COORDINATION
- Created by: ava.scott
- Created on: 13-05-15 11:36
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- Coordination
- The nervous system
- what does it do?
- to detect a change in the environment.
- to initiate a response.
- The central nervous system
- the brain and spinal cord
- processes and initiates a response
- the peripheral nervous system
- pairs of neurones that stem from the spinal cord.
- e.g. sensory and motor neurones.
- they detect stimuli and connect top an effector
- pairs of neurones that stem from the spinal cord.
- what does it do?
- STIMULI
- a detectable change in the internal or external environment.
- Reflex arc
- the basis of involuntary actions fro protection
- closely associated with conscious neural pathways.
- via ascending and descending tracts in the spinal cord.
- Hydra
- simple organism
- small number of stimuli
- so a small number of effectors
- EFECTORS ARE MUSCLES OR GLANDS
- so a small number of effectors
- response is slow because
- transmission is multi-directional
- nervre net system
- Picked up by receptor neurons in sensitive cells in the skin or high specialized organs such as the eye.
- SPINAL CORD PHYSIOLOGY
- Dorsal root ganglion
- cell body within the dorsal root that receives information and sends it to the spinal cord
- dorsal root
- top of diagram
- ventral root
- bottom of diagram (or nearer to belly button)
- white matter
- contains mylelinated axons
- grey matter
- contains darkly staining cell bodies
- central canal
- fluid filled space
- meninges
- outside layers of the spinal cord
- sensory neurone
- enters spinal cord via the dorsal root
- motor neurone
- leaves via the ventral root and is connected to effectors
- relay neurone
- within the grey matter, connecting a sensory neurone and motor neurone
- effector
- muscle or gland
- Dorsal root ganglion
- MAMMALIAN NEURONE
- Physiology
- dendrites
- recieve impulse from many axons
- dendron
- carries information to the cell body
- cell body
- contains granular cytoplasm and nucleus.
- ribosomes associated in Nissl granules
- concerned with synthesis of neurotransmitters
- nucleus
- contains genetic information to code for neurotransmitters
- axon
- carries genetic information away from the cell body.
- myelin sheath
- fatty layer around neurone made from Schwann cells
- nodes of ranvier
- gaps in the myelin sheath allowing saltatory conduction.
- dendrites
- SENSORY
- cell body in middle
- RELAY
- unmyleinated
- within grey matter
- MOTOR
- Cell body within dendrites
- Physiology
- RESTING POTENTIAL
- measured using
- cathode ray oscilloscopes
- microelectrodes
- across giant axons from quid
- usually negative values
- -70mv
- said to be polarised
- inside of axon has a negative charge.
- MAINTENANCE
- pumps
- sodium potassium pump
- 2 K+ in for every 3Na+ out
- channels
- potassium channels remain open
- so these ions can diiffuse out
- sodium channels are closed
- so these ions cannot move in
- potassium channels remain open
- COO- groups and proteins
- these keep the cytoplasm of the axon negative.
- Overall
- 100x more permeable to K+ than Na+
- K+ is high is concentration
- so these positive ions diffuse out, polarising the membrane.
- K+ is high is concentration
- 100x more permeable to K+ than Na+
- pumps
- measured using
- NERVE IMPULSE
- Action potential
- A change in the permability of Na+ in the membrane resulting in a voltage being generated.
- DEPOLARISATION
- suitable stimulus causes Na+ channels to open.
- there is an influx of Na+ ions.
- Creating a positive depolarisation of +40mv
- there is an influx of Na+ ions.
- REPOLARISATION
- K+ ions flood our rapidly
- HYPERPOLARISATION
- there is an overshoot of K+ ions
- the membrabe is -90mv
- REFRACTORY PERIOD
- The sodium- potassium pump restores ionic balance
- importance of refractory period
- limits frequency of action potential generation.
- stops merging of impulses.
- undirectional impulse.
- there is an overshoot of K+ ions
- HYPERPOLARISATION
- K+ ions flood our rapidly
- suitable stimulus causes Na+ channels to open.
- All or nothing law
- The intensity of the stimulus
- does not effect the size of the action potential
- if the stimulus does not reach the threshold, a action potential will not be generated.
- The intensity of the stimulus
- Action potential
- nerve transmission
- PROPOGATION
- depolarization is propagated across the membrane
- by local currents stimulating the next area to become depolarised.
- and repolarisation occurring right behind.
- by local currents stimulating the next area to become depolarised.
- depolarization is propagated across the membrane
- Myelination
- speeds up transmission by
- increasing the distance of which a local current can induce depolarisation.
- as it jumps from node of ranvier to node.
- SALTATORY CONDUCTION
- as it jumps from node of ranvier to node.
- increasing the distance of which a local current can induce depolarisation.
- speeds up transmission by
- the size of the axon also effects the speed of transmission.
- the larger the diameter of the axon, the greater the velocity of impulse.
- PROPOGATION
- SYNAPSE
- Physiology
- Mitochondria
- energy used to regenerate neurotransmitters
- synaptic knob
- presynaptic membrane
- synaptic vesicles
- cleft
- postsynaptic membrane
- Mitochondria
- Transmission
- chemical rather than electrical
- depolarisation reaches the synaptic knob
- causing Ca+ channels to open and a influx of Ca+ ions
- causing synaptic vesicles to fuse with the presynaptic membrane and empty contents into cleft
- neurotransmitter diffuse across the cleft and bind with receptor sites.
- when both receptorsites per sodium gated ion is filled, the gate opens.
- causing an influx of sodium ions into the post-synaptic membrane
- depolarising the next dendron!
- causing an influx of sodium ions into the post-synaptic membrane
- when both receptorsites per sodium gated ion is filled, the gate opens.
- neurotransmitter diffuse across the cleft and bind with receptor sites.
- causing synaptic vesicles to fuse with the presynaptic membrane and empty contents into cleft
- causing Ca+ channels to open and a influx of Ca+ ions
- Neurotransmitters
- noradrenaline and acetylcholine
- acetylcholine breaks into
- ethanoic acid
- acetyl
- by cholinesterase
- acetylcholine breaks into
- broken down in teh synaptic cleft and diffuse back into pre-synaptic knob
- ATP is needed to join components together and package them into esicles
- this prevents
- merging of impulses
- limits the effect of an action potential
- this prevents
- ATP is needed to join components together and package them into esicles
- ORGANOPHOSPHATE FERTILISERS
- imitate action of neurotramsitter
- keeping sodium gated ions open and prolonging effect of impulse
- could also inhibit enzyme action e.g. cholinesterase
- at a neuromuscular junction-repeated firings could lead to a twitch
- imitate action of neurotramsitter
- noradrenaline and acetylcholine
- Functions
- act s as a juntion- vesicles only in pre-synaptic membrane
- one direction impulse
- filters out low level stimli
- protects from over stimulation
- conveys impulse from one neurone to the next
- act s as a juntion- vesicles only in pre-synaptic membrane
- Physiology
- The nervous system
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