Nervous Tissues and Neurons
Explore the world of nervous tissues, neurons, and the functions of the central and peripheral nervous systems. Learn about the structure of neurons, their processes, and the classification of neurons. Discover how nervous tissues play a vital role in sensory input, muscle control, homeostasis, and mental activity.
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Presentation Transcript
Nervous tissues: Cells that comprise the central nervous system *(CNS) and peripheral nervous system(*PNS) Theses cells called neurons and supporting cells associated to neurons. CNS- brain and spinal cord PNS- cranial nerves , spinal nerves, and motor neurons. *CNS : Central Nervous System *PNS : Peripheral Nervous System
Functions of nervous tissue: 1. Sensory input and integration: sensory input- nerve cells receive and process information from external environment. Integration- neurons are able to transmit electrical impulse from one site in the body to anther. 2. Controlling muscles and glands: Some of neurons are able to receive signals from the brain and spinal cord which can cause muscle contraction and affect glands. 3. Hemostasis : It is the ability of the body to regulate it s inner environment to ensure stability every time there is a change in the external environment. 4. Mental activity: it is the total emotional and intellectual response of an individual to external reality.
The Neuron : Neurons = nerve cells Cells specialized to transmit messages. Major parts of neuron: a. Cell body: nucleus and metabolic center of the cell (main part of nerve cell) b. Processes: are used to communicate and interact with other nerve cells and muscle cells
Characteristics of nerve cell body (soma) : Contains the nucleus and a nucleolus . Major biosynthetic center Absence of centrioles Cytoskeleton of neuron is formed by microtubules & neurofilaments
Processes Arm like extensions from the soma. Nerve fiber: term used for nerve cell process. Two types of processes:{ dendrites and axons } 1- Dendrites : Characteristics: Branch extensively to form Dendritic tree . Function: receive impulses and carry them toward the cell body
2- Axon Characteristics: Slender processes of uniform diameter arising from the axon hillock . Function: carries impulses away from the cell body Synapse: it is a neural junction where electrical impulses are transferred from one cell to other. Place where the secretion of the neurotransmitter occurs.
Classification of Neuron 1- Structural: a) Anaxonic neuron. b) Bipolar : two processes (axon and dendrite) c) Unipolar: single, short process (usually dendrite) d) Multipolar : three or more processes
Classification of Neuron 2- Functional: a) Sensory (afferent) : transmit impulses toward the CNS b) Motor (efferent) : carry impulses toward the body surface c) Interneurons (association neurons) : any neurons between a sensory and a motor neuron
Supporting Cells Neuroglia Supporting cells in the Central Nervous System (CNS) are grouped together as Neuroglia .Neuroglia literally means nerve glue The function of neuroglia is to support, and protect the delicate neurons of the brain Types of Neuroglia in CNS: 1. Astrocytes 2. Microglia 3. Oligodendrocytes
Types of Neuroglia in PNS 1. Satellite cells Surround the nerve cells of ganglia Flattened cells with prominent nuclei 2. Schwann cells Form myelin sheath in the peripheral nervous system Flattened cells with flattened nucleus
Myelin :Its made of fatty material covering axons. Myelin is produced by Schwann cells in PNS and Oligodendrocytes in CNS Function: protects/insulates the cells and increases the transmission rate of nerve impulses Nodes of Ranvier gaps in myelin sheath along the axon
