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.

Biochemical substances that are released into the synaptic cleft to stimulate or suppress other neurons.

Dozens of neurotransmitters have been identified.

Contraction of muscles to move our bodies

Release hormones Psychological states of thinking and

emotions

Each type of (NT) has a three-dimensional shape.

The journey across the synapse takes only a thousandth of a second.

Changes have either an excitatory effect or an inhibitory effect.

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

Red light Just say no Less likely that the cell would fire Hooked on to a negative ion channel

Some NT have only Excitatory effects Some NT have only Inhibitory effects Some NT have both

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.

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

NT originate in the body Drugs originate 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

Agonists: drugs that either increase the availability or effectiveness of NT or mimic their actions.

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.

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

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.

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

Prozac acts as a agonist Prozac elevates serotonin levels Best selling antidepressant! 40 million

patients Some other antidepressant drugs raise

serotonin levels

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 Thorazine are antagonists that block receptor sites for 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. Foxhttp://www.youtube.com/watch?

v=ECkPVTZlfP8

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.

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.

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?