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Nervous System
Nervous system cells
 Neurons
OBJ 43
Glial cells
Types of neurons
sensory neuron
(from senses)
interneuron
(brain & spinal chord)
motor neuron
(to muscle or gland…effector cells)
Human brain
8
4
7
3
2
5
6
1
Divisions of the nervous system
OBJ 40
Nervous System Pathway
How messages travel
BC
A
F
CD
E
D
E
G
B
Synapse
Synapse:
Junction between nerve cells

1st cell releases neurotransmitter to
trigger next cell
synapse
OBJ 45
What are some examples of
neurotransmitters?
 Acetylcholine
 Epinephrine (adrenaline)
 Dopamine
 Serotonin
 Endorphins
Simplest Nerve Circuit
 Reflex arc, or automatic response

signal only goes to
spinal cord
 essential actions
 don’t need to think or
make decisions about
 blinking
 balance
 pupil dilation
 startle
Drugs & the Nervous system
What happens when you interfere
with neural communication?
Nicotine
 acts as a stimulant
 mimics acetylcholine
 triggers the release of dopamine,
making it addictive
Alcohol
 Alcohol in drinks is actually ethyl



alcohol
High concentrations can be toxic
Alcohol is a depressant
Excessive amounts of alcohol damages
liver, digestive system, AND NEURONS
Alcohol and teens
 Teens’ brains are specially geared for
optimal learning
 So, teens experience more severe
damage to brain due to alcohol use
(more blackouts, more brain
damage…smaller brain)
Drug effects
 What is going on when someone is addicted
to drugs?



Opiate drugs (heroin, morphine) can mimic
endorphins (a feel-good NT)
Body adjusts to higher amount of endorphinlike chemicals, and can’t do without it
Take more and more of the drug. Without it,
feel pain, nausea, chills, fever, depression
Drug effects
 Marijuana (THC) –
THC blocks the action of
neurotransmitters in the brain affecting
motor skills, memory, concentration
 Long-term effects: loss of memory,
inability to concentrate, lowered
testosterone

Drug effects
 Ecstasy (MDMA)
Causes rush of serotonin
 Interferes with homeostasis (temp.)
 Feel depressed until body makes
enough of its own serotonin to feel
‘normal’ again
 Destroys serotonin neurons axons and
terminals
 After exposure to MDMA for 4 days, it
takes more than 7 years for your brain
to recover.

Drug effects
 Hallucinogens
LSD
 PCP
 Interfere with neurotransmitters in brain

Drug effects
 Cocaine
Causes dopamine to be released
 Not enough is left for normal function,
so users become dependent on it

Even 100 days after a cocaine addict has
stopped using drugs, the decreased metabolism
in the brain's frontal area remains visible. This
region of the brain influences behavior such as
regulating impulsive and repetitive behavior,
planning and organizing activities, and critical
thinking.