NEUROTRANSMITTERS

NEURONS

Neurons don’t actually touch

Separated by a tiny fluid-filled gap called a

synapse

Neural impulses must be ferried across the

synapse by chemical messengers called

neurotransmitters.

NEUROTRANSMITTERS

Biochemical substances that are released into

the synaptic cleft to stimulate or suppress

other neurons.

Dozens of neurotransmitters have been

identified.

NEUROTRANSMITTERS

Contraction of muscles to move our bodies

Release hormones

Psychological states of thinking and emotions

NEUROTRANSMITTER

Each type of (NT) has a three-dimensional

shape.

NEUROTRANSMITTERS

The journey across the synapse takes only a

thousandth of a second.

NT

Changes have either an excitatory effect or an

inhibitory effect.

EXCITATORY

Green light: “yes”

Just do it!

Activates the next cell

Makes an action potential more likely to occur

How? hooked to a positive ion

channel….happens slowly

INHIBITORY

Red light

Just say no

Less likely that the cell would fire

Hooked on to a negative ion channel

NT

Some NT have only Excitatory effects

Some NT have only Inhibitory effects

Some NT have both

PREVENTING THE ENT FROM STIMULATING

A RECEIVING CELL

1. Reuptake: NT not taken up by the receiving cell are reabsorbed by their vesicles to be used again. Nature’s own version of recycling.

1. Enzymes: organic substances in the synapse break down NT, which are then eliminated from the body in the urine.

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3.Neuromodulators: terminal buttons release

these chemicals that either increase or

decrease the sensitivity of the receiving neuron

to NT.

NT

NT originate in the body

Drugs originate outside of the body.

DRUGS/CHEMICALS OUTSIDE OF THE BODY

Antagonists: drugs or chemicals that block the

actions of NTs by occupying their receptor sites.

Antagonists prevent transmission of the messages

carried by the NT

Compete with NTs at the same receptor sites

DRUGS/CHEMICALS

Agonists: drugs that either increase the

availability or effectiveness of NT or mimic their

actions.

5 NT THAT STUDENTS NEED TO KNOW

1. Acetylcholine (ACh): NT that enables motor

function in the body. Ex. Wiggle my fingers.

makes muscles contract (motor cortex)

Role in learning and memory.

If ACh transmission is blocked, the muscles

cannot contract.

ACH

Underproduction of ACh is an important factor in Alzheimer’s disease

Reductions in ACh weaken or deactivate neural circuitry that stores memories.

Absence: Paralysis

Oversupply: violent muscle contractions

Certain spider bites/Black widow

5 NT THAT STUDENTS NEED TO KNOW

2. Endorphins: natural chemicals released in the

brain that have pain-killing and pleasure-inducing

effects. Blocks pain.

Inhibitory NT

Located in the Brain, pituitary gland, and spinal cord.

“runners high”

Morphine and heroin are agonists since they mimic

the effects of endorphins.

5 NT THAT STUDENTS NEED TO KNOW

3. Serotonin: affects mood, hunger, temp regulation

and sleep.

Inhibitory or excitatory

Located in the brain stem, cerebellum, pineal gland,

and the spinal cord.

Undersupply may lead to depression, sleeping and

eating disorders.

Oversupply linked to OCD

SEROTONIN

Prozac acts as a agonist

Prozac elevates serotonin levels

Some other antidepressant drugs raise

serotonin levels

5 NT THAT STUDENTS NEED TO KNOW

4. Dopamine: influences body movement, learning,

attention, reward experiences, and emotion.

Located in the brain and the peripheral nervous

system.

excess dopamine receptor activity linked to

schizophrenia.

Antipsychotic drugs like Theorize are antagonists that

block receptor sites for dopamine.

DOPAMINE

Parkinson’s Disease: a degenerative brain disease that leads to a progressive loss of motor function. Experience tremors, shakiness, rigidity, and difficulty in walking.

Lack normal levels of dopamine.

Ex. Michael J. Fox

Muhammad Ali

5 NT THAT STUDENTS NEED TO KNOW

5. Gamma-aminobutyric acid (GABA): a major inhibitory NT.

Regulates nervous activity by preventing neurons from overly exciting their neighbors.

Located in the retina, spinal cord, hypothalamus, and cerebellum.

Exists in as many as a third of all synapses.

Drugs that boost GABA’s effects have a calming or relaxing effect.

Reduced levels of GABA may play a role in emotional disorders in which anxiety is a core feature.

GABA

Alcohol and antianxiety drugs like Valium, act as

agonists

Rohypnol (roofies): suppress general neural activity by

enhancing the action of GABA. Rohypnol is 10 times

more potent than Valium

Coma, amnesia, respiratory depression, and death.

ASSESSMENT QUESTION

A scientist develops a drug that blocks the actions of cocaine by locking into the same receptor sites as cocaine. So long as a person is taking the drug, cocaine will no longer produce a high. Would this drug be an antagonist or an agonist to cocaine? Why?