1. Mind, Brain & Behavior Monday January 13, 2003

2. Interview with Rodney Brooks Human as machine, machine as human: http://www.aaai.org/AITopics/html/show.html http://www.aaai.org/AITopics/html/show.html http://news.bbc.co.uk/olmedia/cta/progs/02/hardtalk/brooks19aug.ram

3. Nerve Cells & Behavior Chapter 2 Pg 21-28

4. Two Kinds of Cells  Neurons (nerve cells) – signaling units  Glia (glial cells) – supporting elements: Separate and insulate groups of neurons Produce myelin for the axons of neurons Scavengers, removing debris after injury Buffer and maintain potassium ion concentrations Guide migration of neurons during development Create blood-brain barrier, nourish neurons

5. Neuronal Circuits  Neurons send and receive messages.  Neurons are linked in pathways called “circuits”  The brain consists of a few patterns of circuits with many minor variations.  Circuits can connect a few to 10,000+ neurons.

6. Parts of the Neuron  Soma – the cell body  Neurites – two kinds of extensions (processes) from the cell: Axon Dendrites  All parts of the cell are made up of protein molecules of different kinds.

7. How Neurons Communicate  An electrical signal, called an action potential, travels down the axon. An action potential is an all-or-nothing signal. The amplitude (size) of the action potential stays constant because the signal is regenerated. The speed of the action potential is determined by the size of the axon. Action potentials are highly stereotyped (very similar) throughout the brain.

8. How to Tell Axons from Dendrites  Dendrites receive signals – axons send them.  There are hundreds of dendrites but usually just one axon.  Axons can be very long (> 1 m) while dendrites are < 2 mm.  Axons have the same diameter the entire length – dendrites taper.  Axons have terminals (synapses) and no ribosomes. Dendrites have spines (punching bags).  Don’t be fooled by the branches – both have them.

9. Ramon y Cajal’s Principles  Principle of dynamic polarization – electrical signals flow in only one, predictable direction within the neuron.  Principle of connectional specificity: Neurons are not connected to each other, but are separated by a small gap (synaptic cleft). Neurons communicate with specific other neurons in organized networks – not randomly.

10. Ways of Classifying Neurons  By the number of neurites (processes): Unipolar, bipolar, multipolar  By the type of dendrites: Pyramidal & stellate (star-shaped)  By their connections (function) Sensory, motor, relay interneurons, local interneurons  By neurotransmitter – by their chemistry

11. Parts of the Soma (Cell Body)  Nucleus – stores genes of the cell (DNA)  Organelles – synthesize the proteins of the cell  Cytosol – fluid inside cell  Plasmic membrane – wall of the cell separating it from the fluid outside the cell.

12. Organelles Mitochondria – provide energy Microtubules – give the cell structure Rough endoplasmic reticulum – produces proteins needed to carry out cell functioning Ribosomes – produce neurotransmitter proteins Smooth endoplasmic reticulum – packages neurotransmitter in synaptic vesicles Golgi apparatus – Part of the smooth endoplasmic reticulum that sorts proteins for delivery to the axon and dendrites

13. Kinds of Glia  Oligodendrocytes – surround neurons and give them support. In white matter, provides myelination In gray matter, surround cell bodies  Schwann cells – provide the myelin sheath for peripheral neurons (1 mm long).  Astrocytes – absorb potassium, perhaps nutritive because endfeet contact capillaries (blood vessels), form blood-brain barrier.