Communication and Homeostatis Flashcards
Explain why multicellular organisms require communication systems
Organisms need to respond to internal/external changes for survival
- Occurs through the nervous system and hormones in animals
- Occurs through hormones in plants
- Different cells rely on others for materials and removal of waste
- Different organs work together to ensure homeostasis
e.g. brain and skin in temperature control - Cells communicate through cell signalling
List changes to the internal environment that would require a response
- Blood glucose concentration
- Internal temperature
- Water potential
- Cell pH
List changes to the external environment that would require a response
- Humidity
- External temperature
- Light intensity
- Sudden sounds
Describe how cells are able to communicate with one another
- Cell releases a chemical
- Which has an effect on target cell
Outline cell signalling between adjacent cells in animals
Chemicals diffuse from one cell to another
- e.g. neurotransmitters across a synapse
Outline cell signalling between distant cells in animals
Hormones carried by blood to target organ(s)
- e.g. ADH secreted by pituitary gland, acts on kidney cells
What do plant cells use for communication?
Plant hormones
e.g. auxins
Define homeostatis
Maintaining stable internal environment
- Even though environment is changing
- Using negative feedback mechanisms
- Involves hormonal or nervous control
Give examples of homeostasis
- Thermoregulation (controlling body temperature)
- Blood pH
- Blood glucose
- Osmoregulation (water levels)
Define receptor
Detects changes in internal and external environment of an organism
Define effector
Muscles or glands that bring about a change in response to a stimulus
Define positive feedback
- Change in internal environment detected by receptors
- Effectors stimulated to reinforce and amplify response
- End products stimulate effectors to increases response
- e.g. blood clotting cascade
Define negative feedback
- Small change in one direction detected by sensory receptors
- Effectors work to reverse the change and restore conditions
- Conditions restored to base level
- Involved in homeostasis
- e.g. control of blood glucose concentration by insulin and glucagon
Define thermoregulation
Maintenance of a constant core body temperature
Why is thermoregulation important?
Maintains optimum temperature for enzyme activity
Define endotherm
- Organisms that rely on metabolic processes to warm up
- Maintain stable core body temperature in any environment
- e.g. mammals, birds
Define ectotherm
Organisms that use heat from surroundings to warm their bodies
- Core body temperature very dependent on environment
- e.g. insects, reptiles
Where does most of the heat that ectotherms use to increase body temperature come from?
The Sun
Outline how ectotherms increase their body temperature
Behavioural responses
- Bask in the Sun
- Orientate bodies so maximum surface area exposed to Sun
- Press body against warm ground - conduction
- Contract muscles and vibrate to increase exothermic cellular activity
Physiological responses
- Dark coloured skin absorbs more radiation
- Increase heart rate
Outline how ectotherms increase their body temperature
Behavioural responses
- Bask in the Sun
- Orientate bodies so maximum surface area exposed to Sun
- Press body against warm ground - conduction
- Contract muscles and vibrate to increase exothermic cellular activity
Physiological responses
- Dark coloured skin absorbs more radiation
- Increase heart rate
Outline how ectotherms decrease their body temperature
Behavioural responses
- Shelter in shade
- Dig burrows
- Press body against cool earth or stone
- Submerge in water or mud
- Minimise body surface area
- Minimise movement to reduce exothermic cellular activity
Physiological responses
- Light coloured skin absorbs less radiation
- Decrease heart rate
How do endotherms detect temperature change
Peripheral thermoreceptors in skin
- Detect changes in surface temperature
- Likely to be caused by change in environmental temperature
Thermoreceptors in hypothalamus
- Detect temperature change of blood
State where the core body temperature is monitored
Thermoregulatory centre in hypothalamus
Outline the behavioural responses of endotherms to temperature change
- Basking in the Sun
- Digging burrows
- Wallowing in water or mud
- Hibernation
- Wearing clothes (humans)
Outline the physiological responses of endotherms to decrease their core temperature
- Vasodilation of skin arterioles cools body
- Blood carried close to surface so loses more heat to surroundings through radiation
- Sweat glands produce more sweat, as the evaporation of sweat removes heat from body
- Erector pili muscles in skin relax - hair / feathers lie flat so less air trapped. This reduces the insulating effect of air
Outline the physiological responses of endotherms to decrease their core temperature
- Vasodilation of skin arterioles cools body
- Blood carried close to surface so loses more heat to surroundings through radiation
- Sweat glands produce more sweat, as the evaporation of sweat removes heat from body
- Erector pili muscles in skin relax - hair / feathers lie flat so less air trapped. This reduces the insulating effect of air
Outline the physiological responses of endotherms to increase their core temperature
- Vasoconstriction of skin arterioles retains body heat
- Little blood carried through surface capillaries so heat loss by radiation reduced
- Sweat glands produce less sweat
- Less heat lost through evaporation
- Erector pili muscles in skin contract. Hair / feathers raised so more air trapped, which increases the insulating effect of air
- Shivering generates heat through increased exothermic metabolic reactions
- Caused by increase in adrenaline or thyroxine hormones
Describe how body temperature is maintained in humans
Homeostatic process
- Body temperature maintained close to 37°C
- Heat distributed around body by blood
- Peripheral thermoreceptors in skin detect environmental temperature change
- Thermoreceptors in hypothalamus monitor temperature of blood
- Vasodilation of skin arterioles cools body
- Blood carried close to surface so loses more heat to surroundings
- Vasoconstriction of skin arterioles retains body heat
- Blood carried away from surface so retains heat
- Sweat glands produce sweat to cool the body when overheated
- Evaporation of sweat removes heat
- Shivering generates heat
- Hair erection retains heat
Describe and explain the anatomical adaptations of endotherms living in hot climates
Large surface area : volume ratio
- Maximises cooling
- More capillaries close to skin surface
- e.g. large ears
Pale fur/feathers
Reflect radiation
Describe and explain the anatomical adaptations of endotherms living in cold climates
Small surface area : volume ratio
- Reduces cooling
- e.g. small ears
Insulating fat layers
- e.g. blubber in whales
