Introduction Flashcards
What 4 things does the nervous system do?
- Senses input
- Processes
- Reacts
- Memorises
Why does the nervous system need to process information
To decide if the input is important enough to fire action potentials
How does the nervous system ‘react’?
By executing a certain behavioural programme
As well as memorise, when must the nervous system be able to do?
Adapt to changes in the environment
What are 3 important behaviours of an organism?
Mating
Eating
Avoiding predators
What determines how the nervous system is organised?
Example?
Mating, eating, predators of the organism
Killer fly - eats drosophila - fast photoreceptors
Drosophila eats things that don’t move - slow photoreceptors
What is the resting potential of the neuron and why?
-70mV
Due to the selectivity of the membrane channels
Where is sodium high?
Outside the cell
Where is potassium high?
Inside the cell
Describe the action potential
Voltage gated Na channels open Membrane depolarises Membrane potential reaches a peak Na channels close VG K channels open - potential decreases
Undershoot - hyperpolarisation
What regulates the firing rate of the action potentials?
How?
Hyperpolarisation (undershoot)
Longer the undershoot, the smaller the firing rate
How does the action potential propagate along the axon?
As Na moves in through the VG Na channels - Na slightly diffuses away to neighbouring part of the axon
Causes this part of the axon to become slightly depolarised
How is the action potential propagated?
Through saltatory conduction:
- Jumping of the electrical impulse to the Nodes of Ranvier (where there is no myelin sheath)
What does the myelin sheath do around a neuron?
Increases conductance by improving the ‘leakiness’ of the membrane
Which neurons don’t have a myelin sheath and why?
Interneurons and neurons of the retina
They are too short
