AP Psychology - 1.7

Biology

In the early 1800s phrenology (studying bumps on skull) was popular tool for determining a person's mental abilities and character traits
- In fairness this 'science' did lead to the study of localization of function - the idea that various brain regions have particular functions

Neural Communication

Neurons - neural cells specially designed to share information electrochemically with other neurons

Cell body - the cell's nucleus and life support center; AKA Soma

Dendrites - fibers that receive and integrate information, conducting it toward the cell body

Axon - the cell's single lengthy fiber that passes messages through its branches to other neurons

As much as home electrical wire is insulated, a segmented layer of fatty tissue called myelin (or myelin sheath) insulates the axons of some neurons and helps speed their impulses.
- As myelin is laid down up to about age 25, neural efficiency, judgement, and self-control increases.
If the myelin sheath degenerates, multiple sclerosis results - meaning communication to muscles slows, with eventual loss of muscle control.
Supporting these billions of nerves cells are glial cells
- They provide structure, 'insulating' myelin, communication, and mop up neurotransmitters.

The Neural Impulse

Neurons transmit messages when stimulated by our sense or by neighboring neurons

Action potential - neuron sends a message by firing an electrical impulse down its axon

Most neural signals are excitatory; they transmit the flow of information to make an action potential
Nut some are inhibitory; they regulate the activation of excitatory signals
If excitatory signals exceed inhibitory signals by a minimum intensity (threshold), the combined signals trigger an action potential
Neurons fire in an all-or-none fashion.. (think of it like a gun - it fires or doesn't)
Into is sent from the axon terminal of one cell to the dendrite of another, but it must cross the synapse (gap/junction between the two cells)
The messages are sent from the axons across the synapse through the release of neurotransmitters (specialized biochemical messages stored in sacs in the axon terminal); NTs
Excess neurotransmitters are reabsorbed by the sending neuron, or drift away and are broken down by the body's enzyme

Reuptake - a neurotransmitter's reabsorption by the sending neuron

Examples of Various Neurotransmitters

Acetylcholine:

involved in control of muscles & memory
- Myasthenia gravis is a disorder in which the immune system make antibodies that block ACh receptor sites - with fewer receptor sites, the muscles receive fewer signals and become weak

Dopamine:

involved in reward/pleasure/emotion, motor behavior, & attention
- Undersupply -> Parkinson's disease
- Oversupply -> contributes to psychological disorders like Schizophrenia

Serotonin:

Norepinephrine:

Endorphins:

Substance P:

GABA (gamma-aminobutyric acid):

Inhibitory neurotransmitter; increases tranquility
- Undersupply -> linked to seizures and insomnia

Glutamate:

Involved in learning and memory
- Oversupply -> can cause impulsive behavior; can overstimulate the brain thus producing migraines or seizures, which is why some people avoid MSG (monosodium glutamate) in foods

How Drugs and Other Chemicals Alter Neurotransmitters:

The body produces natural chemical substances that are similar or many of the drugs that affect the body. When we introduce a drug, we are either increasing the amount of these substances or we are blocking substances that are supposed to work in a certain way

Agonist - molecule that mimics/increases a neurotransmitter's action

Antagonist - molecule hat inhibits/blocks a neurotransmitter's action

Reuptake Inhibitors - molecules that attach to an axon, blocking reabsorption; build up causes more action potential