Nervous Tissue Histology, Neurons, Nerves and Ganglia
Nervous tissue histology - Neurons are the basic building blocks of the nervous system. Nervous tissue constitutes the primary building block of the nervous system. Read the article to know more.
Dr. Nivedita3 Aug, 2024
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Nervous Tissue
Nervous tissue is the fundamental component of the nervous system which consists of neurons and glial cells.
What is Histology?
Histology is a branch of biology that studies the microscopic anatomy of biological tissues. It involves examining tissues under a microscope to understand their structure, organization, and function. Histological techniques include tissue fixation, sectioning, and staining, which help highlight different cellular components and provide insights into tissue pathology.What are Neurons?
Nerve cells, or neurons, constitute the structural and functional units of the central and peripheral nervous systems. Their role is to receive stimuli and transmit nerve impulses to target organs.Structure of Neurons:
Cell Body (Soma) Contains the nucleus and organelles. It is responsible for maintaining the cell and processing information. Dendrites branch like structures that receive and integrate signals from other neurons or sensory stimuli. Their number can vary, affecting the neuron's connectivity. Axon is a long slender projection that transmits electrical impulses away from the cell body. Each neuron has only one axon. Myelin Sheath is a lipid-rich insulating layer that surrounds the axon, produced by Schwann cells in the PNS and oligodendrocytes in the CNS. It increases the speed of electrical impulse conduction.Types of Neurons:
Multipolar Neurons have one axon and multiple dendrites, allowing them to integrate a vast amount of information from other neurons. They are the most common type in the nervous system. Bipolar Neurons are the which have one dendrite and one axon and are typically found in sensory organs, such as the retina of the eye. Unipolar Neurons lack dendrites, with the axon extending directly from the cell body. They are rare and not found in higher animals. Pseudounipolar Neurons have a single extension from the soma that branches into two distinct structures, resembling both unipolar and bipolar neurons. They are commonly involved in sensory pathways.Histology of Peripheral Nerves
Peripheral nerves are composed of axons and Schwann cells, which together form bundles of nerve fibers wrapped in connective tissue. This organization provides both protection and support, ensuring efficient transmission of nerve impulses throughout the body.Structure of Peripheral Nerves :
Endoneurium is a delicate layer of connective tissue that individually wraps each nerve fiber. Perineurium is a protective sheath that surrounds bundles of nerve fibers, known as fascicles. Epineurium is the outermost layer that envelops multiple fascicles, forming the entire nerve. This layer provides structural integrity and protection against external stress.What are Glial Cells?
Neuroglial cells, commonly known as glial cells or glia, are non-neuronal cells that provide support and protection for neurons. They do not directly participate in synaptic interactions and electrical signaling but are essential for maintaining the overall health and functionality of the nervous system. Glial cells outnumber neurons and perform various crucial functions.Types of Glial Cells in the CNS
There are three types of glial cells namely astrocytes , oligodendrocytes and micro glial cells. Astrocytes maintain the proper chemical environment for neuronal signaling. They also support the blood-brain barrier, which controls the passage of substances from the bloodstream into the brain. Oligodendrocytes Produce myelin, a lipid-rich sheath that insulates axons in the CNS. Myelin significantly increases the speed of action potential conduction. Microglial Cells Act as the resident immune cells of the CNS and they also detect and respond to pathological events, such as infections and inflammation. Glial Cells in the PNS Schwann Cells are the glial cells in the PNS and they produce myelin around peripheral axons. They also assist in the regeneration of damaged nerve fibers.Nervous Tissue Histology FAQs
How do pseudounipolar neurons differ from unipolar and bipolar neurons in their structure?
Pseudounipolar neurons have a single extension from the body, similar to a unipolar cell, which then branches into two distinct structures, resembling a bipolar cell.
What do oligodendrocytes produce, and what is its significance?
Oligodendrocytes produce a lipid-rich sheath known as myelin around some axons, which significantly affects the speed of action potential conduction.
What is the difference between endoneurium and perineurium on the basis of location and wrapping ?
In endoneurium each nerve fiber is individually wrapped in a delicate layer of connective tissue called the endoneurium whereas perineurium is the bundle of nerve fibers surrounded by a protective sheath.
What are peripheral nerves composed of ?
Peripheral nerves are composed of axons and Schwann cells, which form bundles of nerve fibers wrapped in connective tissue.
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