Coordination
- Created by: khodnett
- Created on: 19-02-16 11:29
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- Coordination
- Systems
- Nervous system detects change or stimuli and processes
- Central nervous system is brain and spinal cord
- Peripheral nervous system is nerves carrying impulses from CNS
- Receptors & effectors
- CNS processes initiating response through effectors eg muscles or glands
- Stumulus detected by receptors eg sensory cells or organs
- reflex arc
- involuntary rapid response
- brain is bypassed
- Stimulus causes receptor to signal sensory neurone sending impulse to spinal cord
- relayed by relay neurone connecting sensory neurone to motor neurone
- Signal reaches effector
- Conduction
- 2 factors affect speed
- myelination speeds upas insulates preventing depolarisation
- impulse has to jump between nodes of ranvier
- saltatory conduction
- diameter of axon, greater diameter= greater speed transmission
- Hydra nerve net
- Slow transmission
- Limited responses to limited stimuli
- Simple nerve cells with short extensions
- Motor neurone structure
- scwann cells cells attach to axon forming myelin sheath with interval nodes of ranvier
- membraneous cytoplasmic axon with axon terminals at end are on cell body
- dendrite thin extensions reach out from cell body
- cell body has granular cytoplasm with ribosomes as nissl granules
- Action potential
- k+/Na+ pump restores polarity
- stimulus detected by receptor causing charge reversal on axon membrane
- -70mv to +40mv depolarising membrane
- Na channels open influx of Na+ cause +40mv
- Na Channels close K channels open K+ leave to repolarise
- temporary overshoot on refractory period so another AP cant be generated
- synapse
- diffuses across to receptor sites on postsynaptic membrane for depolarisation for initiation of impulse
- acetyl choline destroyed by enzymes in the cleft to limit effect
- when impulse arrives at synaptic knob the permeability is altered
- Ca+ enters so synaptic vesicles fuse with presynaptic membrane releasing acetyl choline into synaptic cleft
- receptor sites change shape when acetyle choline binds to them opening the channel for Na+ to diffuse in starting an action potential
- cholinesterase produces choline and ethanoic acid that diffuses backwards to presynaptic cleft to reform acetyl choline using atp to form storage vesicles
- effecting transmission
- caffine increases metabolic rate in presynaptic cells
- increased atp production stimulates synthesis of neurotransmitter
- organophosphates are in insecticides that block the enzyme that breaks down neurotranmitter
- acts as neuromuscular junction causing uncontrollable muscle contractions
- flowering
- 3 types of flowering plants
- day neutral unaffected by day length
- long day plants induced by dark periods shorter than critical length
- short day plants are induced by dark periods longer than critical length
- flowering in short day plants is inhibited by exposure to red light which converts pfr to pr
- short day plants only flower if pfr is low enough but this is the opposite for long day plants
- Systems
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