5.1.1 - Communication and Homeostasis Flashcards
Why do multicellular organisms need communication systems?
- to respond to changes in internal environment
- to respond to changes in external environment
- to coordinate activities of different organs
How do cells transfer signals?
- locally (eg. across synapses)
- across long distances (using hormones)
What is homeostasis?
maintaining a stable internal environment regardless of changes in the external environment
What are receptors?
glycoproteins that detect changes in our body and send a signal which triggers a response
What are effectors?
part of the body that carries out a response to a stimulus
eg. gland, muscle
What is a negative feedback loop?
a mechanism that reverses a change in the body to return to optimum conditions
Name some examples of a negative feedback loop
regulating blood glucose levels
thermoregulation
What happens in a negative feedback loop?
- change away from optimum
- receptors detect change
- communication system informs effector
- effector reacts to reverse change
- returns to optimum
What is a positive feedback loop?
a mechanism that amplifies a detected change, moving the conditions away from the normal level
- accelerate a biological pathway
eg. uterus contraction during birth, formation of a blood clot after an injury, etc
Name some examples of a positive feedback loop?
uterus contraction during childbirth
formation of a blood clot at the site of a wound
What are the differences between negative and positive feedback?
Negative feedback: -resists change -more common Positive feedback: -amplifies change -speeds up change/process -less common
What is thermoregulation?
control of internal body temperature
Why is thermoregulation important?
temp effects enzymes (if too high, they denature)
What are endotherms?
animals which maintain a very stable body temperature by relying on metabolic processes
- warm blooded animals
eg. mammals, birds
What are ectotherms?
animals which are unable to control their body temperature so rely on external sources of heat and behavioural mechanisms
- cold blooded animals
eg. reptiles, fish, amphibians
What are the advantages of being an ectotherm?
- use less energy to maintain body temp
- don’t need as much food (less needed for respiration)
- greater proportion of energy used for growth
What are the disadvantages of being an ectotherm?
- extreme weather conditions can make them suffer
- basking in the sun makes them more exposed to predators
- metabolic reactions are slower
- less active in cooler temps
What are the advantages of being an endotherm?
- can survive in a larger range of temps
- have a constant body temp (regardless of external temps)
- less risk of predators (active when cool)
What are the disadvantages of being an endotherm?
- need to eat more food (need more for respiration) so can’t survive for as long without food
- less energy is used for growth
How do endotherms regulate temperature?
physiological responses and behavioural responses
How do ectotherms regulate temperature?
behavioural responses
How do endotherms control body temperature using physiological responses?
- thermoreceptors detect changes in body temp
- thermoreceptors send out a nerve impulse, which travels along a sensory neurone to the hypothalamus in the brain
- hypothalamus sends a nerve impulse along a motor neurone to an effector
- the effector responds to alter the body temp
What physiological responses do endotherms have to reduce body temperature?
- vasodilation
- sweating
- hairs lie flat
What physiological responses do endotherms have to increase body temperature?
- vasoconstriction
- shivering
- hormones
- reduced sweating
- hairs stand up
What behavioural responses do ectotherms have to control body temperature?
- expose body to sun
- increase breathing rate
- change body shape
- change body movement
