Basic Structure of a (most) Neurons Dendrites ell body Axon

Basic Functional Parts of Neurons Not all neurons have this same general shape – e.g., in spinal ganglia

Neurons come in different shapes

Neurons normalky have a small electrical charge “Resting Membrane Potential” Time Voltage Display

Source of the Resting Membrane Potential (Because this quite technical , Feel free to not pay any attention to this slide) Specialized molecules pump ions into and out of the neuron (Na+ out, K+ in), yielding different concentrations of these ions inside vs. outside of the cell. In effect, the pump creates Na+ and K+ “batteries”. (A big part of the neuron energy demand) Specialized channels allow more or less of these ions to flow in (or out) of the cell, in effect “dialing in” more or less of each “battery”

Feel free to not follow the next two slides…

Membrane potential, Sodium (Na+) & Potassium (K+) Outside Outside (Outside) (Outside) Na+ Na+ K+ K+ RNa+ RK+ RNa+ RK+ -90 mV +40 mV K+ K+ Na+ Na+ (Inside) Inside (Inside) Inside

Source of the Resting Membrane Potential (Because this quite technical , Feel free to not pay any attention to this slide) Other ions also contribute, so it’s not as simple as just Na+ and K+… Equivalent electrical circuit: Membrane Potential +40 -90 -70

Okay – no more electrical circuits

How Neurons communicate (basically) If a neuron’s membrane potential gets sufficiently LESS negative (~ - 50 mV), this can trigger an “Action Potential” The Action Potential goes down the axon, and at the end (synapse) causes the release of chemicals onto the next cell The Action Potential is an “all or none” signal (i.e., the neuron can send only one size action potential) Those chemicals then either excite or inhibit that cell. “Excitatory” or “Inhibitoty Post Synaptic Potential”

“Integration” of excitatory inputs http://web.lemoyne.edu/~hevern/psy340_11S/lectures/psy340.03.1.synapse.outline.html

The best analogy for an action potential There is a threshold for triggering action It is self limiting It is “all-or-none” There is a minimum inter-flush interval If you flush too soon after previous flush you can get only a partial flush

Action Potential Propagation – like a burning fuse

How neurons ultimately send a signal – Synaptic Transmission http://commons.wikimedia.org/wiki/File:SynapseIllustration2.png

Neurotransmitters Glutamate – the major excitatory neurotransmitter in the brain GABA - major inhibitory neurotransmitter in the brain Acetylcholine - many different actions in the brain; neuromuscular junction transmitter Serotonin – many different actions; associated with mood, sleep, perception (LSD) Dopamine – many different effects; associated with reward, movement (PD) Opioid peptides (endorphins) – modulate pain signals Substance P – pain signaling Many others (adrenaline, noradrenaline, oxytocin…)

Summary of basic information processing in the brain Action Potential Synapse… Action Potential

Analogy of how neurons communicate

Physiological plasticity Synapses are not static: With repeated use can show “habituation” With intense use can become stronger (“long-term potentiation”) Simultaneous strong inputs can potentiate each other (“fire together, wire together”) Harris & Cotman, 1986

How neurons send a signal – The “Action Potential” http://neuroscience.uth.tmc.edu/s1/chapter01.html

But it’s not so simple - Excitation and Inhibition

Spindel Cells – aka “Von Economo Neurons” Constantin Alexander Freiherr von Economo von San Serff Constantin Economo von San Serff Constantin Freiherr von Economo Example of “Fork cell” found with VENs

Excitement about Von Economo Neurons Much early excitement at their re-discovery Originally found only in humans and great apes Then also found in dolphins, whales and elephants Implications in higher order social interactions!? Most recent evidence is that they are also found in: hippopotamus, cow, manatees, seals, sheep, deer, horse, pig, rock hyrax Still interesting because their numbers are reduced in early-onset schizophrenia, and behavioral variant of FTD in which empathy, social awareness and self- control are seriously compromised