Introduction to the nervous System
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Divisions of the nervous system
• Central nervous system - encased in bone
– Spinal cord – brain
• Peripheral nervous system – everything else
– Somatic nervous system – voluntary control
• Sensory nerves • Motor nerves
– Autonomic nervous system – no conscious control
• Sympathetic nervous system – fight or flight response • Parasympathetic nervous system -
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The spinal cord
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Function of the spinal cord
• White matter – nerve fibers running to and from the brain • Gray matter – neurons and synapses, mediates reflexes • Dorsa horn – sensory • Ventral horn - motor
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The Brain
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Hindbrain
• Medulla – involved with autonomic system –regulating breathing and vomiting, etc. • Reticular activating and raphe system – activates the brain maintaining arousal or reduces arousal for sleep • Locus coeruleus – mood control and alerting response • Cerebellum – coordination of voluntary movements, eye saccades, and simple learning
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Basal ganglia
• Important for the control of voluntary movement • Memory for spatial location • Provides feedback to cortex about movement and initiation of movement
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Periaqueductal Gray
• Carries information about pain from spinal cord to the cortex • Punishment center8
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Limbic System
• Hypothalamus
– Controls eating drinking, sexual, etc. behaviors
• Hippocampus
– Formation of new memories
• Septum
– Emotion and emotional memories
• Amygdala
– Implements aggressive behavior – Active in fear conditioning
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Cortex
• • • Posterior and central areas primarily concerned with sensory and motor functions Frontal lobe – inhibition of behaviors, expression of emotion, availability of rewards Prefrontal areas
– Orbitofrontal – learning reward associations – Prefrontal working memory and thinking – Dorsolateral – maintenance of attentional demands of a task – Anterior cingulate – mediates attention, inhibition of dominant behaviors
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Development of the Nervous System
• Formation of neurons – neurogenesis- largely prenatal
– Majority of cells develop in first 3 months gestation - up to 150,000 cells per minute easily disrupted by chemicals and radiation
• Migration pre and post natal
– Cells move from where they were formed to their target area – They move either toward or away from chemicals released by areas of the brain
• Interconnections develop – largely postnatal • Programmed cell death
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Methods of investigating drug effects on the nervous system
• Electroencephalograms (EEG): Electrodes are attached to the subject’s scalp, and the device records the patterns of brain waves. • Event-Related Potentials: The momentary changes in electrical activity of the brain when a particular stimulus is presented to the subject.
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• Imaging Technology
Methods of investigating drug effects on the nervous system (cont.)
• Magnetic Resonance Imaging (MRI): Gives clear pictures of the structure of the brain. • Functional MRI: Image shows regions of the brain with heightened neural activity, with different colors reflecting high or low levels of blood flow, oxygen uptake, and the like. • PET scans- use radioactive labels attached to glucose
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