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What is a nerve?
A bundle of axons, myelin and small blood vessels encased in tissue
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Label this
- 1: Soma (cell body)
- 2: Dendrites
- 3: Myelin Sheath
- 4: Axon (within the myelin sheath)
- 5: Direction of the action potential
- 6: Terminal Buttons
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What are microglia?
Act as the immune system of the CNS
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What are astrocytes?
- Non-excitable cells
- Maintain the local ionic environment
- Provide metabolites to neurones
- Modulate synaptic efficacy
- Link neurones to blood supply
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What do neuroglia do?
Provide physical support, control nutrient flow, and are involved in phagocytosis
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What do astrocytes do?
- Provide physical support
- Remove debris (phagocytosis)
- Transport nutrients to neurones
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What do oligodendrocytes do?
Provide physical support and form the myelin sheath around axons in the brain
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What do schwann cells do?
Form myelin
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How do electroencephalograms work?
Electrodes infer neural activity by measuring electrical signals produced by neurones
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How do electrocorticograms work?
Same as EEG, but the electrodes are put on the exposed surface of the brain
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How do local field potentials work?
- Spike is implanted into the brain
- Use this to measure electrical signals from nearby neurones
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What voltage constitutes depolarisation?
- Less than -70mV
- Vice versa for hyperpolarisation
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What is an ion?
A molecule that has lost or gained one or more electrons
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What is the difference between a cation and an anion?
- Cations have lost electrons, so are positively charged.
- The opposite is true for anions
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What is a salt?
- Solid substances made of ions
- Always have equal numbers of positive and negative charges (Na+Cl-)
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What are the most important cations (and where do they live)?
- Na+ (mostly extracellular)
- K+ (mostly intracellular)
- Ca2+(almost exclusively extracellular)
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What are the most important anions (and where do they live)?
- Cl- (mostly extracellular)
- Proteins, or An- (mostly intracellular)
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What is an electrical potential?
- The strength of the charge of particles surrounding ions
- This is slightly more negative intracellularly, so the resting potential of axons is slightly negative (-70mV)
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How is the resting potential maintained?
- Through the sodium potassium pump
- ATP is exchanged for the transport of 3 Na+ ions out, and 2 k+ ins in, establishing a concentration gradient for the latter
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Describe an action potential
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Why can fugu kill you?
- Contains tetrodotoxin, which prevents the opening of Na+ channels
- No more action potentials
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What happens when you get multiple sclerosis?
- It breaks down myelin sheaths and
- nerve impulses can no longer be transmitted effectively
- Causes a loss of muscle control, loss of sensation, problems with coordination, visual problems, loss of bladder control, cognitive impairments
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Do you remember synapses?
If not, review the slides
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What do excitatory neutrons do?
- Release glutamate
- Stimulates the opening of channels allowing for the entry of positively charged ions
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What do inhibitory neurones do?
- Release GABA
- Opposite as excitatory, let negatively charged ions in, leads to hyperpolarisation, and more difficulty reaching activation threshold
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