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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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Methods of investigating drug effects on the nervous system

(cont.)• Imaging Technology

• 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