Download * Certain neurons in the brain have receptors (opioid receptors) for

Acupuncture causes the body to release what
substance?
What other functions do enkephalins have?
* Certain neurons in the brain have receptors
(opioid receptors) for opiate drugs such as
morphine and heroin.
* Naturally occurring NT’s called enkephalins bind
to these opioid receptors and have an analgesic
effect “natural painkillers” (200X more strong than
morphine - WOW!)
* Other opioid NT’s such as endorphines have such
analgesic effects too!
A. Drug Dependency & Tolerance:
Dependency - 2 forms of “addiction”
* addiction acts on: thinking, emotions, and behavior.
a. psychological – “a craving for the drug”.
“Gosh, ‘id sure be cool to smoke some pot on Friday night!”
b. physical – requires one to take the drug to avoid
withdrawals (unpleasant symptoms - vomiting).
e.g. methadone is a substitute for heroine addiction;
Methadone Clinics for addicts.
Physical Addiction is Characterized by:
• Progressive increased consumption of drug.
• Persistent tendency to relapse even after abstinence
and withdrawal symptoms are no longer evident.
• Drugs that lead to dependence act on the “pleasure
circuit” in the brain called the VTA, nucleus accumbens
and prefrontal cortex.
Tolerance – to a drug occurs when increasing the dosage of the
drug is required to achieve the effects that initially occurred in
response to a smaller dose.
Two theories below :
1) Based on previous drug use; the presence of the drug stimulates
the synthesis of the enzymes that degrade the drug in the
synaptic jct. As ↑[drug]; ↑[enzymes that degrade drug]; thus,
more of the drug must be administered for the same initial effect.
2) Tolerance can develop as a result of changes in the number
and/or sensitivity of receptors that respond to the drug. For
example, the drug’s effects might ADD to those of normally
occurring neurotransmitter, thereby producing an increased
response that, by feedback inhibition, eventually decreases the
release of the naturally occurring neurotransmitter.
Mechanism for Physical
Dependency to Morphine
Outpatient Methadone Treatment:
Pre and post-treatment statistics
Pre-treatment
89
%
Posttreatment
85
82
42
29
28
22
15 16
Cocaine
use
Heroin
use
(Weekly)
(Weekly)
14
Alcohol Illegal
use
Activity
(Heavy)
No Full-time
Employment
Methadone- a substitute
for heroine addicts
Other Chemicals that Modify the Synaptic Transmission:
Nerve Gas - muscles continue t o contrac t
be cause th e AChE is inhibited by th e nerve gas .
There is no relaxation period and the muscle
does no t r espond t o further nerve stimulations .
Individual exhibits paralysis and asphyxiation.
Curare – binds to ACh receptors in the neuromuscular
junction, thus preventing ACh attachment. This blocks
excitatory stimulus to muscle cells, thus cells do not
contract. Used in surgery to cause partial paralysis of
muscles.
Curare
Botulism – deadly! A t oxin made b y a bac terium;
blocks the release of ACh from the motor neuron.
Ultima tely , i t prevents t he t ransmission of a
chemical signal to muscle .
Botox injec tions– transient facial muscl e paralysis.
Botulism toxin
Tetanus “Lockjaw” (Clostridium tetani) - bacteria that
interferes w/ inhibitory (brake) synaptic mechanisms to motor
neurons. The excitatory (gas) inputs remain “unchecked”;
results in excessive, involuntary skeletal muscle contraction.
Spasms of the jaw muscles are early signs. Tetanus shot!
Disorders:
1. Epilepsy- an electrical storm in the brain! Pets too.
• 2nd most common neurological disorder to strokes.
• b rief attacks of motor, sensory, or psychological
malfunction, i.e. seizures caused by abnormal electrical
discharges from excitatory neurons in the brain due to the
inhibitory mechanism malfunctioning. GABA is implicated.
2. Lou Gehrig’s Disease (ALS) - rare degeneration of motor
neurons; a loss in voluntary movement (skeletal muscle
atrophies). Death w/in 3-5 years. Mind & senses not impaired.
*14 new cases per day in the US. “spirit of Lou Gehrig”
X. Patterns of Neural Processing: (See figure 13.13; pge 461)
Circuits – the patterns of synaptic connections, i.e. excitatory
or inhibitory.
1. Serial Processing – the whole systems works in an all-ornothing manner. One neuron stimulates the next in sequence,
which stimulates the next neuron causing a specific response,
e.g. Reflex Arc (spinal reflex)
* Reflexes – rapid, autonomic (ANS) response to a stimulus,
in which the same stimulus always causes the same motor
response, e.g. jerking your arm away from a hot plate.
Blinking your eye when an object approaches.
Reflex arcs have 5 essential components:
1) sensory receptor, e.g. touch or pain
2) sensory afferent neuron (adds to CNS)
3) integration center “interneurons” (CNS)
4) motor efferent neuron (exits CNS )
5) effector (response)
Reflex Arc