Nervous Tissue - Student Version PDF

NERVOUS TISSUE Basic Histology Insert Image Here  Learning Objectives 1. Describe the structure and function of neurons and explain the main differences between dendrites and axons 2. List and describe the main structural types of neurons 3. Describe the s...

NERVOUS TISSUE Basic Histology Insert Image Here  Learning Objectives 1. Describe the structure and function of neurons and explain the main differences between dendrites and axons 2. List and describe the main structural types of neurons 3. Describe the structure and functions of the different types of glial cells in the PNS 4. Describe how a myelin sheath is formed in the peripheral nervous systems and explain the function of the sheath 5. Describe the structure and functions of the different types of central neuroglial cells 6. Compare oligodendrocytes to Schwann cells, and how they relate to demyelinating disorders of the CNS to PNS 7. Explain the structure and function of the blood-brain diffusion barrier and its pharmacological relevance 8. Describe the location, structure and function of ependymal cells. 9. Briefly discuss the morphological variability of neurons 10. Describe the histological organization of the central nervous system 11. List the main features of the cerebral and cerebellum cortex 12. Explain the histological organization of the spinal cord, and the location of somatic motor and sensory neuron cell bodies. 13. Prepare a diagram showing the different meninges in relationship to bone, nervous tissue and subarachnoid blood vessels. 14. Predict the primary nervous tissue cells involved in the following conditions: Multiple sclerosis, Guillaine Barre, astrogliomas, encephalitis, hydrocephalus (overproduction), Alzheimer’s & meningitis. 15. Outline the path of the sensory and motor fibers through the somatic and autonomic (para/sympathetic) reflex arcs, and the location and structure of the cell bodies of neurons involved. 16. Explain and identify the histological differences between a synaptic transmission and the neuromuscular junction 17. Describe the structure of a nerve, including its connective tissue components (epineurium, perineurium, endoneurium) 18. Outline the histological and structural differences between sensory (dorsal root), sympathetic and parasympathetic ganglia 1: Nervous Tissue Cells - Neurons 2: Nervous Tissue Cells - Glial Cells 3: Central Nervous System 4: Peripheral Nervous System - Somatic 5: Peripheral Nervous System - Autonomic NERVOUS TISSUE  Four Basic Tissue Types Muscle: Contractile Nerve Tissue: Tissue Transmits electrical signals Connective Tissue: surrounds and supports Epithelia: lines or other tissues covers surfaces, ducts and glands  The Nervous System Functional divisions Morphological divisions Somatic: Consciously receive afferent sensory Central Nervous System (CNS): information from most body parts (except viscera, Brain and spinal cord smooth muscle and glands) and sends voluntary Peripheral Nervous System (PNS): motor innervation to skeletal muscles. cranial, spinal, and peripheral nerves, ganglia (outside CNS) Autonomic: Unconsciously receive afferent sensory information from viscera, smooth muscle and glands, and sends involuntary motor innervation to smooth and cardiac muscles, and glands. Sympathetic (Fight or Flight) Parasympathetic (Rest & Digest) Enteric (GI Tract)  Nervous Tissue Cells Concussion Neuroepithelial Cells Gliomas Neuroblasts Gliablasts Neurons: Structural and functional Glial Cells: Physical and metabolic unit of nervous system, electrical support, electrical insulating cells. signaling cells. Post-mitotic cells. Capable of mitosis (Form gliomas). Neuron x Neuroblast x Glial Cell Nissl Stain Golgi Stain  The Neuron Nissl Bodies: clumps of rER Dendrites Neuropil: mesh of axons and dendrites Glial Cells Perikaryon Myelin Axon Axon Hillock Node of Ranvier Synapse Glial cell nucleus Nucleolus  Multipolar neurons convey Motor impulses from CNS (brain, spinal cord, ganglia) to effector cells (muscle, glands, etc.). Somatic and visceral efferent fibers. Pseudo-unipolar or bipolar Integrative Sensory neurons convey impulses from sensory receptors to the CNS. Somatic and visceral afferent fibers. Multipolar neurons form communicating and integrating networks between sensory and motor neurons. 99% of all neurons  Synaptic Transmission Pre-Synaptic Axon Neurons communicate with other neurons by synapses. In a chemical synapse pre- synaptic axons release neurotransmitters (NTs) (Glutamate, Acetylcholine) into a Vesicle with synaptic cleft, where they bind to receptors Neurotransmitters on post-synaptic membrane (usually in dendrites, but can be cell bodies or other axons). NTs are degraded or re-uptaken. Synaptic Cleft Post-Synaptic Membrane (Dendrite, Soma, Axon)  PERIPHERAL NERVOUS SYSTEM CENTRAL NERVOUS SYSTEM Nerves (Axons, Schwann Cells), Neurons (Cell Bodies, Axons, Dendrites), Central Ganglia (Neuron Cell Bodies, Satellite Cells) Neuroglia Oligodendrocyte Schwann Cell  Knowledge Check You examine a histopathological slide of the spinal cord and notice decreased levels of Nissl bodies in the cytoplasm of motor neurons. You are concerned that this may indicate a decreased secretory activity because Nissl bodies are composed of: A. synaptic vesicles and acetylcholine. B. Ribosomes and rough endoplasmic reticulum. C. Golgi Apparatus D. Neurofilaments and microtubules. E. Smooth ER and mitochondria. 1: Nervous Tissue Cells - Neurons 2: Nervous Tissue Cells - Glial Cells 3: Central Nervous System 4: Peripheral Nervous System - Somatic 5: Peripheral Nervous System - Autonomic NERVOUS TISSUE  PNS Glial Cells Schwann Cells: Myelinate axons in PNS. Each Schwann cell myelinates only one axon. An axon is being myelinated by many Schwann cells. Satellite Cells: Surround neuron cell bodies located in the PNS (ganglia) Schwann Cell Axon Myelin Sheath  PNS Myelination The Myelin sheath consists of concentric layers of Guillain-Barré Syndrome lipid membranes and transmembrane proteins (myelin basic protein) insulating the axon. The Schwann cell cytoplasm is extruded into thin layers that wrap around the axon. Cleft of Schmidt-Lanterman Schwann Cell Outer Collar Axon Inner Collar Fused Plasma Membranes Axon Cytoplasm Extracellular Space Cytoplasm  Nodes of Ranvier Axon Junctions between adjacent Schwann cells. Node of Ranvier Devoid of myelin. Facilitate fast saltatory signal transmission. Schwann Cell Cytoplasm Myelin Axon Voltage-gated Na+ and K+ channels  Myelinated Nerve Fibers Cross Section Longitudinal Section Axon Axon Myelin Node of Ranvier Schmidt-Lanterman Schmidt-Lanterman Clefts Clefts Osmium Fixed Toluidine: Stains Myelin PNS Unmyelinated Nerve Fibers Unmyelinated cells axons are still surrounded by Schwann cell cytoplasm (not forming sheaths) One Schwann Cell engulfs many axons.  CNS Glial Cells The CNS contains four types of glial cells, collectively called the central neuroglia. Derived from neuroepithelial cells* lining the neural tube. Visible as small nuclei (compared to neurons), difficult to distinguish. Astrocyte Neuron Microglia Oligodendrocyte Ependymal Cells  Oligodendrocytes Oligodendrocyte Axon Myelin Sheath Neurons Node of Ranvier One cell myelinates many axons, cell processes spiral around different axons, (difficult to distinguish). Demyelinating diseases result in severe neurological disorders such as Multiple Sclerosis (loss of myelination in CNS) Multiple Sclerosis  CNS Myelination Node of Oligodendrocyte Ranvier Myelin Sheath Cell Process Myelin (Membrane) Axon Myelination *Unmyelinated axons in the CNS are often found to be bare  Astrocytes Foot processes form network between capillaries, fibers, and neurons to mediate metabolic exchange, and potassium buffering (difficult to distinguish). Contain intermediate filaments composed of a distinct protein, glial fibrillary acidic protein (GFAP). Contribute to blood-brain barrier. Astrocyte end-feet Myelinated fiber Astrocytes Special Stain Capillary Astrocytoma  Blood-Brain Barrier 1.Complex tight junctions between endothelial cells. 2. Endothelial basement membrane. 3. Astrocyte end-feet surrounding the capillary wall. Astrocyte End-feet Endothelial Cell Pericyte Tight Junction The blood–brain barrier (BBB) protects the CNS from fluctuating levels of electrolytes, hormones, and tissue metabolites circulating in the blood vessels. O2, CO2 and certain lipophilic substances can pass, others (ex. glucose) have to be actively transported by specific receptor-mediated endocytosis. (No BBB in choroid plexus, pituitary gland, pineal gland, and a few others) Microglia Special Stain Highly motile phagocytic cells, reactive to injury, mediate immune reactions. (Derived from monocyte progenitors) Microglia Smallest neuroglia, cytoplasmic extensions (difficult to distinguish) Encephalitis  Ependymal Cells Simple cuboidal-columnar layer of neuroepithelial Spinal Cord cells lining of neural tube. Line the CSF filled cavities: central canal (spinal cord) and the ventricles (brain) Contain cilia and microvilli modifications. Modified to form choroid plexus: produce and maintain CSF (Cerebrospinal Fluid) Brain Surface Central Canal Hydrocephalus Ependymal Cells Ventricle  Knowledge Check Multiple Sclerosis (MS) is an autoimmune disorder of the central nervous system in which the body creates antibodies against myelin. Some people with severe MS may lose the ability to walk independently or at all, while others may experience long periods of remission without any new symptoms. To what type of cell is the antibody in MS produced? A. Oligodendrocyte B. Schwann Cell C. Astrocyte D. Microglia E. Ependymal Cells 1: Nervous Tissue Cells - Neurons 2: Nervous Tissue Cells - Glial Cells 3: Central Nervous System 4: Peripheral Nervous System - Somatic 5: Peripheral Nervous System - Autonomic NERVOUS TISSUE  Neurons in the CNS Neurons are characterized by wide variations in size as well as shape. Can be classified as small (usually interneurons) or large neurons (motor, sensory, projection interneurons). Small neurons are difficult to distinguish from neuroglia. Large neurons in the CNS: Pyramidal cells and Purkinje cells.  CNS Organization CNS consists of the brain (cerebrum, cerebellum, brain stem) and spinal cord Grey Matter: Neuron cell bodies, axons, dendrites, synapses, neuroglia, blood vessels White Matter: Myelinated axons, glia, blood vessels Cavities (CSF, Ependymal Cells): Ventricles (brain), central canal (spinal cord) Meninges (CT coverings): Dura mater, arachnoid and pia mater Brain: Outer grey matter, inner Spinal Cord: Inner grey matter, white matter, deep nuclei. outer white matter Each functional region of the gray matter has a characteristic variety of cell bodies  Spinal Cord Organization of White and Grey Matter Dorsal Horn (Sensory neuron cell bodies Sensory are in the PNS ganglia) Grey Matter Ventral Horn Somatic motor Motor Neuron Spinal Nerves: PNS Cell Bodies White Matter Information In/Afferent (Sensory) = Dorsal (Posterior) ALS: Amyotrophic Information Out/Efferent (Motor) = Ventral (Anterior) Lateral Sclerosis  Granule Cell (Small Neuron) Grey Pyramidal Matter Neuron Cerebral Cortex Organization of Brain’s Cerebrum Cerebellar Cortex Organization of Brain’s Cerebellum Purkinje Cell Molecular Purkinje Cell Layer Purkinje Cell Layer Granular Layer White Matter  Hemorrhages Dura Mater Bone 1. Dura (DCT, continuous with periosteum). Arachnoid 2. Arachnoid (LCT, Trabeculae, space with Subarachnoid CSF and blood vessels). Space ** 3. Pia (LCT, innermost (CSF Filled) adheres to nervous tissue, ** * Pia Mater continuous with * perivascular CT). Nervous Tissue Meninges CT layers that cover the CNS (brain and spinal cord)  Knowledge Check Name the specific region of the spinal cord in which these cells are located. 1: Nervous Tissue Cells - Neurons 2: Nervous Tissue Cells - Glial Cells 3: Central Nervous System 4: Peripheral Nervous System - Somatic 5: Peripheral Nervous System - Autonomic NERVOUS TISSUE  PNS: Somatic Division Somatic peripheral nerves: (spinal or cranial) Ganglia (collections of cell bodies outside the CNS) Specialized nerve endings Conduct conscious sensation to the CNS (afferent sensory fibers from most body parts except viscera), or voluntary commands away from the CNS (efferent motor nerves to skeletal muscle). Exception: Somatic Reflex Arc (Unconscious & Involuntary) Information In/Afferent (Sensory) = Dorsal (Posterior) Information Out/Efferent (Motor) = Ventral (Anterior)  Sensory Receptors Afferent sensory receptors: Specialized structures at the distal tips of the peripheral processes (axons) of sensory neurons. Have many different structures, but all can initiate a nerve impulse in response to a stimulus (touch, temperature, vision, smell, sound) from the external environment. ex. Pain, temperature and touch receptors in the skin.  Sensory Receptors Pain, temperature and touch receptors in the skin Pacinian Corpuscle Meissner’s Corpuscle Free Nerve Endings Ruffini Corpuscle  Dorsal Root Ganglion Thickening of spinal dorsal roots containing cell bodies of afferent somatic and autonomic sensory neurons. Satellite Cells Cell bodies surrounded by a ring of satellite cells. No synaptic connections within the ganglion (little neuropil) Pseudounipolar Neuron  Somatic Motor Neurons Cell bodies are in the ventral horn of the spinal cord grey matter (some in brainstem) Nissl Multipolar Somatic efferent neurons convey Stain Neuron voluntary motor impulses to effector skeletal muscles (involuntary in reflex arc)  Special Stain Motor Neuron Axon Neuromuscular Muscle Fiber Junction Neuromuscular Junction: Specialized synapse between motor neurons and muscles. Transmits a signal to the muscle fiber causing its contraction. A motor unit is a motor neuron and all the muscle fibers it supplies. Neuromuscular Axon Junction Terminal Schwann Cell Primary synaptic cleft Basement Membrane Secondary synaptic cleft Muscle Fiber Voltage-gated Na+ channel Ach receptor  Axon Terminal Synaptic Cleft Synaptic Vesicles Basement Membrane Muscle Fiber  Peripheral Nerves A peripheral nerve is a bundle of nerve fibers (axons) held together by connective tissue. These carry sensory and motor information between the organs and tissues of the body (PNS) and the brain and spinal cord (CNS)  Peripheral Nerve Architecture Epineurium: Endoneurium: DICT around entire nerve LCT around fibers Schwann Cell Perineurium: DICT around fascicles Myelin Unmyelinated Nerve Fiber Fascicle Axon Peripheral nerves can contain thousands of axons Afferent & efferent fibers Somatic (myelinated) Autonomic (myelinated & Myelinated unmyelinated) Nerve Fiber Held together by three distinct types of CT sheaths Peripheral Nerves Cross Section  Peripheral Nerves Myelinated Axon Endoneurium Fibroblast Schwann Cell Cross Section  Peripheral Nerves Myelinated Axon Schwann Cell Fibroblast Longitudinal Section  Knowledge Check What structure would be found in the area indicated by the arrow 1: Nervous Tissue Cells - Neurons 2: Nervous Tissue Cells - Glial Cells 3: Central Nervous System 4: Peripheral Nervous System - Somatic 5: Peripheral Nervous System - Autonomic NERVOUS TISSUE Autonomic Sensory Neurons Somatic and Autonomic PNS have the same organization for peripheral nerves, dorsal root ganglia and sensory neurons (except for the types of sensory receptors). Autonomic receptors respond to stimuli occurring within the body from visceral organs and blood vessels. Autonomic Motor Neurons: Sympathetic Somatic Motor Neuron Autonomic Motor Neurons: Sympathetic Sympathetic Presynaptic Motor Neuron (cell bodies in lateral horn of thoracic spinal cord - CNS) Sympathetic Postsynaptic Motor Neuron (cell bodies in para/pre-vertebral ganglia - PNS) Somatic Motor Neuron Autonomic Motor Neurons: Sympathetic Sympathetic Presynaptic Motor Neuron (cell bodies in lateral horn of thoracic spinal cord - CNS) Sympathetic Postsynaptic Motor Neuron (cell bodies in para/pre-vertebral ganglia - PNS) Somatic Motor Neuron Sympathetic Ganglia Paravertebral (Sympathetic Trunk)  Autonomic Motor Neurons: Sympathetic Sympathetic Presynaptic Motor Neuron (cell bodies in lateral horn of thoracic spinal cord - CNS) Sympathetic Postsynaptic Motor Neuron (cell bodies in para/pre-vertebral ganglia - PNS) Splanchnic Nerve Sympathetic Ganglia Paravertebral (Sympathetic Trunk) Sympathetic Ganglia Prevertebral (Ex. Celiac Ganglion) Autonomic Motor Neurons: Parasympathetic Parasympathetic Motor Neurons Pre-synaptic cell bodies: (CNS) Brainstem, Sacral Spinal Cord Post-synaptic cell bodies: (PNS) Visceral Ganglia Parasympathetic Ganglia (Visceral: near or at target organ)  Sympathetic Ganglia Prevertebral Paravertebral (Sympathetic Trunk) Lipofuscin Multipolar Neuron Satellite Cell  Parasympathetic Ganglia Meissner’s Plexus Enteric Nervous System (Submucosal) Plexuses of parasympathetic ganglia and fibers, and post-synaptic sympathetic fibers. Regulates function of GI tract. Thought to function independently from the CNS. Auerbach’s Plexus DICT (Myenteric) Parasympathetic Ganglion in Pancreas Smooth Muscle  Knowledge Check Which of the following cell types are located in the dorsal root ganglion? A. Sympathetic motor neurons B. Pyramidal neurons C. Autonomic sensory neurons D. Purkinje Cells E. Parasympathetic motor neurons  Relevant Slides Histology Guide Virtual Slide Box: http://www.histologyguide.com/ Neurons and PNS Glial Cells http://134.84.138.9/slide-view/UCSF-163-spinal-cord/06-slide-1.html?x=18583&y=11842&z=25.0&page=1 http://134.84.138.9/EM-view/EM-152-peripheral-nerve/06-photo-1.html?x=9055&y=2253&z=21.3&page=1 Cerebral Cortex http://slides.uwo.ca/Original%20scans/Cerebral%20and%20Cerebellar%20Cortex/61%20-%20Cerebral%20-%20occipital- sm.html http://134.84.138.9/slideview/MHS-284-brain/06-slide-1.html?x=0&y=0&z=-1&page=1 Cerebellar Cortex http://slides.uwo.ca/Original%20scans/Cerebral%20and%20Cerebellar%20Cortex/60%20-%20Cerebellum-sm.html http://slides.uwo.ca/Original%20scans/Cerebral%20and%20Cerebellar%20Cortex/65%20-%20Cerebellar%20cortex-sm.html http://134.84.138.9/slideview/MHS-283-brain/06-slide-1.html?x=0&y=0&z=-1&page=1 Spinal Cord http://slides.uwo.ca/Original%20scans/Cells%20of%20the%20Central%20Nervous%20System/4%20-%20SpinalCord-sm.html http://134.84.138.9/slideview/UCSF-163-spinal-cord/06-slide-1.html?x=0&y=0&z=-1&page=1 http://134.84.138.9/slideview/MH-047-spinal-cord/06-slide-1.html?x=17772&y=9538&z=6.7&page=1  Relevant Slides Histology Guide Virtual Slide Box: http://www.histologyguide.com/ Ependymal Cells http://slides.uwo.ca/Original%20scans/Cells%20of%20the%20Central%20Nervous%20System/161%20-%20SpinalCord- sm.html Meninges http://slides.uwo.ca/Original%20scans/Cells%20of%20the%20Central%20Nervous%20System/8%20-%20SpinalCord-sm.html Peripheral Nerves http://slides.uwo.ca/Original%20scans/Spinal%20Cord%20and%20Ganglia%20&%20Peripheral%20Nerve/29%20- %20Nerve%20L-section%20osmic%20acid-sm.html http://slides.uwo.ca/Original%20scans/Spinal%20Cord%20and%20Ganglia%20&%20Peripheral%20Nerve/30%20- %20Nerve%20X-section%20osmic%20acid-sm.html http://134.84.138.9/slide-view/MH-052-peripheral-nerve/06-slide-1.html?x=0&y=0&z=-1&page=1 Ganglia http://134.84.138.9/slide-view/MH-050-dorsal-root-ganglion/06-slide-1.html?x=6981&y=6998&z=14.7&page=1 http://134.84.138.9/slide-view/MH-059-sympathetic-ganglia/06-slide-1.html?x=10891&y=36676&z=38.2&page=1 http://134.84.138.9/slide-view/MH-123-colon/06-slide-1.html?x=0&y=0&z=-1&page=1