15.1-15.3 Thermoregulation

Question 1

What is homeostasis?

Answer 1

The maintenance of a stable equilibrium of the conditions inside the body

Question 2

What is the negative feedback system and how does it operate?

Answer 2

The negative feedback system is the mechanism that restores the level to normal.
- A small change is detected by sensory receptors and effectors work to reverse the change and restore conditions to base level.

Question 3

Give examples of negative feedback systems

Answer 3

• Controlling blood sugar levels e.g insulin and glycogen
• Temperature control
• Water balance of the body

Question 4

What is positive feedback system and HOW does it work?

Answer 4

• The mechanism that amplifies a change away from normal level.
• A change in internal environment is detected by sensory receptors and effectors are stimulated to reinforce that change and increase the response.

Question 5

Give examples of positive feedback systems.

Answer 5

1) During formation of a blood clot after an injury, platelets become activated and release a chemical- this triggers more platelets to be activated and so on.
- This means platelets very quickly form a blood clot at the injury site.

2) Stimulation of oxytocin production during childbirth, as oxytocin stimulates the uterus to contract

Question 6

What is thermoregulation?

Answer 6

The maintenance of a relatively constant core temperature

Question 7

What are ectotherms?

Answer 7

Animals that are heavily dependent on their environment for regulating core body temperature

Question 8

Give examples of ectotherms

Answer 8

Fish, amphibians, reptiles and invertebrate animals

Question 9

What are endotherms?

Answer 9

Endotherms are animals that rely on their metabolic processes to warm up and they usually maintain a very stable core body temperature.

Question 10

What behavioural adaptations do ectotherms have to increase their temperature?

Answer 10

• Radiation: Basking in the Sun, orientating their bodies so that the maximum surface area is exposed to the Sun. (E.g lizards)
• Conduction: pressing their bodies against the warm ground
• Exothermic metabolic reactions:
• Vibrations: contracting muscles and vibrating, increasing cellular metabolism

Question 11

What behavioural adaptations do ectotherms have to decrease their temperature?

Answer 11

1) Seeking shade
2) Hiding in cracks or rocks
3) Digging burrows
4) Pressing bodies against cool, shady earth or stones
5) Move into water/mud
6) Minimise movements to reduce metabolic heat generated
7) Orientating body so that minimum surface area is exposed to Sun.

Question 12

What physiological adaptations do ectotherms have?

Answer 12

1) Lizards living in colder climates tend to be darker coloured than lizards living in hotter countries. This is because dark colours absorb more radian than light colours.
2) Some ectotherms alter heart rate to increase or decrease metabolic rate.

Question 13

Which receptors detect changes in surface temperature? Where are they?

Answer 13

• The peripheral temperature receptors detect changes in surface temperature.
• They are in the skin.

Question 14

Which receptors detect the temperature of blood deep in the body? Where are they?

Answer 14

The temperature receptors in the HYPOTHALAMUS detect the temperature of the blood deep in the body.

Question 15

What do endotherms use to keep them warm?

Answer 15

Endotherms use their internal exothermic metabolic activities to keep them warm.

Question 16

What behavioural adaptations do endotherms have to temperature changes?

Answer 16

• Being dormant during cold weather (hibernation)
• Basking in Sun
• Pressing themselves to warm surfaces
• Wallowing in water and mud

Question 17

What mechanisms do mammals have to reduce body temperature?

Answer 17

1) Sweating
2) Vasodilation
3) Hairs lie flat

Question 18

What occurs during vasodilation?

Answer 18

• The arteriole near the surface of the skin dilate when the temperature rises.
• The vessels that provide a direct connection between the arterioles and venues constrict.
• This forces blood through the capillary networks close to the surface of the skin.
• The skin flushes, and cools as a result of increased radiation.

Question 19

How does increased sweating occur?

Answer 19

• As core temp increases, rates of sweating also increase.
• Sweat spreads out across surface of the skin.
• As sweat evaporates from the surface of the skin, heat is lost, cooling the blood below the surface.

Question 20

How is the insulating effect of hair or feathers reduced?

Answer 20

• When body temp begins to increase, the erector pilli muscles (hair erector muscles) in the skin relax.
• As a result, the hair or feathers of the animal lie flat to the skin.
• This avoids trapping an insulating layer of air.

Question 21

What anatomical adaptations do endotherms that live in hot climates have?

Answer 21

• A relatively large SA:V ratio to maximise cooling.
  E.g:
• Large ears
• Wrinkly skin
• Pale fur or feathers to reflect radiation

Question 22

What mechanisms do mammals have to INCREASE body temperature?

Answer 22

1) Shivering
2) Less sweating
3) Hairs stand up
4) Vasoconstriction

Question 23

What occurs during vasoconstriction?

Answer 23

• The arterioles near the surface of the skin constrict.
• The arteriovenous shunt vessels dilate, so little blood flows though capillary networks close to the surface of the skin.
• The skin looks pale, and very little radiation takes place.
• The warm blood is kept well below the surface.

Question 24

How are the body hair or feathers raised up?

Answer 24

• As body temperature falls, the erector pili muscles in the skin contract, pulling the hair or feathers of the animal erect.
• This traps an insulating layer of air and reduces cooling through the skin.

Question 25

How does shivering help to increase body temperature?

Answer 25

• As core temp falls, the body begins to shiver.
• This is the rapid, involuntary contracting and relaxing of large voluntary muscles in the body.
• The metabolic heat from the exothermic reactions warm up the body instead of moving it and is an effective way of raising the core temperature.

Question 26

What anatomical adaptations do endotherms that live in cold climates have?

Answer 26

• Minimising SA:V ratio to reduce cooling e.g small ears
• A thick layer of insulating fat underneath the skin e.g blubber in whales and seals
• Some hibernate to build up fat stores

Question 27

What adaptations do polar bears have to survive in the cold?

Answer 27

• Small ears
• Fur on feet to insulate them from the ice
• Hollow hairs to trap a permanent layer of insulating layer
• Black skin underneath to absorb warming radiation
• Dig dens in snow to remain in them warm and insulating

Question 28

What two control centres are there to control thermoregulation?

Answer 28

1) Heat loss centre

2) Heat gain centre

Question 29

When is the heat loss centre activated?

Answer 29

• The heat loss centre is activated when the temp of blood flowing through the hypothalamus increases.
• It sends impulses through autonomic motor neurones to effectors in skin and muscles, triggering responses to lower core temp.

Question 30

When is the heat gain centre activated?

Answer 30

• The heat gain centre is activated when the temperature of the blood flowing through the hypothalamus decreases.
• It sends impulses through the autonomic nervous system to effectors in the skin and muscles, triggering responses to raise core temp.