hart13 ppt ch04
DESCRIPTION
(c) McGraw-Hill 2011TRANSCRIPT
© 2011 McGraw-Hill Higher Education. All rights reserved.
Chapter 4Chapter 4
The Nervous System
© 2011 McGraw-Hill Higher Education. All rights reserved.
HomeostasisHomeostasis
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.
Components of the Nervous Components of the Nervous SystemSystem
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.
NeuronNeuron
© 2011 McGraw-Hill Higher Education. All rights reserved.
Components of the Nervous Components of the Nervous SystemSystem
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.
NeurotransmissionNeurotransmission
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
Action PotentialAction Potential
© 2011 McGraw-Hill Higher Education. All rights reserved.
© 2011 McGraw-Hill Higher Education. All rights reserved.
The Nervous SystemsThe 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.
Somatic Nervous SystemSomatic 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.
Autonomic Nervous SystemAutonomic 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.
Central Nervous SystemCentral 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.
Chemical PathwaysChemical 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.
Chemical PathwaysChemical 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.
Chemical PathwaysChemical 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
pathways5. GABA (Gamma-amino butyric acid) Found in most regions of the brain Inhibitory neurotransmitter
© 2011 McGraw-Hill Higher Education. All rights reserved.
Chemical PathwaysChemical 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.
Common NeurotransmittersCommon NeurotransmittersNeurotransmitter Type of effect CNS changes Drugs of abuse
dopamine
GABA
serotonin
acetylcholine
endorphins
inhibitory-excitatory
inhibitory
excitatory-inhibitory
excitatory-inhibitory
inhibitory
euphoria agitation paranoiasedation relaxation drowsiness depressionsleep relaxation sedationmild euphoria excitation insomniamild euphoria block pain slow respiration
amphetamines, cocaine
alcohol, Valium-type barbiturates
LSD
tobacco, nicotine
opioid
© 2011 McGraw-Hill Higher Education. All rights reserved.
The Brain: Major StructuresThe Brain: Major Structures
Cerebral cortex Basal ganglia Hypothalamus Limbic system Midbrain, pons, and medulla Brain stem
© 2011 McGraw-Hill Higher Education. All rights reserved.
Cross-section of the brain: Major structures
© 2011 McGraw-Hill Higher Education. All rights reserved.
© 2011 McGraw-Hill Higher Education. All rights reserved.
Life Cycle of a Life Cycle of a NeurotransmitterNeurotransmitter
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.
Life Cycle of a Life Cycle of a NeurotransmitterNeurotransmitter
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
Neurons use enzymes to synthesize neurotransmitters
© 2011 McGraw-Hill Higher Education. All rights reserved.
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.
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.
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.
© 2011 McGraw-Hill Higher Education. All rights reserved.
Examples of Drug ActionsExamples 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.
Chemical Theories of Chemical Theories of BehaviorBehavior
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.
Chemical Theories of Chemical Theories of BehaviorBehavior
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
Brain Imaging Techniques: Brain Imaging Techniques: PET ScanPET Scan
© 2011 McGraw-Hill Higher Education. All rights reserved.
Brain Imaging Techniques: Brain Imaging Techniques: MRI ScanMRI Scan
© 2011 McGraw-Hill Higher Education. All rights reserved.
© 2011 McGraw-Hill Higher Education. All rights reserved.
Chapter 4Chapter 4
The Nervous System