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Neuron Anatomy. The nervous system also allows you to react to a stimulus. Stimulus. A stimulus is a change in the environment. Example: A hot stove Or… tripping over a rock. Structure of a Vertebrate Neuron. Anatomy of a Neuron. Cell body: functional portion - PowerPoint PPT Presentation
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Neuron Anatomy
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
Structure of a Vertebrate Neuron
• Cell body: functional portion
• Dendrites: short extensions that receive signals
• Axon: long extension that transmits impulses away
Myelinated Neurons
• Many vertebrate peripheral neurons have an insulating sheath around the axon called myelin which (white matter) is formed by Schwann cells.
• Myelin sheathing allows these neurons to conduct nerve impulses faster than in non-myelinated neurons (gray matter)
• Node of Ranvier is the location where nervous impulses are conducted.
Basic Tasks of the Nervous SystemSensory 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.
Messages carried throughout the body by nerves.
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
The Nerve Impulse
•At rest, the membrane maintains an electrical polarization called the resting membrane potential.–the inside of the membrane is slightly negative with respect to the outside. (approximately -70 millivolts)
Depolarization – influx of Na+ ions
Repolarization – outflux of K+ ions
Nerve Impulse - The Action PotentialNerve Impulse - The Action PotentialThreshold potential will trigger an action potential or nerve impulse
The action potential is an all-or-none response
INTEGRATION WITHIN THE CENTRAL NERVOUS SYSTEM
• The nervous system gathers and processes information from the external and internal environments and then relays a response to the necessary areas of the body.
REFLEX ARC
• Neurons allow the nervous system to relay sensory information to the brain and spinal cord for integration, and to produce a response, as needed, by the effectors.
How does a signal move from one neuron to another?
• A synapse separates 2 neurons• The action potential will not move
across the synapse• Neurotransmitters
– Released by the signal cell to the receiver cell
– Move by diffusion
Types of chemical neurotransmitters
• Acetylcholine: neuromuscular junctions, glands, brain and spinal cord
• Norepinepherine: affects brain regions concerned with emotions, dreaming
Excitatory: helps to initiate a response, making the cell membrane receptors more permeable
Inhibitory neurotransmitters: is able to breakdown the excitatory neurotransmitters to prevent further action potentials from occuring.
Cholinesterase: breaks down acetylcholine.
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 is made of the nerves and the sense organs.
Nerves Sense organs
* 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 Cerebellum3. 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 right and left halves of the cerebral cortex (cerebrum) are made of four pairs of lobes, each of which is associated with particular functions:
• FRONTAL lobes (conscious thought and movements, speech),
• PARIETAL lobes (touch, taste),
• TEMPORAL lobes (hearing and speech),
• OCCIPITAL lobes (vision).
* 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 (MEDULLA OBLONGATA and HYPOTHALAMUS).
* The vertebrae are the many bones that protect the nerves in
the spinal cord.
* The Outer Nervous System’s job is to connect the Central
Nervous System to the rest of the body.
* The outer nervous system carries messages between the central
nervous system and the rest of the body.
* The outer nervous system is made of the nerves and the sense
organs.
Ear
EyeSkin
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 EyeDetectors 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
2. Ear canal3. Ear drum
5. Anvil
6. Stirrup
7. Cochlea
4. Hammer 8. Eustachian tube9. Auditory nerve
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 pinna is the part of the ear that you can see.
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 inner ear is made of the cochlea and liquid.
The cochlea is in the inner ear. The cochlea looks like a shell.
The Eustachian tube controls the amount of pressure in the ear.
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
• 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
Pharmacology of Addictive Drugs
Source: Gray
Transmission Across the Synapse
How Drugs Become Addictive
Detail of Axon
Terminal
Neurotransmitter Neurotransmitter molecules molecules
(e.g., Acetylcholine (e.g., Acetylcholine or Dopamine)or Dopamine)
Postsynaptic membrane
Detail of the Synapse Itself
Binding site
How binding
sites work
Neurotransmitter re-uptake helps keep binding sites clear
Cocaine Cocaine inhibits the re-uptake of dopamine producing effects such as increased heart rate and
blood pressure
NicotineNicotine 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 harmUse 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?
Nicotine Use is Associated With Other Drug Use
0
10
20
30
40
50
60
70
80
Cigarettes smoked per day
% o
f S
tudents
"
5+drugs
1 drug
2-4 drugs
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 AbuseHow 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
