(c) McGraw-Hill 2011

1. Chapter 4
The Nervous System
© 2011 McGraw-Hill Higher Education. All rights reserved.

2. Homeostasis
 Humans must maintain their internal
environment within certain limits
 Temperature
 Acidity
 Water content
 Sodium content
 Glucose concentrations
 Other physical and chemical factors
© 2011 McGraw-Hill Higher Education. All rights reserved.

3. Components of the Nervous
System
 Nerve cells (neurons)
 Analyze and transmit information
 Over 100 billion neurons in system
 Four defined regions
 Cell body
 Dendrites
 Axon
 Presynaptic terminals
 Stimulation of receptors by psychoactive drugs
can activate or inhibit a neuron
© 2011 McGraw-Hill Higher Education. All rights reserved.

4. Neuron
© 2011 McGraw-Hill Higher Education. All rights reserved.

5. Components of the Nervous
System
 Glial cells (Glia)
 Provide firmness and structure to the brain
 Get nutrients into the system
 Eliminate waste
 Form myelin
 Create the blood-brain barrier
 Communicate with other glia & neurons
© 2011 McGraw-Hill Higher Education. All rights reserved.

6. Neurotransmission
 Action potential = a brief electrical signal
transmitted along the axon
 Neurotransmitters are the “messengers”
 Resting action potential is caused by uneven
distribution of ions
 Action potential occurs when sodium ions move
across channels
 Blocking channels prevents the action potential
and disrupts communication between neurons
© 2011 McGraw-Hill Higher Education. All rights reserved.

7. Action Potential
© 2011 McGraw-Hill Higher Education. All rights reserved.

8. The Nervous Systems
 Somatic nervous system
 Sensory information
 Voluntary actions
 Autonomic nervous system (ANS)
 Sympathetic branch
 Parasympathetic branch
 Central nervous system (CNS)
 Brain
 Spinal cord
© 2011 McGraw-Hill Higher Education. All rights reserved.

9. Somatic Nervous System
 Carries sensory information into the
central nervous system
 Carries motor (movement) information
back out to the peripheral nerves
 Controls voluntary actions
 Acetylcholine is the neurotransmitter at
neuromuscular junctions
© 2011 McGraw-Hill Higher Education. All rights reserved.

10. Autonomic Nervous System
 Monitors and controls the body’s internal
environment and involuntary functions
 Many psychoactive drugs affect the brain and
the autonomic nervous system
 Two branches often act in opposition
 Sympathetic branch
 “Fight or flight”
 Parasympathetic branch
© 2011 McGraw-Hill Higher Education. All rights reserved.

11. Central Nervous System
 Consists of the brain and the spinal
cord
 Has many functions
 Integration of information
 Learning and memory
 Coordination of activity
© 2011 McGraw-Hill Higher Education. All rights reserved.

12. Chemical Pathways
1. Dopamine
 Found in basal ganglia and other regions
 Nigrostriatal dopamine pathway
 Related to muscle rigidity
 Mesolimbic dopamine pathway
 Related to psychotic behavior
 Possible component of the “reward” properties of
drugs
© 2011 McGraw-Hill Higher Education. All rights reserved.

13. Chemical Pathways
2. Acetylcholine
 Found in the cerebral cortex & basal ganglia
 Involved in Alzheimer’s disease, learning,
memory storage
3. Norepinephrine
 Regulates level of arousal and attentiveness
 May play a role in initiation of food intake
(appetite)
© 2011 McGraw-Hill Higher Education. All rights reserved.

14. Chemical Pathways
4. Serotonin
 Found in the brain stem raphe nuclei
 May have a role in impulsivity, aggression,
depression, control of food, and alcohol intake
 Hallucinogenic drugs influence serotonin
pathways
5. GABA (Gamma-amino butyric acid)
 Found in most regions of the brain
 Inhibitory neurotransmitter
© 2011 McGraw-Hill Higher Education. All rights reserved.

15. Chemical Pathways
6. Glutamate
 Found in most regions of the brain
 Excitatory neurotransmitter
7. Endorphins
 Opioid-like chemical occurring naturally
in the brain
 Play a role in pain relief, other functions
© 2011 McGraw-Hill Higher Education. All rights reserved.

16. Common Neurotransmitters
Neurotransmitter Type of effect CNS changes Drugs of abuse
dopamine inhibitory- euphoria amphetamines,
excitatory agitation cocaine
paranoia
GABA inhibitory sedation alcohol,
relaxation Valium-type
drowsiness barbiturates
depression
serotonin excitatory- sleep LSD
inhibitory relaxation
sedation
acetylcholine excitatory- mild euphoria tobacco,
inhibitory excitation nicotine
insomnia
endorphins inhibitory mild euphoria opioid
block pain
slow respiration
© 2011 McGraw-Hill Higher Education. All rights reserved.

17. The Brain: Major Structures
 Cerebral cortex
 Basal ganglia
 Hypothalamus
 Limbic system
 Midbrain, pons, and medulla
 Brain stem
© 2011 McGraw-Hill Higher Education. All rights reserved.

18. Cross-section of the brain: Major structures
© 2011 McGraw-Hill Higher Education. All rights reserved.

19. Life Cycle of a
Neurotransmitter
1. Neurotransmitter precursors are found
circulating in the blood supply
2. Uptake: Selected precursors are taken up
by cells, a process requiring energy
3. Synthesis: Precursors are changed
(synthesized) into neurotransmitters through
the action of enzymes
4. Storage: Neurotransmitters are stored in
small vesicles
© 2011 McGraw-Hill Higher Education. All rights reserved.

20. Life Cycle of a
Neurotransmitter
5. When the action potential arrives,
neurotransmitters are released into the
synapse
6. Released neurotransmitters bind with
receptors on the membrane of the next neuron
7. Neurotransmitters may have excitatory or
inhibitory effects
8. Once a signal has been sent,
neurotransmitters are removed from the
synapse; may return or be metabolized
© 2011 McGraw-Hill Higher Education. All rights reserved.

21. Neurons use enzymes to synthesize neurotransmitters
© 2011 McGraw-Hill Higher Education. All rights reserved.

22. Schematic representation
of the action of a synthetic
enzyme. A precursor
molecule and another
chemical fragment both bind
to the enzyme. The fragment
has a tendency to connect
with the precursor, but the
connection is made much
more likely because of the
way the enzyme lines up to
the two parts. After the
connection is made, the new
transmitter molecule
separates from the enzyme.
© 2011 McGraw-Hill Higher Education. All rights reserved.

23. Schematic representation
of the release of
neurotransmitter
molecules from synaptic
vesicles in the axon
terminal of one neuron and
the passage of those
molecules across the
synapse to receptors in the
membrane of another
neuron.
© 2010 McGraw-Hill Higher Education. All rights reserved.

24. Schematic representation of
the action of a metabolic
enzyme. The transmitter
molecule binds to the enzyme
is such a way that the
transmitter molecule is distorted
and “pulled apart.” The
fragments then separate from
the enzyme.
© 2011 McGraw-Hill Higher Education. All rights reserved.

25. Examples of Drug Actions
 Alter neurotransmitter availability
 Agonists
 Mimic neurotransmitters
 Antagonists
 Occupy neurotransmitter and prevent its
activation
 Interference with reuptake
© 2011 McGraw-Hill Higher Education. All rights reserved.

26. Chemical Theories of
Behavior
 Attempts to explain normal variations in
behavior in terms of changes in brain
chemistry
 Greek physician Hippocrates and the four
humors
 Chinese philosophy—yin and yang
© 2011 McGraw-Hill Higher Education. All rights reserved.

27. Chemical Theories of
Behavior
 No single biochemical theory of drug
dependence has achieved sufficient
experimental support
 Monoamine theory of mood—too little activity
in monoamine systems can cause depression,
too much can cause mania
© 2011 McGraw-Hill Higher Education. All rights reserved.

28. Brain Imaging Techniques:
PET Scan
© 2011 McGraw-Hill Higher Education. All rights reserved.

29. Brain Imaging Techniques:
MRI Scan
© 2011 McGraw-Hill Higher Education. All rights reserved.

30. Chapter 4
The Nervous System
© 2011 McGraw-Hill Higher Education. All rights reserved.