Introduction to Neuroscience 2100 (Campeau) Study Guide for First Midterm Exam 1 What are some fun facts about the human nervous system? CNS weighs about 3 pounds (17-pounds in sperm whale) ~86,000,000,000 neurons Each neuron can make anywhere from 1,000 to 10,000 connections with other neurons Number of connections in cortex alone is estimated at 60 trillion Size of neuron is from 4 to 100s of micrometers Length of longest axon known (in a giraffe) is 15 feet Conduction speed of action potentials is 1 to 250 mph History (conceptual and technical approaches and views since the beginnings of civilization): Note: in doing this, place these historical events on a timeline so you keep track of time period! What was the view of the brain in pre-civilized humans? 7,000 to 10,000 ya: Seemingly important. Evidence of trepanation in order to provide a route for evil spirits to escape; also to cure ailments like headaches, seizures, mental illness. Attempts at curing psychological and physical ailments. What did the Egyptians think of the brain? Meh, it’s the heart that stores memories, seat of knowledge, pulled brain out through nostrils and discarded. What were the main views of influential Greek figures (e.g., Hippocrates, Aristotle)? Hippocrates: believed the brain was involved in sensation and was the seat of intelligence. Aristotle believed that the heart was the center of intellect and the brain was a radiator for the cooling of blood that had been overheated by the seething heart. How about influential Romans (Galen)? Galen believed the cerebrum was the recipient of sensations and repository for memory; and the cerebellum is where command of muscles took place. Movement occurred by fluctuations of humors from the ventricle to the nerves. Nerves as hollow conduits or tubes for the flow humors.What is notable about the Middle-ages? Artwork depicting trepanation; dissection banned in Europe During the early Renaissance era, what particular invention facilitated the dissemination of knowledge, including Vesalius' "De Humani corporis fabrica"? Vesalius: Meticulous anatomist; corrected many errors made by Galen, but retained notion of animal spirits; ventricles “pump you up” French inventors began developing hydraulically controlled mechanical devices, which supported the notion that the brain could be machinelike in its function. What were the major conceptual contributions of artists and philosophers such as DaVinci, Willis, Janssen, Hooke, and Descartes during the late Renaissance? DaVinci, Willis: mechanistic view of the world: physical laws Zacharias Janssen 1590: invented compound microscope Robert Hooke: originator of the concept of the cell (cork cell) Descartes: the mind influences the motor response by controlling the pineal gland, which works like a valve to control the movement of animal spirits through the nerves that inflate muscles. Pineal gland is seat of the soul. Descartes articulated clear mind-body distinction; most closely associated with substance dualism. Mind and matter are two different kinds of substances. What were some of the technical advances helping these new conceptual frameworks? Compound microscope! Printing press (Gutenberg 1440) A flurry of scientific activity (scientific revolution!) arose during the Enlightment and Romantic era. Ben Franklin: electric cable theory (1751) Luigi Galvani (c 1780): noticed and experimented on frogs’ legs What were the contributions of Bell and Magendie, Gall, Flourens, and Broca? Bell & Magendie 1810: Cut the dorsal and ventral spinal roots separately to test if they carried information in different directions; cutting only ventral resulted in muscle paralysis. Dorsal roots carry sensoryinformation into spinal cord. Nerve fibers carry information only one direction. Within each nerve is a mixture of many wires, some bring info to brain and spinal cord; others send info to muscles. Gall 1827: According to Gall, different behavioral traits could be related to the size of different parts of the skull. Phrenology. Flourens 1823: Experimental ablation in birds; cerebellum involved in coordination/movement; concluded that cerebrum was involved in sensation and perception. Rejected Gall. Mental functions equally localized throughout the brain. Broca 1861: By carefully studying the brain of a man who had lost the faculty of speech after a brain lesion, he became convinced that different functions could be localized to different parts of the cerebrum. Left frontal lobe = speech Make sure you know the technical and conceptual contributions of scientists such as Schwann, Golgi, Sherrington, Kolliker and Cajal. Theodore Schwann 1839: Discovered “Schwann” cells, which are the principle glia in the peripheral nervous system. Proposed what came to be known as cell theory: all tissues are composed of microscopic units called cells. Microscopy as well Camillo Golgi 1873: developed silver chromate stain to visualize neurons and their neurites, called Golgi stain Proponent of “reticular theory”: CNS exempt from cell theory CNS structure analogous to a spider web Dendrites provide nutrients for the cell, not involved in signal transduction Continuous Sherrington: reciprocal innervation; coined “synapse” Kolliker: histology Santiago Ramon y Cajal 1889: Used Golgi stain to deduce own view (Neuron Doctrine) – contiguous. Neuron Doctrine = the concept that the neuron is the elementary functional unit of the brain and that neurons communicate with each other by contact, not continuity.•referred to as the father of modern neuroscience •refined the Golgi stain •proponent of the “neuron doctrine” 1. Neuron is an anatomical unit; 2. Neuron is comprised of 3 parts: cell body/soma, dendrites, and axon; 3. Neurons are contiguous, not continuous; 4. Connection points between neurons are called synapses; 5. Neuron is a physiological unit Contiguous 2 II. The basic unit of the nervous system: Neurons (mostly) and glia. What is a neuron and what are its main functions? Also known as nerve cell, neurons are electrically excitable cells that process and transmit information through electrical and chemical signals; the information processing cell of the nervous system. Most neurons use action potentials to send signals over a distance, and all neurons communicate with one another using synaptic transmission. What is a nerve? Bundles or strands of many axons in the peripheral nervous system.