Class 15: Communication in the Nervous System (Outline)

   

• Why does cocaine (and "speed" [= methamphetamine]) make some people feel very euphoric and some people very crazy?

• Why do some runners report that they feel extraordinarily good after a very long run?

• Why do soldiers in war who have been wounded sometimes not actually realize they've been hurt?

     

• What is multiple sclerosis? What is Parkinson's disease?

• During the 1980s, the Iraqi Army under the command of Saddam Hussein used nerve gas regularly in suppressing civil war and against the Kurds and the Iranian Army. Similarly the Syrian Army used nerve gas (a chemical weapon) against women and children during the civil war between 2013 and 2018. Why do nerve weapons kill many of the people who breathed the gas?
  

• How are eating disorders possibly related to some types of suicidal acts?

 

1. Nervous Tissue: The Basic Hardware

Neuron

Glia (="Glue")

How does the nervous system transmit signals or information? It uses two methods:

• Electrical signals along the neuron's axon, and
• Chemical signals transmitted from a neuron's terminal button at the end of the axon across a tiny gap (= the synapse) to receptors on the dendrites of other neurons
  

2. The Neural Impulse: Using Energy to Send Information

A. The Neuron at Rest = A Tiny Battery

Outside and inside the neuron's membrane (wall), there are three major kinds of ions, that is, atoms that have an electrical charge:

• Sodium = Na+ (a positively charged ion)
• Potassium = K+ (a positively charged ion)
• Chlorine = Cl- (called "cloride" - a negatively charged ion)

• Resting potential = "a neuron's stable, negative charge when the cell is inactive"

• Resting Potential of the Neuron = -70mV

 

B. The Action Potential = Movement of Ions In/Out of Neuron

• Action potential = "a very brief shift in a neuron's electrical charge that travels along an axon"
  

• Threshold of Excitation @ -40mV
• Depolarization (move from -70mV to +40/50 mV)
• Repolarization (move from +40/50 mV to -90 mV)
• Hyperpolarization (when the voltage goes below -70mV)
• Absolute Refractory Period
• Here is an excellent YouTube video (#013 A Review of the Action Potential from Interactive Biology)  

C. All-or-None Law

3. The Synapse: Where Neurons Meet

• Synaptic Cleft

• Synaptic Vesicles

• Neurotransmitters

• Receptor Sites (on dendrites of Neuron 2)
  

• Re-uptake channels (on Neuron 1)
  

• PSP (Post-synaptic potentials) within Neuron 2
  

• Excitatory
• Inhibitory

• Integrating signals in neural networks
  
• neural networks sculpted by elimination of old synapses = synaptic pruning

4. Neurotransmitters and Behavior

A. Acetylcholine (Ach)

B. Monoamines

1. Dopamine (DA)
2. Norepinepherine (NE)
3. Serotonin (5-HT)

C. GABA & Glutamate (amino acids)

1. GABA (inhibitory PSPs)
2. Glutamate (excitatory PSPs)

C. Endorphins