Section 1 Flashcards
ganglia
nerve cell bodies in PNS
nuclei
nerve cell bodies in CNS
how many neurons in the nervous system
100 billion (10^11)
how many glial cells in the nervous system
1 trillion (10^12)
Santiago Ramon Cajal
father of modern neuroscience, used Golgi staining
Golgi staining
can see the outline of neurons
dendrites
toward cell body
axon
away from cell body
multipolar cell examples
cerebellar Purkinje
cerebellar granule
inferior olive
spinal cord motor
large pyramidal
olfactory cells are _____ cells
bipolar
dorsal root ganglia neuron cell type
pseudounipolar
sympathetic: excitatory or inhibitory?
excitatory
parasympathetic: excitatory or inhibitory?
inhibitory
function of short interneuron
both excitatory and inhibitory
spinal cord reflex: connects sensory neuron directly to motor neuron
function of long interneuron
project from cerebral cortex to spinal cord
astrocyte function
maintain NT levels, ion concentration, metabolic support, BBB
most abundant glial cell
astrocyte
perivascular endfeet
astrocytes that are tightly associated with the capillary to regulate BBB
BBB restrictions
pathogens, certain solutes, peripheral immune factors
neurovascular coupling
increased neuronal activity causes astrocytes to induce vasodilation (higher level of activity leads to more oxygen)
satellite glial cells
cover the surface of neuron cell bodies in ganglia
like peripheral astrocytes
oligodendrocytes
myelinate CNS neurons
Schwann cells
myelinate PNS neurons
can neuron be wrapped in Schwann cells and be unmyelinated?
yes, they contribute to the microenvironment
tract
a bundle of fibers in the nervous system that connects one area to another and usually consists mostly of white matter
commissure
a type of white matter tract that cross the midline, connecting the same cortical area in opposite hemispheres
quiescent vs reactive microglia
regulatory state vs immune state
ependymal cells
glial cells that line the walls of the ventricles and produce CSF
regulate the transfer of fluid and ions between CSF and neurons
medial longitudinal fissue
separates the two hemispheres
central sulcus
separates frontal and parietal lobe
lateral sulcus
separates frontal/parietal from temporal lobe
how to find central sulcus
the gyri on either side project inferiorly whereas the other gyri project in various directions
insula
forms in early brain development
can be seen if frontal and parietal lobe are separated from temporal lobe
parieto-occipital sulcus
separates parietal and occipital lobe
corpus callosum
white matter that connects the cerebral hemispheres
limbic lobe
outside of the corpus callosum
which ventricle is the diencephalon located
third ventricle
internal carotids
provides 80% of blood supply, most of telencephalon and diencephalon
vertebral arteries
supply brainstem and cerebellum
circle of Willis
internal carotid
anterior cerebral
anterior communicating
middle cerebral
posterior communicating
posterior cerebral
posterior cerebral artery projects to …
the primary visual cortex
occlusion of anterior cerebral artery
affects leg and hip regions
occlusion of middle cerebral artery
affects arms and facial regions
ischemic stroke
build up of material in the artery
intracerebral hemorrhage
arterial rupture leads to explosion of blood in head
which week of development does the nervous system arise?
third week
neural plate
longitudinal band of ectoderm that thickens during third week to form the neural plate
neural groove
folding of neural plate
neural tube
next step in development after neural groove
closure of cranial neuropore
day 25
18-20 somites
closure of caudal neuropore
day 27
25 somites
notochord
transient axial mesodermal structure
eventually becomes part of intervertebral discs
somites
mesoderm-derived
form vertebral column and segmental units of muscle and dermis
when are primary vesicles apparent
day 24
cranioarchischisis
open spinal cord and spine
CNS open on dorsal surface
anencephaly
failure of rostral end to close
spina bifida
failure of caudal end to close
cord and meninges are displaced into a cavity on the back
no vertebrate over lesion
cephalic flexure
in mesencephalon
cervical flexure
between spinal cord and rhombencephalon
lamina terminalis
divides two sides of telencephalon
secondary vesicles of prosencephalon
telencephalon
diencephalon
secondary vesicle of mesencephalon
mesencephalon
secondary vesicles of rhombencephalon
metencephalon and myelencephalon
pontine flexure
in the metencephalon
derivative of telencephalon
cerebrum
derivatives of diencephalon
thalamus
hypothalamus
retina
midbrain structures
mesencephalon
midbrain
metencephalon
pons
cerebellum
myelencephalon
medulla
when do the telencephalon and diencephalon fuse?
by the third month
when does the basal ganglia experience downward folding?
in the 2nd month
how does the lateral ventricle get its C-shape?
the cerebral hemispheres grow in a C-shaped manner
week 3 major developments
neural groove and folds
primary vesicles
cervical and cephalic flexures
motor neurons
week 4 major developments
neural tube closures (day 22-26)
neural crest cells migrate
secondary neurulation starts
motor nerves
week 5 major developments
pontine flexure
secondary vesicles
sulcus limitans
sensory ganglia
sensory nerves
basal ganglia begins
week 6-7 major developments
enlarged telencephalon
prominent basal ganglia
secondary neurulation complete
cerebellum and optic nerve begin
choroid plexus
insula
week 8-12 major developments
neural proliferation and migration
cerebral and cerebellar cortex begin
reflexes
week 12-16 major developments
neuronal proliferation and migration
glial differentiation
corpus callosum
week 16-40 major developments
neuronal migration
cortical sulci
glial proliferation
myelination
synapse formation
neural crest
transient migratory population of cells that emerges from the edges of the neural folds as the neural tube separates from the ectoderm
neural crest cells give rise to…
sensory neurons (posterior root ganglia, cranial nerves)
post-ganglionic neurons of ANS
adrenal medulla
Schwann cells
pigmented skin cells
cranial neural crest cells
cartilage and bone
connective tissue
neurons and glia in CNS
trunk neural crest cells
pigment cells
sensory neurons and glia
Scwann cells
CN I
olfactory
CN II
optic
CN III
oculomotor
CN IV
trochlear
CN V
trigeminal
CN VI
abducens
CN VII
facial
CN VIII
vestibulocochlear
CN IX
glossopharyngeal
CN X
vagus
CN XI
spinal accessory
CN XII
hypoglossal
sulcus limitans
divides neural tube into dorsal alar plate and ventral basal plate
alar plate gives rise to …
sensory area of brain and spinal cord
basal plate gives rise to…
motor area of brain and spinal cord
marginal zone of the spinal cord
outer layer where differentiating neurons accumulate
contains post-mitotic neurons
ventricular zone of spinal cord
inner layer containing dividing progenitors
dorsal root ganglia
contains sensory input from the periphery that connects to the spinal cord
Pax2 labels…
interneurons
Isl1 labels…
motorneurons
dorsal horn of spinal cord receives…
nociceptors
mechanoreceptors
proprioceptors
ventral horn of spinal cord receives…
proprioceptors
lateral motor column
innervates limbs
medial motor column
innervates axial muscles
sonic hedgehog (SHH)
released from mesoderm and notochord signals cells to form basal plate
bone morphogenetic proteins (BMPs)
released from ectoderm signals cells to form the alar plate
wingless/int-related proteins (Wnts)
released from ectoderm signals cells to form alar plate
morphogens
SHH, BMPs, Wnts
called this becuase they can pattern tissue in a concentration-dependent fashion
holoprosencephaly
partial or complete failure of the prosencephalon to separate into the diencephalon and telencephalon
(too little SHH)
cyclopia
extreme holoprosencephaly
single brain vesicle
one large eye
too little SHH
how does cell division change as neurogenesis proceeds?
the cleavage plane changes
early neurogenesis
vertical cleavage plane
2 symmetrical progenitor daughter cell
late neurogenesis
horizontal cleavage plane
basal daughter cell is postmitotic
how is the cerebral cortex developped?
new neurons migrate along a radial glial fiber supplied by a neural progenitor to the cortical layer from the ventricular layer
bergmann glia
radial fiber
more superficial layers of the cortex are born first
false
deeper layers are born first and the superficial layers have to migrate past the deeper layers
how are inhibitory neurons born?
they arise from the ganglionic eminence in the ventral telencephalon and have to migrate long distances
organizer region
in the mid-hindbrain junction
also called the MHB
expresses signalling molecules and DNA binding transcription factors that specify the adjacent regions of the brain
Hox gene
transcription factor along chromosomes
expression is conserved from flies to humans
rhombomeres
morphologically distinct segments of the hindbrain
each defined by a unique “bar code” including Hox genes
which rhombomeres have cell bodies of motor ganglia
even-numbered ones
how do cranial ganglia form?
from the intermixing of migrating neural crest cells interacting with ectodermal thickenings (placodes)
how do cranial nerves form?
each rhombomere expresses unique transcription factors
neural crest cells migrate from them in a patterned manner
how many spinal segments?
31 total
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal
how many vertebral segments?
33 total
7 cervical
12 thoracic
5 lumbar
5 sacral
4 coccygeal
foramen magnum
space that the spinal cord passes through to connect to the brainstem
which cervical nerves pass above respective vertebrae?
C1-C7
where does C8 (cervical nerve) pass?
above T1 vertebra
which cervical nerves pass below respective vertebrae?
T1- the rest
where do the coccygeal nerves pass?
below the first coccygeal vertebra
cervical spinal segments are responsible for…
arms and head
thoracic spinal segments are responsible for…
trunk
which spinal segments control the legs?
lumbar, sacral, and coccygeal
dermatome
area of skin whose sensory information project via certain spinal nerves
most ventral aspect of the vertebra
vertebral body
parts of the vertebra
vertebral body
spinous processes
vertebral foramen
superior and inferior articular process
intervertebral foramen
intervertebral disc
facet joint
function of superior and inferior articular process
help connect vertebrae to one another via the facet joint
function of intervertebral foramen
space that spinal nerves pass through the vertebrae
function of intervertebral and facet joint
cartilaginous joint
movement of spine
ligaments to hold vertebrae together
shock absorbers
spinal cord arteries
anterior spinal artery
two posterior spinal arteries
segmental arteries that branch off into radicular arteries and run along the dorsal and ventral nerve roots
arachnoid mater
important for CSF circulation and blood vessel supply
denticulate ligaments
extensions of the pia mater that anchor the spinal cord to the dura mater
located between spinal nerves
lumbar cistern
space in vertebral column after spinal cord ends
filled with CSF
ideal for lumbar punctures
conus medullaris
tapering of the spinal cord located around L1
filum terminale
extension of pia mater that helps anchor spinal cord to vertebral canal
internum: strictly pia mater
externum: fuses with dura mater
cauda equina
bundle of spinal nerves after spinal cord ends
spinal dorsal roots
sensory axons that enter the spinal cord
dorsal root ganglia
cells bodies of sensory neurons (outside spinal cord)
ventral root of spinal cord
motor axons that leave the spinal cord
spinal nerve
contains both motor and sensory axons leaving and entering the spinal cord
ventral ramus
motor and sensory axons innervating the ventral portion of the body (wrap around the trunk)
dorsal ramus
motor and sensory axons innervating dorsal portion of the body (stays near spinal cord)
sympathetic ganglia
located near the intervertebral foramen at each spinal segment
contain afferent and efferent cell bodies responsible for sympathetic
white matter of spinal cord
exterior portion (axons)
gray matter of spinal cord
interior portion (cell bodies)
dorsal horn of spinal cord
mostly interneuron cell bodies for sensory integration
ventral horn of spinal cord
mostly cell bodies of motor neurons, and interneurons
Lissauer’s tract
ascending and descending small fibres that terminate in the substantia gelatinosa
pain, temp, light touch
substantia gelatinosa
cells that receive direct input from the dorsal roots
pain, temp, light touch
nucleus proprius
cells that receive direct input from the dorsal roots
pain, temp, light touch
more ventral and medial than the substantia gelatinosa
spinal cord sulci
posterior (dorsal) median
posterior intermediate
posterolateral
anterolateral
anterior (ventral) median
quantity of white matter ________ from rostral to caudal segments of spinal cord
decreases
quantity of gray matter ______ from rostral to caudal segments of spinal cord
increases
cervical enlargement
responsible for upper limbs
lumbar enlargement
responsible for lower limbs
stretch reflex
purely spinal
activation of stretch receptors in a muscle then activates motor neurons there
monosynaptic
reciprocal inhibition
inhibition of antagonistic muscles
disynaptic
flexor reflex
purely spinal
activation of pain receptors activates motor neurons of flexor muscles
polysynaptic
crosses reflexes
during the flexor reflex, pain signals from one leg cross to the other leg to activate extensor muscles
polysynaptic
maintains balance during flexor reflex
sympathetic and parasympathetic preganglionic neurons are segregated in the spinal cord
true
where are sympathetic neurons located?
sympathetic ganglia of the thoracic and lumbar spinal cord (outside)
where are parasympathetic neurons located?
directly inside the brainstem and sacral spinal cord
where is rhythmic locomotion generated?
in the spinal cord
central pattern generator (CPG)
collection of interneurons in the spinal cord responsible for driving rhythm of locomotion and pattern of motor neuron activity
CPG is modulated by…
visual system
vestibular system
proprioceptive and sensory systems
what initiates locomotion?
brain and brainstem
what maintains locomotion?
spinal cord
what modulates locomotion?
many systems
nonencapsulated cutaneous receptors
root hair plexus
Merkel cells
free nerve endings
root hair plexus
touch receptors that wrap around hairs to detect their movements
Merkel cells
sensory cells located below the epidermis and connect to nerve endings of the skin (touch)
free nerve endings
branching sensory nerve terminals with no complex structures
in the skin
touch, pain, temp, itch
encapsulated cutaneous receptors
Meissner corpuscles
Pacinian corpuscles
Ruffini endings
Meissner corpuscles
located below the epidermis and responsible for detecting fine touch and pressure
Pacinian corpuscles
deeper sensory receptors for vibration and deep pressure
proprioception
Ruffini endings
located below the epidermis and responsible for detecting skin stretch, pressure, joint movements, and temperature
muscle spindles
wrap around intrafusal muscle fibres
detect muscle stretch and velocity
Golgi tendon organs
comprised of free endings that are wrapped in between collagen fibers
detect muscle tension
located within the tendons
where do small sensory fibres enter spinal cord?
in Lissauer’s tract to terminate in substantia gelatinosa and nucleus proprius
where do large sensory fibres enter the spinal cord?
medial to Lissauer’s tract
ascending tracts are usually ______
polysynaptic
where are first order neurons of ascending tracts?
dorsal root ganglia
fasciculus gracilis
transmits conscious sensory information from below T6 segment
fasciculus cuneatus
transmits conscious sensory information from above T6 segments
posterior medial-lemniscus system
fasciculus gracilis and cuneatus
first order neuron: DRG
second: medulla oblongata
third: thalamus
crossing at the medial lemniscus in the brainstem
conscious tracts
medial-lemniscus
spinothalamic
conscious spinothalamic tracts
form anterolateral system
lateral and anterior tracts
first order neuron: DRG
second: nucleus proprius
third: thalamus
information crossing in the spinal cord before entering tracts
lateral spinothalamic tract
responsible for pain and temperature
anterior spinothalamic tract
responsible for crude touch and pressure
projections of conscious sensory tracts are ______
contralateral
unconscious tracts
spinocerebellar (ventral and dorsal)
first order: DRG
second: in spinal cord
ipsilateral
dorsal spinocerebellar tract
sends proprioceptive information to the cerebellar
(what is actually occurring)
ventral spinocerebellar tract
sends locomotor-related interneuronal information to the cerebellum
(this is what I want to occur)
does the dorsal spinocerebellar tract cross?
no
does the ventral spinocerebellar tract cross?
double cross, first in spinal cord then again in brain stem
lateral corticospinal tract
voluntary motor
90% of the corticospinal tract
upper motor neurons are in the motor cortex and lower are in the spinal cord
information crosses at the medulla oblongata
arms and limbs
anterior corticospinal tract
voluntary motor
10% of the corticospinal tract
upper motor neurons are in the motor cortex and lower are in the spinal cord
information crosses in the spinal cord
trunk muscles
vestibulospinal tract
drives locomotor reflexes and behaviour to maintain balance
tectospinal tract
head and eye movement
directs body towards sights and sounds
terminates in the cervical spinal cord
reticulospinal tract
postural control and locomotion
rubrospinal tract
locomotion
terminates in cervical and thoracic spinal segments
responsible for trunk and upper limb movements
how much does brain weigh?
1500g in air
50g in CSF
dura mater layers
periosteal (outer)
meningeal (inner, only around the brain, not present around spinal cord)
falx cerebri
meningeal layer of dura mater goes between the two cerebral hemispheres
tentorium cerebelli
meningeal layer of dura mater goes between occipital lobe and cerebellum
arachnoid mater
adhered to inner surface of dura
CSF flows through
pia mater
tightly adhered to the surface of the brain (goes into the sulci)
sinus
separation of the two dura mater layers
where venous blood drains from cerebrum and CSF from arachnoid space
arachnoid trabeculae
“spidery” extensions within the arachnoid layer that allow the CSF to flow through
epidural space
potential space between skull and dura
subdural space
potential space between meningeal dura and arachnoid
subarachnoid space
true space between arachnoid and pia, filled with CSF
cisterns
true space between two layers of dura filled with cerebral magna
bridging vein
drains venous blood into the superior sagittal sinus
epidural hematoma
from getting hit really hard leading to laceration of the middle meningeal artery
blood collects between dura and periosteum
chronic subdural hematoma
rupture of bridging veins
usually becuase atrophy allows brain to move freely
acute subdural hematona
rupture of bridging vein immediately after high velocity impact
interventricular foramen
connection between lateral and third ventricles
cerebral aqueduct
connection between third and fourth ventricles
parenchyma
30% of CSF production
cells in the brain
choroid plexus
70% of CSF production
CSF characteristics
500mL per day
total volume is 90-140mL
low protein content <0.45g/l
clear, colourless and sterile
presence of WBC indicates infection
function of ventricles
removes metabolites from CNS
stabilizes ionic composition of CNS
cushion to dampen effect of trauma
arachnoid granulations
extensions of arachnoid that protrude into the sinus and release CSF into the blood
non-obstructive hydrocephalus
impairment of arachnoid granulations
obstructive hydrocephalus
CSF-flow obstruction of the portals that it normally flows through
pontomesencephalic junction
between midbrain and pons
which cranial nerves have nuclei in the brainstem
CN III to CN XII
pyramids
conduit for descending motor (corticospinal tract)
in medulla
cerebral peduncles
conduit for descending white matter in the midbrain
anterior median fissure
separates the pyramids
anterolateral sulcus
separation of the olives (inferior olivary nuclei)
roof of fourth ventricle
superior cerebellar peduncle and superior medullary velum
name the cranial nerves
I: olfactory
II: optic
III: oculomotor
IV: trochlear
V: trigeminal
VI: abducens
VII: facial
VIII: vestibulocochlear
IX: glossopharyngeal
X: vagus
XI: accessory
XII: hypoglossal
where are motor roots located in the brainstem?
along the midline
CN with pure motor function
3, 4, 6, 11, 12
where do axons of CN exit the brainstem?
ventral side
except for CN IV (trochlear)
autonomic function of cranial nerves
always parasympathetic
oculomotor nerve function
all extraocular eye muscles except lateral rectus and superior oblique
levator palpebrae superiosis
autonomic: pupillary constriction
trochlear nerve function
superior oblique
depresses and abducts
abducens nerve function
lateral rectus
abducts
hypoglossal nerve function
all intrinsic and most of the extrinsic muscles of the tongue
(tongue movement)
pathway of hypoglossal nerve
upper motoneuron: corticobulbar neuron
corticobulbar tract
hypoglossal nucleus
hypoglossal nerve
intrinsic tongue muscles
right CN XII palsy
tongue deviates to the right
eye adduction
medial rectus, CN III
eye abduction
lateral rectus, CN VI
eye elevation
superior rectus, CN III
inferior oblique, CN III
eye depression
inferior rectus, CN III
superior oblique, CN IV
lifting eyelid
levator palpebrae superiosis, CN III
how to test superior rectus
look laterally and upward
how to test inferior rectus
look laterally and downward
how to test lateral rectus
look laterally
how to test medial rectus
look medially
how to test inferior oblique
look medially and upward
how to test superior oblique
look medially and downward
right CN VI palsy
prevent from looking laterally with right eye
left CN IV palsy
prevent looking down and medially with right eye
nucleus of edinger westphal
rostral midbrain
source of preganglionic parasympathetics carried by CN III to the ciliary ganglia (pupil constriction)
miosis
constriction of the pupil by the sphincter pupillae which is innervated by the postganglionic parasympathetics
lesion to right CN III
right eyelid is shut (ptosis)
can’t look up or medially
pupil is dilated
lesion to left CN VI
left eye cannot look laterally
branches of trigeminal nerve
ophthalmic branch (V1)
maxillary branch (V2)
mandibular branch (V3)
which branch of trigeminal nerve has motor function?
mandibular branch
muscles of mastication
temporalis
masseter
medial and lateral pterygoids
pathway of motor control of pterygoids
UMN in precentral gyrus of motor cortex
projects to motor nucleus CN V
LMN innervates muscle
functions of tensor tympani
reduce auditory sounds (chewing, speech)
activates in response to very loud noises
modality of spinal trigeminal nucleus
pain and temp (face)
modality of main sensory nucleus (CN V)
discriminative touch and proprioception (face)
modality of mesencephalic nucleus (CN V)
stretch reflex associated jaw muscle of mastication
rules of CN V
- 1st order sensory neurons located in trigeminal ganglion
- 2nd order sensory neurons located in distinct subnucleus of CN V
- 2nd order neurons project to 3rd order neurons in the contralateral VPM of thalamus
- 3rd order neurons project to the “face region” of the postcentral gyrus
- lower motor neurons innervating muscles of mastication located on the trigeminal motor nucleus
which area of the pons does the trigeminal nerve pass through?
lateral area of pons
second order neuron of pain begins in…
the spinal nucleus
second order neuron of proprioception begins in…
the chief sensory nucleus of CN V
pain tract for the face (sensory)
trigemino-thalamic
proprioception tract for the face (sensory)
trigeminal lemniscus
third order neuron of pain begins in…
VPM
third order neuron of proprioception begins in…
VPL
clinical disorders associated with CN V
loss of face sensation
trigeminal neuralgia
loss of corneal reflex (afferent limb is CN V)
paralysis of muscles of mastication
deviation of jaw to weak side
loss of lacrimal reflex (afferent)
loss of jaw jerk reflex
trigeminal neuralgia
sharp stabbing pain on one side of face
caused by virus (herpes) or occlusion of arterial blood flow
corneal reflex
afferent: CN V
efferent: CN VII
causes both eyes to blink
lacrimal reflex
afferent: CN V
efferent: CN VII
tear secretion
jaw jerk reflex
tapping between the chin and lower teeth causes the jaw to jerk shut
