Introduction to the nervous System 1 Divisions of

Introduction to the nervous System 1

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 - 2

The spinal cord 3

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 4

The Brain 5

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 6

Basal ganglia • Important for the control of voluntary movement • Memory for spatial location • Provides feedback to cortex about movement and initiation of movement 7

Periaqueductal Gray • Carries information about pain from spinal cord to the cortex • Punishment center 8 8

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 9

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 10

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 11

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. 12

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 13