PSYC 415 -- Study Points for Neurons (revised 18 Aug 2020)

Information Processing in the Nervous system

I. to be useful your brain must
    A. receive information from the environment - sensation
    B. process this information - perception
    C. think about it - cognition
    D. decide on a course of action - decision making
    E. send commands out to muscles and glands - create behavior

II. neurons - the information processing cells of the nervous system
    A. neurons are little electrical devices
    B. they must
        1. receive input from other neurons
        2. process that information and decide on output
        3. send output to other neurons
    C. a typical (multipolar) neuron
        1. dendrites - receive input from other neurons and sensory recepptors
        2. nucleus - contains the genetic material (for the most part, a
           neuron has the same organelles as any other cell you've learned
           about in biology classes)
        3. cell body
        4. axon - a specialized structure for transmitting nerve impulses
           over distances up to six feet (in the human nervous system,
           farther in giraffes and whales)
        5. myelin sheath - insulates the axon and increases conduction speed
           (not actually part of the nerve cell but contributed by glial cells)
        6. terminals - occur where the neuron passes info to other neurons at
           synapses
    D. pyramidal neurons in the cortex - primary output neurons of the cortex
    E. neurons are electrically polarized - which means a voltage can be
       measured across the membrane due to a separation of electric charges
        1. resting potential - about 70 mV negative inside when the cell is
           not doing anything
        2. graded potentials - small, variable voltage changes that can only
           be propagated for short distances (2 or 3 mm)
        3. action potentials - large, all-or-none voltage changes on the axon
           responsible to transmitting info over long distances
    F. changes in the membrane potential are caused by movement of charged
       particles across the membrane (ions, mostly sodium and potassium,
       sometimes chloride)
    G. excitatory vs. inhibitory changes
        1. excitatory - movement of sodium into the cell
        2. inhibitory - movement of potassium out of the cell (or somethings
           chloride into the cell)

III. neural transmission
    A. activity occurs at synapses on the dendrites or cell body
    B. causes excitatory or inhibitory changes on the membrane
    C. these changes propagate (move) along the dendrites and cell body as
       graded potentials (which can't go far)
    D. when the reach the axon, they either increase or decrease the rate at
       which the axon is firing action potentials
    E. action potentials can propagate along the entire lenght of the axon
       without dying out
        1. information is encoded in the rate at which action potentials are
           being fired - the rate law
        2. when they reach the terminals they depolarize the terminals causing
           a release of neurotransmitter

IV. synapses
    A. action potential arrives
    B. terminal is depolarized by influx of calcium ions
    C. calcium triggers the release of neurotransmitter
    D. neurotransmitter binds to receptors on the postsynaptic membrane
    E. this causes opening of ion channels on that membrane
    F. if these are sodium channels, this is an excitatory effect that increases
       the rate at which the axon of the cell will fire action potentials
    G. the neurotransmitter is inactivated, usually by being transported back
       into the terminal - reuptake

V. neurotransmitters - chemical substances released by the terminal
    A. glutamate - the primary excitatory neurotransmitter in the brain
    B. GABA - the primary inhbitory neurotransmitter in the brain
    C. serotonin, dopamine, norepinephrine, acetylcholine, and many others are
       modulatory (i.e., the increase or decrease the excitability of the cell)
    D. acetylcholine is the primary excitatory neurotransmitter in the
       peripheral nervous system
    
VI. drugs work by modifying the activity of neurotransmitters at the synapse
    A. amphetamine - stimulates the release of dopamine and norepinephrine
    B. cocaine - prevents the inactivation of dopamine
    C. antipsychotics block dopamine receptors
    D. antidepressants prevent the inactivation of serotonin
    E. tranquilizers increase the activity of GABA

VII. glial cells
    A. there are about 10X as many glial cells as neurons
    B. they contribute the myelin sheath
    C. they contribute to the blood-brain barrier
    D. they are key components of the brain's immune system
    E. they form scar tissue at injured spots

VIII. demyelinating diseases
    A. multiple sclerosis (MS)
    B. vitamin B12 deficiency
    C. tabes dorsalis due to untreated syphilis
    D. progressive multifocal leucoencephalopathy
    D. optic neuritis

IX. disease involving changes in neurtransmitter activity
    A. myasthenia gravis - acetylcholine
    B. Parkinson's disease - dopamine
    C. excitotoxicity - glutamate
    D. epilepsy, depression, schizophrenia, OCD, and others

X. blood-brain barrier
    A. tight junctions between cells that make up the capillaries
    B. astrocytes (glial cells) plastering blood vessels with end feet
    C. prevents blood-borne toxins and pathogens from entering the brain
    D. various diseases result when the BBB breaks down

XI. ion channel poisons - can shut down the entire nervous system
    A. tetrodotoxin - from the Japanese puffer fish (and other sources)
    B. it cannot be used to create zombies!