3. Diversity of Nervous Systems
Simple, slow
moving animals
like hydra have
neurons arranged
in a network of
bipolar neurons
called a nerve
net.
4. 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.
5. Anatomy of a nerve
• Cell body: functional
portion
• Dendrites: short
extensions that receive
signals
• Axon: long extension
that transmits impulses
away
6. Nerve Impulse –
The Action Potential
Threshold potential will
trigger an action potential
or nerve impulse
The action potential is an
all-or-none response
7. Nerve Impulse –
The Action Potential
A nerve is stimulated, (A.P.)
usually at one point, and then
is propagated along the axon.
The role of sodium and potassium
ions in propagating an Action
Potential is crucial.
Na+ and K+ both move in apposing
directions to generate a potential
difference all along the axon.
Positive and negatives attract.
8. 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.
9. 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
10. How does a signal move from one
neuron to another?
• A synapse divides 2 neurons
• The action potential will not move
across the synapse
• Neuro transmitters
– Released by the signal cell to the receiver
cell
– Move by diffusion
11.
12. Types of chemical synapse
• Acetylcholine: neuromuscular
junctions, glands, brain and spinal
cord
• Norepinepherine: affects brain
regions concerned with emotions,
dreaming
13. Spinal Reflex
• Knee-patellar is the classic example,
but there are many reflexes
• Blinking your eye
• Salivating when expecting food
• Going to the toilet as an infant
14.
15. The Autonomic Nervous System
• 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.
16.
17. The sense organs - eye
• Sense organs carry messages about the
environment to the central nervous system
18.
19. 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.
25. 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
32. Cocaine inhibits the re-uptake
of dopamine producing effects
such as increased heart rate and
blood pressure
33. Nicotine fills & activates acetylcholine
binding sites producing effects such as
increased heart rate and blood pressure
34. 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
35. 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?
36. 80
Nicotine Use is Associated With
Other Drug Use
5+drugs
% of Students "
70
60
50
2-4 drugs
40
30
20
1 drug
10
0
NO
NE
(
ON
E
61.
2)
(14
.7
OC
C
(8.
7)
1- 5
/d (
7. 6
)
)
Cigarettes smoked per day
6- 1
0/d
(3.
4)
11
+/d
(4.
4)
Kozlowski, Coambs, et al., 1989
Nicotine Use is Associated With Other Drug Use
37. 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
38. 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
39. 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
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
