15.1-15.3 Thermoregulation Flashcards
What is homeostasis?
The maintenance of a stable equilibrium of the conditions inside the body
What is the negative feedback system and how does it operate?
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.
Give examples of negative feedback systems
- Controlling blood sugar levels e.g insulin and glycogen
- Temperature control
- Water balance of the body
What is positive feedback system and HOW does it work?
- 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.
Give examples of positive feedback systems.
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
What is thermoregulation?
The maintenance of a relatively constant core temperature
What are ectotherms?
Animals that are heavily dependent on their environment for regulating core body temperature
Give examples of ectotherms
Fish, amphibians, reptiles and invertebrate animals
What are endotherms?
Endotherms are animals that rely on their metabolic processes to warm up and they usually maintain a very stable core body temperature.
What behavioural adaptations do ectotherms have to increase their temperature?
- 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
What behavioural adaptations do ectotherms have to decrease their temperature?
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.
What physiological adaptations do ectotherms have?
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.
Which receptors detect changes in surface temperature? Where are they?
- The peripheral temperature receptors detect changes in surface temperature.
- They are in the skin.
Which receptors detect the temperature of blood deep in the body? Where are they?
The temperature receptors in the HYPOTHALAMUS detect the temperature of the blood deep in the body.
What do endotherms use to keep them warm?
Endotherms use their internal exothermic metabolic activities to keep them warm.
What behavioural adaptations do endotherms have to temperature changes?
- Being dormant during cold weather (hibernation)
- Basking in Sun
- Pressing themselves to warm surfaces
- Wallowing in water and mud
What mechanisms do mammals have to reduce body temperature?
1) Sweating
2) Vasodilation
3) Hairs lie flat
What occurs during vasodilation?
- 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.
How does increased sweating occur?
- 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.
How is the insulating effect of hair or feathers reduced?
- 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.
What anatomical adaptations do endotherms that live in hot climates have?
- A relatively large SA:V ratio to maximise cooling.
E.g: - Large ears
- Wrinkly skin
- Pale fur or feathers to reflect radiation
What mechanisms do mammals have to INCREASE body temperature?
1) Shivering
2) Less sweating
3) Hairs stand up
4) Vasoconstriction
What occurs during vasoconstriction?
- 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.
How are the body hair or feathers raised up?
- 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.
