Unit 4 - Spinal Cord Flashcards
What are the 3 functions of the spinal cord?
- process reflexes
- integrate EPSP and IPSPs
- conducts sensory impulses to the brain and motor impulses to the effectors
Where does the spinal cord begin and terminate? What is its shape and length?
begins as an extension of the medulla oblongata at level of foramen magnum
terminates at the level of L2 (conus medullaris)
oval, 42-45 cm`
What are the two enlargements of the spinal cord? What do they indicate? What is the filum terminale?
cervical enlargement - C4-T1: indicates nerves for upper limb
lumbar enlargement - T9-T12 indicates nerves for lower limbs
filum terminale - extension of the pia matter that extends inferiorly and uses with other meninges to angle the spinal cord to coccyx
- caudia equina: roots of lower spinal nerves angle inferiorly to the filum terminale like whips of hair
Compare the dorsal root and ventral root of the spinal cord
dorsal root - sensory axons
- has DORSAL ROOT GANGLIA - swelling on dorsal root that contains the soma of sensory neurons
ventral root - motor neuron axons
Describe what each part of the spinal cord contains: posterior gray horns, anterior gray horns, lateral gray horn
posterior gray: cell bodies and axons of interneurons and sensory neurons
anterior gray - contain somatic motor nuclei for skeletal muscle contraction
lateral gray - contain autonomic motor nuclei that regulate cardiac and smooth muscle and glands
How many spinal nerves are there? How are they organized?
31 pairs of spinal nerves
8 cervical - 1st pair emerges between occipital bone and atlas
- C1-7 emerge above corresponding vertebrate
- C8 exits btw vertebrate C7 and T1
12 thoracic - T1-L5 exit vertebral canal below corresponding vertebrae 5 pairs lumbar 5 pairs sacral 1 pair coccygeal
What are the names of the CT surrounding spinal nerves?
endoneurium: wraps individual axons
perineurium: wraps bundles of axons called fasciles
epineurium: outermost covering of the entire nerve
What are rami? describe the functions of the posterior and anterior ramus, meningeal branch, and the rami communicantes
Rami - branches of spinal nerves
posterior: serves deep muscles of skin of posterior surface of the trunk
anterior - serves muscles and structures of the upper and lower limbs, and the skin of the lateral and anterior surfaces of the trunk
meningeal branch - supplies the vertebrae, vertebral ligaments, and blood vessels of the spinal cord and the meninges
rami communicates - component of autonomic nervous system
What is the purpose of the cervical plexus? What is the phrenic nerve?
supplies the skin and muscles of hear, neck, superior portion of the shoulder and chest and diaphragm
phrenic = supplies diaphragm
Describe the cdntipons of the 5 important nerves from the brachial plexus
roots (anterior rami) of C5-C8, T1
- axillary nerve - supplies deltoid and teres minor
- Musculocutaneous nerve - supplies anterior muscles of the arm
- Radial nerve - supplies muscles of post aspect of arm and forearm
- Median nerve - supplies most of the muscles of anterior forearm and some of the muscles of the hand
- Ulnar nerve - supplies the anteromedial muscles of the forearm and most of the muscles of the hand
What are some brachial plexus injuries?
wrist drop - injury to radial and axillary nerve
winged scapula - injury to long thoracic nerve - medial border of scapula procures
Describe the functions of the lumbar plexus. Describe the function specifically of the femoral and obturator nerve
roots (anterior rami) of spinal nerves L1-L4 supplies:
- anterolateral abdominal wall
- external genitals
- part of the lower limbs
femoral: largest nerve from lumbar plexus, distributed to flexor muscles of hip joint and extensor muscles of knee joint, skin over anterior and medial aspect of thigh and medial side of leg and foot
obturator: adductor muscles of hip joint, sin over medial aspect of thigh
Describe the sacral and coccygeal plexuses
sacral - anterior rami of spinal nerves L4-5
- supplies buttocks, perineum and lower limbs
coccygeal - anterior rami of spinal nerves S4-5
- supplies area of skin in coccygeal region
What part of the spinal cord receives and integrates information?
gray matter
Describe the spinothalamic and posterior column tract for nerve impulses in the spinal cord
spinothalamic tract: conveys nerve impulses for sensing pain, temp, itching, tickling, deep pressure and crude touch
posterior column: consists of the gracile fasciculus and the cuneate fasciculus
- conveys nerve impulses for discriminative touch, light pressure, vibration and conscious proprioception
Describe the following reflexes: spinal, cranial, somatic, autonomic
spinal - integration takes place in the spinal cord gray matter
cranial - integration occurs in the brain stem
somatic - involves contraction of skeletal muscles
autonomic - involved response o]f smooth muscle, cardiac muscle and gland - typically not perceived
Describe the stretch reflex. What is reciprocal innervation>
causes contraction of a skeletal muscle in response to stretching of the muscle
- MONOSYNAPTIC, IPSILATERAL - sensory nerve enters spinal cord on same side nerve impulse leaves
- elicited by tapping on tendons
- prevents overstretching of muscles
RECIPROCAL INNERVATION - when the stretch muscle contacts, antagonistic muscles that oppose the contraction relax
- polysynaptic, antagonistic reflex arc occurs at same time
- 3 neurons, 2 synapses
- helps maintain posture
What is the tendon reflex?
operates as feedback mechanism to ctrl muscle tension by causing muscle relaxation before muscle force to prevent a torn tendon
- MONOSYNAPTIC, IPSILATERAL
tendon organs - sensory receptors that lie within a tendon near its junction with a muscle
Describe the flexor and crossed extensor reflexes
flexor:
intersegmental reflex arc: single sensory neuron activates several motor neurons (effectors)
- moves entire lower or upper limb away from painful stimulus
crossed extensor: maintains balance after pulling leg away from painful stimulus
- AcH released by motor neurons causes extensor muscles in thigh of unstimulated leg to contract
- contralateral reflex arc: sensory stimulus on one side of the spinal cord and motor impulses exit on opposite side
- synchronized with the extension of the contralateral its with the flexion of the stimulated limb
Describe the degenerative disorders of the spinal cord: Amyotrophic lateral sclerosis, shingles, and polio
ALS - muscle weakness and atrophy
shingles - herpres voster remains in post rood ganglion
polio - virus can produce paralysis by destroying cell bodies of motor neurons
Describe the traumatic injuries of the spinal cord: complete transection, hemi section and spinal shock. What causes spinal cord compression>?
complete transection: loss of all sensation and voluntary movement below the level of transection
hemi section - partial transection of the cord
spinal shock - immediate response to spinal cord injury characterized temporary areflexia, loss of reflex function
spinal cord compression: fractured vertebrae, herniated discs, tumors, osteoporosis and infections
