TEMPERATURE REGULATION

Question 1

What is heat regulation known as? (1)

Answer 1

Thermoregulation

Question 2

What is thermoregulation? (1)

Answer 2

Involves controlling the amount of heat lost and heat gained through the skin surface. Heat may be transferred between an animal and the environment by convection, radiation and conduction.

Question 3

Summarise the process of convection by heat. (1)

Answer 3

Convection of heat by the upward flow of warm air or the downward flow of cold air past the body.

Question 4

Summarise the process of radiation of heat. (1)

Answer 4

From a body to a colder object not in contact; the heat is transferred by infra-red waves

Question 5

Summarise the process of conduction of heat. (1)

Answer 5

From the hotter to the colder of two surfaces in contact.

Question 6

Summarise the process of evaporation. (1)

Answer 6

The change of liquid to vapour - accompanied by cooling; the evaporation of water has a marked cooling effect.

Question 7

Describe the conditions of heat regulation in fish. (1)

Answer 7

Fish are unable to regulate body temperature, the huge hill surface area over which water move continuously for gaseous exchange is also efficient for heat exchange. The temperature inside the body is approximately the same in the outside environment

Question 8

Why do fish have the same temperature as the outside environment? (1)

Answer 8

This is because any body heat is quickly lost the surroundings, fish are good ‘non-regulators’

Question 9

Explain the heat regulation in reptiles. (1)

Answer 9

Temperature control is exercised by behavioural changes to take in heat as needed, exploiting any heat available in the external environment

Question 10

What is a reptile an example of? (1)

Answer 10

An ectotherm

Question 11

What is an ectotherm? (1)

Answer 11

An organism that relies on external heat sources for Thermoregulation

Question 12

How do mammals maintain a constant body temperature? (1)

Answer 12

They achieve this by using heat energy generated by metabolism within their bodies, or by generating additional heat in their muscles when cold and carefully controlling heat lost through the skin.

Question 13

What is an endotherm? (1)

Answer 13

An animal that relies on heat energy generated by internal metabolism for Thermoregulation

Question 14

How is heat produced in the human body? (1)

Answer 14

The major of the heat are produced in biochemical reactions of metabolism which generate heat as a waste product. From the site of production the heat reaches the rest of the body through the blood vessels. The bulk of the body heat is produced through the organs.

Question 15

What role does the skin have in heat regulation? (1)

Answer 15

Heat exchange occur at the skin, the outer layer of the skin (the epidermis) consists of stratified epithelium. The cells in its basal layer (the malpighian layer) constantly divide, pushing the cells above them towards the skin surface. These upper cells are progressively flattened and the cell contents turn into keratin. The outermost layer of cells is continuously being rubbed off, but replaced from beneath so it does not wear away.

Question 16

What occurs at the dermis layer of skin? (1)

Answer 16

At the dermis blood capillaries, the hair follicles with hair erector muscles and the sweat glands, the sense receptors and sensory nerve endings are also found in this layer, and there are especially numerous in certain parts of the skin, which are consequently sensitive.

Question 17

What is the dermis layer? (1)

Answer 17

This is a much thicker layer that consists of elastic connective tissue

Question 18

What occurs at the adipose tissue? (1)

Answer 18

Has a limited blood supply and is a poor conductor of heat, so it insulates internal organs against heat loss.

Question 19

What is the adipose tissue? (1)

Answer 19

The base of the dermis, a major site of fat storage in mammals.

Question 20

How do the capillary networks control heat loss? (1)

Answer 20

The artérioles supplying them are widened (vasodilation) when the body needs to lose heat, but constricted (vasoconstriction) when it needs to retain heat.

Question 21

How do the hair erector muscles control heat loss? (1)

Answer 21

These contract when heat must be retained, raising the hairs to trap a thicker layer of insulating air, but relax when more heat needs to be lost.

Question 22

How do the sweat glands control heat loss? (1)

Answer 22

These produce sweat only when heat needs to be lost. The evaporation of the liquid sweat into vapour requires significant amounts of heat energy (specific latent heat if vaporisation) which is taken from the skin.

Question 23

What is vasodilation? (1)

Answer 23

The widening of arteries and artérioles in the circulatory system

Question 24

What is vasoconstriction? (1)

Answer 24

The narrowing of arteries and artérioles in the circulatory system.

Question 25

What are some other mechanisms of thermoregulation? (2)

Answer 25

-changing metabolic rate -behaviour changes

Question 26

What is the mechanism of changing the metabolic rate? (2)

Answer 26

The rate of heat release by an organism at rest is dependent on its basal metabolic rate, this is under the control of two hormones.

Question 27

What hormone controls the metabolic rate in the short terms? (1)

Answer 27

in the short term it is regulated as a role of the hormone adrenaline.

Question 28

What hormone controls the metabolic rate in the long term? (1)

Answer 28

In the longer term it is controlled by the hormone thyroxine which is secreted by the thyroid gland.

Question 29

What is the basal metabolic rate? (1)

Answer 29

The rate of heat release by metabolic reactions when an organism is at rest.

Question 30

What is a specialised site of heat production in mammals? (1)

Answer 30

A tissue known as brown fat.

Question 31

What is the role of brown fat? (1)

Answer 31

To generate heat, when tissue is stimulated by sympathetic nerves, respiration of glucose formed from surrounding fat reserves is speeded up. The ATP formed in the brown fat cells is immediately hydrolysed to ADP and Pi and all the free energy of this reaction is released as heat and circulated in the blood.

Question 32

What are brown fat cells? (1)

Answer 32

Groups of cells around the thorax of mammals capable of releasing heat using very high rates of respiration.

Question 33

What happens to muscles under cold conditions? (1)

Answer 33

Heat output from body muscles increases, live muscle has a firm and solid feel, this is caused by many tiny contractions within the muscle and is normally used to maintain posture. These contractions can be sped up to produce heat.

Question 34

Where is the Thermoregulatory centre? (1)

Answer 34

A region of the forebrain called the hypothalamus

Question 35

Describe the thermoregulatory centre and its function. (1)

Answer 35

The hypothalamus has a ‘heat loss centre’ and a ‘heat gain centre’ the centre receives information from temperature-sensitive nerve endings monitoring blood temperature in the hypothalamus itself, as well as others found in the skin and many major organs.

Question 36

How does the hypothalamus communicate with the rest of the body? (1)

Answer 36

Using the automatic nervous system with its antagonistic divisions of sympathetic and parasympathetic neurones.

Question 37

LOWER TEMP How. Does the thermoregulatory centre work? (2)

Answer 37

If the body temperature is low, the heat-gain centre inhibits the activity of the heat loss centre, impulse are sent down sympathetic nerves to skin, hair erector muscles, sweat glands and elsewhere to decrease heat loss.

Question 38

HIGHER TEMP How. Does the thermoregulatory centre work? (2)

Answer 38

When the temperature is higher, the heat loss centre inhibits the heat-gain centre and impulses are sent to the same organs but through parasympathetic nerves, which initiate actions to increase heat loss.

Question 39

What are some actions that increase heat gain? (1)

Answer 39

Vasoconstriction, shivering and increased brown fat respiration

Question 40

What are some actions that increase heat loss? (1)

Answer 40

Vasodilation, sweat production and inhibiting brown fat respiration