CNS Physiology Flashcards
tau fx
binds and stabilizes microtubules
problems –> neurofibrillary tangles (NFTs)
e.g. AD
astrocytes
bbb
regulate extraneuronal ion conc
remove nt’s
form scars in response to injury (can be good or bad)
oligodendricytes
form myelin in CNS
1 cell –> up to 10 axons
microglia
macrophage-like
gray matter
cell bodies
e. g.
- cortex (surrounds brain or cerebellum)
- nucleus (cluster of gray matter within brain, i.e. surrounded by white matter)
- ganglion
- horn (spinal cord)
white matter
fibers/axons
e. g.
- nerve (PNS)
- tract (CNS)
- – named “from-to” e.g. corticospinal = from cortex (brain) to spinal cord
- fasciculus
- lemniscus
- column
- capsule
- commissure
- peduncle
pain receptors in meninges
in dura mater only
ependymal cells
line the ventricles make CSF (most specifically choroid epithelial cells do, which are a specialized form of ependymal cell)
nissl substance
ribosomes and rER of neuron
stains blue with nissl stain
ventricular system and embryologic origin
makes CSF
from vesicles in neural tube
CSF flows from:
- lateral ventricles to
- third ventricle to
- cerebral aqueduct to
- fourth ventricle to
- subarachnoid space (especially large cisterns; no longer part of ventricular system)
lateral ventricles supply
forebrain (telencephalon)
third ventricle supplies
forebrain (diencephalon)
cerebral aqueduct supplies
midbrain (mesencephalon)
fourth ventricle supplies
hindbrain (rhombencephalon)
- cerebellum, pons, medulla
most specifically, what makes CSF and (roughly) how?
choroid epithelial cells
- specialized ependymal cells
- make up choroid plexus
- line ventricles
- most abundant in lateral ventricles
filters blood, adds extra ions
foramen of monro
connects lateral to third ventricle (allows CSF flow)
exit point of CSF from ventricular system
afer 4th ventricle
- 1x foramen of magendie (medial)
- 2x foramen of luschka (lateral)
cisterns
large spaces of subarachnoid space collect CSF (passively) upon exit from ventricular system
flow of CSF once out of ventricular system
- subarachnoid space to
- superior sagittal sinus
- – reabsorbed by arachnoid villi, clustered in arachnoid granulations
arachnoid villi
reabsorb CSF
in superior sagittal sinus
cluster in arachnoid granulations
if decussation occurs, it’s at level of ____ order neuron
second order neuron (cell body)
afferent fiber types by size and conduction velocity
biggest = fastest
- A-alpha (largest)
- A-beta
- A-delta
- C (smallest, unmyelinated)
the ____(biggest/smallest) afferents are involved in balance
biggest
A-alpha fibers
biggest, fastest
balance
primary muscle spindles
Golgi tendon
A-beta fibers
skin mechanoreceptors
secondary muscle spindles
A-delta fibers
coarse touch
temperature
sharp pain
C fibers
smallest, slowest
unmyelinated
affective touch
aching pain
location of afferent n. cell bodies
dorsal root ganglia
afferent n. enter at ___ horn
dorsal
gracile tract
carries afferents from below T6 (lower limbs and body)
more medial in spinal cord
DC-ML pathway
cuneate tract
carries afferents from above T6 (upper limbs and body)
more lateral in spinal cord
DC-ML pathway
first synapse gracile tract fibers
gracile nucleus
first synapse cuneate tract fibers
cuneate nucleus
second order DC-ML afferent n. form ___
internal arcuate fibers of caudal medulla
decussates to medial lemniscus
second order DC-ML afferent n. terminate in
ventral posterior lateral (VPL) nucleus of thalamus
VPL neurons project to
primary somatic sensory cortex
via posterior limb of internal capsule
lassauer’s tract
carries first order sensory discriminative afferents
key component of central pain pathways
spinothalamic tract
carries second order sensory discriminative afferents
central pain pathway
spinothalamic tract n. terminate in
VPL of thalamus
DC-ML pathway senses ___
light touch
vibration
2 point discrimination
position
spinothalamic pathway senses
pain
temperature
coarse touch
periacqueductal gray
one of key regions in affective-motivational component of pain (i.e. descending control)
Golgi tendon organ
lie between group of muscle fibers and tendon
sense muscle tension
autogenic inhibition
negative feedback loop to control muscle tension
corticospinal tract
~85% of descending motor control
location in spinal cord:
- lateral
fx:
- isolated, skilled movement of digits
- voluntary, goal-directed, skilled movement
pathway:
- cell body: primary motor cortex
- thru posterior limb of internal capsule
- cerebral peduncles
- to corticospinal and corticobulbar tracts
- thru pyramids of medulla
- pyramidal decussation
- crossed fibers –> lateral corticospinal tract, others to anterior
rubrospinal tract
location in spinal cord:
- lateral
- adjacent to corticospinal tract
fx:
- flexor and distal muscle of upper limbs
pathway:
- cell bodies: red nucleus (midbrain)
- immediate decussation
reticulospinal and vestibulospinal tract
location in spinal cord:
- medial
fx:
- extensor muscles
- automatic control of posture and balance
- proximal/axial musculature
decussation of corticospinal tract
pyramids of medulla
in corticospinal tract legs are more ___ (position in spinal cord) and arms are more ___
legs = lateral arms = more medial
decussation of rubrospinal tract
immediate (red nucleus, midbrain)
location of CN nuclei
brainstem
CN III fx
oculomotor:
- superior rectus (up)
- inferior rectus (down)
- medial rectus (aDduction/medial)
- inferior oblique (extortion)
- levator palpeerde superioris (raise eyelid)
Edinger-Westphal nucleus:
- pupil constriction
- lens accommodation
- ipsilateral
- L lesion affects L eye
CN III origin
oculomotor nucleus
rostral midbrain
pupillary light reflex
light in one eye –> constriction in both eyes
CN IV fx
superior oblique
CN IV origin
caudal midbrain
immediate decussation
exits dorsally
CN VI fx
lateral rectus (aBduction)
CN VI origin
caudal pons
aBducens nuclei
CN V fx, nuclei
fine touch and proprioception from face
- sensory nucleus/main nucleus
pain, temperature, coarse touch from face
- spinal nucleus of trigeminal complex
mastication, middle ear muscle (tensor tympani)
CN V divisions
V1: opthalmic
V2: maxillary
V3: mandibular
CN VII fx, nuclei (there are 3)
taste (anterior 2/3 of tongue)
- nucleus of solitary tract
facial expression
- facial nucleus
salivary and other glands/membranes
- superior salivary nucleus
CN IX fx, nucleus
- glossopharyngeal
- carotid body
- sensory from oral and nasal cavities
- taste from posterior 1/3 of tongue
- motor control of stylopharyngeus
- – nucleus ambiguus
CN X fx, nuclei (there are 3)
autonomic motor
- dorsal motor nucleus of vagus
- incl most muscles of palate, pharynx, and larynx
- – this is from nucleus ambiguus
visceral sensory
- nucleus of solitary tract
- incl taste from epiglottis and larynx
- incl chemo- and pressure receptors from aortic arch
CN XI fx, nucleus
motor control of SCM and trapezius
- LMNs in ventral horn of spinal cord
- origin in (very) caudal medulla
CN XII fx, nucleus
- intrinsic muscles of tongue
- Hypoglossal nucleus
gracile nucleus
- tactile from lower half of body
location
- caudal medulla (closed)
cuneate nucleus
- tactile from upper half of body
location
- caudal medulla (closed)
medial lemiscus
- tactile from gracile and cuneate nuclei (whole body)
- contralateral
location
- caudal medulla (closed)
- rostral medulla (open)
- caudal pons
- rostral pons
- caudal midbrain
- rostral midbrain
anterolateral tract
- pain from body
location
- caudal medulla (closed)
- rostral medulla (open)
- caudal pons
- rostral pons
- caudal midbrain
- rostral midbrain
spinal nucleus of trigeminal
pain from face
location
- caudal medulla (closed)
- rostral medulla (open)
- caudal pons
nucleus ambiguus
- motor neurons of pharynx and larynx
- shared b/w CN IX and X
location
- caudal medulla (closed)
corticospinal tract
motor information to body
location
- caudal medulla (closed)
rostral nucleus of solitary tract
- taste
- shared among CN VII, IX, and X
location
- caudal medulla (closed)
- rostral medulla (open)
caudal nucleus of solitary tract
- visceral receptors for cardio and respiratory reflexes
- shared CN IX (carotid body) and X (aortic arch)
location
- caudal medulla (closed)
- rostral medulla (open)
dorsal motor nucleus of vagus
- thoracic and abdominal viscera
- para pre
location
- caudal medulla (closed)
- rostral medulla (open)
hypoglossal nucleus
motor neurons of tongue
location
- caudal medulla (closed)
- rostral medulla (open)
medial longitudinal fasiculus (MLF)
- oculomotor connections
- tectospinal and medial vestibulospinal tracts
- CN XI
location
- caudal medulla (closed)
- rostral medulla (open)
- caudal pons
- rostral pons
- caudal midbrain
- rostral midbrain
vestibular nuclei
proprioception
- linear and angular acceleration info from CN XIII
location
- rostral medulla (open)
- caudal pons
inferior cerebellar peduncle
- input to cerebellum
- from posterior spinocerebellar tract and medulla
- some output to medulla
location
- rostral medulla (open)
inferior olivary nucleus
- input to cerebellum
location
- rostral medulla (open)
cochlear nuclei
- auditory info from CN VIII
location
- rostral medulla (open)
sensory nucleus of trigeminal
tactile from face
CN V
location
- caudal pons
motor nucleus of trigeminal
motor neurons for mastication
location
- caudal pons
middle cerebellar peduncle
- main input to cerebellum
- from pontine nuclei
location
- caudal pons
pontine nuclei
- input from ipsilateral corticopontine fibers
- to contralateral cerebella via pontocerebellar fibers
location
- caudal pons
- rostral pons
- caudal midbrain
corticobulbar fibers
- motor information to medulla
location
- caudal pons
- rostral pons
corticospinal fibers
- motor info to body
location
- caudal pons
- rostral pons
aBducens nucleus
- motor to lateral rectus (CN VI)
location
- caudal pons
facial nucleus
motor to face (CN VII)
location
- caudal pons
superior olivary nucleus
first step of auditory processing from cochlear nucleus
location
- caudal pons
superior cerebellar peduncle
- main output from cerebellum
- to thalamus and red nucleus
location
- rostral pons
- caudal midbrain (decussation)
- rostral midbrain
lateral lemniscus
- auditory info from cochlear and superior olivary nuclei
location
- rostral pons
- caudal midbrain
decussation of trochlear nerve
Immediate
motor to superior oblique (crossing over point)
location
- rostral pons
inferior colliculus
- second step of auditory processing
- from lateral lemniscus
location
- caudal midbrain
cerebral peduncle (what fibers/tracts)
- corticopontine, corticobulbar, and corticospinal fibers
location
- caudal midbrain
- rostral midbrain
periaqueductal gray
- descending control of pain
- etc.
location
- caudal midbrain
- rostral midbrain
trochlear nucleus
motor to superior oblique (CN IV)
location
- caudal midbrain
decussation of superior cerebellar peduncle
Level of inferior colliculi
- crossing over of main output of cerebellum
- to thalamus and red nucleus
location
- caudal midbrain
superior colliculus
- shift of gaze (head and eyes)
- attention
location
- rostral midbrain
brachium of inferior colliculus to and from
- auditory from inferior colliculus
- to medial geniculate nucleus
location
- rostral midbrain
substantia nigra and its parts
- part of basal ganglia
- compact part: dopaminergic neurons to striatum
- reticular part: from striatum to thalamus
- damaged in PD
location
- rostral midbrain
edinger-westphal nucleus
para pre neurons for pupil constriction
location
- rostral midbrain
oculomotor nucleus
motor to superior rectus, inferior rectus, medial rectus, inferior oblique (CN III)
location
- rostral midbrain
red nucleus
- motor control via inferior olivary nucleus and rubrospinal tract
location
- rostral midbrain
ventral tegmental area
- reward and reinforcement of behavior
location
- rostral midbrain
mechanisms of regulation of regional cerebral blood flow (rCBF)
- metabolic coupling
- need for O2 and glucose (metabolic demand) increases volume of blood flow - PaCO2
- increase –> vasodilation - cerebral perfusion pressure
- differential to MAP
- autoregulated to maintain a more consistent pressure vs MAP, between ~70 and 140 MAP - neural control
- intrinsic and extrinsic
components of BBB
- endothelial cells w/ tight junctions
- basal lamina = ECM connecting endothelial cells to astrocytes
- astrocytic end feet: biochemical support to endothelial cells
- pericytes: wrap around endothelial cells, structural support and vasodynamic capacity to microvasculature
mx of BBB regulation
- enzymes on cell surface inactivate many drugs
- tight junctions restrict paracellular diffusion
- located at both endothelial cells and epithelial cell surface of choroid plexus
immune recruitment to CNS
- immune cells have components that can break down BBB
- paracellular and transcellular
- shown in many neuro disorders incl MS, stroke
reticular formation
- not a nucleus or tract
- central core of brainstem from midbrain to medulla
- heterogenous cluster of neurons make net-like (reticular) appearance
- neurons can have long-range projections thru brain and spinal cord
fx:
- modulate excitability of distant neurons
- arousal and consciousness
- pain pathways
- gaze control
- respiration
- sneezing
- swallowing (includes nucleus ambiguus)
- control of movement - connections w/ spinal cord and cerebellum
serotonergic system
fx:
- depending control of pain
- sleep-wake
- affect
nuclei:
- raphe nuclei in brainstem
noradrenergic system
fx:
- attention and vigilance
- sleep-wake
nuclei:
- locus ceruleus
- reticular formation
- both in brainstem
dopaminergic system
fx:
- initiation and speed of movement
- motivation, reward, reinforcement
nuclei:
- substantia nigra
- ventral tegmental area
- both in midbrain
reticular activating system
fx:
- maintaining consciousness (bilateral lesions –> coma)
nuclei:
- midbrain and rostral pontine tegmentum
general cerebellar pathway
- input >
- thru cerebellar penduncle
- cerebellar cortex
- cerebellar nuclei
- back thru cerebellar peduncles
- > output
feedback loop - outputs to cortex tend to go back to sources
cerebellar fx
detect and reduce discrepancy between intended and actual actions
mainly understood as involved in motor response, but likely involved in other actions as well
anatomic divisions of cerebellum
lobe
- lobule
- folia (run width of cerebellum, give distinctive texture)
is cerebellum ipsi or contralateral?
ipsilateral
functional distribution cerebellum
name indicates input:
vestibulocerebellum: vestibular inputs (and outputs)
- inferior cerebellar peduncle (ICP) input and output
- balance
- posture
- head position
- reflexive eye movements
spinocerebellum: input from spine and vestibular system
- ICP input
- SCP and ICP output (mostly to thalamus via SCP)
- limb movement
- extremity muscle tone
- balance and posture during movement
cerebrocerebellum: input from cerebral cortex via pons
- MCP input
- SCP output
- output dentate nucleus –> thalamus –> cortex
- coordination of precise movements
- cognition, higher cortical processing
deep cerebellar nuclei
3x contain most output of cerebellum - fastigial from vermis - interposed from intermediate zone - dentate from cerebrocerebellum
superior cerebellar peduncle
output to cortex via thalamus
decussates in midbrain
middle cerebellar peduncle
input from cortex via pontine nuclei
pontocerebellar/transverse fibers
decussate before MCP
inferior cerebellar peduncle
input from spine, medulla, vestibular system
output to brainstem nuclei
most ipsilateral
purkinje cell
output cell of cerebellum
inhibitory
intrinsically active
inhibition –> target excitation
vestibulocerebellum
- vestibular inputs (and outputs)
- inferior cerebellar peduncle (ICP) input and output
- balance
- posture
- head position
- reflexive eye movements
spinocerebellum
- input from spine and vestibular system
- ICP input
- SCP and ICP output (mostly to thalamus via SCP)
- limb movement
- extremity muscle tone
- balance and posture during movement
cerebrocerebellum
- input from cerebral cortex via pons
- MCP input
- SCP output
- output dentate nucleus –> thalamus –> cortex
- coordination of precise movements
- cognition, higher cortical processing
ICP outputs of cerebellum
- immediate need
- vestibulospinal pathways: balance, posture
- reticulospinal pathways: eye movement, stability, control during movement
MCP outputs of cerebellum
none, input only (cortex > pons > cerebrocerebellum)
SCP outputs of cerebellum
- everything the ICP doesn’t
- less immediate
- voluntary gaze (superior colliculus)
- other movements (thalamus > cortex)
- non-motor (thalamus > cortex)
red nucleus
feedback to inferior olivary nucleus
an SCP output of cerebellum
superior colliculus
voluntary gaze
an SCP output of cerebellum
basal ganglia fx
action production
motor processes, likely non-motor as well
input basal ganglia
to striatum
from:
- excitatory: cerebral cortex
- dopaminergic: substantia nigra pars compacta (SNc), ventral tegmental area (VTA)
output basal ganglia
to globus pallidus internal segment (GPi)
or substantia nigra pars reticularis (SNr)
direct pathway basal ganglia
facilitates action
indirect pathway basal ganglia
inhibits action
GPi neurons are (excitatory/inhibitory) and (constitutively active/inactive)
- inhibitory
- constitutively active
- “foot on the brake”
STN neurons are (excitatory/inhibitory) and (constitutively active/inactive)
- excitatory
- inactive at baseline
dopamine receptors of direct and indirect pathways
direct = excitatory (net effect) = D1 indirect = inhibitory = D2
dopamine facilitates action in both cases:
- direct: increases drive
- indirect: inhibits inhibitory D2 receptors –> increases drive
posterior limb of internal capsule
white matter tract
contains most ascending and descending pathways
anterior limb of internal capsule
white matter tract
contains only ascending and descending pathways going to/from frontal pole and medial prefrontal cortex
semicircular canals
proprioception- angular acceleration
inner ear
otolithic organs
proprioception - linear acceleration
utricle and saccule
inner ear
endolymph
surrounds hair cells in cochlea
high K+ concentration (K+ influx depolarizes hair cell)
ossicles
middle ear
bones
malleus, incus, stapes
middle ear
ossicles
connection to Eustachian tube
cochlear nuclei
carry info from one ear
only part of CNS auditory pathway that only contains info from one ear
thalamus
relay station
plus other stuff
supraoptic and paraventricular nuclei
produce ADH and oxytocin
hypothalamus
preoptic nuclei
produce GnRH
hypothalamus
suprachiasmatic nucleus
circadian rhythm
hypothalamus
ventromedial nucleus
satiety
hypothalamus
lateral nuclei
hunger
hypothalamus
inputs to VPL
VPL = part of thalamus
- spinothalamic tract
- medial lemniscus
- trigeminal lemniscus
inputs to LG
LG = lateral geniculi = part of thalamus
- optic tract
inputs to MG
MG = medial geniculi = part of thalamus
- inferior colliculus
- lateral lemniscus
anterior nucleus
thermoregulation
hypothalamus
semicircular canals
angular acceleration
works by inertia of circulating fluid within the canals
opposite canals (e.g. left and right horizontal) act as push-pull
otolithic organs
utricle and saccule
linear acceleration
mx similar to semicircular canals (inertia of fluid detected by hair cells) but anatomy/position better suited to detecting linear acceleration
also static tilt of head relative to gravity based on orientation of hair cells at rest
proprioceptive pathways
sensory organs:
- semicircular canals
- otolithic organs - utricle and saccule
vestibular nuclei
- inferior vn
- medial vn
- lateral vn
- superior vn
outputs of vn:
- cerebellum
- lateral vestibulospinal tract (LVST)
- medial VST (MVST)
- reticular formation
- thalamus
- cortex
- eye movement control nuclei
- contralateral vestibular nuclei
LVST
lateral vestibulospinal tract
cell bodies in lateral vestibular nucleus (LVN)
projects to IPSI-lateral spinal cord
- balance and posture
e. g. stumbling, feeling dizzy when you stop spinning
MVST
medial vestibulospinal tract
cell bodies in MVN
projects BI-laterally to upper cervical cord
- head position
thalamus and cortex in proprioception
vestibular nuclei –> BI-laterally to thalamus –> parietal cortex
step (eye movements)
sustained nerve activity/steady firing that maintains the eye in position
pulse (eye movements)
burst of rapid nerve firing that moves the eye
eye movement pathway
paramedian pontine reticular formation (PPRF) - abducens nucleus superior colliculus frontal eye field (cortex) primary motor cortex
horizontal eye movements:
- pons
vertical eye movements
- midbrain
saccadic eye movements
bring object of interest onto fovea, e.g. scanning a text or image 2-3x/second generally automatic, can be voluntary "ballistic" physiologic
smooth pursuit eye movements
keep moving objects on fovea
driven by visual input
can be driven by *slow head movement
e.g. tracking moving finger, following car
vergence eye movements
convergence or divergence
focuses/detects depth
VOR
vestibulo-ocular reflex
coordinates ocular movement with proprioception
*keeps focus on one object/doll eyes
e.g. eyes move right when head moves left to keep looking “forward”
nystagmus
can be physiologic or pathological
rapid, repeated eye movements
physiologic: if eye rotates too far in one direction, it springs to center
- also caloric nystagmus, which responds to change in temperature in one ear
pathologic: this happens too often/repeatedly; slow phase generally is the underlying disorder (e.g. eye drift)
directionality (L/R) defined by direction of fast phase (spring back)
decussation of optic nerve / tract
partial decussation in optic chiasm
each cerebral hemisphere covers contralateral hemifield
- L side of L eye (lateral) and L side of R eye (medial) both covered by R hemisphere
- t/f lateral/temporal hemifield will be ipsilateral while medial/nasal hemifield will be contralateral
pretectum
in midbrain
pupillary light reflex
what makes aqueous humor (eye)
ciliary epithelium
what controls accommodation (lens)
ciliary muscle
flow of aqueous humor
produced: ciliary body
flow: pupil
exit: anterior chamber angle
angle closure –> extremely high IOP
dopamine metabolism
DA –> DOPAC via MAO
DOPAC –> HVA (end-product) via COMT
activating dopamine receptors
D1, D5
inhibitory dopamine receptors
D2-4
