Homeostasis and Thermoregulation

Question 1

Define homeostasis

Answer 1

Homeostasis is defined as the ability to maintain a constant internal environment.

Question 2

Explain the term negative feedback

Answer 2

Negative feedback is a mechanism in which deviations in a condition triggers effectors to respond to restore the condition back to a set value.

Question 3

Humans lose heat through which few ways?

Answer 3

1. Latent heat of vapourisation - the change of liquid to vapour - accompanied by cooling; the evaporation of sweat has a marked cooling effect
2. Convection of heat by the upward flow of warm air or the downward flow of cold air past the body
3. Radiation of heat from a body to a colder object not in contact, heat is transferred by infrared waves
4. Conduction of heat from hotter to colder of two surfaces in contact

Question 4

State role of capillary networks in thermoregulation

Answer 4

1. Vasodilation of skin arterioles under warm conditions. Skin arterioles are dilated, by-pass arteriole are constricted, thus more blood flows to the skin surface, resulting in more loss of heat energy.
2. Vasoconstriction of skin arterioles under cold conditions. Skin arterioles are constricted, by-pass arterioles are dilated, thus less blood flow to the skin surface, resulting in reduced loss of heat energy.

Question 5

State role of hair erector muscles in thermoregulation

Answer 5

1. Hair erector muscles relax under warm conditions. The hair lays flat and little still air is retained against the skin, hence heat loss is increased.
2. Hair erector muscles contract under cold conditions. The hair stands erect and much still air is retained against the skin, hence heat loss is reduced.

Question 6

State role of sweat glands in thermoregulation

Answer 6

1. Sweat gland produces more sweat under warm conditions. More evaporation of sweat from the skin surface results in increased heat loss through the latent heat of vaporisation.
2. Sweat gland produces less sweat under cold conditions. Less evaporation of heat from the skin surface results in reduced heat loss through the latent heat of vaporisation.

Question 7

State the role of shivering in thermoregulation

Answer 7

Under cold conditions, the body experiences a sudden loss of heat. Shivering occurs as the non-coordinated contraction of skeletal muscles, raising muscle heat production to about five times above the basal rate

Question 8

State the coordinating role of the hypothalamus in thermoregulation

Answer 8

The hypothalamus acts as a thermoregulation centre. Neurones detect changes in the temperature of the blood flowing through the brain. Hypothalamus receives information via sensory nerves from thermoreceptors located in the skin. Hypothalamus communicates with the rest of the body via the nervous system.