Lab # 2: Spinal Cord & Nerves, Reflexes and General Senses A & P II Spring, 2014
Objectives Be able to identify specified spinal cord structures and spinal nerves on models Be familiar with spinal nerve plexuses and the major nerves arising from each plexus, and the anatomical structures/muscles innervated by these nerves Know the different parts of the nervous system, origins of different neurons in the spinal cord, cholinergic and adrenergic neurons and receptors Be able to compare and contrast different reflexes Be familiar with the specified sensory receptors
Overview of the Nervous System Difference between spinal cord & nerves: Spinal cord: Spines and skull protect the nerves Spinal nerves: No skeletons protect the nerves feedback output Sympathetic: Fight & flight Parasympathetic: Feed & Breed
Rami (branches) Sympathetic chain Ganglion: a nerve cell cluster Pre- Post- Sympathetic Chain: Synapse closer to spinal cord, so we got more control of it which make the response quicker (fight and flight)
Adrenal gland Sweat gland Blood vessel Only controlled by sympathetic system
Neurotransmitters and Receptors N= Nicotinic receptor M= Muscarinic receptor Pre-Ach-N Post-Ah-M Small nerves in the Adrenal medulla, release NT when needed
CNS-Spinal Cord Transverse view D-outer, thickest A-middle, spider web like P-innermost, hug spinal cord CSF Cerebrospinal fluid here
Spinal Cord Anatomy Lateral horn Posterior Median Sulcus Dorsal horn Central canal (contains CSF) Dorsal root ganglion Spinal nerve Ventral horn Anterior Median Fissure Ventral root
Spinal Cord Anatomy
Spinal Cord Segments Large anterior horns, small posterior horns Small anterior & posterior horns, Small lateral horn present Large anterior & posterior horns Lateral horn present Large/thick anterior & posterior horns
Peripheral Nervous System: Autonomic NS Sympathetic (thoraco-lumbar) Parasympathetic (cranio-sacral)
Spinal Nerves 31 Pairs attached to Spinal Cord 8 Cervical 12 Thoracic 5 Lumbar 5 Sacral 1 Coccygeal 4 Spinal Plexuses Cervical Brachial Lumbar Sacral 2 Enlargements Cervical Enlargement (C 3 or C 4 to T 1 ) contains nuclei for upper extremities Lumbar Enlargements (T 9 to T 12 ) contains nuclei for lower extremities Cauda equina Spinal Nerves extend inferiorly to the spinal cord and form a cauda equina.
Spinal Nerves (12) & Plexuses (4) Cervical Plexus Phrenic Brachial Plexus Axillary Ulnar Median Musculocutaneous Radial o Lumbar Plexus o Femoral o Obturator o Sacral Plexus o Pudendal o Sciatic o Tibial o Common Fibular
Cervical Plexus Phrenic Innervate diaphragm Irritaion of the phrenic nerve causes diaphragm spasms or hiccups
Axillary Innervate shoulders area Deltoid, teres minor Brachial Plexus Ulnar Innervate flexors Flexor carpi ulnaris, flexor digitorum profundis, lumbricals, opponens digiti minimi, flexor digiti minimi, abductor digiti minimi, adductor pollicis Median Innervate flexors and lumbricals Anterior compartment of the forearm, lumbricals Musculocutaneous Innervate biceps, brachialis Anterior compartment of the arm Close to biceps Radial Innervate extensors Posterior compartment
Anterior view of left shoulder Axillary Ulnar Median
Axillary Anterior view of left shoulder Median Musculocutaneous Bicep Ulnar
Axillary Median Musculocutaneous Ulnar Radial Median Ulnar
Median Radial Phrenic Ulnar
Lumbar Plexus Femoral Innervate anterior compartment of the thigh Innervate extensors of upper leg Obturator Innervate medial compartment of the thigh Innervate Adductors
Sacral Plexus Pudendal Innervate penis and anal sphincter Sciatic (upper leg) Posterior compartment of the thigh Pass under piriformis muscle and moves down the posterior leg Tibial (lower leg & foot) Branches from sciatic nerve Moves down the lower posterior leg Innervate posterior compartment of leg (flexors), and medial compartment of leg Gastrocnemius, flexor digitorum longus, flextor halluces longus, lumbricals Injury: pain in the bottom of foot and toes Common fibular (lower leg & foot) Branches from sciatic nerve Mover down the lower anterior leg Innervate anterior compartment of leg (extensors), lateral compartment of leg extensor digitorum brevis Injury: foot drop (not able to do dorsi flexion)
Sciatic Femoral Nerve Fibular Nerve Tibial Nerve Anterior view Posterior view
Fibular Nerve Tibial Nerve (medial foot) MEDIAL VIEW
General Senses Sensory receptors respond to changes from the environment Unencapsulated (free) or encapsulated Sensory Receptors (classified by stimulus type) Mechanoreceptor: mechanical force (touch/pressure/vibration) Meissner corpuscle, hair root plexus, merkel discs, ruffini corpuscle, pacinian corpuscle Thermoreceptors: temperature Photoreceptors: light Nocioceptors: pain Proprioceptors: stretch (muscle-sense)
Mechanoreceptor Locations
Specific Types of Mechanoreceptors Merkel Disk (slow-adapting) Unencapsulated (free) Superficial - very sensitive Respond to light touch (pressure and texture) Meissner corpuscle (fast-adapting ) Superficial, located in the glabrous skin on fingertips and eyelids Respond to touch and vibration Ruffini corpuscle (slow-adapting) More deeper compared to Merkel disc and Meissner corpuscle Respond to sustained pressure, skin stretch Hair root plexus Sensitive Wrapped around every hair follicle Pacinian corpuscle (fast-adapting, ) Respond to vibration and deep pressure
Two Point Discrimination An indirect measure of cutaneous touch receptor density Tactile sensitivity varies by body part Number of receptors in area (touch receptor density) Amount of brain tissue devoted to sensory information
Two Point Discrimination Test Directions Eyes closed during test Put 2 caliper points together and place on skin area. Be sure to place both points at the same time Ask if 1 or 2 points were felt Increase caliper distance until 2 points are felt Finger & Palm: +1mm Cheek, forearm, leg: +2mm
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