NEUROTRANSMITTERS
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?