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72 Cards in this Set
- Front
- Back
Where does the spinal cord begin and end?
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Start: Medulla Oblongata
End: superior border of 2nd lumbar vertebra, 3rd or 4th in newborns |
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What are the gray and white matter of the spinal cord?
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gray: site for integration of post synaptic potentials (EPSP and IPSP), H or butterfly shapped inner part of spinal cord.
consists of dendrites, cell bodies of neurons, unmyelinated axons, and neuroglia white: contains major sensory and motor tracts, surrounds the gray matter of spinal cord and is outer part. consists of bundles of myelinated axons of neurons |
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What are the protective structures of the spinal cord?
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each provide protection and physical stability
1. bony vertebrae & ligaments - vertebral foramina stacked on top of each other form the vertebral cavity 2. CT meninges 3. CSF |
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What are the Meninges?
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outer layer - dura mater (from foramen magnum to skull of 2nd sacral vertebra)
middle layer - arachnoid mater inner layer - pia mater (contains many blood vessels which provide nutrients and oxygen to spinal cord) epidural space - bet w/ dura and vertebral cavity; contains fat and CT subdural space - betw/ dura and arachnoid; contains interstitial fluid subarachnoid space - between arachnoid and pia; contains CSF all 3 meningeal layers cover the spinal nerve roots up to where spinal nerves exit intervertebral foramina |
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What are denticular ligaments?
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triangular membranous extensions of pia mater that suspend spinal cord in middle of its dural sheath
protect spinal cord against sudeen displacement which could lead to shock |
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What is spinal tap?
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also known as Lumbar Puncture, site is inferior to spinal cord
needle inserted into subarachnoid space between 3rd-4th or 4th-5th lumbar vertebrae under anesthesia used to: 1. withdraw CSF for diagnostics 2. give antibiotics 3. introduce contrast media for myelography 4. give anesthetics 5. administer chemotherapy 6. measure CSF pressure and evaluate effects of treatment for diseases such as meningitis |
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What are the 2 enlargements seen in the Spinal cord?
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superior enlargement - cervical enlargement (C4-T1) and all the nerves to and from upper limbs
inferior enlargement - lumbar enlargement (T9-T12) and all nerves to and from lower limbs |
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What are all the Spinal Nerves?
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cervical: C1 - C8
thoracic: T1 - T12 lumbar: L1 - L5 sacral: S1 - S5 Coccyx: Co1 |
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What are the spinal nerve roots?
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Posterior (dorsal) root - axons of sensory to skin, muscles, and internal organs into CNS, contain a swelling that has cell bodies of sensory neurons called posterior root ganglion
Anterior (ventral) root - axons of motor neurons, from CNS to effector tissues |
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What happens in Spinal Nerve Root Damage?
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most common cause is herniation to IVD
other causes of damage to vertebrae are due to osteoporosis, osteoarthritis, cancer, or injury symptoms: pain, muscle weakness, and loss of feeling treatments: rest, physical therapy, angesics and epidural injections |
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What are Tracts, Nerves, Ganglia, and Nuclei?
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Tracts - collection of axons in CNS
Nerves - collection of axons in PNS Ganglia - collection of neuronal cell bodies in PNS Nuclei - collection of neuronal cell bodies in CNS |
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What are some specific properties of gray matter?
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subdivided into horns
anterior (ventral) gray horns - contain somatic motor nuclei, provide impulses for contraction of skeletal muscles posterior (dorsal) gray horns - somatic and autonomic sensory nuclie lateral gray horns - in bet w/ other two, present only in thoracic, upper lumbar and sacral, contain autonomic motor nuclei that regulate activity of smooth muscle, cardiac muscle, and glands |
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What are the commissures?
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gray commissure - cross bar of the H
anterior white commissure - connects white matter of right and left side of spinal cord |
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What is the central canal?
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center of gray matter
extends entire length of spinal cord and is filled with CSF at its superior end is continuous with 4th ventricle in medulla oblongata |
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What are specific characteristics of white matter?
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two grooves divide white matter
anterior median fissure - deep wide grove posterior median sulcus - shallow and narrow gray matter horns create columns each column contains distinct bundle of axons extending upward or downward known as tracts 1. anterior (ventral) white column 2. posterior (dorsal) white column 3. lateral white column |
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What is the cauda equina?
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known as "horsetail"
the collective roots of the lumbar (after and including L2), sacral, and coccygeal nerves that exit the IVF at an angle for their respective nerve root |
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What are the connective tissue coverings of the spinal nerves?
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endoneurium - innermost covering where individual axons within a nerve are wrapped
perineurium - middle layer that wraps around fascicles epineurium - outmost layer that wraps around entire nerve and is fused with the dura mater of the spinal cord |
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What are rami?
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braches of spinal nerves
posterior (dorsal) ramus - serves the deep muscles and skin of the dorsal surface of the trunk anterior (ventral) ramus - serves muscles of upper and lower limbs and skin of lateral and ventral surfaces of trunk, axons only go directly to body structure they supply in thoracic nerves T2-T12 rami communicantes - components of ANS |
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What is the meningeal branch?
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branch off spinal nerve which supplies vertebrae, vertebral ligaments, blood vessels of the spinal cord and meninges
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What are networks of axons?
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anterior rami of adjacent spinal nerves called plexuses
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What do plexuses do?
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give rise to nerves which proceed to specific regions/structures
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What are intercostal nerves?
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anterior rami of spinal nerves T2-T12, they do not form plexus
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What is the cervical plexus and its nerves?
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formed by anterior rami of C1-C4 with contribution of C5
on both sides of neck from C1-C4 supplies skin and muscles of head, neck, and superior part of shoulders and chest nerves include: lesser occipital, greater auricular, transverse cervical, supraclavicular, ansa cervicalis, phrenic, and segmental branches 2 cranial nerves run parallel: XI (accessory) and XII (hypoglossal) |
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What is the phrenic nerve?
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arise from anterior rami of C3, C4, C5
supplies motor to diaphragm injury causes respiratory arrest, breathing stops as diaphragm (major muscle for breathing) is no longer supplied by phrenic nerve |
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What are the major parts of the brachial plexus?
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roots - anterior rami of spinal nerves C5-T1
trunks - superior (C5-C6), middle (C7) and inferior (C8-T1) divisions - anterior and posterior cords - lateral (anterior divisions of superior and middle trunks), medial (ant div. of lower), and posterior (post. div of all 3 trunks, named so according to relationship with axillary artery) nerves come off the cords |
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What are the nerves of the Brachial plexus?
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brachial plexus supplies shoulders and upper limbs
axillary nerve (C5-C6) - supplies deltoid and teres minor muscles musculocutaneous nerve (C5-C7) - supplies flexors of the arm Radial Nerve (C5-T1) - supplies muscles on posterior aspect of arm and forearm Median Nerve (C5-T1) - supplies muscles of the anterior forearm and some muscles of hand Ulnar Nerve (C8-T1) - supplies anteromedial muscles of forearm and most of muscles of the hand Long Thoracic Nerve (C5-C7) - supplies serratus anterior muscle |
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What are some injuries to nerves of brachial plexus?
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Erb-Duchenne palsy or waiter's tip position - injury to superior roots (C5-C6)
shoulder adducted arm medially rotated elbow extended forearm pronated wrist flexed sensory loss along lateral side of arm injury at roots occurs do to forceful pulling away of head from shoulder commonly occurred from a heavy fall on the shoulder or excessive stretching of an infant's neck during birth |
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What is radial nerve injury?
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inability to extend wrist and fingers (wrist drop)
known as radial nerve palsy, crutch palsy, or Saturday night palsy sensory loss is minimal due to overlapping sensory innervation occurs when cast is applied too tightly around midhumerus, stab wound at or below clavicle, improper use of crutches injury to radial nerve and axillary nerve also happens when intramuscular injection to deltoid is improperly administered |
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What is median nerve injury?
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known also as median nerve palsy
numbness, tingling, and pain in palm and fingers inability to pronate forearm and inability to flex digits at proximal interphalangeal joints and distal interphalangeal joints of 2nd and 3rd digits weak flexion and adduction of wrist w/ weak thumb movements |
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What is ulnar nerve injury?
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ulnar nerve palsy
inability to abduct and adduct the fingers atrophy of interosseus muscles of the hand, hyperextension of metacarpophalangeal joint and flexion of interphalangeal joints, known as clawhand lost of sensation of little finger |
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What is long thoracic nerve injury?
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lead to paralysis of serratus anterior muscle
medial border of scapula protrudes when arm is raised leading to winged scapula abduction of arm beyond horizontal position is impossible |
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What are the intercostal nerves?
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also known as thoracic nerves
anterior rami of spinal nerves T2-T12 T2 - innervates intercostal muscles of 2nd intercostal space, skin of axilla, and posteromedial aspect of arm T3-T6: supply intercostal muscles and skin of anterior and lateral chest wall T7-T12: intercostal muscles, abdominal muscles, and overlying skin posterior rami of T2-T12 supply deep back muscles and skin to posterior aspect of thorax injury to intercostal nerves causes pain, numbness, tingling, weakness and sometimes paralysis of supplying part |
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What is the lumbar plexus?
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anterior rami of L1-L4
on either side of first 4 lumbar vertebrae posterior to psoas major, anterior to quadratus lumborum supplies anterolateral abdominal wall, external genitals, and part of lower limbs |
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What are the major branches of the lumbar plexus?
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iliohypogastric
ilioinguinal genitofemoral lateral cutaneous nerve of thigh femoral - largest nerve of lumbar plexus, arises from posterior division of nerve roots L2-L4, supplies flexor muscles of thigh and extensor muscles of leg, skin over anteromediual aspect of thigh and medial side of leg and foot obturator - anterior division of L2-L4, supplies adductor muscles of leg and skin over the medial aspect of thigh lumbosacral trunk |
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What some injuries in the lumbar plexus?
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Femoral nerve injury - inability to extend leg and loss of sensation of skin over anteromedial aspect of thigh, can happen by gun shot or stab wound
obturator nerve injury - causes paralysis of adductor muscles of leg and loss of sensation in skin over medial side of thigh, pressure to nerve by fetal head during pregnancy can cause injury |
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What is the sacral plexus?
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anterior rami of L4-S4
anterior to sacrum, supplies buttocks, perineum and lower limbs |
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What is the major nerve of the sacral plexus and its divisions?
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Sciatic nerve - largest nerve in body, divides into 2 branches, tibial and common fibular, before division supplies hamstring muscles and adductor magnus muscle of thigh
2 divisions: tibial nerve - supplies gastrocnemius, plantaris, soleus, popliteus, tibialis posterior, flexor digitorum longus and flexor hallucis longus, divides into medial and lateral plantar nerves Common fibular nerve 2 branches: 1) superficial fibular: supplies fibularis longus and brevis, skin over distal third of anterior aspect of leg and dorsum of foot 2) deep fibular: supplies tibialis anterior, extensor hallucis longus, extensor digitorum longus and brevis and skin adjacent to great and second toes |
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What are some injuries to sacral plexus?
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sciatic nerve - sciatica in which pain extends from buttock down the posterior and lateral aspect of foot, most common form of back pain
causes of sciatica: herniation of discs, dislocated hip, osteoarthritis of lumbosacral spine, pregnancy, inflammation or infection of nerve, improperly administered glutueal intramusclar injection most commonly affected part is common fibular portion |
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What are foot drop, equinovarus, and cacaneovalgus?
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causes of injury to common fibular nerve of sciatic, loss of function at anterolateral aspects of leg and dorsum of foot and toes
foot drop - plantar flexion of foot equinovarus - inversion of foot injury to tibial portion of sciatic nerve: calcaneovalgus - injury to tibial portion which causes dorsiflexion of foot and eversion of foot, loss of sensation of sole |
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What is the coccygeal plexus?
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anterior rami of S4-S5
smallest and supplies skin in coccygeal region |
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What are dermatomes?
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area of skin that provides sensory input to the CNS via posterior root of one pair of spinal nerves to trigeminal nerve
each spinal nerve provides muscle innervation of a particular dermatome and conveys sensory information from the same dermatome most possible to locate damaged regions of spinal cord therapeutic use, can block pain permanently ONLY C1 DOES NOT HAVE DERMATOME BECAUSE IT IS ONLY MOTOR SUPPLY |
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What are features of sensory tracts?
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sensory systems let CNS know about changes is internal and external environment
sensory receptors propagate up through the spinal cord to the brain along three tracts: spinothalamic, trigeminothalamic, and posterior columns spinocerebellar tract: somatic sensory information from proprioceptors in the trunk and lower limbs through spinal cord to cerebellum 3 types of sensory neurons: 1st, 2nd, and 3rd order |
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What are 1st, 2nd, and 3rd order sensory neurons?
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1st order: impulses from somatic sensory receptors into brain stem or spinal cord
cranial nerves carry impulses from face, mouth, teeth, and eyes to brain stem spinal nerves carry impulses from neck, trunk, limbs, and posterior aspect of head to brain stem 2nd order: from brain stem or spinal cord to thalamus decussate in brain stem or spinal cord before reaching thalamus, therefore all somatic sensory info from one side of body reaches thalamus on opposite side 3rd order: from thalamus to primary somatosensory area of cortex on same side |
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What is the Posterior column-medial lemniscus pathway?
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1st order synapse with 2nd order in gracile nucleus or cuneate nucleus of medulla
impulses from neck, upper limbs, and upper trunk go along axons in cuneate fasciculus (upper thoracic and cervical) --> cuneate nucleus lower trunk and lower limbs propagate in gracile fasciculus (cocygeal, sacral, lumbar, and lower thoracic) --> gracile nucleus impulses from face go through trigeminal (trigeminothalamic tracts) axons of 2nd order cross to opposite side of medulla and go to thalamus as medial lemniscus pathway medial lemniscus pathway extends from medulla to ventral nucleus of thalamus, synapse w/ 3rd order neurons of thalamus 3rd order neurons from thalamus go to primary somato-sensory area of cerebral cortex |
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What are the functions of the Posterior column-medial lemniscus Pathway?
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Fine touch - ability to recognize info about touch sensation such as site of touch, size, shape and texture
Proprioception - awareness of precise position of body parts while static and during movements (kinesthesia) Stereognosis - ability to recognize size, shape, and texture w/ eyes closed Vibration - ability to detect/perceive rapidly changing touch stimuli Tactile localization - localize which part of skin is touched Tactile Discrimination - recognize two separate parts on skin when touched at same time Weight discrimination - assess weight of object |
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What is the medial lemniscus pathway?
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extends from medulla to ventral nucleus of thalamus
axons of 2nd order neurons cross opposite side of medulla and propagate to thalamus, synapse with 3rd order in thalamus 3rd order goes to primary somatosensory area of cerebral cortex lowest ganglia = medial highest ganglia = lateral |
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What are the Spinothalamic pathways?
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known as anterolateral pathways
1st order connect sensory receptors of neck, trunk or limbs w/ spinal cord cell bodies in posterior root ganglion synapse with 2nd order in posterior gray horn of spinal cord 2nd order cross to opposite side of spinal cord go to thalalmus in either lateral or anterior spinothalamic tract 2nd order ends in VPN of thalamus where synapse w/ 3rd order 3rd order go from thalamus to primary somatosensory area on same side |
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What do lateral and anterior spinothalamic tracts convey?
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Lateral - pain and temperature
Anterior - tickle, itch, crude touch, and pressure |
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What is Syphilis?
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sexually transmitted disease caused by bacteria Treponema pallidum
if gets to 3rd stage causes neurosyphilis causes degeneration of posterior portions of spinal cord: posterior columns, posterior spinocerebllar tracts, and posterior roots gait becomes uncoordinated and jerky, no somatic sensations treated with penicillin and doxycycline |
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What are Lower Motor Neurons (LMNs)?
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motor neurons that extend from the brain stem and spinal cord toward skeletal muscles
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What are somatic motor pathways?
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provide input to lower motor neurons, provide final output from CNS
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What are Upper Motor Neurons (UMN)?
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originate from motor areas of cerebral cortex and brain stem (red, vestibular, superior colliculus, and reticular formation)
give input to local circuit neurons --> LMN, some synapse directly with LMN from cerebral cortex - planning, initiating & directing sequences of voluntary movements brain stem - muscle tone, posture, balance and position of head and body also have little influence from basal ganglia and cerebellum |
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What do neurons of BG and Cerebellum do?
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basal ganglia connects with motor areas of cerebral cortex, thalamus, subthalamic nucleus and substantia nigra
initiate & terminate movements, suppress unwanted movements, and establish muscle tone cerebellum connects with motor cortex via thalamus and brain stem coordinates body movements and maintains normal posture and balance |
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What are direct and indirect motor pathways?
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direct (pyramidal):
-voluntary movements -large, pyramid-shaped cell bodies -go from cerebral cortex through internal capsule to medulla -90 % decussate at pyramids of medulla, 10 % are ipsi until they reach spinal cord level of synapse with interneurons or LMNs indirect (extra-pyramidal): -regulate axial muscles that maintain balance and posture and muscles controlling coarse movements of proximal portions of limb, head, neck, and eye movements. -brain stem gives input to LMN, brain stem receives signals from BG, cerebellum, and cerebral cortex include rubrospinal, tectospinal, vestibulospinal, lateral & medial reticulospinal tracts |
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What is the Lateral Corticospinal tract?
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direct motor pathway
UMNs decussate in medulla lateral white column of spinal cord synapse with interneurons or LMNs in anterior gray horn of spinal cord controls muscles of distal part of limbs and responsible for precise, agile, and highly skilled movements of limbs, hands, and feet |
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What is the Anterior Corticospinal tract?
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direct motor pathway
does NOT decussate at medulla, occupy anterior white column of spinal cord decussate at each level of spinal cord via anterior white commissure, synapse with interneurons or LMNs in anterior gray horn of spinal cord LMNs of these tracts exit cervical and thoracic segments in anterior roots of spinal nerves control movements of neck muscles, part of trunk, proximal part of limbs, and coordinated movement of axial skeleton |
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What happens in LMN damage vs. UMN damage?
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LMN:
-flaccid paralysis of the muscles of the same side of the body -no movement of muscles, no reflex action, and muscle tone is less or lost UMN: -spastic paralysis of muscles of opposite side of body -reflexes are exaggerated, even pathological reflexes are present and increased muscle tone |
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What is Amyotrophic Later Sclerosis (Lou Gehrig's disease)?
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attacks motor areas of cerebral cortex, axons of UMNs in lateral white columns (corticospinal and rubrospinal) and LMN cell bodies
causes muscle weakness and atrophy starting with hands and spreading to whole body 2-5 years death happens 15 % inherited, 85 % non-inherited excess glutamate due to mutation of protein that deactivates glutamate in non-inherited (sporadic) - free radicals, autoimmune, viral, deficiency of nerve growth, apoptosis, environmental toxins, and trauma treatment: riluzole reduces damage, drugs for relief of pain, fatigue, spasticity, and supportive therapy |
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What is a reflex?
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fast, involuntary, unplanned sequence of actions (motor activity) that occurs in response to a particular stimuli (sensory activity)
the pathway for the reflex activity is called the reflex arc (reflex circuit) helps to diagnose disease and damage |
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What are the components of a reflex arc?
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sensory receptor:
receives stimulus, produces a graded or receptor potential, sends info to CNS, it reaches threshold sends nerve impulse through sensory neuron Sensory neuron: -nerve impulse propagate to the integration center which is located in gray matter of spinal cord or brain stem -sensory neuron enters CNS via dorsal root of spinal nerves or via crainal nerves and their cell bodies lie in DRG or homologous ganglia of CN Integration center (center of reflex arc): -gray matter of CNS (sometimes more than one region) -contains interneurons which relay impulses to other interneurons as well as to motor neurons Motor Neuron: -impulses from integration center going out of CNS to effector tissue Effector: -part of body which responds to motor nerve impulse (skeletal (somatic or autonomic reflex), smooth, cardiac muscles; and glands -action is called reflex activity |
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What are the afferent, efferent limb of reflex arc; and what are the poly and monosynaptic reflex arc?
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afferent limb - sensory receptor and neuron
efferent limb - motor neuron and effector polysynaptic - more than one CNS synapse between sensory and motor neuron mono - 1 CNS synapse |
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What are the important somatic spinal reflexes?
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Stretch reflex:
-skeletal muscles stretches causing contraction in response -monosynaptic & ipsilateral -elicited by tapping tendons of elbow, wrist, knee, and ankle joints Tendon reflex: -relaxation of the muscle in response to increased tension -can override stretch when tension is great, ex. drop a very heavy weight -ipsilateral but polysynaptic -sensory receptors called tendon (golgi tendon) organs which lie near junction of tendon and muscle -sensitive to change in muscle tension caused by passive stretch or muscular contraction flexor reflex: -known as withdrawal reflex, ex. step on a tack you immediately withdraw leg -polysynaptic and ipsilateral -intersegmental - activate interneurons in several segments of spinal cord Crossed Extensor Reflex: -polysynaptic, intersegmental, contralateral -when step on tack withdrawal is in same leg but extension is in opposite leg to maintain balance |
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What are the events in a stretch reflex?
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1. stretching stimulates sensory receptors which are muscle spindles (used to monitor change in muscle length)
2. muscle spindles generate one or more nerve impulses that propagate along a somatic sensory neuron 3. reaches integration center in spinal cord via posterior roof of SN, excitatory synape activates motor neuron (in anterior gray horn of SC) 4. propagation of one or more motor neurons via anterior roof of spinal nerves to stimulated muscle 5. release of Ach at NMJ causes AP in muscle (effector). Therefore, stretching of muscle is followed by contraction of that muscle, which relieves stretching |
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What is the importance of the stretch reflex?
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all monosynaptic reflexes are ipsilateral but not vice versa
muscle spindles innervated by small diameter motor neurons from brain which regulate their sensitivity and maintain muscle tone brain also receives input about state of stretch, enabling it to coordinate muscle movements helps to maintain posture and prevents overstretching ex. standing person leans forward, calf is stretched, stretch reflexes cause contraction of calf which establish body's upright posture |
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What is reciprocal innervation?
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polysnaptic reflex arc operated to antagonist muscles
when neural circuit simultaneously cause contraction of one muscle and relaxation of its antagonists vital in coordinating body movements ex. stretched muscle contracts during stretch reflex, antagonist muscles relax |
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What are the events of a tendon reflex?
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1. increase tension
2. stimulation (depolarized to threshold) 3. nerve impulse propagates along sensory neuron to integration center (spinal cord) 4. activation of inhibitory interneuron which synapse with motor neuron 5. hyperpolarization of motor neuron causes relaxation of relieves excess tension example of reciprocal innervation causes contraction of antagonistic muscles too |
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What are the events of the flexor reflex?
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1. stepping on tack
2. nerve impulses via sensory neuron to integration center (spinal cord) 3. activation of interneurons across few asc. and desc. spinal cord segments 4. activation of motor neurons in several spinal cord segments 5. contraction of flexor muscles of the thigh (effectors) 6. withdrawal of leg protective reflex, contraction of flexor muscles moves limb from a damaging stimulus |
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What are the events of the crossed extensor reflex?
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1. stepping on a tack
2. nerve impulse leading to activation of interneurons 3. activation of motor neurons 4. muscle contraction causing flexion of leg stepping on a tack & extension on the opposite side |
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What is the patellar reflex?
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known as knee jerk
extension of knee due to contraction of quadriceps femoris muscle L2, L3, L4 absent in people with diabetes mellitus, neurosyphilis; exaggerated in disease involving motor tracts descending from the brain |
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What is the Babinski sign?
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known as plantar flex
causes dorsiflexion of great toe known as 'babinski positive' which is normal for children up to a year and half due to incomplete myelination of fibers in corticospinal tract positive after this age is abnormal and indicates damage to upper corticospinal tract normal is 'babinski negative' plantar flexion reflex which is curling of all toes |
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What are the conus medullaris and the filum terminale?
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conus medullaris - tapering, conical structure end of inferior enlargement (at IVD of L1-L2), most inferior part of spinal cord
filum terminale - extensions of pia mater that arise from conus medullaris, anchor the spinal cord to coccyx |
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What are the major nerves of the Sacral Plexus?
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superior gluteal, inferior gluteal, sciatic (common fibular and tibial), posterior cutaneous, perforating cutaneous, pudendal
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