Communication and homeostasis Flashcards
What conditions need to be maintained inside cells ?
- temperature
- pH
- aq environment that keeps substrates and products in solution
- freedom from toxins and excess inhibitors
Features of a good communication system
- covers the whole body
- enables cells to communicate with each other
- enable specific and rapid communication
- enable both short-term and long-term responses
What’s cell signalling?
communication between cells
2 major systems of communication that work by cell signalling
- hormonal system
- neuronal system
Define homeostasis
MAINTAINING A CONSTANT INTERNAL ENVIRONMENT despite changes in internal or external factors
Define negative feedback
MECHANISM that reverses a change, bringing system back to the optimum
Define positive feedback
mechanism that increases a change, taking system away from the optimum
What’s a sensory receptor?
cells or sensory nerve endings that respond to a stimulus in internal/external environment of organism and creates action potentials
aspects maintained by homeostasis
- body temperature
- blood glucose conc
- blood salt conc
- water potential of blood
- blood pressure
- carbon dioxide conc
mechanism of homeostasis
stimulus –> receptor (sensory cell) –> cell signalling –> effector–> response
Where are thermoreceptors?
- skin
- brain
Will conditions remain perfectly constant as a result of negative feedback?
No. there will be fluctuation around the optimum as it may take time to respond and the response may overshoot slightly
What’s an endotherm?
organism that uses heat from metabolic reactions to maintain body temperature
What’s an ectotherm?
organism that relies on external sources of heat to maintain body temperature
How do ectotherms try to absorb more heat when they’re not warm enough?
- move into sunny area
- lie on warm surface
- expose a larger surface area to the sun
How do ectotherms avoid gaining more heat when they’re too hot?
- move out of the sun
- move underground
- reduce body surface exposed to the sun
Advantages of ectothermy?
- less of their food is used in respiration
- more energy and nutrients from food converted to growth
- need to find less food
- can survive long periods of time without food
Disadvantages of ectothermy?
- less active in cooler temperatures so increased risk of predation as they’re unable to escape
- can’t take advantage of food available while they’re cold
What’s the hypothalamus?
- the part of the brain that coordinates homeostatic responses
- detects change in core temperature
What are exergonic reactions?
those that release energy in the form of heat
How does the skin respond when the body is too hot?
- vasodilation of capillaries directs blood to skin surface so more heat radiated from body
- sweat released, heat from blood used to evaporate it.
- hairs and feathers lie flat to reduce insulation and allow greater heat loss
How does the skin respond when the body is too cold?
- vasoconstriction of capillaries, blood diverted away from skin surface, less heat is lost
- less sweat secreted, less evaporation, less heat loss
- hairs and feathers stand erect to trap air, which insulates body
How does the gaseous exchange system respond when body is too hot?
- panting increases evaporation of water from surface of lungs and airways using heat from blood.
How does the gaseous exchange system respond when body is too cold?
- less panting so less heat lost.
How does the liver respond when the body is too hot?
- less respiration, less heat released
How does the liver respond when the body is too cold?
- increased respiration in hepatocytes, more energy from food converted to heat
How do skeletal muscles respond when the body is too hot?
- fewer contractions so less heat released
How do skeletal muscles respond when the body is too cold?
- shivering, releasing heat
How do blood vessels respond when the body is too hot?
dilation to direct blood to extremities so more heat lost
How do blood vessels respond when the body is too cold?
constriction to limit blood flow to extremities so blood is not cooled to much, may lead to frostbite in extreme cases
behaviours of endotherms if they’re too hot?
- hide away from sun in the shade
- orientate body to reduce SA exposed to sun
- remain inactive and spread limbs for greater heat loss
- wet skin to use evaporation to cool body
behaviours of endotherms if they’re too cold?
- lie in the sun
- orientate body towards sun to increase SA exposed
- become active to generate heat in muscles
- remain dry
Advantages of endothermy
- maintain fairly constant body temp regardless of external temperature
- remain active even at low temps so can escape from predators and hunt
- INHABIT COLDER PARTS OF THE PLANET
Disadvantages of endothermy
- use a lot of energy intake to maintain body temp in the cold so a lower proportion of energy and nutrients used for growth
- need more food
- overheat in hot weather
How is the control of temperature regulated?
- temperature receptors (thermoregulatory centre) in hypothalamus detect change
- hypothalamus sends impulses. Output can be transmitted by the neuronal system for quick responses or hormonal system for longer term responses
What does the hypothalamus cause when body temperature is too low?
- changes to skin to reduce heat loss (vasoconstriction)
- release of heat through extra muscle contraction
- increased metabolism to release more energy from exergonic reactions
What’s the role of peripheral temperature receptors?
- peripheral temperature receptors in skin monitor temperature in extremities
- info fed to the thermoregulatory centre in hypothalamus
- brain initiates behavioural mechanisms to maintain body temp (move into shade)
