Transcript 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.
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NEUROTRANSMITTERS
Biochemical substances that are released into
the synaptic cleft to stimulate or suppress
other neurons.
 Dozens of neurotransmitters have been
identified.
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NEUROTRANSMITTERS
Contraction of muscles to move our bodies
 Release hormones
 Psychological states of thinking and emotions
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NEUROTRANSMITTER
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Each type of (NT) has a three-dimensional
shape.
NEUROTRANSMITTERS
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The journey across the synapse takes only a
thousandth of a second.
NT
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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
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INHIBITORY
Red light
 Just say no
 Less likely that the cell would fire
 Hooked on to a negative ion channel
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NT
Some NT have only Excitatory effects
 Some NT have only Inhibitory effects
 Some NT have both
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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.
2.
Enzymes: organic substances in the synapse
break down NT, which are then eliminated from
the body in the urine.
NT
NT originate in the body
 Drugs originate outside of the body.
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DRUGS/CHEMICALS OUTSIDE OF THE BODY
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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
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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.
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ACH
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Underproduction of ACh is an important factor in
Alzheimer’s disease
Reductions in ACh weaken or deactivate neural
circuitry that stores memories.
ACH
Absence: Paralysis
 Oversupply: violent muscle contractions
 Certain spider bites/Black widow
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BROWN RECLUSE SPIDER
5 NT THAT STUDENTS NEED TO KNOW
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2. Endorphins: natural chemicals released in the
brain that have pain-killing and pleasure-inducing
effects. Blocks pain.
Inhibitory NT
ENDORPHINS
Located in the Brain, pituitary gland, and spinal
cord.
 “runners high”
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Morphine and heroin are agonists since they
mimic the effects of endorphins.
5 NT THAT STUDENTS NEED TO KNOW
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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
 Best selling antidepressant! 40 million patients
 Some other antidepressant drugs raise
serotonin levels
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5 NT THAT STUDENTS NEED TO KNOW
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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.
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
http://www.youtube.com/watch?v=ECkPVT
ZlfP8
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5 NT THAT STUDENTS NEED TO KNOW
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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
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Alcohol and antianxiety drugs like Valium, act as
agonists
GABA
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.
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ASSESSMENT QUESTION
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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?