5.1.1 Communication And Homeostasis Flashcards
Why do multicellular organisms need communication systems
To maintain a constant internal environment (homeostasis) as different organs have different functions in large animals
How do cells signal to eachother
Local signals e.g. between neurones at synapses, uses neurotransmitter
Transferring signals across large distances can be done with hormones
What does a receptor do
Detects change in internal and external environment of an organism
What does an effector do
Muscles or glands that react to the stimulus and bring about a change in response
What is a negative feedback system
Small change in one direction detected by sensory receptors, effectors work to reverse the change and restore conditions to base level
What is a positive feedback system
Change in internal environment detected by sensory receptors, effectors stimulated to reinforce the change and increase the response
What is thermoregulation
Maintaining constant core body temperature
How can organisms lose heat
Evaporation of water due to high latent heat of evaporation of water
Conduction to surroundings
Convection to surroundings
Radiation to surroundings
How can organisms gain heat
Respiration
Conduction from surroundings
Convection from surroundings
Radiation from surroundings
What is an ectotherm
Core body temperature is dependent on environment
E.g. invertebrates, fish, amphibians, and reptiles
What is an endotherm
Maintain stable core body temperature regardless of environment
E.g. birds and mammals
Behavioural responses of ectotherms
Basking in the sun or orientate body towards sun, increases surface area exposed to the sun, maximises radiation absorbed
Lie on warm ground, increases conduction to body
Contract muscles and vibrate body/wings to increase cellular metabolism
Opposite for cooling down
Physiological responses by ectotherms
Darker colours to absorb more radiation from the sun
Alter heart rate to change metabolic rate
How are temperature changes detected by endotherms
Peripheral temperature receptors in skin, detect change in surface temperature
Temperature receptors in hypothalamus detect temperature of blood deep in the body
What internal temperature should be maintained for humans
37ºC
Behavioural adaptations of endotherms
Basking in sun
lying on warm surfaces
wallowing in water or mud
digging burrows
Becoming dormant in winter or summer
How do endotherms cool down (physiological adaptations)
Vasodilation, arterioles near surface of skin dilate so blood is forced in capillaries near surface of skin, heat radiates or can cool from conduction if pressed against cool surface
Sweating increases, sweat evaporates from surface of skin and heat is lost
Reduce insulation from hair, erector pili muscles relax, hair lies flat, no air trapped as insulation
Anatomical adaptations in endotherms
Cooling down:
Large surface area (large ears and wrinkled skin)
Pale fur or feathers to reflect radiation
Warming up:
Opposite
Thick layer of insulating fat underneath skin
Hibernation (build up fat stores, lower metabolic rate, build insulated shelter)
How do endotherms warm up (physiological adaptations)
Vasoconstriction, little blood flows in capillary networks near surface of skin, little radiation takes place
Decreased sweating
Erector pili muscles in skin contract, insulating layer of air is trapped
Shivering, rapid, involuntary contraction of large voluntary muscles in the body, metabolic heat released
How is thermoregulation controlled through the heat loss centre
Activated when temperature of blood flowing through hypothalamus increases,
sends impulses through autonomic motor neurones to effectors in skin and muscles, triggers responses that lower core temperature
How it thermoregulation controlled through the heat gain centre
Activated when temperature of the blood flowing through hypothalamus decreases, sends impulses through autonomic nervous system to effectors in skin and muscles, triggers responses that raise the core temperature
