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78 Cards in this Set
- Front
- Back
Each pair of spinal nerves receives sensory info and...
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relays motor signals to muscles/glands
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The spinal cord is part of which nervous system?
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CNS
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Spinal nerves are part of which nervous system?
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PNS
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Functions of the spinal cord: Conduction
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bundles of fibers pass info up & down
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Functions of the spinal cord: Locomotion
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* Repetitive, coordinated actions of several muscle groups
* Central pattern generators are pools of neurons providing control of flexors & extensors (ex = walking) |
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Functions of the spinal cord: Reflexes
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* involuntary, stereotyped responses to stimuli (ex = remove hand from hot stove)
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Anatomy of the spinal cord
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* nerve tissue cylinder within vertebral canal
* thick as a finger * only extends to L1 * cervical & lumbar enlargements * 31 pairs of spinal nerves |
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Spinal nerves (how many, regions)
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* 31 pairs of spinal nerves
* Cervical, thoracic, lumbar & sacral regions * Named for level of vertebral column where nerves exit * Each segment gives rise to a pair of spinal nerves |
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Medullary Cord (conus medullaris)
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tapered tip
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Cauda Equinae
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* L2-S5
* Nerve roots resemble horse's tail * Spinal nerves L2-S5 that come off of bottom portion of cord |
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3 Meninges of spinal cord
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* Dura Mater > Arachnoid Mater > Pia Mater
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Spinal Dura Mater
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* tough collagenous memebrane
* surrounded by epidural space - filled with fat, blood vessels - epidural anesthesia |
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Spinal Arachnoid Mater
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layer of simple squamous epithelium lining dura mater & loos mesh of fibers filled with CSF
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Spinal Pia Mater
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delicate membrane adherent to spinal cord
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Filium Terminale (terminal filum)
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forms part of coccygeal ligament to anchor cord to coccyx
within pia mater |
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Denticulate Ligaments
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extend from pia mater thru arachnoid to dura and anchor cord
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Spinal Bifida
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* Neural tube defects - congenital, abnormal fetal development of neural tube & vert column
* 1/1000 * 1+ ver fail to form complete neural arch to enclose cord * Common in lumbosacral region * Risks reduced by folic acid during pregnancy |
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Spina Bifida Cystica
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sac protrudes from spine
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Cross-sectional anatomy of spinal cord
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gray matter surrounded by 3 columns of white matter
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Gray matter
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neuron cell bodies w/ little myelin
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White matter
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myelinated axons
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Where are the sensory fibers in the spinal cord?
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dorsal or posterior horns
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Where are the motor fibers in the spinal cord?
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ventral or anterior horns
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Another name for white matter columns in the spinal cord and where/what are they?
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Funiculi - dorsal, lateral and anterior.
Myelinated axons carring signals up/down cord and to/from brainstem |
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Decussation
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nerve fibers cross sides
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Contralateral
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origin & destination are on opposite sides
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Ipsilateral
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origin & destination are on same side
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How many spinal tracts are there and what are they called?
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2 - ascending & descending
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Polioyelitis (Polio) - what is it & what are the symptoms (8)?
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* virus that destroys motor neurons in brainstem & ventral horn
* spread via fecal contam. in water * signs - muscle, pain, weakness, reflex loss, paralysis, muscular atrophy, respiratory arrest |
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Amyotrophic Lateral Sclerosis (ALS, Lou Gehrig disease)
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* Unknown cause
* sclerosis (tissue hardening) of spinal cord - astrocytes fail to reabsorb glutamate neurotransmitter. * sensory/intellectual functions UNAFFECTED * signs = muscular weakness, difficulty speaking, swallowing |
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A nerve is a bundle of...
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nerve fibers (axons)
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Epineurium
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covers nerve - most superior
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Perineurium
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surrounds a fascicle - middle membrane
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Endoneurium
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separates individual nerve fibers - deepest/most interior membrane
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To what level of nerve membranes due blood vessels go?
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perineurium
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What is a Ganglia in the PNS
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cluster of neuron bodies within nerve
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What kind of cells are in a dorsal root ganglion?
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sensory cell bodies. Remember - dorsa/posterior horns contain sensory fibers
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Where does the most superior spinal nerve come out of the spinal column?
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Above C1
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Where does the most inferior spinal nerve come out of the spinal column?
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coccygeal region
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Ventral root of proximal branch is _________ ________ of spinal cord
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motor output
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Dorsal root of proximal branch is _________ ________ of spinal cord
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sensory input
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The dorsal ramus of the distal branch supplies....
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dorsal body muscle & skin
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The ventral ramus supplies.....
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ventral skin, muscles & limbs
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Meningeal branch goes to ....
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meninges, vertebrae & ligaments
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Three parts of the distal branches of spinal nerves?
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dorsal ramus, ventral ramus, meningeal branch
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Spinal nerves per region?
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Cervical - 8
Thoracic - 12 Lumbar - 5 Sacral - 5 Coccygeal - 1 * Dorsal & Ventral ramus for each |
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Where are spinal roots?
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They run from just anterior of the vertebral processes and go in/out of the spinal cord. (so they run lateral-medial)
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Where are the spinal rami?
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Dorsal & ventral roots combine to become the ventral ramus - the dorsal ramus splits off of the ventral ramus
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plexus
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where the spinal cord branches meet up with other nerves
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What is the purpose of a plexus?
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provides alternate pathways for nerve signals
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Ventral rami do what to form what? (anastomose)
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anastomose repeatedly to form the 5 nerve plexuses
anastomose - reconnecting of branches |
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Location of the 5 nerve plexuses
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CERVICAL C1-C5 (neck) - neck & phrenic
BRACHIAL C5-T1 (armpit) - upper limb & some shoulder/neck LUMBAR L1-L4 (low back) - abdominal wall, anterior thigh & genitalia SACRAL L4,L5 & S1-S4 (pelvis) - remainder of butt & lower limbs COCCYGEAL S4,S5 & C0 |
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Phrenic Nerve
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plexus at C5, C4, C3
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Sciatic Nerve
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longest nerve in the body
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Dermatome
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area of skin specific to each nerve that nerve receives sensory input from - overlap at edges by 50%
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Shingles
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* skin eruptions along path of nerve
* varicella-zoster or herpes-zoster virus (chicken pox) remains for life in dorsal root ganglia * After age 50 if immun compromised * No special treatment |
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Varicella-zoster or Herpes-Zoster
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Chicken Pox
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Somatic reflexes are....
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quick, involuntary, stereotyped reactions to sensory stimulation
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Somatic reflexes function by means of a....
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somatic reflex arc
* stimulation of somatic receptors * afferent fibers carry signals to dorsal horn * 1+ more interneurons integrate info * efferent fibers carry impulses to skeletal muscles * muscles respond |
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What is the muscle spindle
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Proprioceptor (sense organ) - monitors length of muscles & how fast length changes
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Stretch (Myotatic) Reflex
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When muscle is stretched, it contracts & maintains increased tonus
Tonic contraction of the muscles in response to a stretching force, due to stimulation of muscle proprioceptors |
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What is the purpose of stretch reflexes & example
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* Helps maintain equilibrium & posture
* Stabilize joints by balancing tension in extensors & flexors smoothing muscle actions Ex = head tips forward when you fall asleep in class --- muscles contract to raise head |
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Tendon reflex
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very sudden muscle stretch
ex = knee-jerk (patellar) reflex |
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testing somatic reflexes helps...
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diagnose many diseases
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Reciprocal inhibition prevents...
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muscles from working against each other
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Flexor (withdrawal) Reflex
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withdrawl of foot from pain
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Crossed-Extensor Reflex
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maintains balance by extending other leg
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The patellar tendon reflex arc includes which 2 reflexes?
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flexor (withdrawl) and crossed-extensor (balance w/ other leg)
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Neural circuitry in spinal cord controls sequence and duration of...
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muscle contractions
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Golgi Tendon Reflex
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* Proprioceptors in tendon near its juction w/ muscle
* 1mm encapsulated nerve bundle * Excessive tension on tendon INHIBITS motor neurons (muscle contraction decreased) * Also functions when muscles contract unevenly |
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Which is a known viral disease of the central nervous system - myasthenia gravis, spina bifida cystica, Amyotrophic Lateral Sclerosis (ALS), Lou Gehrig's disease, Poliomyelitis??
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Poliomyelitis
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General points about spinal cord trauma
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* 10-12K people/yr paralyzed
* 55% from traffic accidents * Risk of respiratory failur * Early symptoms called spinal shock * Tissue damage at time of injury is followed by post-traumatic infarction |
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where are the enlargements of the spinal cord?
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cervical & lumbar regions
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The _____ nerves arise from the cervical plexus & innervate the diaphram
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phrenic
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Proprioception
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non-visual awareness of a body's position & movements
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The tibial nerve & common fibular nerve collectively make up what nerve?
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sciatic
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T/F - some spinal nerves are sensory & others are motor
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false - all are mixed, none are purely 1 or the other
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T/F - somatic reflexes are those that don't involve the brain
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false - the are mediated primarily thru the b rain & cerebellum
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