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PERIPHERAL NERVOUS SYSTEM FUNCTION CONSISTS OF Sensory division – Motor division – COMPOSITION Two subdivisions: Somatic Nervous System - Autonomic Nervous System - Two subdivisions: SENSORY RECEPTORS Classified by location or type of stimulus detected. CLASSIFICATION BY LOCATION Exteroreceptors - Examples: Free nerve endings - Merkel’s Discs - 1 Meissner’s corpuscles - Krause’s end bulbs - Pacinian corpuscles - Ruffini’s corpuscles - Interoreceptors (visceroreceptors) - Examples: Propioceptors - Examples: CLASSIFICATION BY STIMULUS TYPE DETECTED Mechanoreceptors - Examples: Chemoreceptors Examples: 2 Photoreceptors Thermoreceptors Examples: Examples: Nociceptors Examples: PAIN Pain Receptors Pain Classification Somatic Pain - Visceral Pain - CRANIAL NERVES NOTES CRANIAL NERVES I Olfactory Nerve – Sensory only 3 II Optic Nerve – Sensory only III Oculomotor Nerve – Motor, sensory, and parasympathetic fibers IV Trochlear Nerve – Motor and sensory V Trigeminal Nerve – motor, sensory Motor and sensory Composed of three major branches: Opthalmic branch V1 – Sensory Maxillary branch V2 – Sensory Mandibular branch V3 – Motor and sensory VI Abducens Nerve – Motor and sensory 4 VII Facial Nerve – Motor, sensory and parasympathetic fibers VIII Vestibulocochlear Nerve – Sensory Composed of two branches: Cochlear branch – Sensory Vestibular branch – Sensory IX Glossopharyngeal Nerve – Motor, sensory and parasympathetic fibers X Vagus Nerve – Motor, sensory and parasympathetic fibers 5 XI Spinal Accessory Nerve – Mainly motor and some sensory XII Hypoglossal Nerve – Mainly motor and some sensory SPINAL NERVES GENERAL FEATURES Numbers Spinal nerves are numbered: Cervical nerves (8 pairs) C1 – C1 – C8 – C8 – exits below C7 (it is above T1) Thoracic nerves (12 pairs) Lumbar nerves (5 pairs) S1 – S5 – Coccygeal nerves (1 pair) L1 – L5 – Sacral nerves (5 pairs) T1 – T12 – Co1 – Composition – Dorsal root – 6 Dorsal root ganglion – Ventral root – Divisions Dorsal ramus – Ventral ramus – Meningeal branches – Rami communicantes – PLEXUSES T2 – T12 ventral rami – Cervical Plexus – Phrenic nerve – Brachial Plexus – Roots (ventral rami) C5 – T1 Trunks [upper, middle, lower] Divisions [anterior and posterior of each trunk] Cords [lateral, medial, posterior] Peripheral Nerves Brachial Plexus Nerves 7 Musculocutaneous nerve (from lateral cord) – Median nerve (from a branch of the lateral and medial cords) – Ulnar nerve (from medial cord) – Radial nerve (from posterior cord) – Axillary nerve (from posterior cord) – Lumbosacral Plexus – Innervates the lower limb, some of the abdomen and pelvis Lumbar plexus – Sacral plexus – Lumbosacral Plexus Nerves Femoral nerve – Obturator nerve – Sciatic nerve – Tibial nerve – Common peroneal nerve (fibular) – Superficial branch – Deep branch – NERVE DAMAGE Sciatica – 8 Brachial Plexus Injuries – Median Nerve Damage – Ulnar Nerve Damage – Radial Nerve Damage – REFLEX ACTIONS REFLEX ACTION – Reflex arcs Types of Reflexes Monosynaptic reflex – Example: Quadriceps muscle stretches when tendon is tapped muscle spindles send an impulse that the muscle is stretching spinal cord motor neuron carries and impulse back to the quadriceps quadriceps muscle contracts Polysynaptic reflex – Example: Pain receptors spinal cord association neuron integration motor neurons to flexor muscles for contraction flexors contract extensors extend (called the crossed extensor reflex to keep the body balanced) Examples of Reflexes Knee Jerk Reflex (stretch reflex) – Ankle Jerk Reflex – Photopupil Reflex – 9 Accommodation Reflex – Convergence – Referred Pain – 10
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