Definition of Homeostasis
the maintenance of a constant internal environment
how is blood sugar controlled
- when blood sugar is high, pancreas releases insulin
- insulin causes cell to take in glucose from the blood + muscle and liver to convert glucose to glycogen
- when blood sugar is low, glucagon is released
- glycogen converted to glucose
definition of thermoregulation
the homeostatic process of maintaining a constant internal temperature
how change in body temperature is detected
- receptors in thermoregulatory centre in hypothalamus
- skin sends signal to thermoregulatory centre
control of increase in temperature
- vasodilation: vessels dilate and move to the surface of the skin so more heat is lost through radiation
- sweat glands excrete sweat for evaporation on skin to cool down
- hair excreter muscle relax -> hair flattens
control of decrease in temperature
- vasoconstriction: vessels constrict -> decrease blood flow
- capillaries moves away from skin -> decrease heat loss
- hair excreter muscles contract -> hair stands up, creating a layer of insulation
- increase in metabolic rate
- shivering
definition of stimulus
a change in an organism’s internal and external environment
definition of response
reaction to the stimulus
definition of effector
the muscles or glands that carries out a response to correct the effect of the stimulus
definition of receptor
detects the stimulus
how an organism detects a stimulus and respond to it
- receptor detects stimulus
- receptor carries message to CNS via an electrical impulse or hormone
- message passed onto effector
effector respons
features of the nervous system
- sends message along nerves
- sends message as electrical impulse
- message travels very fast
- localised effect - impulse act on individual cell
- response is short lived
features of endocrine system
- message sent as hormone
- message carried by blood
- message travels slow
- widespread effect on different organs
- hormones are produced by endocrine glands
what is the nervous system formed from
- peripheral nervous system
- central nervous system (brain and spinal chord)
3 types of neurone
- sensory neurone: receptor to CNS
- Relay neurone: takes impulse to appropriate area of CNS
- motor neurone: CNS to effector
what is the synapse and how is electrical impulse transmitted
- synapse= gap between the neurones
- electrical impulses transmitted by neurotransmitters - diffuses across synapse
- neurotransmitters binds with receptor molecule on membrane of next neurone
why plants need to respond to stimuli
- to increase chance of survival
- to avoid being eaten
- to respond to abiotic stress
what is phototropism
direct growth in response to light - grows towards the light
what is geotropism
direct growth in response to gravity - grows In the direction of gravity
role of auxin
- auxin produced at the tip
- auxin diffuses down to the shoot, collecting at the shaded area
- Auxin stimulates faster growth - shaded area elongates
- shoot begins to grow towards the light and bends
response of the shoot (phototropism & geotropism)
positively phototrophic
- shoot tip produces Auxin and the shoot bends towards the light
negatively geotropic
- gravity produces unequal distribution of auxin (growing sideways)
- more auxin accumulates on lower side
- lower side elongates upwards
response of the root (phototropism & geotropism)
negatively phototrophic
- auxin accumulate on the shaded side
- top layer of cell elongates -> root moves downwards
positively geotropic
- grows downwards
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Topic 1 (characteristics of living organisms) / Topic 2 (cells and organisation)37
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topic 3 - 4 movement in and out of cells/variety of living organisms58
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Topic 6 ( enzymes and digestive system )50
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topic 5 - biological molecules and diet42
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Topic 7 - Respiration23
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Topic 8 Gas exchange25
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Topic 9 Photosynthesis29
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Topic 10 - Transpiration23
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Topic 11: transport (humans - blood, heart, circulatory system)32
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Topic 12: excretion15
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Topic 13: coordination22
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Topic 13: coordination (eye structure and hormones)22
