Nervous Tissue Structure & Function PDF

# Nervous tissue - Prepared by Dr. Ahmed Morsi - Assistant professor of Histology & Cell Biology ## Learning objectives By the end of this lecture, you will be able to: - Classify neuroglia - Enumerate neuroglial cells based on their location - Describe the structure of neuroglia - Understand the...

# Nervous tissue - Prepared by Dr. Ahmed Morsi - Assistant professor of Histology & Cell Biology ## Learning objectives By the end of this lecture, you will be able to: - Classify neuroglia - Enumerate neuroglial cells based on their location - Describe the structure of neuroglia - Understand the function of each neuroglia in relation to structure ## II. Neuroglia: 10 times more abundant than neurons - Classification: - **Neuroglia in the central nervous system** - **Astrocytes** - Protoplasmic astrocyte - Fibrous astrocyte - **Oligodendrocytes** - **Microglia** - **Ependymal cells** - **Neuroglia in the peripheral nervous system** - **Satellite cells or capsular cells** - **Schwann cells or neurolemmocytes** ## 1- Astrocytes: - Star-shaped glial cells with many radiating processes - They are of 2 types: - **Fibrous astrocytes** (with few long and relatively straight processes) - **Protoplasmic astrocytes** (with many short and branching processes) - **Function:** - Share in the formation of the blood-brain barrier - Provide structural support > Astrocytes are the most abundant CNS neuroglia. ## 2- Oligodendrocytes: - Glial cells that are responsible for myelination of the nerve fibers in the CNS. - One oligodendrocyte can myelinate a short segment of several nerve fibers (axons). ## 3- Microglia: - Small-sized glial cells with short irregular processes. - Are common as neurons. - They are mobile cells that migrate throughout the nervous tissue, scanning for damaged cells & microorganisms. (**phagocytic cells of the nervous tissue**) ## 4- Ependymal cells: - Cuboidal shaped cells that line the central canal of the spinal cord & brain ventricles. - Secrete the cerebrospinal fluid (CSF). ## 5- Schwann cells: - Glial cells that are responsible for myelination of the nerve fibers in the PNS. - Unlike oligodendrocytes, one Schwann cell can myelinate a short segment of one axon. ## 6- Satellite cells: - Called capsular cells as it forms a covering layer around the neuronal cell bodies in the ganglia. - They provide supportive, nourishing, insulating and regulating microenvironment for these neurons. ## Neuroglia - **Neuroglia are found in:** - **Central Nervous System** - Astrocytes - Maintain blood-brain barrier - Provide structural support - Regulate ion, nutrient, and dissolved gas concentrations - Absorb and recycle neurotransmitters - Form scar tissue after injury - Oligodendrocytes - Myelinate CNS axons - Provide structural framework - Microglia - Remove cell debris, wastes, and pathogens by phagocytosis - Ependymal cells - Line ventricles (brain) and central canal (spinal cord) - Assist in producing, circulating, and monitoring of cerebrospinal fluid - **Peripheral Nervous System** - Schwann cells - Surround axons in PNS - Are responsible for myelination of peripheral axons - Participate in the repair process after injury - Satellite cells - Surround neuron cell bodies in ganglia - Regulate $O_2$, $CO_2$, nutrient, and neurotransmitter levels around neurons in ganglia ## Reference: - Junqueira's Basic Histology: Text and atlas, 13th Edition, 2013. - Anthony L. Mescher ***