Neural Tissues Lecture 2022-2023-10-17 PDF

Introduction Definitions Neurons Glia Pathologies Neural Tissues Structures, Functions, Cell Types Dr. Harry Witchel Discipline Leader in Physiology Room 2.04 Trafford Centre 01273 873 549 [email protected] 1 /35 Introduction Definitions Neurons Glia Pathologies Learning Outcomes Intro: ner...

Introduction Definitions Neurons Glia Pathologies Neural Tissues Structures, Functions, Cell Types Dr. Harry Witchel Discipline Leader in Physiology Room 2.04 Trafford Centre 01273 873 549 [email protected] 1 /35 Introduction Definitions Neurons Glia Pathologies Learning Outcomes Intro: nervous system as a communication network Definitions: structures & directions Neurons: Classification and functions  Recognise histology & know functions Glial cells: Classification and functions  Recognise histology & know functions Pathologies: Examples  Gliomas and Neuroblastomas 2 /35 Introduction Definitions Neurons Recommended Reading Tortora  Chapter 12 (Nervous Tissue) Kandell, 5th ed.  Much more detailed text book Pathologies Glia  Chapter 4: esp. Cytology of Neurons  Some anatomy is not covered Guyton does not really cover this  This topic is more anatomy & histology 3 /35 Introduction Definitions Purpose of Nervous System Neurons Communication: Via Information Processing Glia Pathologies Sensory Detection Behaviour Motor Activity 4 /35 Introduction Definitions Neurons Glia Central vs. Peripheral Nervous Systems Central Nervous System (CNS) Peripheral Nervous System (PNS) Brain & Spinal Cord Information processing including reflexes and behaviour Sensory detection Pathologies Motor activation Nervous system derived from ectoderm *E 5 /35 Introduction Definitions Complexity: Many cells Neurons 1011 neurons 1014 synapses 1.5 kilograms 108 neurons (more than in spinal cord) Pathologies Glia Milky Way (Galaxy) Enteric nervous system 1010 stars 6 /35 afferent neuron: transmit sensory information to brain/spinal cord A Introduction Definitions Neurons Glia Pathologies Afferent vs Efferent E efferent neuron: motor neurons transmitting information from brain to effector organ i.e. muscle afferent connection arrives at VS. an efferent connection exits — the brain7 /35 Introduction Definitions Motor ganglion: Glia group of cell bodies outside CNS Neurons ganglion Autonomic. Parasympathetic ganglion  Pathologies Smaller neurons eccentric nuclei In CNS groups of neurons called “nucleus” Example of Sensory ganglion: Dorsal root ganglion Big neurons, central nuclei 8 /35 DORSAL Dorsolateral ROSTRAL Ventrolateral Introduction Neurons Definitions Directions in human prefrontal cortex DORSAL Pathologies Glia CAUDAL Rostral – caudal axis bends Dorsomedial Dorsal – lateral axis bends Ventromedial 9 /35 Introduction Definitions Neurons Glia Pathologies Brodmann Areas* of the Neocortex Brodmann Area 4 = ~primary motor cortex Regions of cortex are numbered 1-52. Boundaries determined by cellular architecture Brodmann Area 17 = ~primary visual cortex Each Brodmann area has a particular set of inputs and outputs. Often a Brodmann area will have a function * You do not need to know what each Brodmann area does or where it is, but you do need to know the name “Brodmann”, that there is a system for naming cortical areas, and how to use a Brodmann diagram to 10 find /35 a particular brain region Introduction Definitions Neurons Glia Pathologies neurons CNS neuron: nucleus within cell body and extends one or more processes Input Output boutons) From Pocock & Richards 11 /35 Introduction Definitions Myelin - Wrapped around axon Pathologies Glia Neurons Electrically Insulates. Made of many layers of cell membrane Peripheral Nerve in X-section Black circle = myelin surrounding axon Node of Ranvier Myelin’s Purpose:  conduction velocity So does  diameter Long section 12 /35 Introduction Definitions all neurons have just 1 axon Pathologies Glia neurons: multipolar, bipolar and unipolar Neurons neuron classifications majority of neurons several dendrites = “multipolar” Schematic 13 /35 Pyramidal cell neocortex Purkinje cell cerebellum Dorsal Root Ganglion (DRG) Sensory Neuron Introduction Glia Neurons Definitions Important Neurons Axon Pseudounipolar Pathologies Santiago Ramon v Cajal 14 /35 Introduction Definitions Neurons Glia Pathologies neuron classifications Bipolar one dendrite one axon least numerous sensory neurons – e.g. retina Pseudounipolar * one axon one dendrite e.g. dorsal root ganglion 15 /35 Introduction Definitions Synaptic transmission: chemical Synapse = A functional link Neurons Post-synaptic cell =  neuron,  myocyte, or  gland Glia Chemical Synapse  Big gap = ~ 30 nm  Common throughout nervous system  Signalling is NOT in retrograde direction* E Pathologies *E There are some exceptions Presynaptic cell releases neurotransmitter Postsynaptic cell receptor —> electric signal 16 /35 Introduction Definitions Divergent = A single neuron sends its output signal to many neurons Convergent = multiple inputs influence a single neuron Neurons Convergent vs. Divergent Here the output from neuron A diverges to neurons J, K & L Here the outputs from neurons P, Q & R converge onto neuron Z  E.g. Retina .  E.g. Skin P Glia J Pathologies A K L Z Q R 17 /35 Introduction SPINAL CORD (CNS) Neurons Definitions Interneurons occur only in CNS. They are neither motor nor sensory. They process signals sensory Glia To peripheral nervous system (rest of body) Pathologies motor 18 /35 have no action potentials *E X do not form synapses *E X Introduction Pathologies Glia Neurons Definitions glia differ from neurons. glia: are able to divide # # form the myelin sheathes and are the most common source of tumours of the nervous system 19 /35 Introduction Definitions Neurons Glia Pathologies In Class Question Which Brodmann area is most rostral?  10  8  17  20 20 /35 Introduction Definitions Neurons Glia Pathologies In Class Question Which Brodmann area(s) corresponds to the sensory cortex?  9  4 1, 2 & 3 41 & 42 21 /35 Introduction Definitions glial cells supportive protective neurons basic nerve cells impulse conducting Also called neuroglia Pathologies Glia Neurons Many More Glial Cells than Neurons 1 : 10 - 50 22 /35 Introduction Definitions Neurons Glia Pathologies Glial Cell Types: Overview microglial cell ependymal cell neuron oligodendrocyte astrocyte pia mater 23 /35 production / maintenance of myelin sheath in CNS Introduction Pathologies Glia Neurons Definitions oligodendrocyte (CNS): One oligodendrocyte myelinates multiple axons (from different neurons) 24 /35 Introduction Definitions astrocyte (CNS) Pathologies Glia Neurons supports neurons: assists neuronal development / growth (neurotrophic), protects neurons from harmful substances, astrocyte Its “feet” on processes abut blood vessel endothelium – influence BLOOD FLOW and BLOOD-BRAIN BARRIER Star-shaped 25 /35 Introduction Definitions immune cells, protect neurons from disease, migrate to injury sites, engulf microbes / debris, mesodermal origin Processes very active! See movie listed in notes Pathologies Glia Neurons microglia (CNS): Of mesodermal origin (like other immune cells) Also develop from monocytes 26 /35 line brain’s ventricles and central canal of spinal cord, form CSF Introduction Pathologies Glia Neurons Definitions ependymal cells (CNS): cilia + microvilli on apical membrane 27 /35 production / maintenance of myelin sheath, PNS regeneration Introduction Pathologies Glia Neurons Definitions Schwann cells (PNS): 1 axon wrapped per Schwann cell Compare to oligodendrocytes (in CNS) 28 /35 support neurons, regulate exchange of materials between neurons and interstitial fluid Introduction Pathologies Glia Neurons Definitions satellite cells (PNS): Perform analogous role in PNS to what astrocytes do in CNS These images are from dorsal root ganglia (just outside spine). The big round cells are pseudo-unipolar neurons, and the small nuclei (dark blue dots) surrounding the neurons belong to satellite cells. 29 /35 Introduction Definitions Neurons glial classifications Central Nervous System  Astrocyte  Oligodendrocyte  Ependymal cell  Microglial cell Pathologies Glia Peripheral Nervous System  Schwann cell  Satellite cells 30 /35 Introduction Neurons Definitions Meninges Spinal cord Pathologies Glia Brain DM Ar PM A WM = dura mater = arachnoid = pia mater = arteriole = white matter See Anatomy lecture on meninges for explanation of topographic anatomy 31 /35 Introduction Definitions Neurons glial pathology: glioma glioma • largest group of primary tumours derived from glial cells • usually highly malignant Pathologies Glia • grow rapidly • difficult to remove completely with surgery • Usually Wordpress inside cranium 32 /35 Introduction Definitions Neurons Neural pathology: Neuroblastoma • tumour (cancer) • most common in children & infants • outside cranium • derived from neural crest cells from sympathetic NS Glia •  Catecholamine levels (often) • Survival rates vary: depends on type Pathologies • Initial prognosis is typically good • Survivors often develop neurological problems ~30 years later • treatment depends on type 33 /35 Introduction Definitions Neurons Glia What You Have Learned Neurons  Types: Unipolar, Bipolar, Multipolar  Sensory, Motor, Interneuron  Cells: Pyramidal, Purkinje, DRG Sensory Glia  Cells types: Astro, Oligo, Satel, Eppen, Schwann  Myelin Pathologies Central vs Peripheral 34 /35