Main Theory:

The human nervous system consists of billions of individual nerve cells called neurons.

There are more possible ways in which the neurons in a single human brain can be interconnected than there are atoms in the known universe.

Neurons are:

• The basic unit of the nervous system

• A cell that conducts electrochemical signals

• Highly specialized cells of the nervous system that respond to stimuli and transmit impulses from one body part to another

You DO NOT necessarily need to know the parts of a neuron but it’s good to know the names:

• Dendrites

• Cell body (soma)

• Axons

• Myelin sheath

• Axon terminals

Grey matters are cell body + dendrites

White matter is a bundle of axons

Dendrites

• Thin extensions of a neuron that receive information from other neurons

• Mature neurons generally can't divide, however, they can grow new connections to other neurons, which is the basis of learning.

Cell body (soma)

• Contains the nucleus, containing the genetic information of the cell, as well as other structures vital to its functions.

Axons

• Sends information away from the cells body, to other neurons, or to the muscles and glands.

Myelin

• A white protective sheath that insulates the axons

• Not present on all neurons

• When present helps spreading the transmission.

Axon terminal

• Extension of the neuron that conducts messages away from the cell

• There is a gap separates the axon terminals from dendrites

• The gap is called a synapse

Neurons send messages from one cell to another through the release of chemicals called neurotransmitters.

Dendrites have receptor sites, which only react to neurotransmitters that fit. If enough neurotransmitter is received, then the next neuron will fire (called an action potential).

• If the neurotransmitter doesn't fit in the receptor, it wouldn't cause an impact.

• A dendrite can receive messages from different types of neurotransmitters.

• If it can't receive the message, reuptake will occur and take them back or enzymes will clean it up.

• Like a key in a lock, a neurotransmitter's shape must precisely match the shape of the receptor site on the postsynaptic neuron's dendrites for the neurotransmitter to have an effect on that neuron.

Neurotransmitters exert one of two basic effects on neurons.

• Excitatory post synaptic potential (epsp)

  • If the neurotransmitter is excitatory it increases the likelihood that a nerve impulse will occur.

• Inhibitory post synaptic potential (ipsp)

  • In contrast, if the neurotransmitter is inhibitory its effects decrease the likelihood that a nerve impulse will occur.

• Action potential is the electro part

• Neurotransmitter is a electrochemical process

• Neurotransmitters can be recycled by protein

• Every neuron have a threshold needed to reach before they are fired

• If it exceeds the threshold then action potential will start the action potential

Drugs pretend to be a neurotransmitter

• Drugs are neither excitatory nor inhibitory.

• Drugs are either agonist or an antagonist.

• They are always exogenous, as they were externally created.

• Drugs impact the neurotransmitter which causes a change in behavior, emotion, and cognition.

• Agonist will enhance the neurotransmitter's impact, it stimulates the neurotransmitter's activity. Think of it as a buff. It amplifies the nature of the original neurotransmitter.

• Antagonist will calm the neurotransmitter's impact, it will decrease the neurotransmitter's activity. Think of it as a nurf.

• Excitatory enhances the chance of the neuron firing and inhibitory decreases the chance of them firing.

• Neurons can receive both excitatory and inhibitory neuro impulses.

All neurotransmitters are endogenous agonists.

The function of neurotransmitters:

Neurotransmitters are released from the terminal buttons.

They fit into receptor sites on the post-synaptic membrane. Neurotransmitters are agonists.

Neurotransmitters can either excite a neuron- these are called excitatory neurotransmitters, or they can inhibit a neuron - these are inhibitory neurotransmitters.

Excitatory neurotransmitters: make the next neuron more likely to fire.

Inhibitory neurotransmitters: make the next neuron less likely to fire.