Homeostasis

Question 1

Physiological homeostasis

Answer 1

Maintenance of the body’s internal environment within certain tolerable limits despite changes in the body’s external environment.

Question 2

How is homeostasis brought about?

Answer 2

By the process of negative feedback.

Question 3

Does negative feedback require energy?

Answer 3

Yes

Question 4

Principle of negative feedback control -

Answer 4

A factor can increase or decrease from its norm, this will be sensed by receptors for that factor. Messages will be sent form the receptors to the effectors which bring about a corrective response to lower or raise the factor back to its norm or set point.
If no change in factor nothing will happen.

Question 5

2 types of thermoregulation

Answer 5

Ectotherm and endotherm

Question 6

Ectotherm

Answer 6

An animal which is unable to regulate its heat by physiological means - they obtain most of their body heat by absorbing it from their surroundings. (Conformer)

Question 7

Examples of ectotherms

Answer 7

Fish, amphibians and reptiles

Question 8

Endotherm

Answer 8

An animal which is able to maintain its body temperature at a relatively constant level irrespective of external temperature changes. Heat generated by their high metabolic rate. (Regulator)

Question 9

Examples of endotherms

Answer 9

Birds and mammals

Question 10

Importance of temperature regulation -

Answer 10

So that the temperature is kept at an optimum for enzyme controlled reactions and diffusion rates for maintenance of metabolism.

Question 11

How is diffusion affected by temperature?

Answer 11

Diffusion such as oxygen and carbon dioxide are faster at warmer temperatures

Question 12

Which has higher energy cost ectothermic or endotherm?

Answer 12

Endotherm

Question 13

What does negative feedback and thermoregulation require?

Answer 13

Hypothalamus, nerves, effectors and skin.

Question 14

The hypothalamus is …

Answer 14

The body’s temperature monitoring centre.

Question 15

How does hypothalamus work?

Answer 15

Receives impulses form the heat and cold receptors of the skin, it also contains thermoreceptors which detect changes in blood temperature which reflect changes in the body core temperature.

Question 16

Temperature control by the hypothalamus-

Answer 16

After detecting changes in blood temperature or from nerve impulses from the skin, the hypothalamus will send messages to the sweat glands, skin arterioles, hair erector muscles and skeletal muscles.

Question 17

Role of skin in temperature regulation

Answer 17

In responses to nerve impulses form the hypothalamus, the skin will act as an effector

Question 18

Vasodilation

Answer 18

When too hot, capillaries to the skin surface dilate allowing the blood to the surface to lose heat by radiation

Question 19

Increased rate of sweating

Answer 19

Heat energy is used to convert the water in sweat to vapour bring about a lowering of body temperature

Question 20

Relaxation of hair erector muscles

Answer 20

Prevents heat being trapped in a layer of air next to the skin and allows heat being lost.

Question 21

How is overheating corrected in relation to metabolism.

Answer 21

Metabolism decreases so heat produced is decreased.

Question 22

How is overheating corrected

Answer 22

Relaxation of hair muscles, vasodilation, decrease in metabolism and increased rate of sweating

Question 23

Vasoconstriction -

Answer 23

When body temperature decreases, the arterioles constrict which allows only a small volume of blood flow to the surface capillaries, so less blood flow to the skin - decreasing the temperature lost by radiation.

Question 24

Corrective responses to decrease in body temperature

Answer 24

Vasoconstriction, decreased rate of sweating, hair erector muscles contract, increased metabolic rate and shivering.

Question 25

Decreased rate of sweating -

Answer 25

Reduces heat lost by evaporation of sweat.

Question 26

Hair erector muscles contract -

Answer 26

Raised hairs will trap a layer of insulating air reducing heat loss

Question 27

Increased metabolic rate -

Answer 27

Means more heat will be produced

Question 28

Shivering -

Answer 28

Muscle contractions generate heat.

Question 29

How does the thermoregulating centre (hypothalamus) communicate with the effectors

Answer 29

Via nerve impulses