INTRO TO THE NERVOUS SYSTEM Exercises 16 and 20 Nervous System Anatomy CNS Function CSF FlowAgenda • Prelab • Intro to the Nervous System • CNS • PNS • Cell Types • The Brain • Brain Stem • Diencephalon • Cerebellum • Cerebrum • CSF Flow • Preceptor Presentation • PracticalsNervous System Organization • Central Nervous System • Brain and Spinal Cord and all the nuclei and tracts therein • Peripheral Nervous System • Ganglia and nerves outside of the CNS • Other Nervous System Subdivisions • Enteric Nervous System • Neural plexi that help to regulate the GI Tract • Works in concert with CNS • CAN work completely independent of the CNS • Autonomic Nervous System • Parasympathetic - “rest and digest” • Sympathetic - “fight or flight” • Somatosensory Nervous System • Sensory and motor neurons(a)!PNS:!Cranial !nerves!Spinal!nerves!Ganglia!Enteric!plexi!in small!intestine!Sensory!receptors!in skin!CNS:!Brain!Spinal!cord!Nervous(System-Organiza4on-Cell Types • Two Overarching Cell Types in the Nervous System • Neurons • Cells that send and receive action potentials that allow for integration of messages • Neuroglia • “support” cells for the neurons • Essential to protection and possibly play role in disease? • Each type can be further divided into more specific typesNeurons • Three Subtypes of Neurons • Unipolar • One central “neurite” that exends that length of the neuron • A dendritic tree at one end then an axon terminal at the other • Cell body isnt between the two • Uncommon in humans, but present in the cerebellum and cochlear nuclei • Bipolar • Two main extensions • Common in interneurons and special sensory neurons (retina) • Multipolar • Common type of neuron • Single axon, many dendrites that arise from soma • Receive information from many different placesNeurons-Myelin • Myelinated or Unmyelinated • Myelin is a fatty tissue that surrounds some axons • Oligodendrocytes or Schwann cells • Insulate the axons • Increases conduction velocity • Further propagation of the A.P. • Multiple Sclerosis • Nodes of Ranvier • Gaps in the myelin sheath • Action potentials are “recharged” at these nodes • High density of v-gated Na+ channelsAfferent vs. Efferent • Afferent Neuron – Running from the periphery to the CNS • Sensory Neurons! • Take info from periphery to the brain for integration • Unipolar • Efferent Neuron – Running from the CNS to the periphery • Motor Neurons! (also autonomic neurons) • Take info from the brain and cause an action in the periphery • Multipolar • S.A.M.ENeurons-Interneuron Motor SensoryNeuroglia • “Glial Cells” • Maintain the surrounding environment • Form myelin • Provide and maintain support • 6 Types • CNS Neuroglia • Astrocytes • Oligodendrocytes • Microglia • Ependymal Cells • PNS • Schwann Cells • Satellite CellsNeuroglia • Astrocytes – Maintain the cellular environment, keeps neurons in place and forms the blood-brain barrier • Oligodendrocytes – Processes from the cell form the myelin sheath around axons • Microglia – Engulf invading microbes/debris/necrotic tissue • Ependymal Cells – Line the walls of the 4th ventricle, chorid plexus and central canal. Form/circulate CSF • Schwann Cells – Entire cell forms the myelin sheath of PNS neurons • Satellite Cells – Corvers the sensory neuron cell bodies/maintain environement-CNS-Ventricle!Cells of pia mater!Oligodendrocyte!Microglial cell!Neuron!Fibrous astrocytes!Protoplasmic astrocyte!Microglial cell!Ependymal cell!Protoplasmic astrocyte!Myelin sheath!Oligodendrocyte!Neurons!-PNS-Node of Ranvier!Schwann cell!Axon!Myelin sheath!Schwann cell!Unmyelinated axons!-PNS-Transverse section of myelinated axon!Schwann cell:!5000x!TEM!Nucleus!Cytoplasm!Neurolemma!Myelin!sheath!Myelinated!axon!BRAIN STRUCTURE AND FUNCTIONRostral vs Caudal • New directional terms! • Rostral – situated toward the front/tip of the brain (frontal lobe) • Caudal – at or near the tail or posterior of body. In humans, it means toward the feetThe Brain • Complex Structure within the central nervous system • Four Principle Regions • Brain Stem • Diencephalon • Cerebellum • Cerebrum • Highly organized • Distinct areas and structures with very specific functions • NOTE • Brain “talks” with different areas in order to integrate many different stimuli • One area typically doesn’t control everything, but could be essential to that function (sufficiency vs necessity) • PlasticityBrainstem • Three Regions of the Brainstem • Medulla Oblongata • Houses nuclei and ganglia responsible for control of basal functions • Heart Rate, Blood Pressure, Respiration, Reflexes, Parasympathetic nerves • Pons • Houses mainly respiratory control centers • Breathing Rate and Depth of Breathing • Midbrains • Two man Sections • Inferior Colliculi • Part of Auditory system • Controls startle reflex, pitch and frequency processing, spatial localization of sound • Superior Colliculi • Integrates visual cortex • Help to activate eye movements • Following and orienting visual stimuliThe(Brainstem-Midbrain • Superior colliculi • Inferior colliculi Pons • respiratory center Medulla • respiratory • cardiovascular • reflexCerebellum • Means “little brain” • Two hemispheres connected by the vermis • Cerebellar Cortex • Superficial grey matter • Arbor Vitae • Deep white matter • Folia • Cerebellar folds • Controls • Motor function and muscle control/balanceThe(Cerebellum-Cerebellum!Cerebellum • Posture • Balance • CoordinationDiencephalon • Three Main Regions • Thalamus • Hypothalamus • EpithalamusThalamus • This is the “relay station” per se in the brain • Communicates motor and sensory information from cortical areas to lower areas as well to/from the spinal cord • Acts as a Filter • Helps control •