evolution of neuroscience theories Flashcards
three disproven theories of how neurons/NS work
- Sprits running through hollow nerve fibres, conveying impressions to
the brain and activating muscles - Mini explosions caused by fermentation upon the mixing of fluid
droplets from the nerve ends and blood, activating muscle - Vibrations, light of different energies transferred vibrations to nerves,
conveying sensations to the brain
what disproved previous theories
limbs do not
increase in volume when muscles are activated. Nerves cut underwater did
not result in bubbling ferment. Ligation of nerves did not cause them to
accumulate fluid, and it was suspected that fluid of any sort could not move
fast enough to explain the speed of nervous system function.
experimental proof for nerves using electrical signals
Galvani - showed spark jumping onto nerve can cause muscle contraction
Aldini - activated facial muscles by stimulating brain of severed heads
Now we can use glass electrodes to measure electrical transmission
what observations supported the existence of a junction as opposed to fusion between neurons before synapses were able to be seen?
- degeneration of the nervous system always resulted in a discrete, demarcated pattern of loss (rather than diffuse).
- The reflex responses which he was studying were much slower than was explicable by the speed of nerve conduction (there was a delay somewhere)
- Something makes reflex conduction unidirectional
hippocrates view
brain is responsible for intellect & mental experiences
aristotle view, timeline & justification
POST hippocrates
cardiocentric view
Reasons:
1. heart moves, brain doesnt
2. warmth (& therefore life) emenates from the heart
3. simple animals w no brain can move & react
galen view & timeline
POST hippocrates
Believed in brain as seat of intellect but also in the humours of the body (instinct = liver, passions & living = heart)
Discovered the ‘third system’ -> nerves
