Last updated: September 24, 2021

Class 14: Communication in the Nervous System

Each of the questions below relate directly to the question of how the nervous system actually communicates when it is working.
[snort] [runners] Wounded Soldier 

  [MS]  [Nerve Gas]  [No-L-ITA]

1. Nervous Tissue: The Basic Hardware

The basic "nerve cell" is call a neuron

The Neuron

Glia (="Glue")

glial cells

2. The Neural Impulse: Using Energy to Send Information

The Neuron at Rest = A Tiny Battery
[Resting Potential]

The Action Potential => Movement of Ions In/Out of Neuron

Here is an excellent YouTube video (#013 A Review of the Action Potential from Interactive Biology) that reviews what I've described above. (Note: In this video, the commentator talks about the depolarization going to +40 mV. That specific number is at the low end of what is reported in research studies. I more often see the figure of +50 mV. He also uses the value of -55mV as the threshold of excitation, that is, when the action potential begins; that is a higher number than I usually see. These specific differences are not very important.)

All-or-None Law

All or Nothing Domino Effect

3. The Synapse: Where Neurons Meet

The Synaptic Cleft
4. Neurotransmitters and Behavior
A. Acetylcholine (Ach)

    Motor neurons and muscles
    Attention, arousal & memory
    Can be mimicked by Nicotine (AGONIST = molecule which fills slot & causes neuron to fire)
    Too little Ach in Alzheimer's disease
B. Monoamines

1. Dopamine (DA)
  • Motor control: loss of DA = Parkinson's Disease
  • Both an increase in pleasurable emotions and a sense of wanting/urgency (salience) in the "reward pathway" in the medial forebrain bundle
  • Too much activity at DA receptors => associated with SCZ (schizophrenia)
  • Cocaine & amphetamines elevate activity at DA sites. High levels of DA associated with addictive disorders 
2. Norepinepherine (NE)
    Modulation of mood and arousal
    Cocaine & amphetamines also raise activity at NE sites
    Lowered levels may be related to depression
3. Serotonin (5-HT)
    Regulation of sleep & wakefulness, eating, aggression
    Low levels associated with depression, obsessive-compulsive disorder (OCD), eating disorders
    Prozac and other antidepressant drugs affect serotonin circuits
C. GABA & Glutamate (both amino acids)
1. GABA (gama-aminobutyric acid)
  • Produces only inhibitory PSPs
  • Serves to inhibit central nervous system
  • Regulates anxiety (too little GABA = increased anxiety)
2. Glutamate
  • Produces only excitatory PSPs
  • The major excitatory neurotransmitter in the brain.
  • Key component to memory via LTP (long-term potentiation) of sites that become permanently more excitable
  • Some sense that glutamate may also be involved in SCZ
[Pert &
                Snyder]D. Endorphins
  • Candace Pert & Solomon Snyder discovered endorphins
  • How does morphine (derived from opium) work?
    • Binds to receptor sites in brain and rest of body
    • Why? Body produces naturally-occurring opiate molecules
  • Endorphins = body own molecules - similar in effect & structure to opiates. These provide pleasure and relief from pain