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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
output feedback
Sympathetic: Fight & flight Parasympathetic: Feed & Breed
• 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)
Sympathetic chain
Rami (branches)
Adrenal gland Sweat gland Blood vessel Only controlled by sympathetic system
N= Nicotinic receptor M= Muscarinic receptor
Small nerves in the Adrenal medulla, release NT when needed Pre-Ach-N Post-Ah-M
Neurotransmitters and Receptors
CNS-Spinal Cord
Cerebrospinal fluid here
D-outer, thickest A-middle, spider web like P-innermost, hug spinal cord
Transverse view
CSF
Lateral horn Dorsal root ganglion
Ventral root Spinal nerve
Ventral horn
Dorsal horn Central canal (contains CSF)
Anterior Median Fissure
Posterior Median Sulcus
Spinal Cord Anatomy
Spinal Cord Anatomy
Spinal Cord Segments
Large/thick anterior & posterior horns
Small anterior & posterior horns, Small lateral horn present
Large anterior horns, small posterior horns
Large anterior & posterior horns Lateral horn present
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 (C3 or C4 to T1)
• contains nuclei for upper extremities • Lumbar Enlargements (T9 to T12)
• contains nuclei for lower extremities
• Cauda equina • Spinal Nerves extend inferiorly to the spinal cord
and form a cauda equina.
• 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 (C3 or C4 to T1)
• contains nuclei for upper extremities • Lumbar Enlargements (T9 to T12)
• 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
Brachial Plexus • Axillary • Innervate shoulders area • Deltoid, teres minor
• 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
Axillary
Ulnar
Median
Anterior view of left shoulder
Bicep
Median
Musculocutaneous
Axillary
Ulnar
Anterior view of left shoulder
Axillary Median
Radial
Ulnar
Median
Musculocutaneous
Ulnar
Median Radial
Ulnar
Phrenic
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)
Tibial Nerve Femoral Nerve
Sciatic
Fibular 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
Next Week – Exam 1
Exam 1