Lab+10+-+PNS+and+special+senses

Lab+10+-+PNS+and+special+senses - Peripheral Nervous System...

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Peripheral Nervous System and Special Senses PNS overview Nerve structure Cranial & spinal nerves Major peripheral nerves of the body Autonomic nervous system Special senses: vision, taste, hearing, olfaction
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PNS = all nervous tissues outside brain & spinal cord Sensory division Motor division
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Components of the PNS Neurons and glial cells (supporting cells) Ganglia – clusters of PNS cell bodies Nerves – bundles of PNS axons Can contain sensory or motor axons or both Sensory receptors – pick up stimuli (changes in the environment) from inside and outside the body; initiate impulses in sensory axons Motor endings – axon terminals in motor neurons that innervate muscle fibers and glands
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CNS vs. PNS CNS Brain, spinal cord Process information from PNS Cell body aggregates = nuclei Cell process aggregates = tracts Oligodendrocytes PNS Cranial & spinal nerves Transmit information to and from CNS Cell body aggregates = ganglia Cell process aggregates = nerves Schwann cells
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Oligodendrocytes & Schwann cells
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Glial Cells of the PNS Satellite cells – surround neuron cell bodies within ganglia, provide support/nutrition Schwann cells – surround axons and produce myelin sheaths Unlike oligodendrocytes, Schwann cells can myelinate only one axon at a time. satellite cells Schwann cells
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Satellite cells surrounding a neuron cell body
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Satellite cells and neurons in the DRG
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Node of Ranvier Schwann cell surrounding axon
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Nerves Composed of sensory or motor axons or both Surrounded by connective tissue at multiple levels to form hierarchy of bundles (like muscles) Endoneurium : around individual axons & myelin Perineurium : around a fascicle (bundle of axons) Epineurium : around bundles of fascicles
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fascicle perineurium blood vessel epineurium all part of one nerve
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Longitudinal section
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Sensory Receptors Classified by location Exteroceptors at or near body surface Interoceptors in viscera (organs and glands) Proprioceptors in muscles, tendons, joints, ligaments Classified by type of stimulus detected Thermo- , mecho- , chemo-, photo-, nociceptors Classified by structure free (unencapsulated) nerve endings encapsulated nerve endings
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Exteroceptors respond to external stimuli Located at or near body surface Sense touch, pressure, pain, temperature Can be: Encapsulated Sit within a connective tissue capsule Unencapsulated Free nerve endings
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Interoceptors respond to visceral stimuli Also called visceroceptors Only have unencapsulated nerve endings
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Lab+10+-+PNS+and+special+senses - Peripheral Nervous System...

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