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PNS includes all nervous structures found where?
- outside the CNS requiring three components:
- 1. sensory receptors-pick up stimuli & send signals to CNS
- 2. motor endings (axon synapse with effectors like muscles and glands)
- 3. nerves and ganglia-neurons and cell bodies outside of CNS
- NOTE: almost all nerves are mixed carrying both sensory and motor neurons
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Peripheral Sensory Receptors
receptors are either dendritic ends of sensory neurons that monitor general sensory information over wide areas
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Exteroceptors
receptors receiving stimulus from environment are sensitive to pressure, pain, smell, sight, and hearing (external stimulus & 4-5 senses
free nerve endings, merkel discs, hair follicle receptors, meissner's corpuscle, pacinian corpuscle, ruffini endings
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Interoceptors
receptors sensitive to body's internal changes, either visceral or chemical changes, taste, & tempherature (homeostasis internal signal to CNS)
free nerve endings
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Proprioceptors
receptors found within skeletal muscles, tendons, joints, & ligaments monitor amount of stretching sending input on movement (balance, coordination movement signal to CNS)
free nerve endings, pacinian corpuscle, ruffini endings, muscle spindles, tendon organs, joint kinesthetic receptors
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What are the Classification by Location of sensory receptors?
- Exteroceptors
- Interoceptors
- Proprioceptors
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Mechanoreceptors
are stimulated by mechanical forces such as touch, pressure, ect. (mechanical forces)
free nerve endings (pressure), merkel discs (light pressure), hair follicle receptors (hair deflection), meissner's corpuscle (light pressure, discriminative touch, vibration of low frequency), pacinian corpuscle (deep pressure, stretch, vibration of high frequency), ruffini corpuscle (deep pressure & stretch), muscle spindles (muscle stretch), tendon organs (tendon stretch), joint kinesthetic receptors
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Thermoreceptors
stimulated by temperature changes (temperature)
free nerve endings (heat & cold)
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Chemoreceptors
respond to chemicals changes in blood, taste, or smell. (chemical changes)
free nerve endings
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Photoreceptors
respond to light such as those found in the eye. (light)
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Classification by stimulus detected
- Mechanoreceptors
- Thermoreceptors
- Chemoreceptors
- Photoreceptors
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Free dendritic endings
sense pain & temperature changes along with some sense light touch (itch receptors are also free dendritic ends
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Encapsulated dendritic endings
nerve endings wrapped in connected tissue serving as mechanoreceptors
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Meissner’s corpuscles
detect light touch in the skin
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Krause’s End bulbs
detect fine touch in mucus membranes
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Pacinian Corpuscles
found in deep connective tissue (hypodermis) respond to vibration and briefly respond to deep pressure.
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Ruffini’s Corpuscles
found in dermis respond to continuous pressure
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Proprioceptors
found in muscle tissue, tendons, and ligaments monitoring stretch in locomotory organs
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Classification by structure
- free dendritic endings
- encapsulated dendritic endings
- meissners corpuscle
- krause's end bulb
- pacinian corpuscle
- ruffini's corpuscle
- proprioceptors
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Peripheral Motor Endings
axons synapsing with either muscle or glands to activate them
- 1. Neuromuscular junction
- 2. motor neuron
- 3. acetylcholine (ACH)
- 4. acetylcholinesterase (ACHS)
- 5. motor unit
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