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72 Cards in this Set

  • Front
  • Back
Where does the spinal cord begin and end?
Start: Medulla Oblongata

End: superior border of 2nd lumbar vertebra, 3rd or 4th in newborns
What are the gray and white matter of the spinal cord?
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
What are the protective structures of the spinal cord?
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
What are the Meninges?
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
What are denticular ligaments?
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
What is spinal tap?
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
What are the 2 enlargements seen in the Spinal cord?
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
What are all the Spinal Nerves?
cervical: C1 - C8

thoracic: T1 - T12

lumbar: L1 - L5

sacral: S1 - S5

Coccyx: Co1
What are the spinal nerve roots?
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
What happens in Spinal Nerve Root Damage?
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
What are Tracts, Nerves, Ganglia, and Nuclei?
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
What are some specific properties of gray matter?
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
What are the commissures?
gray commissure - cross bar of the H

anterior white commissure - connects white matter of right and left side of spinal cord
What is the central canal?
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
What are specific characteristics of white matter?
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
What is the cauda equina?
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
What are the connective tissue coverings of the spinal nerves?
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
What are rami?
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
What is the meningeal branch?
branch off spinal nerve which supplies vertebrae, vertebral ligaments, blood vessels of the spinal cord and meninges
What are networks of axons?
anterior rami of adjacent spinal nerves called plexuses
What do plexuses do?
give rise to nerves which proceed to specific regions/structures
What are intercostal nerves?
anterior rami of spinal nerves T2-T12, they do not form plexus
What is the cervical plexus and its nerves?
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)
What is the phrenic nerve?
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
What are the major parts of the brachial plexus?
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
What are the nerves of the Brachial plexus?
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
What are some injuries to nerves of brachial plexus?
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
What is radial nerve injury?
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
What is median nerve injury?
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
What is ulnar nerve injury?
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
What is long thoracic nerve injury?
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
What are the intercostal nerves?
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
What is the lumbar plexus?
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
What are the major branches of the lumbar plexus?
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
What some injuries in the lumbar plexus?
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
What is the sacral plexus?
anterior rami of L4-S4

anterior to sacrum, supplies buttocks, perineum and lower limbs
What is the major nerve of the sacral plexus and its divisions?
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
What are some injuries to sacral plexus?
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
What are foot drop, equinovarus, and cacaneovalgus?
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
What is the coccygeal plexus?
anterior rami of S4-S5

smallest and supplies skin in coccygeal region
What are dermatomes?
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
What are features of sensory tracts?
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
What are 1st, 2nd, and 3rd order sensory neurons?
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
What is the Posterior column-medial lemniscus pathway?
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
What are the functions of the Posterior column-medial lemniscus Pathway?
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
What is the medial lemniscus pathway?
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
What are the Spinothalamic pathways?
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
What do lateral and anterior spinothalamic tracts convey?
Lateral - pain and temperature

Anterior - tickle, itch, crude touch, and pressure
What is Syphilis?
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
What are Lower Motor Neurons (LMNs)?
motor neurons that extend from the brain stem and spinal cord toward skeletal muscles
What are somatic motor pathways?
provide input to lower motor neurons, provide final output from CNS
What are Upper Motor Neurons (UMN)?
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
What do neurons of BG and Cerebellum do?
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
What are direct and indirect motor pathways?
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
What is the Lateral Corticospinal tract?
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
What is the Anterior Corticospinal tract?
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
What happens in LMN damage vs. UMN damage?
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
What is Amyotrophic Later Sclerosis (Lou Gehrig's disease)?
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
What is a reflex?
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
What are the components of a reflex arc?
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
What are the afferent, efferent limb of reflex arc; and what are the poly and monosynaptic reflex arc?
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
What are the important somatic spinal reflexes?
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
What are the events in a stretch reflex?
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
What is the importance of the stretch reflex?
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
What is reciprocal innervation?
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
What are the events of a tendon reflex?
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
What are the events of the flexor reflex?
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
What are the events of the crossed extensor reflex?
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
What is the patellar reflex?
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
What is the Babinski sign?
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
What are the conus medullaris and the filum terminale?
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
What are the major nerves of the Sacral Plexus?
superior gluteal, inferior gluteal, sciatic (common fibular and tibial), posterior cutaneous, perforating cutaneous, pudendal