Thyroid hormones are released tonically, derived from tyrosine and require iodine from the diet. Out of T3 and T4, which is more potent?

Answer 13

T3.

Question 14

How is T4 transformed into T3?

Answer 14

In the bloodstream or target tissues, it is reduced by the removal of one iodine by deiodinase.

Question 15

What are the two main effects the thyroid hormone actions have?

Answer 15

1. Growth/development effects.

2. Metabolic effects,

Question 16

What are the growth/development effects from the thyroid hormone action?

Answer 16

Synapse formation and myelin formation in utero and in infancy.

Question 17

What are the metabolic effects from the thyroid hormone action?

Answer 17

Increased ATP production, increased BMR and enhanced ATP and oxygen consumption.