1. Structural Components of PNS
    • Sensory receptors- detect stimuli
    • Motor endings- innervate effectors
    • Nerves and Ganglia- bundles of axons and clusters of cell bodies
  2. Peripheral Sensory Receptors- Free Nerve Endings
    Monitor most types of general sensory info, touch, pain, pressure, proprioception, temp.)
  3. Peripheral Sensory Receptors- Complete Receptor Cells
    Monitor special senses, (taste, vision, hearing, balance)
  4. Peripheral Sensory Recprtors-Location
    • Exteroceptors- stimuli outside the body
    • Interoceptors- stimuli inside the body
    • Proprioceptors- musculoskeletal
  5. Peripheral Sensory Receptors- Stimulus Detected
    • Mechanoreceptors- mechanical forces
    • Thermoreceptors- temperature
    • Chemoreceptors- chemicals
    • Photoreceptors- light
    • Nocireceptors- pain
  6. Peripheral Sensory Receptors- Structure
    • Free nerve endings- abundant in epithelia and its corresponding CT
    • -Merkel discs-light touch
    • -Hair follice- wrap around follicles, light touch, rapid adapting
    • -Itch receptor- located in dermis
  7. Encapsulated Nerve Endings
    • -One or more end fibers of sensory neurons enclosed in CT capsule
    • -All are mechanoreceptors
    • -Amplify stimulus or filter stimuli
  8. -Encapsulated NE- Meissner's corpuscles
    Beneath epidermis, fine touch - mostly areas w/o hair
  9. Encapsulated NE- Pacinian Corpuscles
    Located in deep CT (hypodermis) sense vibration
  10. Encapsulated NE- Ruffini's Corpuscles
    • -Located in dermis, joint capsules, hypodermis
    • -Monitor continuous pressure
  11. Encapsulated NE- Proprioceptors
    • -Muscle spindles - measure change in muscle length
    • -Golgi Tendon Organs- near muscle tendon junction, measure tension in tendon
    • -Joint kinesthetic receptors-measure stretch in synovial joints
  12. Peripheral Motor Endings- Skeletal Muscle
    • -One neuromuscular junction associated with each muscle fiber
    • -Axon terminals release neurotransmitter, which crosses to sarcolemma
    • -Motor unit: a motor neuron and all muscle fibers it innervates(all fibers contract)
  13. Periperal Motor Endings- Visceral Muscle and Glands
    -Visceral motor axon swells into row of knobs(varicosities), releases neurotransmitter
  14. Cranial Nerves
    • -12 pairs, numbered I-XII (rostal to caudal)
    • -First 2 pairs attach to forebrain, and rest attach to brain stem
    • -Generally serve head and neck
  15. I- Olfactory
    • -smell
    • -sensory only
    • -most superior, most anterior arises from forebrain
    • -input goes to riencephalon
  16. II- Optic
    • -vision
    • -sensory only
    • -input- rods and cones in retina, goes through thalamus, then to occipital lobe
    • -arises from forebrain
    • -Severed=blindness
  17. III- Oculomotor
    • -Primarily motor- report back the position of the eyeball
    • -Controls 4-6 muscles(skeletal) that move eye in orbit and iris(autonomic)
    • -Somatic branch of NS
    • -Arises from midbrain
    • -Severed= eyeball droop/no movement
  18. IV- Trochlear (pulley)
    • -small mixed nerve, comes from midbrain
    • -innervates superior oblique muscle of eye that is responsible for downward and outward (latertal) movement
    • -Damage impairs movement
  19. V-Trigeminal
    • -Mixed nerve- largest cranial nerve
    • -Arises from pons
    • -3 different nerves- opthalamic, maxillary, mandibular
    • -Motor with chewing
    • -Sensory Func.- info from skin & musclesof face, teeth
    • -Novicain Nerve
    • -Trauma=impaired chewing, lack of sensation in face
  20. VI- Abducens
    • -Originates from inferior pons
    • -Mostly motor
    • -Innevates lateral rectus muscle of eye(abducts)
    • -Damage causes crossed eyes(esotropia)
  21. VII-Facial
    • -Arises from pons
    • -Mixed Nerve
    • -Inervates muscle of facial expression(skeletal)
    • -Innervates salivary glands(exocrine)- autonomic
    • -Taste sensation, anterior 2/3 of tongue(sweet)
    • -Damage= inability to contract facial musc., distorted taste
    • -Bell's palsy- affected side of face to sag
  22. VIII- Vestibulochlear(auditory)
    • -Only cranial nerve that doesnt exit cranium through foramen
    • -Purely sensory
    • -Arises from both pons and medulla
    • -2 main branches
    • --Vestibular nerve- balance (damage= dizziness/imbalnace)
    • --Cochlear nerve- hearing(damage=sensory deafness)
  23. IX-Glossopharyngeal(glossa=tongue, pharynx=throat)
    • -Mixed nerve
    • -Originates in medulla
    • -Innervates muscles of throat and tongue
    • -Innervates salivary glands
    • -Controls taste in post 1/3 of tongue(bitter/sour)
    • -Damage=loss of bitter/sour taste, impairs swallowing)
  24. X-Vagus
    • -Arises from Medulla
    • -Goes through thoracic and abdominal cavity
    • -Key autonomic nerve, mixed
    • -Both vagus nerves damaged= death
    • -Damage to one= vocal impairment, difficulty swallowing, visceral issues
  25. XI-Accessory
    • -Arises from medulla and part of spinal cord
    • -Motor only
    • -Moves head/neck/shoulders(shrug)
    • -Damge= difficulty w/ movement
  26. XII-Hypoglossal
    • -Motor only
    • -Originates in medulla
    • -Innervates tongue muscles
    • -Damage= difficulty speaking, swallowing, protruding tongue
  27. Cranial Nerves
    • -Sensory neuron cell bodies are located in receptor organs or cranial sensory ganglia
    • -Motor neuron cell bodies located in ventral gray matter of brain stem
    • -Purely sensory, purely motor, mixed
  28. Spinal Nerves
    • -31 pair(62 nereves)
    • -Exit spinal column via intervertebral foramina
    • -Nerves C1-C7 leave above corresponding vertebrae
    • -Thoracic nerves leave below corresponding vertebrae
    • -Lumbar, sacral, and coccygeal also leave below corr. bones
    • -All are mixed
  29. Spinal Nerve Anatomy-Roots
    • -Structures that enter and exit spinal cord, are sensory only or motor only
    • -Converge together in order to exit invertebral foramen
  30. Spinal Nerve Anatomy- Rami
    • -Branches that occur after sensory and motor re-join
    • -Dorsal(posterior) ramus
    • -Ventral(anterior) ramus
  31. Spinal Nerve Anatomy- Sympathetic Rami
    • -2 branches from each spinal nerve that connect to sympathetic trunk ganglion, part of ANS
    • -Composed of gray ramus and white ramus
    • -Serve as a place where sympathetic nerves separate from somatic motor neurons
    • -Consider them as sideroads that carry impulses up and down b/w segements
  32. Nerve Plexuses
    • -In most spinal nerves, the anterior rami combine and spolit again as plexuses
    • -Nerve Plexus= network of nerves(fromed by anterior/ventral rami)
    • -Within plexus, fibers from different rami crisscross
  33. Cervical Plexus
    • -Includes anterior rami of C1-C4 and part of C5
    • -Branches innervate skin and muscles of neck, portions of head and shoulders
    • -Some fibers combine w/ cranial nerves
    • -Phrenic nerve- innervates diaphragm(sensory and motor)
  34. Brachial Plexus
    • -Primarily serves arm muscles, some neck and shoulder
    • -Formed by C5-T1- very complex
    • -Median Nerve- innervates most muscles of anterior forearm and laterall palm
  35. Lumbar Plexus
    • -Formed by mostly L1-L4
    • -Serves muscles of abdomen, anterior/medial parts of leg
    • -Obturator Nerve- runs through obturator foramen
  36. Sacral Plexus
    • -Formed by L4-S5
    • -Serves muscle of pelvic area, posterior/lateral parts of leg, lower back, dorsal and plantar foot
    • -Sciatic Nerve- largest nerve in body, passes through pelvis and down back of leg(2 nerves- tibial and common fibular)
  37. Joint Innervation
    • -Every joint capsule receives sensory branches from several nerves
    • -Hilton's Law- any nerve that innervates a muscle producing movement at a joint also innervatesthe joint itself(and skin over it)
  38. Dermatomes-Skin Innervation
    • -Area of skin innervated by cutaneous branches from a single spinal nerve
    • -All spinal nerves except C1 involved
    • -Trunk Region- Horizontal
    • -Limb Regions- Vertical (sort of)
    • -Trunk dermatomes can overlap A LOT, limbs LESS overlap
    • -Clinical Use- pinpoint level of sopinal injuries, anesthesia
  39. PNS Disorders
    • -Shingles- viral infection of sensory neurons involving the skin, rash of scaly, painful blisters- along a dermatome, stems from chickenpox, virus lies dormant in sensory ganglion
    • -Myasthenia- Disorder of neuromuscular junction, weakening of muscles, autoimmune disorder(destroys ACh receptors)
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