1. Introduction to Cognitive Neuroscience Topic 2: The Nervous System

2. Neurons: The rock stars of the nervous system  Santiago Ramon y Cajal  The father of modern neuroscience  Did extensive study of neuronal structures

3. Neurons: the rock stars of the nervous system  2 types of nerve cells  Neurons (transmit signals)  Glia (provide support and structure; repair  2 types of “brain matter”  Grey matter – neuronal bodies (soma)  White matter - axons

4. Neuron Structures  Soma = body  Nucleus (all cells have it) inside soma  Axon  Terminal Bouton (axon terminal)  Dendrites  Myelin Sheath (composed of Schwann cells)

5. How do neurons communicate?  Axon meets dendrite  The space between the axon and dendrite is called the SYNAPSE  The neuron SENDING information is called the presynaptic neuron (because it is BEFORE the synapse)  The neuron RECEIVING information is called the postsynaptic neuron (because it is AFTER the synapse)

6. How do neurons communicate?  Electrical signals  Action potential  Chemical signals  Neurotransmitters

7. How do neurons communicate?  The lipid bilayer  Vesicles  Vesicles bind to the terminal bouton (the axon terminal) and NTs are released into the synapse  The NTs are taken up by receptors on the postsynaptic neuron – they tell the next neuron what to do

8. How do neurons communicate?  Action potentials  Electrical signals that travel down the axon to stimulate the release of NTs  When a neuron is not sending a signal, it is “at rest.” This is called the resting potential.  Resting potential is at about -70 mV (millivolts)  Action potentials are caused when different ions permeate the cell membrane  Na+ Cl- and K+

9. How do neurons communicate?  The process of an action potential 1. Stimulus – may be chemical or electrical 2. Ion pumps open and change the polarization of the cell 3. The cell hyperpolarizes past the threshold level (typically around +30 - +40 mV 4. This causes a wave of hyperpolarization down the cell (through the myelin sheath; nodes of Ranvier) 5. When the AP reaches the axon hillock, NTs are stimulated to be released 6. NTs travel to post-synaptic cell; depending on the type they may stimulate or suppress another AP

10. How to neurons communicate?  The myelin sheath  Composed of Schwann Cells  A special type of Glial cell, primarily located in the PNS  These coat the axon and allow potentiation to “jump” down the axon  The un-myelinated regions are called the Nodes of Ranvier  Demyelination is thought to be a primary contributor to dementia (Alzheimer’s disease) and Multiple Sclerosis (MS)