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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