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
Is GABA excitatory or inhibitory?
Inhibitory
Is glutamate excitatory or inhibitory?
Excitatory
What allows rapid release of neurotransmitter from the presynaptic terminal?
Some vesicles containing neurotransmitters are already docked at the membrane
What happens when an action potential reaches the presynaptic terminal?
- Depolarisation of the membrane
- Ca2+ influx through voltage gated channels
- Triggers a conformational change in SNARE proteins
- Vesicles fuse with the presynaptic membrane
- Neurotransmitter release
What is an EPSP?
Excitatory postsynaptic potential:
- A TEMPORARY increase in the membrane potential in the post synaptic neuron
What can occur if there is enough EPSPs?
May change the membrane potential in the postsynaptic membrane high enough and trigger an action potential
What 2 ways can an action potential occur in the post synaptic membrane?
Spatial summation
Temporal summation
What are the 3 types of glutamate receptors?
Are these ionotropic or metabotropic?
NDMA
AMPA
Kainate
Ionotropic
What ions pass through AMPA receptors and how is this different to NDMA receptors?
AMPA: Na in and K out
NDMA: Na and Ca in and K out
Which glutamate receptors are important in triggering LTP and LTD?
NDMA receptors
What is an IPSP?
What neurotransmitter can trigger this?
Inhibitory post synaptic potential
Triggered by GABA
What receptor is usually present on a postsynaptic membrane, which triggers an EPSP?
Which ion is this channel permeable to?
GABAa receptor
Permeable to Cl
What happens to the postsynaptic membrane during an IPSP?
What does this result in?
In is HYPERpolarised
Making is HARDER for an action potential to occur
What determines if an action potential occurs in a postsynaptic neuron?
The balance between all the EPSPs and IPSPs
