Lecture 1- Introduction

Lecture 1- Introduction

1. Nerves

   • Comminication over long distances
   • send signals along branches using changes in membrane potential
     • change in voltage means change in signal
     • change in membrane voltage by change in membrane permeability
       • voltage gated ion channels
         • only letting +vely charge sodium ions through when voltage of membrane is a specific voltage
           • change in action potentials = +ve feedback change in permeability
             • more -ve instead at resting, Na+ high conc outside so diffuses in bringing +ve charge,
               • charge onside goes up, opening more gates letting more Na+ in
                 • potassium gates open slower, which let out potassium out of the cell
                   • bringing it down to negative
                     • waves are unidirectional because of over polarisation
   • nerves are electo chemical signaling devices

2. Neurones

   • Synapes
     • specialised for integration and modulation of signals.
     • changes underlie learning and mem
   • Dendrites recieve, axons send else where
   • they arent important by the selves, only groups of neurones
   • they use electricity to transmit signals

3. myelination

   • white matter - myelinated axons
     • grey matter - cell bodies, synapses and non myelinated axons
       • myelin sheeth takes up space so not all neurones have them

4. the synapse

   • connection between 2 neurones
     • pre-synaptic actional potentials increase membrane pot.
       • influx of Ca+
         • vesicles fuse with membrane and release their contents (NT)
           • neurotransmitters diffuse across the gap and bind to post synatpic receptors
             • generate post synaptic potentials
   • neuromusclar junction
     • specialised nerves "Alpha" motor neurones connect to muscles
     • Muscles are excited to contract by motor neurones at the neuromuscular junction (NMJ)

5. measuring cell activity

   • EMG - Electrical skin discharge from single musclee through skin
   • EEG
     • - largely driven by the post-synaptic potentials, not by action potentials • - tiny signals so need to average across many trials • scalp conduction blurs spatial resolution
   • PET - chemical changes (Ca+ or NTs
     • PET and MRI
       • spatial resolution limited by local changes in blood supply, less than 5 mm • temporal resolution low (> 5s) • need to average a few (10) cycles of each behavioural condition • but, luckily, brain function is localised • can see the network of activity across the whole brain
   • single cell recording
     • invasive and rare in humans
   • fMRI
     • local changes in blood oxygen levels • brain energy consumption is largely spent on synaptic processes • BOLD reflects local processing, not the output of that region
   • "Raster Plots"
     • behaviour and rate coding of a single cell
       • • Individual trials showing each action potential (and stimulus onset) • Averaged activity across trials