Handout Module A 1 ES 348 8 29 2023 Neuroscience ES OT 342 By the end of this module you will be able to Describe the elementary components of the nervous system as they pertain to a simple reflex Describe basic features of neuronal signaling by considering some structural and functional properties of different segments of the neuron Understand the function and role of various glial cells in promoting neuronal function Describe the neuronal transport mechanism required to maintain the integrity of distal neuronal components Complete on line Assignment Fall 2023 Graded Syllabus Assignment before deadline Complete on line Quiz Module A 1 Cytology Graded Assessment before deadline 1 Handout Module A 1 CYTOLOGY OF NEURONS Handout A 1 Copyright 2020 cannot be reproduced sold unless for use within the confines of this course Goals for today s lecture Bear 4th Ed Chapter 2 1 2 3 4 To describe the basic cells that comprise the nervous system To describe the fundamental features of neuronal signaling by considering some structural and functional properties of different segments of the neuron To understand the basic role of various glial support cells To describe a specialized transport mechanism used to shuttle particles along the axon required to maintain the integrity of distal neuronal components REFLEX ARC Recorded Video Lecture 1A Introduction The Reflex Arc REVIEW BEFORE LECTURE 1 Why Study Reflexes Reflexes are simple and nearly instantaneous motor responses to a given stimulus A reflex is made possible by local neural circuits neurons nerve cells called A reflex does depend on conscious thought or processing by the brain A reflex provides a simple understanding of how neurons function and Components of a Reflex i ii iii iv Receptor Sensory Neuron Motor Neuron Effector 2 Handout Module A 1 Patellar tap knee jerk reflex Review Spinal Reflex U tube video https www youtube com watch v 6 wsNvZtcA4 What do test of simple reflexes reveal Reflexes are evaluated because they provide information about the tone of the Nervous System As a general rule 1 in reflexes hyporeflexia are associated mainly with dysfunction in the Peripheral Nervous System PNS 2 in reflexes hypereflexia are associated most often with dysfunction in the Central Nervous System CNS 3 Handout Module A 1 In Class Lecture Cytology 1 INTRODUCTION The Neuron In class lecture A 1B The best estimate is that the human brain contains about 100 BILLION neurons Although nerve cells can be classified into perhaps as many as nevertheless share many common features 10 000 different types they An important point is that nerve cells with basically similar properties can produce very different actions because of connections with each other and with sensory receptors and muscle Precise The nervous system has two distinct classes of cells Resting state interrupted to communicate called action potential ex speaking in classroom to students i ii Neurons Actually participate in communication and action Glial Cells Not excitable but are higher in number 2 NEURONS Neurons are the functional units of the nervous system and differ from most other cells in the body in being excitable see Bear Fig 2 8 4 Handout Module A 1 Myelin used to help action potential move faster 5 Handout Module A 1 A typical neuron has four morphologically defined regions Read Bear P 29 42 Cell Body Soma metabolic center of the neuron helps maintain the vitality of the whole cell ten percent of the neuron Dendrites receptive portion of the neuron similar to antenna receiving information from other neurons 10 000 communication nerves 8 000 go to the dentrites main receptive portion i ii iii Axons Largest axon can be up to 40 inches long 120 m s rate at which messages allows for conducting iv Terminal Sites pre synaptic area Note Mature neurons do not undergo proliferation doesn t multiply Therefore most disease processes that affect neurons are associated with neuronal degradation and loss DAMAGED NEURONS ARE NOT REPLICATED THEY ARE REMOVED IN A MATURE SYSTEM GLIAL CELLS CAN REPLICATE Ramon y Cajal Read P 27 a neurobiologist working around the turn of the last century was responsible for the following doctrines i Neuron Doctrine ii Principle of dynamic polarization iii Principle of connection specificity entails three important considerations a 6 Neuronal differentiation The feature that most dramatically distinguishes one neuron from another is specifically the and form of a neurons processes Neurons are classified into three large groups based on the number of neurites see Bear Fig 2 22 Handout Module A 1 b c a Unipolar cells b Bipolar Neurons c Multipolar Neurons Neurons can also be further classified by shape or function into three major groups 7 Afferent feeding information TOWARDS the CNS Efferent Carrying descending information away from the CNS Interneurons Provide links between afferent and efferent un certain parts of Handout Module A 1 a b c afferent neuron bipolar neuron soma nodes of ranvier axon hilcock multipolar excitability dendrites 3 GLIAL CELLS Read Bear pages 49 52 In class lecture A 1C Nerve cell bodies and axons are surrounded by glial cells Greek glia glue There are between and times more glial cells than neurons in the CNS of vertebrates Glial cells are non excitable Glial cells are probably not essential for processing information but they are though to have several other vitally important roles i Supporting Element provide firmness to the brain ii Form myelin allows axon to move messages faster increase Myelin in CNS is supported by oligodendrocytes glial cell Provides myelin in multiple areas Shwaan cells in PNS iii Scavengers in the CNS after any injury they clean up areas where cells died and make scar tissue 8 Handout Module A 1 iv Buffer ions and neurotransmitters v Guide neurons during development v form the blood brain barrier provide barrier in the brain from certain chemicals from entering the blood vii Nutritive Function Glial cells in the vertebrate nervous system are divided in two major classes based on their size 1 Microglia Bear p 52 act as the immune system in the CNS come after injury infection or disease ii Macroglia Bear p 49 a Oligodendrocytes provide myelin in the CNS b Schwann cells Myelin in the PNS c Astrocytes Most abundant 1 3 4 5 6 7 functions from above glial cells clinical context glial cells can reproduce glioma cancer from glial cells 9 Handout Module A 1 4 AXOPLASMIC AXONAL TRANSPORT In class lecture A 1D The