 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. Fox ZlfP8

 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?