OT1024 Lecture #4 Nerve Fibers, Neuroscience PDF

|NEUROSCIENCE OT1024: Nerve fibers, PN, Receptors, Muscle activity In the PNS, forms the peripheral nerves OUTLINE Two types of nerve...

|NEUROSCIENCE OT1024: Nerve fibers, PN, Receptors, Muscle activity In the PNS, forms the peripheral nerves OUTLINE Two types of nerve fibers: I. Nerve Fibers ○ Myelinated fibers A. Myelin Sheath ○ Non-myelinated fibers a. Myelinated Nerve Fibers b. Nonmyelinated Nerve Fibers II. Peripheral Nerve A. Classification of myelin sheath a. Epineurium b. Perineurium c. Endoneurium B. Classification of Nerve Fibers C. Spinal Nerves and Spinal Nerve Roots D. Ganglia a. Craniospinal b. Autonomic Schwann cell- responsible for myelination III. Autonomic Nervous System A. Sympathetic Division B. Parasympathetic Division myelin sheath C. Differences between sympathetic and Not part of the axon parasympathetic divisions Not part of the neuron but formed by neuroglia D. Peripheral Nerve Plexus ○ In the CNS, function of a. Cervical Plexus oligodendroglia b. Brachial Plexus c. Lumbar and Sacral Plexus ○ IN PNS, function of schwann cell Myelin sheath is segmented from the initial IV. Receptors segment of axon to the telodendria A. Receptor Organs of Sensory Neurons Segmented, discontinuous layer a. Receptor by stimulus Internodes: 0.5- 1mm b. Receptor by adaptation ○ a segment that is myelinated c. Receptor by structural Nodes of Ranvier complexity ○ unmyelinated part of the axon B. Neuromuscular Spindles a. Types of sensory innervation C. Neurotendinous Spindles D. Effector Endings a. Motor Innervation b. Sensory Innervation E. Motor Unit F. Neuromuscular Junction in Skeletal Muscles a. Muscle depolarization and contraction G. Neuromuscular Junction in Cardiac and Smooth Muscle V. Dermatomes and Muscle Activity A. Dermatome B. Myotome C. Muscle Tone VI. Axonal Injuries A. Wallerian Degeneration Nerve Fibers The axon (or a dendrite) of a neurons is often referred to as the nerve fiber Different processes of the neurons Myelinated Nerve Fibers Collection of axons located outside the nervous system which are the peripheral nerves. Nerve fiber surrounded by a myelin sheath In the CNS, forms the nerve tracts CNS: Oligodendrocytes ○ vasicullus, lemniscus ○ myelinated up to 60 nerve fibers ○ can form several internodes LUCKY 10 | 1 OT 1024 1st SEMESTER | Neuroscience PNS: Schwann cells ○ one schwann cell can only form one internodes ○ one segment Most axons >1 μm in diameter are myelinated Peripheral Nerves Peripheral nerve – composed of nerve fibers that Pseudopods will twirl of oligodendroglia., may vary in size around the central axon. As it twirls around the ○ myelinated or nonmyelinated, and axon, counter clockwise, the cytoplasm would be transmit nerve impulses to or from the squeezed out and the nucleus would be seen central nervous system which is located at the periphery of the schwann ○ nerve fibers located outside the brain cell. and the spinal cord ○ Plasma membrane is composed of lipid 12 pairs of cranial and 31 pairs of spinal bilayer, phospholipid. nerves ○ Myelin sheath is a lipid insulation Each PN is surrounded by connective tissue because of the phospholipids that are sheaths located at the plasma membrane. Myelin sheath segments interrupted by nodes of Ranvier Acts as a insulator Saltatory conduction – leaping of action potential from one node to the next ○ occurs in myelinated nerve fibers ○ In the propagation of nerve impulse, it doesn't need to depolarize the whole axolemma or whole length of axon. ○ This allows axon potential to jump Motor can either be somatic or visceral from initial segment of axon to nodes ○ Somatic Motor - cranial and visceral of ranvier nerves ○ Depolarization happens in node of 3 parts of the connective tissue sheath ranvier Epineurium ○ There would be faster propagation of ○ outermost covering nerve impulse. ○ continuous with the dura mater Perineurium ○ continuous with the pia-arachnoid membrane ○ Nerve fascicle - grouping of nerve fibers Endoneurium Nonmyelinated Nerve Fibers Axons