Lecture 1

Lecture 1

1. Aspects of movement

   • Humans vs. animals
     • Unique use of hands
       • General specialists
     • Planning on a spectrum
     • Wolpert (2010)
       • All memory, cognition, sensory processes for movement
   • Psychological
     • Sensation
     • Learning/memory
     • Action-perception interaction

2. Neuronal membranes

   • Phospholipid bilayer
   • Protein channels
     • Over half membrane
     • Leakage
     • Voltage-gated
     • Ligand-gated
     • Second messenger operated
       • Transmembrane G-protein
     • Mechanosensitive
     • Na/K pump
       • 3 Na out, 2 K in Na bind to high affinity sites Aspartic beta-carboxylic acid residue is phosphorylated Na released, opens K sites K binds, causes dephosphorylation K released
       • Can reverse
       • Count with radioactive ouabain
   • Ion movement across
     • Determined by
       • Concentration gradient
       • Electrical potential difference
     • Equilibrium
       • Nernst equation
         • E_k=(RT/zF)×ln[K_o/K_i ]
         • K hypothesis
           • Bernstein
           • Resting potential
           • Hogkin and Huxley
           • Minor Na leakage
         • Equilibrium potentials
           • K = -90mV
           • Na = +55mV
     • Na
       • Overton
         • Action potential peak not 0
       • Voltage clamp technique
   • Resting potential = -65mV
     • Polarised

3. Action potentials

   • 1. Sensory input, some Na leaks in
   • 2. Reach threshold, opens channels, Na influx
     • Depolarisation
     • +15mV
   • 3. +50mV, action potential
   • 4. Na channels close when positive, delayed rectifier K channels open
   • 5. Hyperpolarisation
     • Both leakage and delayed rectifiers open
   • Uni-directional conduction
     • Refractory period
       • Hyperpolarisation
     • Self-replicating wave of local currents
       • Depolarisation = sink of current
   • Conduction velocity
     • Determined by
       • Membrane resistance
       • Capacitance
       • Internal axon resistance
     • Myelination
       • Schwann cells
       • Increased resistance, decreased capacitance
       • Saltatory conduction
       • Multiple sclerosis

4. Neuromuscular junction

   • Easy to isolate
   • Synapse
     • Presynaptic neuron
     • Synaptic cleft
     • Postsynaptic motor endplate
     • Chemical transmission
     • Acetylcholine
   • Chemical transmission
     • Dale's criteria
       • 1. Synthesis enzymes present presynaptic
       • 2. Substance released with activity
       • 3. Substance activates postsynaptic receptors
       • 4. System for removing substance
       • 5. Pharmaceutics can prevent each stage
     • Electrical resistance high
     • Neurotransmitters

5. Methods to record neuronal activity

   • fMRI
     • Blood oxygen level
       • Most activity = most change
   • Single cell
     • Invasive
     • Raster plots
     • Alternatives
       • Single muscles
         • EMP
       • Neuron populations
         • EEG
       • Neurotransmitters
         • PET
   • MRI
     • Imaging technique
     • Low spatial/temporal resolution
   • Correlational