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Nervous Systems
Structure of a Vertebrate Neuron
Diversity of Nervous Systems
Simple, slow moving animals like hydra have neurons arranged in a network
of bipolar neurons called a nerve net.
Basic Tasks of the Nervous System
Sensory Input:
Monitor both
external and internal
environments.
Integration: Process
the information and
often integrate it with
stored information.
Motor output: If
necessary, signal
effector organs to
make an appropriate
response.
A system that controls all of the
activities of the body.
The nervous system is made of:
The brain
The spinal cord
The nerves
The senses
The nervous system also allows you to
react to a stimulus.
A stimulus is a change in the environment.
Example: A hot stove
Or… tripping over a rock
Your reactions are automatic.
Automatic means that you do not
have to think about your reactions.
Example: If a bug flies by your eye,
you will blink.
An organ that controls your
emotions, your thoughts, and every
movement you make.
The Central Nervous System is made
of the brain and the spinal cord.
The Central Nervous System controls
everything in the body.
The Outer Nervous System (Peripheral
Nervous System)is made of the nerves
and the sense organs.
Nerves
Sense organs
Messages carried throughout the body
by nerves.
You have a nerve along your whole arm.
The “funny bone” is the only place on
the arm where the nerve is not
protected.
The “funny bone” is on the elbow.
• Cell body: functional
portion
• Dendrites: short
extensions that receive
signals
• Axon: long extension
that transmits impulses
away
Nerve Impulse - The Action Potential
Threshold potential will trigger
an action potential or nerve
impulse
The action potential is an all-ornone response
Myelinated Neurons
• Many vertebrate peripheral neurons have an insulating sheath around
the axon called myelin which is formed by Schwann cells.
• Myelin sheathing allows these neurons to conduct nerve impulses
faster than in non-myelinated neurons.
Saltatory Conduction in Myelinated Axons
Myelin sheathing has bare patches of axon called nodes of Ranvier
Action potentials jump from node to node
Fig. 48.11
How does a signal move from
one neuron to another?
• A synape divides 2 neurons
• The action potential will not move
across the synape
• Neuro transmitters
– Released by the signal cell to the
receiver cell
– Move by diffusion
Types of chemical synapse
• Acetylcholine: neuromuscular junctions,
glands, brain and spinal cord
• Norepinepherine: affects brain regions
concerned with emotions, dreaming
* The Central Nervous System controls
all of the body’s activities.
* The Central Nervous System is
made of two main organs.
1. The brain
2. The spinal cord
* The spinal cord sends messages to the
brain.
* The spinal cord is the part of the
nervous system that connects the brain
to the rest of the nervous system.
* The brain controls everything in the
body.
* The brain is made of more than 10
billion nerves!
* The brain is divided into three
parts and is protected by the skull.
* The Brain has three main parts…
1. The Cerebrum
2. The Cerebellum
3. The Brain Stem
* The Cerebrum is the largest part of
the brain.
1. The cerebrum controls your thinking.
2. The cerebrum controls your memory.
3. The cerebrum controls your speaking.
4. The cerebrum controls your movement and identifies
the information gathered by your sense organs.
* The cerebellum is below and to the
back of the cerebrum.
1. The cerebellum controls you balance.
2. The cerebellum controls your posture.
* The Brain Stem connects the brain to
the spinal cord.
* The nerves in the brain stem control
your heartbeat, breathing, and blood
pressure.
* The vertebrae are the many
bones that protect the nerves in
the spinal cord.
* The outer nervous system carries
messages between the central nervous
system and the rest of the body.
* The Outer Nervous System’s job
is to connect the Central Nervous
System to the rest of the body.
* The outer nervous system is made of
the nerves and the sense organs.
Ear
Skin
Eye
Nerves
Tongue
* An automatic reaction that
happens without thinking about it.
* A reflex happens quickly in
less than a second.
* The outer nervous system
controls the body’s activities
that you don’t think about.
* The outer nervous system controls
activities in your small intestine, your
breathing, and your heartbeat.
controls
Sense organs
carry messages
about the
environment to
the central
nervous
system.
The eyes, ears, nose, tongue, and
skin are examples of sense organs.
The sense organs gather
information (light, sound, heat,
and pressure) from the
environment.
The environment is everything
outside the body.
The sense organs gather
information from outside the
body, then send the messages to
the brain.
Vision is your ability to see.
Vision involves the eye and the brain.
Parts of the Eye
Detectors on the Fovea
– Rods
• light intensity and motion sensitive
– Cones
• color sensitive
The blind spot for the eye is cause by
the optic nerve.
Myopia (Near-Sightedness)
People with near-sightedness
cannot see clearly at distance.
Hyperopia (Farsightedness)
People with far-sightedness
cannot see clearly up close
When a sound is made, the air
around the sound vibrates.
Hearing starts when some of the
sound waves go into the ear.
There are nine main parts of the ear.
1. Pinna
5. Anvil
2. Ear canal
6. Stirrup
3. Ear drum
7. Cochlea
4. Hammer
8. Eustachian tube
9. Auditory nerve
The pinna is the part of the ear
that you can see.
The ear canal is the tube between the
outside of the ear and the ear drum.
The ear drum is in the middle ear. It
vibrates when sound waves hit it.
The three smallest bones in the body, the
hammer, the anvil, and the stirrup,
are in the middle ear.
The hammer gets the vibrations from the
eardrum, then sends them to the anvil.
The anvil passes the vibrations to the stirrup.
The stirrup passes the vibrations
to the inner ear.
The Eustachian tube controls the amount
of pressure in the ear.
The inner ear is made of
the cochlea and liquid.
The cochlea is in the inner ear. The
cochlea looks like a shell.
The auditory nerve carries the
hearing information to the brain and
the brain tells us what we heard.
The ear works with the brain to
control your balance.
All of your movements are controlled
by balance and muscles.
The liquid in your inner ear is responsible
for your balance.
The liquid in your ear moves when we move.
The liquid movement sends information to the
brain to tell it how we are moving.
The sense of touch is located in the skin.
The nerves in the skin allow us
to feel texture, pressure,
heat, cold, and pain.
Texture is how something feels.
The nose controls your sense of smell.
The nose is able to smell 80
different kinds of smells.
Your sense of taste comes from the
taste buds in the tongue.
Taste buds are the parts on the tongue
that allow us to taste.
The four kinds of taste buds are
sweet, sour, bitter, and salty.
Tastes and smells work
together to make flavors.
Flavors are the tastes
of food and drinks.
Addictive Drug Use:
Tobacco, Alcohol, &
Illicit Drugs
Dr. Robert B. Coambs
Psy333
November, 2002
Pharmacology of Addictive Drugs
• All addictive drugs produce:
• Short-term pleasure to some degree
• Long-term negative consequences
• Tolerance & physical dependence
• A withdrawal syndrome
• Activation of dopamine neurons in
the Nucleus Accumbens
Transmission
Across the
Synapse
Source: Gray
How Drugs Become Addictive
Detail of
Axon
Terminal
Detail of the
Synapse Itself
Neurotransmitter
molecules
(e.g., Acetylcholine
or Dopamine)
Postsynaptic
membrane
How
binding
sites work
Binding site
Neurotransmitter re-uptake
helps keep binding sites clear
Cocaine inhibits the re-uptake
of dopamine producing effects
such as increased heart rate and
blood pressure
Nicotine fills & activates acetylcholine
binding sites producing effects such as
increased heart rate and blood pressure
What is Addiction?
• All definitions describe behaviour which
produces positive sensations in the short
term, but negative consequences in the
long term
• A straightforward definition:
–Compulsive use
–Loss of control
–Use despite harm
* Portnoy
How People Start Using Drugs
• Genetics
• Predisposing risk factors:
– Age 11-22 for onset
– Primitive character structures
• Especially Conduct Disorder
– Peer influence
– Parental influence
– Smoking and alcohol use
• Constricted temporal focus?
80
Nicotine Use is Associated With
Other Drug Use
5+drugs
70
% of Students "
60
50
2-4 drugs
40
30
20
1 drug
10
0
NO
NE
(
ON
E
61.
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OC
C
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11 +
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/d (
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Cigarettes smoked per day
Kozlowski, Coambs, et al., 1989
Nicotine Use is Associated With Other Drug Use
Some People Never Start
• Factors which reduce risk:
–Age 35+
–Nuanced character structures
–No Peer influence
–No Parental drug use history
–No other smoking or alcohol abuse
• E.G., the SISAP
Basic Treatment For Addiction
• Treat the urges directly, if possible
• Establish why the person uses the
drug
• What needs are being fulfilled by
that drug?
• Find methods to fulfil those needs
without the drug
How People Quit Drug Abuse
• Most quit on their own (cold turkey)
• Most use no medication
• Probably those people who can quit
easily do so
• Clinicians tend to see the difficult
cases
• Ambivalence is normal
• Most quit by age 40
Relapse Prevention
• Plan for relapse: Abstinence Violation
Effect
• Relapse is common: it is not failure!
• Repeated relapse is associated with
success in quitting
• Learn from it in next attempt
• Find a way to control urges