Neural Activity 2

Action potential

Hyperpolarisation

Increased polarisation across membrane

Depolarise

Reduce polarisation toward zero across membrane (+40mV)

Threshold

minimum amount of membrane depolarisation necessary to trigger action potential (-55mV)

Resting State

- 40mV

Myelin Sheath

Saltatory conduction

Refractory Period

time when cell resists production of further action potential

Relative Refractory Period

Time after absolute refractory period that requires stronger stimulus to initiate action potential

Absolute Refractory Period

Unable to produce action potential

Synapse Steps

1. AP arrives at synapse

chemicals stored in vesicles of pre-synaptic terminal

Opens calcium ions

Calcium evokes release of neurotransmitter into cleft

2. increased calcium lets synaptic vesicles fuse with terminal membrane

3. neurotransmitter released into synaptic cleft

4. neurotransmitter bins on ligand gated ion channels

5. post synaptic ion channel results in EPSP or IPSP

Excitatory post synaptic potential

Depolarisation

Inhibitory post synaptic potential

Hyperpolarisation

Properties of Synapses

Temporal Summation

Cumulative effect of repeated stimuli within brief time

Spatial Summation

Combination of effects of two or more synapses into single neuron

Channels & Pumps

Ligand Gated channel

Active transport pump

sodium-potassium pump

Transports sodium out of the cell and potassium into the cell.

Gap junctions

Voltage-gated channels

Neurotransmitters and Receptors

Ionotropic receptors

Receptor binding immediately opens ion channels

Glutamate receptor (NMDA & AMPA)

ESPS

Depolarises neuron from influx of positive ions causing action potential

GABA receptor

ISPS

Hyperpolarisation of neuron from influx chloride

Metabotropic receptors

Activation of second messanger without opening channel

Activation of G-protein.