Nervous Tissue PDF

NERVOUS TISSUE NEUROGLIA (or glial cells) – support, protect, & nourish neurons. Does not conduct electrical Central Nervous System CNS – interpret impulse...

NERVOUS TISSUE NEUROGLIA (or glial cells) – support, protect, & nourish neurons. Does not conduct electrical Central Nervous System CNS – interpret impulses. Maintains the integrity and functions all the data gathered and store them to of our neurons. decide responses. o Brain – responsible for controlling majority of the body. Histology of Neuron o Spinal Cord – responsible for transmitting signals from PNS to the Brain. Coordinates Reflexes. Principle cells or Nervous Tissues Peripheral Nervous System PNS – acts as the communication between the 3 Basic parts: brain and spinal cord. 1. Cell body (Perikaryon/Soma) o Nerve fiber 2. A single Axon o Nerve ganglia 3. Multiple Dendrites o 2 Types: ▪ Somatic – for voluntary movement in arms and Cell Body (Perikaryon) legs The central portion of the nervous ▪ Autonomic – for They are considered polygonal involuntary movements in the body (digestion) It has various shapes and sizes o 2 Types of Nerves: It has a nucleus, perinuclear, and cytoplasm (ER, Golgi, & mitochondria). 1) Sensory (Afferent) – for the carry of sensory information. 2) Motor (Efferent) – to command Dendrites the CNS to move (e.g. muscles Multiple elongated processes & glands) Branch-like structure that can receive signal (input) from the other neurons) NEURON – responsible for the communication in the nervous system. It sends signals using Receives stimuli. electrical impulses & chemical Transmission to the cell body. The signal neurotransmitters which produces stimuli will create electrical impulse. (respond). Axons Single process up to 100cm  Originate from axon hillock (junction of c. Maintains BBB (blood brain the cell body) barrier) where foreign particles are filtered Devoid ribosomes d. Chemical balance – maintain Conducting impulses away from the the extracellular ions soma e. Metabolic Support It maintains axonal transport. 3. Ependymal Cells Signal transmission in the synapses (gap between the neurons). a. Lines the brain cavities. o Myelin sheath acts as an b. Produce and circulate CSF insulator and increases the 4. Microglia speed of electrical impulse a. Immune defense of the CNS o Axon Terminal signals to the target cells. b. Phagocytosis (cell eating/engulfing) c. Responds to inflammation, Neuroglial Cells infection, & injury. PNS Metabolic and mechanical support for 1. Schwann Cells neurons. Stabilizing the position of neurons. a. Form the myelin sheath around the axons in the PNS Have phagocytic function. b. Ability for nerve regeneration 10x more abundant than neurons 2. Satellite Cells Neuroglial cells undergo mitosis a. To surround neurons with cell Maintains homeostasis body b. Provides support, regulate, & provide nutrition for neurons. CNS Neuroglia includes: Grey & White Matter 1. Oligodendrocytes a. Produces and maintain myelin sheath CNS Grey Matter 2. Astrocytes 1. Neuronal cell bodies a. Star-shaped cells with 2. Neuropil – composed of dendrites & numerous branching process. unmyelinated axons b. Provides support and structure  3. Glial cells – composed of astroglia & b. Less critical (Pain & oligodendrocytes Temperature sensation) Its Grey matter because it is UNMYELINATED Connective Tissue Investment of Nerves Location: Brain – cerebral cortex (outer layer), Epineurium – outer layer. Composed of dense Spinal cord – central part (butterfly shaped) collagenous CT with thick elastic fibers. Perineurium – middle layer. Dense CT and layers of epithelioid. Isolates neural environment White Matter (Blood-nerve Barrier) 1. It is composed of bundles of Endoneurium – inner layer. Loose CT, regulation MYELINATED nerve cell processes. of microenvironment of the nerve fibers. 2. It consists of glial cells and myelinated axons. GANGLIA – ovoid structure containing neuronal cell bodies and glial cells supported by Location: Brain - corpus callosum (connector connective tissues between 2 hemisphere of the brain), Spinal cord Function: relay stations to transmit impulses – outside of the butterfly shaped. Types: Sensory Ganglia Autonomic Ganglia Nerve Fibers o Sympathetic – fight or flight Consists of axons enveloped by a special sheath. response A group of fibers constitutes the peripheral nerve. o Parasympathetic – found near or within target organs. Involved in rest & digest Two types: activities. 1. Myelinated Fibers MENINGES a. Have a fatty insulation layer Dura Mater – outermost shield called myelin sheath around Arachnoid – CSF circulation, serves as their axons conduit for the flow of CSF. Also, a b. Allows for faster transmission of barrier. electrical impulses. Pia Mater - Protection: Final layer of 2. Unmyelinated Fibers meninges. Provides nutrients & O2 supply. They can carry blood vessels. a. Lack a myeline sheath, resulting in slower signal transmission. CEREBELLAR CORTEX – the surface of the cerebellum shows transverse fissures, which divides the cerebellum into several lobules. 1. Molecular Layer – outer layer, directly beneath the Pia Mater. Integrates signals, synapses between Purkinje & Granule cells. 2. Purkinje Cell Layer – Middle layer, between the molecular layer & granular layer. The ONLY OUTPUT NEURONS, able to send signals to the cerebellar nuclei. 3. Granular Layer – innermost layer. The PROCESSING INPUT from the spinal cord, transmits signal (sensory & motor) to molecular layer for further process for stimuli.