Exam 1: The Nervous System Flashcards
neuroepithelium
gives rise to all CNS neurons and glial cells (except microglia)
tissue outside of neural tube
sclerotome mesoderm
3 regions the neuroepithelium can be divided into
ventricular, mantle, marginal
ventricular neuroepithelium
gives rise to the ependymal cells (produce CSF)
closer to the inner membrane
Mantle neuroepithelium
gives rise to most of the grey matter and neuron cell bodies , gives most macroglia (astrocytes)
- between the ventricular and marginal layers
marginal neuroepithelium
gives rise to white matter, myelinated axons
highest concentration of glial cells is oligodendrocytes
development of neuroepithelium in the brain vs spinal cord
in the brain it will be flipped so the myelination is on the inside and the grey matter is on the outside
sulcus limitans
groove that separates dorsal region from the ventral region
near the midline
alar plate
dorsal region
sensory function
basal plate
ventral region
motor function
(sends info out forward / ventrally)
As the spinal cord matures you get _____ showing up
ventral and dorsal which is for info coming in ?
horns
ventral - cell bodies and tracts going out
dorsal - tracts coming in (NOT cell bodies)
where are cell bodies in dorsal horn located?
dorsal root ganglion
what protective layers does the sclerotome mesoderm give rise to?
vertebrae
annulus fibrosis of discs
meninges
sclerotome mesoderm
not part of nervous system
part of protective layers
connective tissue supportive
annulus fibrosis
outer, tougher, connective portion to the intervertebral discs, encase the discs
meninges
protective layer wrap around brain and spinal cord
vertebral discs are formed from what 2 regions of the mesoderm
- notochord which initiates neurulation
- nucleus pulposus - remnant of notochord
nucleus pulposus composition and function
gel-like center of the disc (collagen and elastin fibers)
- loose matrix
- living cells that produce proteoglycan (mostly protein but have carb chains - attract water)
more proteoglycan = more hydration
responsible for shock absorbency of disc from elastin fibers
annulus fibrosis
made of fibrocartilage
- cells of sclerotome that surround the notochord in many layered structure (lamination)
- layers:
collagen parallel fibers
elastin fibers between each layer to lock them together
what keeps the vertebrae together at each joint?
one = 2 vertebrae with a disc in between
thin layer of hyaline cartilage on either side of disc to lock in place
What happens to the vertebral discs as you age?
get less proteoglycan produced by the cells, cells die off in pulposus, degeneration of discs
- not putting out as much proteoglycan = not as much hydration - no osmotic pressure
- does not hold shape easily, collapses when pressure on it
- disorganization:
not static , have living cells , branching, weak points, fissures forming , can cause bulging, herniation
How many cervical vertebrae? thoracic? lumbar? sacral? coccyx?
cervical: 7
thoracic: 12
lumbar: 5
sacral: 5
coccyx: 3-5
primary curvatures
thoracic and sacral
- convex, bending over
- fetal position curved like a C
secondary (compensatory) curvatures
cervical (begins in utero to 3 months)
lumbar (begins at 12 months) - can stand up
- concave
- babies lift head and get more control
abnormal curvature of spine also occurs if irregularity is more lateral
scoliosis
kyphosis
extreme curvature in upper thoracic
bending over, hunched back
lordosis
extreme curvature in lumbar region
- bending backwards
- in pregnant women in last trimester or overweight in abdominal region
contains adipose and areolar CT that supports blood vessels and spinal nerves
epidural space
epidural anesthesia
administered into epidural space
- labor and delivery
- have patient curl up to open the space, insert needle or catheter and constantly add more anesthesia to numb nerves in the area and below it
- to numb higher up areas recline patient - it goes towards gravity
dense CT, double layered - no separation of layers in the spinal cord
dura mater
supportive network of CT
extensions of CT to pia
arachnoid
outer region of CSF circulation
extensions from arachnoid reabsorb into venous system
subarachnoid apace
spinal anesthesia - injection
taking a sample of CSF if think someone has meningitis
take from subarachnoid space
surface of spinal cord
composed of astrocytes and CT
cannot separate from spinal cord or brain without ripping it off - it is fused to the surface
pia mater
differences between meninges of spinal cord and brain
- brain has no epidural space
- dura connects to the skull directly in the brain
- layers of dura separate in brain
2 parts of the dura mater and what they are
periosteal: stays with inside of skull
meningeal: inner layer that follows contours of brain
- meningeal goes down into fissures and sulci of brain, periosteal stays - get sinuses that reabsorb CSF and drain into venous system
similarity between meninges of brain and spinal cord
arachnoid and pia the same
subdural hematoma
- rupture of bridging veins, slow development, under the dura (where arachnoid is CSF)
- MIDLINE shift - crosses suture lines
- crescent shape
- slow bleed
- elderly, alcoholics, shaken baby, whiplash
epidural hematoma
- damaged artery - middle meningeal artery usually
- rapid expansion due to high P in arteries
- usually secondary to temporal fracture or concussion
NO midline shift - does not cross suture lines - oval shape
traumatic
subarachnoid hemorrhage
- rupture of an aneurysm or bleed from arteriovenous malformation
- blood into sulci
- hemorrhagic stroke - bleed in brain, not blockage
- thunderclap headache (do not want to give clot busters bc it would make worse)
gray matter
neuron cell bodies arranged in functional aggregates or nuclei
sensory nuclei located…
motor nuclei located…
sensory: dorsally/posteriorly
motor: ventrally/anteriorly
somatosensory
proprioception
ex: romberg exercise - close your eyes and can feel body shifting to maintain balance
visceral sensory
monitoring BP, whether or not you should be secreting digestive enzymes
visceral motor
step up peristalsis ways
if sat down, relaxing, bringing BP down
somatic motor
felt changes in shifting result in you sending somatic motor responses down so you did not fall over
white matter
formed by bundles of axons - most myelinated
funiculi or tracts
bundles of axons that create white matter
what are groups or tracts referred to as
columns
ascending tracts carry…
descending tracts carry…
ascending carry sensory info
descending carry motor info
somatosensory neuron orders (1,2,3)
always do 1 and 2
1: sensory neuron entering dorsal root ganglion
2: interneuron in spinal cord or brainstem
3: to thalamus (conscious)
Breaking down nomenclature:
spinothalamic
corticospinal
spinothalamic: coming from the spine and going to the thalamus
ascending so sensory
corticospinal: coming from cortex going to spinal cord
descending so motor
fasiculus gracilis
extrapyramidal tracts
fasiculus gracilis: fasiculus is a bundle, gracilis is in the medulla, so it is heading for the medulla, ascending so it is sensory
extrapyramidal tracts: coming out from medulla, descending so motor
3 major sensory, ascending tracts
dorsal/posterior column
spinothalamic tract
spinocerebellar tract
dorsal column function
conscious awareness
proprioception
fine touch
pressure and vibrations (highly localized)
large diameter, highly myelinated - rapid conduction
Does the dorsal column decussate, if so where?
YES
at medulla
contralateral
Divisions of the dorsal column
fasciculus cuneatus
fasciculus gracilis
fasciculus cuneatus
somatosensory from T6 and above
arms, torso, neck
fasciculus gracilis
somatosensory below T6
think a ballerina is graceful on pointe and the pointe shoes are the lower half of body
How to test for lesion to dorsal column
usually have them close eyes, if gracilis start at bottom of tract like big toe have them tell you if you bent their toe up or down
could also use vibration with a tuning fork
2 part discrimination test
spinothalamic function
conscious
pain, T, crude touch and pressure (poorly localized)
small diameter and sparsely myelinated - slower conduction
does the spinothalamic pathway decussate, if so where?
YES
at entry - spinal cord
contralateral
divisions of spinothalamic and their functions
lateral: pain and T
anterior: crude touch and pressure
how to test spinothalamic damage?
pin test or cold water
spinocerebellar function
unconscious!!!
proprioception
moderate diameter, moderately myelinated
does spinocerebellar decussate, if so where?
- dorsal: NONE ipsilateral
- ventral: double decussation ipsilateral (at entry and at cerebellum)
divisions of spinocerebellar
- dorsal: proprioception
- ventral: monitors activity within spinal cord
spinal cord descending motor tracts
pyramidal
extrapyramidal
pyramidal tracts
conscious
voluntary control
variation in diameter and myelination
where do pyramidal tracts decussate?
medulla
contralateral
what are the divisions of the pyramidal tracts
- lateral corticospinal
- anterior corticospinal
- corticobulbar
lateral corticospinal pyramidal tract
90%
movement of limbs - arms, legs - need more fine motor control in hands and legs
anterior corticospinal pyramidal tract
10%
pectoral and pelvic girdles, core - helps keep you upright
corticobulbar pyramidal tract
neurons from motor cortex synapse with cranial nerves (spinal accessory, facial, trigeminal, oculomotor, hypoglossal
extraocular facial movement and voice production
- comes down same tracts as lateral and anterior corticospinal but does not extend to same extent
- facial expressions, voice production, gestures, speaking
ocular saccade - corticobulbar tract
voluntary
eye movement from one spot to another
- looking from one finger to another - if no nerve issues they have no problem focusing
extrapyramidal tracts
unconscious control - reflexive
- neurons originate in subcortical regions of midbrain
diameter and myelination vary
where do extrapyramidal tracts decussate?
if it happens, in midbrain (does not have to occur)
- higher up than medulla
divisions of extrapyramidal tracts
vestibulospinal
tectospinal
rubrospinal
reticulospinal (medial and lateral)
vestibulospinal - extrapyramidal tract
ipsilateral
maintains equilibrium
postural reflexes and ocular saccades
- helps pull you back up when you start to fall asleep in class
- ocular saccades- if loud noise your eyes automatically go to it involuntarily
tectospinal extrapyramidal tract
both contralateral and ipsilateral
postural reflexes to auditory and visual stimuli
- bright light shining in eyes, loud noise and you jump
rubrospinal extrapyramidal tract
contralateral - upper body especially upper limb postural reflexes
- from red nucleus , part of midbrain
interacts with reticulospinal
reticulospinal extrapyramidal tract
muscle tone - walking coordination - modulates pain - extensors and flexors
medial: ipsilateral stimulate extensors, inhibits flexors
lateral: contralateral inhibits extensors, stimulates flexors
progressive neurodegenerative disease involving loss of neurons in anterior ventral horns and progressive demyelination of corticospinal tracts
ALS
dorsal rami
innervate skin and muscles of the back
ventral rami
innervate ventrolateral body wall and limbs - sides and abdominal region
spinal nerves are part of what nervous system?
peripheral nervous system (PNS)
endoneurium
perineurium
epineurium
endoneurium: surrounds a single neuron
perineurium: surrounds fassicle
epineurium: surrounds entire nerve
how are spinal nerves named
- identified by vertebrae under which they are located T1 spinal nerve comes out under T1
- EXCEPT for cervical vertebrae it begins above the atlas C1 is above atlas
4 spinal nerve plexuses
cervical
brachial
lumbar
sacral
cervical plexus
C1-C5 and cranial nerve 12 (hypoglossal)
- innervates neck muscles and some shoulder muscles
-phrenic nerve (C3-C5) innervates diaphragm
ansa cervicalis
BOTH sensory and motor
ansa cervicalis
C1-C3
in carotid triangle
innervates infrahyoid muscles involved in swallowing and larynx movement
btw strap muscles
brachial plexus
rami from C5 to T1
innervates shoulder, axillary region, arm
sensory and motor
organization of brachial plexus
roots: rami
trunks: superior, middle, inferior where the roots fuse
division: each trunk divides into anterior and posterior regions
cords: lateral, posterior, medial - refusion in diff combo
branches: peripheral nerves
Brachial Plexus nerves
musculocutaneous axillary radial medial ulnar
musculocutaneous nerve
flexes upper arm (“make a muscle”)
axillary nerve
lifting arm to show armpit, trying to elevate arm by shrugging
radial nerve
goes down radial surface - supination and extension
when you put your arm out “here take this”
medial nerve
comes down , only nerve to go through a tunnel (carpal tunnel)
to first 3.5 fingers
allows you to flex fingers and all of them move at once - grabbing things
can get inflamed, tendon is tough and does not give, tingling, numbness and pain from compressed nerve
- can get muscular atrophy thenar muscles rounded part near thumb
ulnar nerve
flexes 4th and 5th fingers
bend pinky and other fingers go with it
goes all around ulnar when you hit funny bone you get tingling from this nerve
lumbar plexus
rami from T12 - L4
innervates abdomen, skin on butt and genitalia, quadriceps, majority of adductors, majority of skin on thigh and leg
femoral and octurator
lumbar plexus - femoral
L2-L4
innervates quads, hip flexors, some adductors, anteromedial skin of thigh, leg, foot
lumber plexus - obturator
L2-L4
innervates adductors, and small area of medial skin of thigh
sacral plexus
rami from L4-S4
innervates butt muscles, hamstrings, muscles of external genitalia and perineum, muscles of lower leg and foot, skin of posterior region of leg
sciatic nerve
sciatic nerve
sacral plexus
L4-S3
innervates hamstrings, adductor magnus, branches extend to lower leg and foot
Erb’s Palsy
common during baby delivery
injury to brachial plexus
cervical stingers or burners from football can lead to same thing
stretched nerve, ruptured, or evulsed
trouble grasping things - one arm droops one arm grasps in babies
reflex arc
sensory info coming in, motor info going out
reflex arc
sensory info coming in, motor info going outmo
reflex arc
sensory info coming in, motor info going out
monosynaptic reflex
sensory info directly to motor in spinal cord
stretch receptors - patellar reflex, achilles reflex
ALWAYS ipsilateral
polysynaptic reflex
most common
ALWAYS has interneuron between sensory and motor
touch something and you pull your hand back
can be ipsilateral or contralateral
shifting weight in feet when walking - contralateral
ALL contralateral are polysynaptic
