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BASIC TISSUES - NERVOUS TISSUE (Synapse (Junction between presynaptic and…
BASIC TISSUES - NERVOUS TISSUE
Function
Conducts impulses used to help control and coordinate body activities
Divided into:
Central nervous system
Brain and spinal cord and neural parts of the eye
Peripheral nervous system
Peripheral ganglia, nerves and nerve endings connecting ganglia with CNS, receptors and effectors of body
Motor
Somatic division
Control of skeletal muscle
Autonomic division
Parasympathetic
Sympathetic
Control of smooth and cardiac muscles and glands (involuntary)
Cells of nervous system
Neurons - produces and conducts electrical impulses
Types
Sensory
Afferent, periphery to CNS
Unipolar
Motor
Efferent, CNS to periphery
Multipolar
Inter
Connect spinal and sensory neurons
Communicate with each other
3 main parts
Dendrites
Cytoplasmic extensions
Receive input
Cell body
Contains nucleus
Metabollic centre - provides proteins
Main conc. of organelles
Axon
Contains single extension
Conducts nerve impulses
Neuroglia
Supporting
Non neuronal cells that maintain homeostatis, form myelin and provide support and protection for neurons
2 types in PNS
Schwann cells - form myelin around axons
Satelite cells - support neuron cell bodies
4 types of CNS
Oligodendrocytes - forms myelin around axons
Microglial cells - phagocytose/ degenerate foreign material
Astrocytes - regulate external environment, provides structural support and nutrients
Ependymal cells - line CSF filled ventricles in brain and central canal of spinal cord, produces cerebrospinal fluid that cusions neurons
Synapse
Junction between presynaptic and postsynaptic neuron
Can be excitatory or inhibitory
Transmission electrical or chemical
Operates in unidirectional manner
Myelin
Insulating layer surrounding some axons
Made up of protein and fatty substance
Allows electrical impulses to transmit quickly and efficiently along nerve cell
Made by oligodendrocytes (CNS) and schwann cells (PNS)
Spinal Cord
White matter
Contains myelinated axons
Has spinal tracts which ascend and descend the spinal cord
Grey matter
Area of cell bodies, dendrites and unmyelinated axons of motor and inter neurons
Sensory motor neuron connections occur
Spinal nerve
Dorsal root ganglion is a cluster of neurons in a dorsal root of a spinal nerve
Spinal ganglia contain cell bodies of sensory neurons entering cord at that region
Satellite cells
Glial cells found in PNS
Compose the thin cellular sheaths that surround individual neurons in ganglia
Peripheral nerve
Nerve = collection of axons linked together by CT
Composed of:
Axons (non / myelinated)
Schwann cells which make myelin
Spindle shaped fibroblasts which produce CT
Blood vessels
3 types of CT in fascicles
Endoneurium = surrounds individual axons and their schwann cells
Perineurium = surrounds groups of axons to form fascicles
Epineurium = outer sheath that binds individual fascicles into a nerve