9 4 Lecture 1 Ch 1 Introduction Ch 2 Neurons Glia Why study the nervous system Curiosity about how the brain and mind function Develop better treatments for neurological and psychiatric disorders Brain function can be described in terms of basic physical and chemical properties Although much still to be understood scientific methods have provided major insights into brain function o 1 The nerve cell is the basic functional unit of the nervous system and behavior o 2 Nerve cells are connected together in circuits and communication between o 3 All parts work together but specific regions of the brain peripheral nervous nerve cells in involved in all behavior system have definable functions Heart vs Brain The idea that the heart is the center for emotions turns up in many civilizations Origin may be that emotions activate autonomic nervous system resulting in increased heart rate and more forceful heart contractions Trepanation drilling holes in the skull o Evidence of this from 1000s of years ago o Anthropologists think this was an attempt to treat mental and neurological disorders History Ancient Egypt Heart was considered center of the intellect and emotions Heart not the brain was considered the center of intelligence and the place where memories were stored o In preparing body of the dead for afterlife brain discarded but heart preserved o However written documents from physicians of Ancient Egypt show that they were aware of symptoms of brain damage Edwin Smith Surgical Papyrus 1700 B C 48 case histories describing how to diagnose treat head spinal cord injuries Brain injuries are associated with changes in the function of other parts of the body especially the lower limbs In Western cultures the view that the heart was the center of the intellect and emotions was not challenged until the time of Hippocrates Ancient Greece Some Greek philosophers believed brain not heart was seat of intelligence o Hippocrates was most influential Based this on fact that head specialized for sensing environment contains eyes ears nose and tongue These ideas were not universally accepted Aristotle went back to heart centered ideas o Thought eyes and ears were connected to the heart and that the blood vessels carried sensations there o Thought the brain functioned as a cooling system for the heart The Roman Empire intellect movement functional losses Roman physician Galen embraced Hippocrates view of brain as center for sensations Galen noticed fluid filled ventricles o Believed nerves were hollow tubes and sensations reached brain by fluid Galen was a physician to the gladiators and saw connections between head injuries and The Renaissance through 18th Century 1600s Descartes advocated fluid mechanical theory similar to Galen o Fluids were forced out of the ventricles through hollow nerves and pumped up muscles to produce movement 18th century scientists moved away from focus on ventricles and noticed white and grey matter o White matter nerve fibers that carry information to and from grey matter o Grey matter cell bodies of nerve cells Gross anatomy of nervous system o CNS and PNS o Lobes of cerebrum described Nineteenth Century Luigi Galvani muscles twitch when nerves are stimulated electrically Nerves are wires that conduct electrical signals to and from brain o Disproved notion that nerves communicate with brain by fluid movement Not known if same nerve carried signals from brain to muscles and signals from sense organs back to brain bidirectional information flow or if separate nerves carried information to and from brain Bidirectional communication suggested by observation that loss of both movement and sensation usually occurs after nerve is cut But Charles Bell and Francois Magendie found within each nerve fiber information flows only in one direction Many nerve fibers travel together in nerves Incoming sensory fibers and outgoing motor fibers divide at point where nerves attach to spinal cord o Ventral roots contain only motor fibers o Dorsal roots contain only sensory fibers Specific functions are localized in the brain Paul Broca had a patient who could understand language but not speak After patient s death Broca examined brain and found a lesion in left frontal lobe Broca concluded correctly that this region is responsible for speech production Wernicke s Aphasia left occipital lobe could speak but not understand language The reticular theory vs the neuron doctrine Early 19th century cell recognized as fundamental unit of living organisms Early neurobiologists did not agree this applied to nervous system o Reticular theory nervous system a continuous mass Camillo Golgi Golgi said nervous system was exception to the idea that cell is fundamental unit thought nervous system was continuous mass of units o Neuron doctrine nerve cells are fundamental unit of nervous system Santiago Ramon Y Cajal Inferred that there were gaps between neurons Golgi Cajal Golgi wrong about reticular theory Golgi stain for unknown reasons randomly stains about 1 of cells Outlines entire cell Invented Golgi stain in 1873 o Makes it possible to study nerve cells in isolation from neighbors Cajal right about neuron doctrine Nervous system made up of discrete signaling units neurons that communicate at synapses Golgi Cajal shared 1906 Nobel Prize in Medicine The basic parts of a neuron dendrites cell body soma and axon Dendrites extend from cell body up to 2 mm o Act as antennae receive input signals Axons can extend for very long distances 1 meter or more o Act as a wire carry out signals of neuron Information flows in one direction within each neuron From dendrite which receive synaptic input o Synaptic inputs received by each neuron varies from 1 to 100 000 To cell body To axon Axon Axon terminal cell The initial part of the axon is called the axon hillock o Electrical pulse called action potential generated here Axons may branch branches are called axon collaterals Axon terminal contacts another neuron gland or muscle cell at synapse At synapse electrical signals that travel down axon causes release of neurotransmitters Neurotransmitter molecules diffuse across synapse and bind to receptors in post synaptic Glia Cells Neurons are specialized for electrical signaling o Human brain contains about 100 billion neurons Specialized for conducting electrical impulses in one direction via dendrites input and axons output Release neurotransmitter from axon terminal at synapse neurotransmitters interact with