Introduction to the nervous System

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 -

The spinal cord

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

The Brain

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

Basal ganglia Important for the control of voluntary movement Memory for spatial location Provides feedback to cortex about movement and initiation of movement

Periaqueductal Gray Carries information about pain from spinal cord to the cortex Punishment center8

Limbic System Hypothalamus Hippocampus Septum Amygdala Controls eating drinking, sexual, etc. behaviors Hippocampus Formation of new memories Septum Emotion and emotional memories Amygdala Implements aggressive behavior Active in fear conditioning

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

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

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.

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