Nerves summary

i separated communication & homeostasis and nerves into two different summaries for some reason, but here's nerves in pdf!

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  • Created by: amehlia
  • Created on: 21-04-16 20:49
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Amelia Kirk
Nerves Summary
Sensory Receptors
Receptors: detect stimuli
Effectors: respond to a stimulus, communicate w/ effectors via the nervous system
Survival: responding to change (a stimulus)
The Parietal Lobe - figures out messages received from 5 senses, damage can result in a lack of
- neurones surrounded by a myelin sheath (fatty sheath) that insulates the neurone from the
electrical activity of nearby cells
- myelin sheath is made up of Schwann cells
- gaps between Schwann cells are called nodes of Ranvier
- dendrites connect to other neurones
Sensory neurone: transmit nerve impulses from a receptor to the CNS
Motor neurone: transmit nerve impulses from the CNS to an effector such as a muscle or gland
Interneurone: transmit nerve impulses between neurons, for example between a sensory & a motor
Generating nerve impulses
- cell membranes in neurones have specialised channel proteins specific to sodium & potassium
ions, called sodium/potassium pumps
- have voltage gated sodium channels which can open & close
Resting Potential - neurones at rest
- 3Na+ transported out of cell for every 2K+ transported in
- inside of cell relatively more negative than the outside
- cell membrane is said to be polarised
- this is called a resting potential

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What causes the resting potential: at rest, Na+/K+ ion pump uses ATP to move 3 sodium ions out
for every 2 potassium ions that enter, plasma membrane is more permeable to potassium ions
(because of some open potassium ion channels) so many potassium ions diffuse out of the cells
again, cytoplasm also contains large anions (-ve charge) & attract potassium ions in
Action potential - when the neurone is stimulated
- gate can open/close the channel to sodium ions (usually closed in resting cells)
-…read more

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Nerve juntions
Synapse: junction between two or more neurones
Cholinergic synapse: synapse using acetylcholine as a neurotransmitter
Presynaptic membrane
- synaptic knob (bulb): swelling at end of presynaptic membrane
- synaptic knob contains: many mitochondria, smooth ER, vesicles containing acetylcholine,
voltage gated calcium ion channels in the membrane
Transmission across the synaptic cleft
I. An action potential arrives
II. Calcium ion channels open
III. Vesicles containing acetylcholine move to the presynaptic membrane
IV.…read more


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