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