L5-Cell Physiology and Nervous System PDF

L5- CELL PHYSIOLOGY AND NERVOUS SYSTEM STRUCTURAL ORGANIZATION OF NERVOUS SYSTEM Dr.Pugazhandhi Bakthavatchalam Assistant Professor of Anatomy and Physiology, AUACAS, American University of Antigua 10-Jun-22 2  The nervous tissue has the property of: Irritab...

L5- CELL PHYSIOLOGY AND NERVOUS SYSTEM STRUCTURAL ORGANIZATION OF NERVOUS SYSTEM Dr.Pugazhandhi Bakthavatchalam Assistant Professor of Anatomy and Physiology, AUACAS, American University of Antigua 10-Jun-22 2  The nervous tissue has the property of: Irritability Conductivity Because of these properties nerve cells are capable of receiving the information like pain, touch, temperature, pressure etc… Initiates & executes motor responses Receives stimuli from within & outside the body Integrates sensory information 10-Jun-22 3  The nervous tissue is composed of: a. Nerve cell(neuron) b. Nerve cell processes (dendrites and axons) c. Neuroglia (supporting cells- cellular connective tissues of CNS) CELLS OF NERVOUS TISSUE: Two cells: a. Nerve cell (neuron) b. Glial cells (neuroglia) A. NEURON: Functional cell of a nervous tissue Highly specialised to carry information in the form of electric signals from one cell to another B. GLIAL CELLS (NEUROGLIA): - Supporting Cells 10-Jun-22 4 10-Jun-22 5 10-Jun-22 6 10-Jun-22 7  Neurons are the structural & functional units of nervous system Neurons are highly differentiated cells They do not have the power of cell division Present in the range of 100 billions Excitability & conductivity are their main properties 10-Jun-22 8 10-Jun-22 9 10-Jun-22 10  NEURON TYPE LOCATION Pseudo-unipolar neuron Dorsal sensory ganglia of spinal nerves Sensory ganglia of cranial nerves Bipolar neuron Retina of eye, olfactory epithelium, vestibulocochlear ganglia Multipolar neuron Motor neurons forming tracts of brain & spinal cord Motor neurons of anterior horn cells forming peripheral nerves Motor neurons of autonomic ganglia 10-Jun-22 11 10-Jun-22 12  A B 10-Jun-22 13  AMACRINE CELLS LACK AN AXON 10-Jun-22 14 Provides structural & functional support to axons Plays NO ROLE in propagation of nervous impulses They are more than neurons (about 5-10 times more) They form more than half of the brain’s weight Highly branched cells which can produce CSF 10-Jun-22 15 Neuroglial cells in CNS Astrocytes Oligodendrocytes Ependymal cells Microglial cells Neuroglial cells in PNS Satellite or capsular cells Schwann cells or neurolemmocytes 10-Jun-22 16 10-Jun-22 17 10-Jun-22 18 10-Jun-22 19   Axons of a nerve cell is called a NERVE FIBER  Bundles of nerve fibers within the CNS are called TRACTS  Bundles of nerve fibers within the PNS are called PERIPHERAL NERVES  FIBERS OF CNS ARE MYELINATED BY OLOGODENDROCYTES  FIBERS OF PNS ARE MYELINATED BY SCHWANN CELLS 10-Jun-22 20   Endoneurium – delicate connective sheath covering a nerve fiber  Perineurium – connective sheath which covers a group of nerve fibers  Epineurium – dense connective tissue sheath which covers the entire nerve 10-Jun-22 21  Spinal nerves arise form the spinal cord within the vertebral canal  Spinal nerves exit through intervertebral foramen  ALL SPINAL NERVES ARE MIXED NERVES 10-Jun-22 22 10-Jun-22 23 GANGLION- Aggregations of the neuronal cell bodies in PNS, ovoid structures surrounded by a capsule SPINAL NERVE: Each spinal nerve is connected to spinal cord by two roots A ventral root (motor) & a dorsal root (sensory) Dorsal root is characterized by the presence of a spinal ganglion at its distal end, which lies in the intervertebral foramen Both roots unite at the intervertebral foramen to form the typical spinal nerve 10-Jun-22 24   Cutaneous area supplied by one spinal nerve, through both its rami is called DERMATOME  No area of skin is supplied by a single spinal nerve because of adjacent dermatomes overlap  The upper half of each zone of the body segment is supplemented by the nerve  Knowledge of a dermatome map is important for clinical above and the lower half by consideration the nerve below  Loss of sensation in a dermatomal pattern provides information about the location of nerve damage 10-Jun-22 25 10-Jun-22 26 10-Jun-22 27 10-Jun-22 28  Specialized structures located at the distal tips of the sensory neurons. Initiate an impulse in response to a stimulus. Classified as: A. Exteroceptors react to stimuli from the external environment (touch, temperature, smell, sound and vision) B. Interoceptors react to stimuli from within the body (the degree of filling of the alimentary canal, urinary bladder) C. Proprioceptors react to stimuli from within the body, provide sensation of body position and muscle tone 4-Feb-25 29  D. Free nerve endings (mostly found in epithelium) E. Encapsulated nerve endings: - with connective tissue sheaths are located mostly in the skin and skeletal muscle. It includes: 1. Krause’s end bulb- cutaneous receptors found in nerve terminals of skin, mucosa of oral cavity 2. Ruffini’s corpuscles- sensory end organs in the subcutaneous connective tissue of fingers 3. Meissner’s corpuscles- tactile corpuscle(mechanoreceptor in the skin) 4. Pacinian corpuscles- perceives deep pressure in the skin 4-Feb-25 30  Drake R.L., Gray’s Anatomy for Students, 2nd Edition, 2009, Churchill Livingstone Moore, Clinically Oriented Anatomy, 6th Edition, 2009, Lippincott Williams & Wilkins Standring, Gray’s Anatomy: The Anatomical Basis of Clinical Practice, 40thEdition, 2008 Johannes W Rohen, Color Atlas of Anatomy: A photographic study of the human body, 7th Edition, Lippincott Williams & Wilkins Kenneth S Saladin, Human Anatomy, 2nd Edition, 2008, McGraw-Hill Companies 10-Jun-22 31 10-Jun-22 32