Week 2 Lectures Flashcards
What is similar about CN 3, 4, 6, 12?
They exit medially/midline –> purely motor
What is similar about CN 5, 7, 8, 9 10?
They exit laterally –> both motor and sensory
How many cranial nerves enter/exit the brainstem?
9 (except 1, 2, 11)
Which cranial nerves exit the midbrain?
3 and 4
Which cranial nerves exit the pons?
5, 6, 7, 8
Which cranial nerves exit the medulla?
9, 10, 12
The medullary pyramid is….
the corticospinal tract/pyramidal tract
What is the only dorsally exiting CN?
4 –> under calliculi –> only completely crossed CN –> motor neurons are found on the side of the midbrain opposite to ascent/descent
What structure separates the cerebellum from the pons and medulla?
4th ventricle
Corticospinal tract courses _____ and _____ through the brainstem.
ventral and medial –> medial brainstem blood supply and lesioned with medium brainstem vascular lesion
What happens if we lesion the corticospinal tract below the brainstem?
UMN loss ipsilateral and below
What happens if we lesion the corticospinal tract in the brainstem?
UMN loss contralateral and below
What is the role of medial motor systems?
bilateral postural control
Medial lemniscus moves from _____ to ______ as it ascends the brainstem?
medial to lateral –> change source of blood
What happens if we lesion the corticospinal tract below the brainstem?
ipsilateral and below
What happens if we lesion the corticospinal tract above the brainstem?
contralateral and below
Where does the anterolateral system course?
laterally through the brainstem
T/F the anterolateral system courses straight to the thalamus.
F –> projects into other neurons in the brainstem to modulate the pain elicited by the stimulus
What happens if we lesion the corticospinal tract below the brainstem?
contralateral and below lesion
What happens if we lesion the corticospinal tract above the brainstem?
contralateral and below lesion
What aspect of the brain controls autonomic function?
hypothalamus
What system conducts sympathetic control of the face, scalp, and orbit?
2 neuron pathway from T1 involving a second neuron in the superior cervical ganglion –> horner’s syndrome
When you lesion descending hypothalamic fibers, what syndrome do patients present with?
central horner’s syndrome
When a patient presents with horner’s it is ipsilateral/contralateral to the lesion?
ipisilateral ALWAYS
Where do descending hypothalmic fibers run in the brainstem?
lateral near the spinothalamic tract –> shared blood supply
When there is interrupted lateral blood supply to the brainstem, which tracts are lesioned?
spinothalamic + sympathetic
Medial longitudinal fasciculus
links ocular CN nuclei and vestibular system –> conjugate horizontal gaze –> motor CNs 3 and 6 and vestibular system
What will be found in every brainstem section?
- long tract (corticospinal, dorsal column, spinothalamic, MLF, central tegmental tract)
- cranial nerve nucleus or nerve
- trigeminal nucleus
- cerebellar peduncle or fibers forming one (ICP-medulla, MCP-pons, SCP-midbrain)
LMN in a CN arise from?
corticobulbar or corticonuclear axons –> mostly bilateral UMN –> cranial nerve muscles often cross the midline
What would happen if we lesion all the corticobulbar axons emerging from one hemisphere?
not much –> still have innervation from opposite size
*exception: LMN in facial nerve have some muscles that are unilaterally innervated (muscles of nose and mouth are only contralateral)
What happens with a lesion of a LMN in the facial nerve?
ipsilateral effects –> bell’s palsy
What happens with a lesion of the UMN of the facial nerve?
only the muscles for wrinkling forehead and shutting the eyes have dual cortical innervation –> contralateral weakness of the lower face
Embryonic sulcus that separates sensory and motor areas
sulcus limitans
Functional columns
GSE GVE SVE | SVA/GVA SSA GSA
Motor Functional Columns
GSE = garden variety skeletal muscle (motor only: 3, 4, 6, 11, 12); GVE = parasympathetics (3 and mixed: 7, 9, 10); SVE = pharyngeal arch muscle (mixed only: 5, 7, 9 , 10)
What is the only motor cranial nerve that carries autonomics?
3- oculomotor
Sensory Functional Columns
GSA = pharyngeal arches (mixed only: 5, 7, 9, 10) --> mostly trigeminal; GVA = stretch and baroreceptors (9 and 10) SVA = taste (7, 9, 10)
Functional Columns- garden variety skeletal muscle
3 (adduct eye, raise eyelid), 4 (depress eye), 6 (abduct eye), 12 (move tongue), (and 11)–> most medial and motor
Where do the crossed oculomotor nerves go?
to the superior rectus and superior oblique on the contralateral side
Functional Columns - preganglionic
3 (Edinger Westphal - pupil constriction, near response), 7 (Superior salivatory nucleus - lacrimation), 9 (Inferior salivatory nucleus-parotid), 10 (Dorsal motor nucleus-gut)
Which axons exit the midbrain with the oculomotor nerve and synapse with neurons in the ciliary ganglion and where do they arise?
preganglionic parasympathetics from Edinger Westphal nucleus
What are the initial signs of CN3 compression?
dilated pupil, loss of lightreflex, and loss of near response on side of lesion
What nucleus gives rise to parasympathetic axons in the facial nerve?
Superior salivatory nucleus in the caudal pons –> pterygopalatine, lacrimal, and submandibular
What is the result of a lesion of parasympathetic axons in CN7?
loss of lacrimation–> dry ey on side of lesion
Where and what is the nucleus that gives rise to parasympathetics in CN9?
inferior salivatory nucleus in the rostral medulla –> otic ganglion –> parotid gland
A lesion of CN9 may result in what?
reduction in parotid secretions
What nucleus contains parasympathetics that exit with CNX?
dorsal motor nucleus lateral to hypoglossal nucleus in the floor of 4th ventricle –> terminal ganglia in thoracic/abdominal viscera –> slow heart rate, constrict bronchial smooth muscle, promote peristalsis
Where is the motor nucleus of V located?
rostral pons –> muscles of mastication and mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini
Unilateral lesion of the motor fibers of CN V may cause what?
devision of jaw upon protrusion toward side of lesion
The facial motor nucleus is where?
caudal pons –> axons form the facial colliculus in the floor of 4th ventricle by wrapping around abducens nucleus –> stapedius, stylohyoid, posterior belly of digastric
With what nerve do facial motor axons run laterally to the genu?
sensory and parasympathetic fibers of hte nervus intermedius of the facial nerve
Lesions of the skeletal motor axons in the facial nerve may result in?
complete paralysis of muscles of facial expression ipislateral to lesion and hyperacusis due to weakness of stapedius (also weakness in forehead wrinkling, eye shutitng, nostril flaring on the side of lesion)
Which nucleus contains LMN of CN 9 and 10?
nucelus ambiguus (some of these neurons contribute to parasympathetic innervation of heart)
A lesion of motor axons from CN 10 from nucleus ambiguus may cause?
ipsilateral weakness of soft palate, nasal regurgitation of liquid, deviation of uvula away from side of lesion, weakness of pharygneal muscles/dysphagia, weakness of laryngeal muscles/hoarsness
Where does the accessory nerve arise?
accessory nucleus between C1 and C5 –> pass through foramen magnum –> exit jugular foramen –> SCM and trapezius
Where are parasympathetic neurons of 10 located?
nucleus ambiguus and dorsal motor nucleus
Which axons loop around the abducens nucleus?
Facial nerve axons
Parasympathetics and special pharyngeal arch axons are exiting from a _____ nerve from a _____ position on the brainstem.
mixed, ventrolateral
What nucleus conducts visceral sensory fibers for taste and pressure?
Solitary nucleus –>medulla (taste= 5,9,10 superior to carotid sinus,body = 9,19)
A bilateral lesion of the solitary nuclei may cause ________.
respiratory failure (possibly preceded by ataxic respiration)
The gag reflex utilizes visceral sensory fibers in CN ____ and skeletal motor fibers in CN ____.
9 and 10
The cough reflex utilizes both sensory and motor fibers in CN___.
10
What do cochlear (CN8) nerve fibers do upon entereing the brainstem at the pontomedullary junction?
birfucates and gives rise to processes that synapse in both ventral and dorsal cochlear nuclei
Which ganglion contains the cell bodies of the cochlear nerve fibers?
spiral ganglion in cochlea
The ventral cochlear nuclei project bilaterally to neurons in the _______.
superior olivary nuclei in the pons
The first auditory nuclei to receive binaural inputs are?
the superior olivary nuclei
From which sources does the lateral lemniscus convey auditory input from?
cochlear nuclei and superior olivary nuclei to the inferior colliculus in the midbrain
In patients with an ipsilateral sensorineural hearing loss, the lesion is most likely at _____ but not at _____.
inner ear, CN8, cochlear nuclei but not at higher levels of central auditory system that receive input from both ears
A lesion to CNS auditory structures in the brain stem above the cochlear nuclei, in the thalamus, or in the cortex may result in…?
slight bilateral hearing loss and decreased ability to localize a sound source
The vestibular nerve innervates…?
hair cells in the three semicircular ducts and hair cells in the utricular and saccular maculae
The utricle and saccule contain hair cells that respond to…?
linear acceleration
The semicircular ducts contain hair cells that respond to…?
angular acceleration
Where do central processes of vestibular nerve fibers that enter the brain stem terminate?
vestibular nuclei and flocculonodular lobe of cerebellum
4 vestibular nuclei
superior, lateral ,medial, inferior
Patients with a vestibular lesion may have?
vertigo –> severe in peripheral lesions and mild in central lesions
Patients with Meniere’s may have…?
abrupt, recurrent vertigo + tinnitus + ipsilateral sensorineural hearing loss + nausea/vomiting/ear pressure
Axons of vestibular nuclei join what tract?
medial longitudinal fasiculus
What does the MLF connect vestibular nuclei to?
centers for conjugate gaze and oculomotor, trochlear, and abducens nuclei
Where do axons of CN 5 enter the brainstem?
rostral pons
Main, Chief, or Principal Nucleus
at entry of CN 5: touch
Mesencephalic Nucleus
CN 5: proprioception (superior)
Spinal nucleus
CN 5: pain and termperature (inferior)
3 components of spinal nucleus
- nucleus oralis - face touch
- nucleus interpolaris - tooth pulp pain
- nucleus caudalis - face pain and temperature
What is the only example of neural crest cells that have migrated into the brainstem?
the neurons in the mesencephalic trigeminal nucleus
Facial touch pathway
trigeminal ganglion –> ipsilateral principal nucleus of trigeminal complex –> cross over and ascend in medial lemniscus to VPM –> cortex
Forehead face pain and temperature axons enter the pontomedullary junction and ascend/descend to the top/bottom of the nucleus caudalis before crossing over and ascending to the cortex.
descend to the bottom
Facial pain and temperature pathway
Trigeminal ganglion –> descend in spinal trigeminal tract –> nucleus caudalis –> cross over –> ascend in trigeminothalamic tract to VPM –> cortex
A patient with a lesion of the lower pons may present with?
only loss of pain and temperature in face
Which cerebellar peduncle carries ascending information?
inferior: spinocerebellar pathways (limb position sense) + inferior olivary nucleus (cerebellar input)
Which cerebellar peduncle carries information from the cortex into the cerebellum?
middle
Which cerebellar peduncle carries information from cerebellum to UMN?
superior
With regards to vascular insults, ____ CN will be affected in medial tract syndromes.
Motor
With regards to vascular insults, ____ CN will be affected in lateral tract syndromes.
Mixed
Which artery supplies the posterolateral medulla?
PICA from vertebral
Which artery supplies the medial aspect of the medulla?
Vertebral artery
Which artery supplies the anteromedial aspect of the medulla?
Anterior spinal artery
Which artery supplies the posterior of the midbrain?
Quadrigeminal artery
Which artery supplies the lateral aspect of the midbrain?
Anterior choroidal artery
Which artery supplies the anterior aspect of the midbrain?
Thalamoperforating branches of PCA
Which artery supplies the posterior aspect of the pons?
Superior cerebellar artery
Which artery supplies the posterolateral aspect of the pons?
AICA from basilar
Which artery supplies the ventrolateral aspect of the pons?
Short circumferential branches of the basilar
Which artery supplies the anterior aspect of the pons?
paramedian branches of the basilar artery
Most of the diencephalon is composed of?
thalamus + hypothalamus
The thalamus is bounded laterally by the ____ and medially by the _____.
internal capsule and third ventricle
All connections between cortex and thalamus travel in what structure?
internal capsule
5 anatomic thalamic nuclei:
Medial Lateral Internal Intralaminar Reticularis
Input-output thalamic nuclei:
Relay (sensory, motor, limbic); Association (pulvinar, mediodorsal); Non-specific (intralaminar)
Sensory Relay nuclei
auditory –> medial geniculate –> auditory cortex; visual –> lateral geniculate –>visual cortex; somatosensory –>ventrobasal –> somatosensory cortex
Motor Relay nuclei
basal ganglia and cerebellum –> ventral anterior and ventral lateral –> motor
Limbic Relay nuclei
mammillary bodies –> anterior nucleus –> cingulate gyrus (Papez circuit)
Pulvinar Association nuclei
parietal-occipital-temporal association cortex
Mediodorsal Association nuclei
prefrontal cortex
Intralaminar Non-specific nuclei
non-specific projections to widespread area of cortex; receives input from basal ganglia
Basal ganglia
participate in parallel anatomical circuits through thalamus and cortex –> each loop with different motor, cognitive, or affective function
Reticular nucleus
has no projects outside thalamus
Sensory and motor areas of the cerebral cortex receive inputs from what thalamic nuclei?
Relay
Prefrontal and parietal-occipital-temporal cortex receive input from what nuclei?
Association
Which thalamic nucleus projects to the basal ganglia?
intralaminar nucleus
What kind of cell constitute 80% of all neurons in thalamic nuclei?
glutaminergic excitatory projection neurons also called thalamocortical cells
The neurons of the ______ form a thin layer of exclusively _____ inhibitory cells, surrounding the thalamus in its lateral and dorsal aspects and projects to _____.
nucleus reticularis, GABAergic inhibitory cells, projects to other thalamic nuclei
T/F only axons from the cortex leave collaterals for the reticular nucleus.
F. axons from the cortex and the thalamus do this
T/F thalamocortical cells maintain connections to one another.
F
How many layers does the neocortex have?
6 (layer 4 = granular)
Agranular cortex lacks what kind of cells?
stellate/granule cells
Which area of neocortex contains large pyramidal cells?
mainly layer 5
What kind of cortex constitute primary sensory areas?
granular cortex = mainly small cells with few large pyramidal cells/few long axons
The study and definition of cortical areas in terms of parameters reveealed by stains of RNA of cell bodies is called_____.
Cytoarchitecture (e.g. Broadmann)
The columnar organization probably reflects a general strategy used in the construction of neocortex and suggests that the cortex works as what kind of device?
massive parallel processing –> applying similar operations locally to many aspects of the same information
2 types of excitatory cells in the cortex that use glutamate as a neurotransmitter
granular/spiny stellate and pyramidal cells
Pyramidal cells
80% of neurons in neocortex; excitatory; project to cortex via apical dendrite; system of basal dendrites branch near hte soma in the same layer; giants = betz cells
Granular cells
layer 4; receive thalamic input and output to neocortex layers 2 and 3 –> prominent in sensory areas
T/F inhibitory neurons have spines.
F
Circuit in thalamus
TC –> cortex –> TC with collaterals of each nerve to nucleus reticularis
Circuit in neocortex
thalamus –> layer 4/granular excitatory –> layer 2/3/supragranular excitatory–> layer 5/6/infragranular –> out of cortex
*all excitatory inputs also activate local interneurons (gabaergic inhibitory) which inhibit each cell in the pathway and also self-regulate
Supragranular neocortex 2/3 project to ____.
other cortical areas
Infragranular neocortex 5/6 project to ____.
out of cortex to brainstem, psinal cord, thalamus, superior colliculus
T/F All relay operations are under heavy control of cortical feedback.
T
2 Functions of thalamus
relay function (specific information transfer to cortex) and gate function (control of the functional state of the forebrain)
Transition between waking and sleep states is modulated by changes in ______.
neuromodulation
2 Functions of cortex
- generate sensory/motor representations of external and internal worlds using a combination of sensory driven activity, internally generated activity, and memory storage
- generate consciousness//only a small portion of the activity in corticothalamic networks is accessible to consciousness
T/F The generation of representations and consciousness depends on recurrent loops between cortex and thalamus.
T
The _____ is the most useful lab test to help establish the diagnosis of epilepsy and assist in the accurate classification of seizures and specific epileptic syndromes.
EEG
The EEG reflects intra/extracellular currents from the summated excitatory and/or inhibitory synaptic potentials of large numbers of cortical neurons.
extracellular; excitatory and inhibitory
Low amplitude and high frequency EEG = awake/asleep
awake
During waking _____ single thalamic spikes represent the inputs from sensory stimuli. Upon sleep these spikes become _____.
irregular; regular and rhythmic
The single most important factor responsible for the change in brain activity in the transition from waking to sleep is _____.
the change in thalamic firing mode –> transition from single spike tonic firing in waking to bursting firing mode –> due to hyperpolarization of cells
Bursting in thalamic cells is due to _________ current called ___ that generates an all or none triangular shaped potential with a low threshold called the _____.
low threshold calcium current; called It/ T type calcium channel; with a potential called the low threshold spike (LTS)
Which thalamic current is blocked by TTX? Cobalt?
TTx = sodium; Cobalt = calcium
T/F Hyperpolarization during sleep brings about the bursting behavior because it allows T channels to be open, resulting in rhythmic thalamic cells that engage the cortex in a rhythmic fashion as well.
T
Why is bursting an unreliable response and incompatible with coding of information?
- it has an all or none intrinsic response that doesn’t relay information about stimuli; 2. rhythmic firing results in a refractory period
Single spike mode shows a ____ and reliable relationship with stimulus intensity while bursting shows a ____ function.
linear vs. step
The combination of what three features blocks sensory input form the periphery to the cerebral cortex during sleep.
unreliable responses, generation of rhythmic bursting, and large scale synchrony
Why do thalamic neurons become hyperpolarized during sleep?
loss of neuromodulatory systems allows Vm closer to the resting K potential.
involuntary coordinated patterns of muscle contraction and relaxation elicited by peripheral stimulation that is stereotyped and modulated by descending inputs.
reflex movements
chewing, swallowing, scratching, locomotion, involving central pattern generating (CPG) circuits in spinal cord and brainstem are:
rhythmic movement
goal directed, purposeful movements that are generated internally, improve with practice, correct for external perturbations, and involved feedback and feedforward control are:
voluntary movements
anticipatory control (for example, for balancing when moving limbs) is called:
feedforward
error signals that lead to compensatory change are called:
feedback
3 key principles of feed-forward systems
- essential for rapid action, 2. depends on ability to make prediction, 3. can modify the operation of feedback mechanisms
T/F feedback can override reflexes in voluntary movement.
T
The motor areas of the cerebral cortex influence the spinal cord either directily or through the _____ of the brain stem.
descending systems
All 3 levels of motor control receive sensory inputs and are under the control of two independent subcortical systems which are:
- basal ganglia, and 2. cerebellum
The basal ganglia and cerebellum act on cerebral cortex via ___ and ____.
VA and VL
Processing of sensory inputs and motor commands is distributed in _______ interconnected areas.
hierarchically
motor nuclei in the spinal cord and brainstem are called
lower motor neurons
motor control centers in the brainstem are called
medial and lateral systems
upper motor neurons are located in _____.
cerebral cortex
motor commands and feedback sensory information related to movement is processed in what relationship in various systems.
parallel
medial-lateral arrangement of motor nuclei follow what rule
proximal-distal
propriospinal neurons are _____ between lateral motor nuclei and _____ for medial nuclei
short and long
Visual input travels through the tectospinal tract to the ____ nuclei of the spinal cord and influence axial and proximal muscles.
medial –> visually guided postural control
Balance signals travel in the ______ tract to the medial nuclei of the spinal cord to influence axial and proximal muscles.
Vestibulospinal tract
The _______ tract receives many sensory inputs and helps control posture generally.
Reticulospinal tract
The only lateral brainstem pathway begins at the ______ and extends fibers through the ______ lateral column and terminates in the _______ ventral horn. This system contributes to goal directed movements of the arm and hand (reaching and manipulating).
red nucleus; contralateral; contralateral
3 medial brainstem pathways
tectospinal, reticulospinal, vestibulospinal
1/3 of the axons in the corticospinal tract arise in the ______ cortex, 1/3 in _____ and 1/3 in ______.
1/3 motor, 1/3 premotor, and 1/3 somatosensory
____% of the motor axons in the corticospinal tract cross the midline.
75
The uncrossed corticospinal axons control what?
axial muscles/extensor postural muscles –> medial
T/F M1 cells have receptive fields in the periphery and receive proprioceptive inputs from the muscles to which they project and mechnoreceptive information from the overlying skin.
T
T/F Stimulation of premotor cortex produces movement at a higher threshold. These movements are complex and involve multiple joints and resemble natural coordinated movements.
T
T/F termination areas of motor and premotor project in spinal cord overlap
T
Premotor cortex, somatosensory cortex, and association motor cortex project to ______.
Motor cortex
Parietal area 5 is where visual input converges with _______.
somatosensory input
Motor cortex projects to basal ganglia and cerebellum via ______.
pontine nuclei
The activation of any given muscle or set of muscles is carried out by a distributed population of neurons. What is this called?
Population encoding
T/F As movement becomes more practiced, it is represented more extensively in primary motor cortex.
T
T/F The firing of the corticospinal neurons is related to the force exerted and not hte displacement of the wrist (in Everton’s expt).
T
Premotor cortex
projects to spinal cord with motor cortex; damage causes more complex motor impairments; involved in in planning and preparation of movement
Complex movements initiated internally involve the ______ area.
supplementary motor area
Movements triggered by external sensory stimuli involve lateral ______ areas.
premotor
T/F Mental rehearsal invokes premotor areas.
T
T/F Premotor areas that are active during movement change progressively as performance becomes automatic.
T
M1 vs SMA vs LatPreM
M1 = specific parameters of movement; SMA = specific order of responses based on memory and internally generated plan; LatPreM = sensory motor integration
T/F Spinal circuits involved in posture are extensively regulated by descending cortical projections.
T
Supraspinal projections of the lateral motor system
- crossed corticospinal tract, 2 rubrospinal tract
Supraspinal projections of the medial motor system
reticulospinal tract, vestibulospinal tract, and uncrossed corticospinal tract
T/F Medial Motor Systems function bilaterally
T
The primary brainstem regions that influence posture and blaance in the vestibulospinal tract are:
vestibular nuclei (lateral and medial)
The primary brainstem regions that influence posture and balance in the reticulospinal tract are:
pontine and medullary reticular formation motor nuclei
In general, the _______ contract during the stance phase and the _____ contract during the swing phase.
extensor vs. flexor
T/F The muscles of the same type (extensor/flexor) that cause contraction at the three leg joints contract in a temporally overlapping but not simultaneous pattern.
T
T/F For stability during walking, the opposite limbs show an overlapping pattern only during the swing phase.
F –> They overlap during stance to ensure stability
CPG
central pattern generator is a source of rhythm and pattern of movement
The rhythmic motor network (central pattern generator; CPG) that generates locomotion is located in the ____ spinal segments that contain the motor neurons that innervate limb muscles, and it is regulated (e.g. initiated, modulated, terminated) by descending projections, primarily from the ______ (i.e. reticulospinal pathways), as well as by sensory feedback from sensory structures in the limb muscles, joints and overlying skin.
same spinal segments that contain the motor neurons that innervate limb muscles and is regulated by descending projections primarily from the brainstem
T/F the basic motor pattern for a given behavior (e.g. for locomotion) can continue to be elicited in the completely isolated spinal cord (in animal models), in the absence of both descending (i.e. RST for locomotion) and ascending (i.e. sensory) inputs.
T
CPG-generated rhythmic motor patterns in the isolated CNS are often termed _________ because the motor pattern is similar to that occurring in the behaving animal but only the CNS is present.
fictive behaviors/fictive locomotion
The spinal locomotor CPG is a _________ network located in the _____________ zone of the same spinal segments containing the motor neurons that innervate the limbs (i.e. C5 – T1; L2 – S3).
bilateral; intermediate
One common feature of CPG organization is ______ between functional antagonists.
reciprocal inhibition
T/F The locomotor CPG is hypothesized to be composed of a flexor CPG module (local circuit) and an extensor CPG module at each joint.
T
Lecture example of a candidate locomotor CPG
HB9
Descending control of spinal locomotor CPG
cortex –> MLR (mesencephalic locomotor region) –> pontine and medullary reticular formation (brainstem) –> reticulospinal tract–> CPG –> motor neurons –> muscles –> sensory
- parallel compensatory postural system + visual postural system
The spinal locomotor CPG “self-organizes” to generate the appropriate movement pattern based on the _______ of unpatterned input from the mesencephalic locomotor region (MLR).
intensity
T/F Stepping movements are adapted by visual input that is routed through the motor cortex.
T
T/F Feed-forward (Anticipatory) Postural Control is initiated by the same set of descending motor cortical signals that drive a voluntary movement.
T
T/F the feed-forward postural control pathway involves Cortical activation of Reticulopinal and Vestibulospinal Neurons which in turn modify the Medial Spinal Motor System in advance of the onset of the voluntary movement (driven by the Lateral Motor System).
T
T/F The feedback postural control system utilizes spinal reflex pathways to provide compensatory corrections when necessary.
T
The Medial Motor System provides voluntary control. The Lateral Motor System enables postural movements.
F The Medial Motor System provides postural control. The Lateral Motor System enables voluntary movements.
T/F the cerebellum evaluates disparities between intention and action and generates correction signals to cortex and brainstem.
T
T/F the cerebellum receives efferent copies of every motor command.
T
What are the consequences of cerebellar lesions?
- loss of spatial accuracy and temporal coordination of movement, 2. impairment of balance and loss of muscle tone, 3. no loss of sensory thresholds or strength of muscle contraction
T/F a cerebellar lesion can result in loss of sensory thresholds or strength of muscle contraction.
F –> cerebellum modifies movement but does not directly communicate with motor neurons
Cerebellar outputs
to brainstem (via spinal descending motor system) and to motor and premotor cortical systems (via thalamus)
Key anatomical features of cerebellum
- gray-white matter organization; 2. folia, 2 transverse fissures, 3 lobes; 4. 3. deep cerebellar nuclei, 4. three white matter bundles;5. 3 mediolateral regions: vermis, and 2 hemispheres
To what structure does the cerebellar cortex project?
deep cerebellar nuclei
2 cerebellar input systems
- climbing fibers and 2. mossy fiber/parallel fiber system
Climbing fibers originate in the _____ and terminate in the ______ of ______ cells.
inferior olive and dendrites of purkinje cells
Purkinje fibers receive input from _____ climbing fibers whereas one climbing fiber contacts _____ purkinje cells.
one and 5-10
Mossy fibers originate from nuclei in the ____ and _____ and carry sensory information from the periphery as well as information from the cerebral cortex. They terminate on ______ which send their axons to the _____ layer, forming parallel fibers.
spinal cord and brainstem; terminate on granule cells and send axons to the molecular layer
Mossy fibers and climbing fibers are 2 _________ excitatory input systems.
glutaminergic
Climbing fibers originate in the ______ and ascend into the cerebellum via the ______
contralateral inferior olive; inferior cerebellar peduncle;
Cerebellar output from purkinje cells to DCN is modulated by ______ (neurotransmitter).
GABA
A parallel fiber is the axon of a ______ cell.
Granular
Each half of the cerebellum influences movements of _______ limbs.
ipsilateral
The DCN are _______ cells.
excitatory
The vestibulocerebellum is the ______ lobe.
flocculonodular
The spinocerebellum takes inputs from the _______.
spinocerebellar tracts and trigeminal
The _______ peduncle is formed by _____ fibers from the ______ that are traveling to the cerebellum.
mossy; Pontine nuclei
The ______ is the only cerebellar component that projects directly out of the cerebellum and goes to the _____.
vestibulocerebellum –> vestibular nuclei (balance and eye movements)
The purkinje cells in the _____ project to medial DCN (fastigial nucleus) which project to the ________ systems.
medial spinocerebellum/vermis –> fastigial –> medial descending systems (motor execution) (axial)
Lateral portions of the spinocerebellum project to the _______ nuclei which project through the ________/______.
interposed nuclei –> lateral descending systems/red nucleus (contralateral limbs)
The cerebrocerebellum projects to the ______ nucleus that projects to the _______ thalamus.
dentate –> VA/VL motor
Lesion of the vestibulocerebellum
- inability to control eyes with head movement; 2. difficulty maintaining balance –>vertigo, widespread stance, frequent falls; 3. no problems lying down
Lesion of interpositus
- cerebellar hypotonia, 2. dysmetria (errors in direction and extent of movement); 3. cerebellar ataxia (lack of coordination of joints); 4. terminal tremor; 5. pendular reflexes (oscillations of stretch reflex)
Lesion of dentate
- delay in initiating movement; 2. irregularity in timing of movement components/decomposition of movements; 3. inability to judge elapsed time in tasks
Lesion of inferior olive
similar to acute destruction of entire contralateral half of cerebellum –> persistent deficit in the motor learning fxns of cerebellum
Lesion in right cerebellar hemisphere
delays initiation of movement
Dysdiadochokinesia
irregular pattern of alternating movement
The ________ are a collection of subcortical nuclei deep within the brain at its base.
basal ganglia
Functions of basal ganglia
- selection, activation, termination of innate and learned motor programs; 2. facilitate learning of appropriate context-dependent motor behavior
T/F Pathologic changes in basal ganglia lead to disabling involuntary movements and disorders in balance, muscle tone, and gait.
T
T/F There is no weakness in basal ganglia pathologies.
T
T/F Pathologic changes in basal ganglia lead to cognitive changes only.
F also affect emotions
The basal ganglia contain nuclei of what embryologic origin?
telencephalic, diencephalic, mesencephalic
Input nuclei of the basal ganglia
striatum (caudate and putamen)
Output nuclei of the basal ganglia
Substantia nigra pars reticularis (SNr), Globus pallidus interna (medial) (GPi)
Intrinsic nuclei of the basal ganglia
Globus pallidus externa (GPe), Substantia nigra pars compacta (SNc), Subthalamic nucleus (STN)
What structure separates the caudate and putamen?
Internal capsule
Most input to the striatum comes from _____.
cortex
the putamen is ventral/dorsal to the caudate.
ventral
The majority of the caudate is more rostral and receives input form the cortical association areas especially the _______ and the ______areas.
premotor and supplementary motor
3 portions of caudate
head, body, tail
Role of subthalamic nucleus
helps modulate interaction between the globus pallidus externa and interna; lies ventromedial to the pallidum
______ is the main NT of the substantia nigra.
Dopamine
2 components of substantia nigra
pars compacta (dopaminergic neurons that project to striatum) and pars reticularis (which receives projection from striatum and forms other ocmponent of direct pathway
T/F the basal ganglia only modulates motor outputs from the brain and does not communicate directly with motor neurons.
T
Basal ganglia pathway
Cortex –> striatum –> globus pallidus/substantia nigra reticularis –> cortex via VA and VL
What is the recipient of basal ganglia output?
frontal lobe –> motor, premotor, supplementary motor, frontal eye fields
The _____ pathway is thought to be the most important for the initiation of movement, and for the learning of positive outcomes associated with specific behaviors.
direct pathway
The ______ pathway is thought to be hte most important for the termination of movement and for the learning of negative outcomes associated with specific behaviors.
Indirect
Direct pathway
excitatory cortex –> striatum –> increase inhibition to internal segment of globus pallidus and substantia nigra pars reticularis (reinforced by dopaminergic input from substantia nigra pars compacta to striatum –> + feedback) –> project to thalamus (pause in inhibition) –> transient disinhibition of thalamic neurons –> increased cortical activity –> excitation of cortex
Indirect pathway
excitatory signal from cortex –> striatum –> increase inhibition of external segment of globus pallidus –> pause in inhibitory output of the external pallidal segment which terminates on STN –> excitation of internal segment of globus pllidus and substantia nigra pars reticularis –> increased thalamic inhibition –> increased cortical inhibition
In the indirect pathway, dopaminergic input from the substantia nigra pars compact is ______, opposite that of the cortical input. In the inhibitory pathway, the dopamine interacts with _____ receptors.
inhibitory; D2
Which brain structure receives the major output from the basal ganglia?
Thalamus
Excitatory receptors for dopamine in the striatum of the basal ganglia are ____ receptors.
D1 receptors
Parkinson’s is due to a slow, progressive brain degeneration related to the accumulation of the protein __________ into cytoplasmic aggregates called ________.
alpha synuclein –> Lewy bodies
Cardinal signs of Parkinson’s
bradykinesia, rigidity, resting tremor, stooped posture (also depression, constipation, urinary symptoms, sleep disorders)
Parkinsonian symptoms ultimately result from abnormal ______ of the thalamus.
inhibition –> via loss of dopamine in the striatum (knock out the substantia nigra pars compacta)
T/F it is believed lack of cortical stimulation causes the symptoms of parkinson’s.
T
Huntington’s is due to the selective loss of _______ergic neurons of striatum whose output is through the ______ pathway.
GABA; indirect
Symptoms of Huntington’s
chorea, athetosis, mental decline, personality changes
Parkinson’s is a ______ disorder while Huntington’s is a _____ disorder.
hypo vs hyperkinetic
T/F CAG copy number influences severity of Huntington’s.
T
Neuropathology of Huntington’s is most severe in the _____ and involves reduction in the ________ of thalamic neurons by GPi/SNr.
striatum –> reduce inhibition of thalamic neurons –> increased stimulation of cortex
Which of the following is not a symptom of Parkinson’s? (weakness, slowness, tremor, stiffness, postural changes)
weakness
Striatum interneurons communicate with _____ (NT)
ACh –> M1 (excitatory) and M4 (inhibitory) receptors
Communication between STN and GPi/SNr occurs via ___ (NT).
glutamate
4 pathways that use dopamine
- mesocortical (schizophrenia); 2. mesolimbic (reward); 3. nigrostriatal (PD); 4. tuberoinfundibular (prolactin)
Side effects of dopamine
addictive behaviors and psychosis
dopamine is derived from _____
tyrosine –> LDOPA (rate limiting enzyme = tyrosine hydroxylase)
T/F LDopa can cross the BBB but dopamine can’t.
T
What is the best therapy for PD?
repletion of dopamine using L-dopa
L-dopa is converted to dopamine where in the body?
intestine, liver, kidney, blood vessel endothelia –> peripheral –> need peripheral inhibitors to prolong breakdown of L-dopa until it enters BBB
The inhibitor of dopa decarboxylase (DDC) that is administered with levodopa is_____.
carbidopa
Symptomatic treatment in Huntington’s can be modulated with ______.
dopamine blockade
Chorea
irregular, rapid random movements that flow from one body part to another
Ballism
form of chorea with large-amplitude jerking or flinging movement (proximal extremities)
Athetosis
writhing movements of flexion, extension, pronation, supination of fingers and hands
Dystonia
sustained muscle contraction producing twisting movements or abnormal postures that are patterned and directional
Tremor
rhythmic, oscillatory movmenets caused by alternate contraction of opposing muscle groups
Tics
intermittent repeated, and stereotyped movements or sounds under some voluntary control
Myoclonus
shock-like or lightning-like contraction or jerk
Jerky movements
myoclonus, chorea, ballism, tics
Non-jerky movments
Dystonia, athetosis, tremor
Parkinsonism
akinesia/bradykinesia and rigidity
How to tell PD from Essential tremor
ask pt to write –> PD = small writing; ET = jagged, saw tooth script
The most common hereditary form of generalized dystonia is due to mutations in the ____ gene.
DYT1
Free nerve endings are tuned for _____, ______, and ______.
pain, temperature, and crude touch
T/F Pacinian corpuscles tranduce mechanical deformations and provides tonic information to the CNS.
F –> no tonic information. only start and end of a stimulus
T/F The pacinian corpuscle is a rapidly adapting receptor.
T
Where is the start of action potentials in peripheral receptors?
The first node of ranvier.
T/F A alpha, beta, and delta fibers innervate the skin.
F –> there is no A alpha
Large diameter axons are more/less vulnerable to anoxia than small diameter axons.
More sensitive to anoxia
Local anesthetics are more effective on small/large diameter axons.
Small diameter is more sensitive
Somatosensory receptive field
portion of skin which when appropriately stimulated affects the firing of the cell
T/F Receptive fields of cutaneous dorsal root axons are round/elliptical in shape and uniform in response to stimuli.
T
Dorsal root cutaneous axons _______ to synapse with many CNS neurons and each CNS neuron receives ________ from many dorsal root axons.
diverge; convergence
Surround/lateral inhibition
dual process of divergence and convergence results in dilution of signal as it is split among more and more neurons at each level –> addition of inhibitory interneurons narrows the discharge zone on either side of the excitatory region
Surround inhibition serves to ______ detection of edges and ________ information about the absolute amount of stimulus energy.
enhance or sharpen; reduce
VPl and VPm (ventral basal complex) project to the _______ gyrus.
postcentral
T/F Within any region of S1 cells sharing inputs from a single class of receptors are stacked vertically into cortical columns that extend across all cortical layers.
T
Columns of stacked receptors within S1 represent either _____ or______ receptor types.
rapidly or slowly adapting receptors
Components of S1
3a (muscle afferents), 3b (cutaneous receptors), 1 (rapidly adapting cutaneous), 2 (deep pressure)
_______ of existing connections is the most likely explanation of modifications of cortical maps based on manipulations at receptors.
Unmasking
What thalamic nucleus provides input to the anterior cingulate gyrus? What is hte major input to this nucleus?
anterior nucleus; mammillary bodies
T/F Affect is processed in a different region of the brain than S1.
T
Receptive field changes in adjacent areas after trauma are likely due to _____.
temporal correlation
The brain receives about _____% of cardiac output.
20
2 pairs of blood vessels responsible for arterial supply of brain.
Vertebrals –> posterior circulation and internal carotids –>anterior circulation
T/F the internal carotids and vertebrals have branches in the neck.
F
1st branch of internal carotid
Opthalmic
The internal carotid enters the skull at the _________.
Foramen lacerum.
Oclusion of the opthalmic artery causes ___________ blindness.
Ipsilateral monocular blindness
Branches of internal carotid
Opthalmic, Anterior choroidal, posterior communicating, anterior cerebral and middle cerebral
Branches of vertebrals
anterior and posterior spinal, posterior inferior cerebellar (PICA)
Vertebral artery climbs up the neck via the ________.
transverse foramina of cervical vertebrae
VA enters the skull via the _____.
Foramen magnum
Posterior communicating artery connects ______ with ______.
ICA and posterior cerebral artery
Occlusions of VA and PICA are characterized by _______ syndrome.
lateral medullary/Wallenburg syndrome
The ____ divides into two major trunks and divides again into 5-7 branches to supply the majority of the lateral hemisphere, frontal lobe, temporal lobe, insular cortex, putamen, and deep white matter.
MCA
Occlusion of the MCA can result in a clinical syndrome characterized by:
contralateral hemiparesis (face, arm, leg), aphasia, neglect, contralateral visual hemifield or quadrant defect, deviation of gaze, cortical sensory deficits
The _____ supplies the medial frontal lobe and medial deep structures like the cingulate, corpus callosum, and the caudate nucleus.
ACA
Occlusion of the ACA is characterized by:
contralateral lower extremity weakness
Branches of basilar.
AICA, SCA, two PCAs
Occlusion of the BA results in:
Weber Syndrome, Pontine/Locked In Syndrome; generally: crossed facial sensory and body motor signs, diplopia, facial numbness/weakness, vertigo, nausea and vomiting, hearing loss, ataxia, gait abnormality, etc.
Occlusion of the PCA can cause:
occipital infarction and contralateral visual field loss (hemianopsia)
The vertebral arteries supply the ____ and the _____.
medulla and cerebellum (PICA)
The basilar artery supply the ____ and the _____.
pons and cerebellum (AICA)
The superior cerebellar arteries supply the _____ and the _____.
midbrain and cerebellum (SCA)
Tongue and swallowing problems (along with contralateral hemiparesis) may come from occlusion of the ______.
vertebral arteries
A hallmark of a lower brainstem lesion is:
crossed sensory signs: one side of face and opposite side of body
Contralateral weakness with eye movement abnormalities is associated with occlusion of _______.
distal basilar (midbrain or pontine lesion)
Weber Syndrome
distal BA occlusion involving proximal PCA and/or circumferential branches –> CN 3 + motor fibers = ipsilateral CN3 palsy + contralateral hemiparesis
Locked in/Pontine Syndrome
proximal/midbasilar occlusion resulting in pontine infarction –> bilateral damage leading to coma and death or destruction of descending motor pathways but preservation of dorsal pons (consciousness) –> locked in but can’t move
Wallenburg Syndrome
Occlusion of PICA or VA resulting in lateral medullary symptoms: crossed signs of contralateral pain and temp, ipsilateral loss of pain and temp on face, Horner’s, ataxia, nausea, vertigo etc.
Cerebellar infarct
usually due to PICA occlusion (but also SCA and AICA) –> ataxia, vertigo, possible hydrocephalus if compression of 4th ventricle
Clinical lacunar syndrome
Small vessel strokes/lacunes (often of small offshoots of MCA) –> no cortical involvement
Which vessel? R face/arm/leg weakness and trouble finding words
left MCA
Which vessel? R leg weakness and confusion
left ACA
Which vessel? R face/arm/leg weakness
left MCA deep perforator
Spontaneous hemorrhages in the brain are usually ____ or _____.
Subarachnoid or intraparenchymal
______ is usually due to rupture of a macrovascular arterial structure directly in the corresponding space.
Subarachnoid
SAH presentation
worst headache of life + stiff neck + photophobia; with or without focal findings, CT scan + lumbar puncture, bloody and xanthochromic (yellow) CSF, angiography
Most important causes of spontaneous SAH
rupture berry aneurysm (branch points), arteriovenous malformations (anywhere)
The presence of intraparenchymal blood and SAH is likely due to _____
AVM rupture.
Aneurysm key locations
Anterior and posterior communicating arteries + middle cerebral branchpoint
One of the major causes of death and disability after aneurysmal SAH is ______ or narrowing of cerebral arteries resulting in ischemic injury.
vasospasm
Neurologic injury due to vasospasm can be treated with _________.
Ca channel blocker –> nimodipine or angioplasty.
_______ is a spontaneous hemorrhage into the brain parenchyma.
Intracerebral hemorrhage –>CT scan
Most ICH is caused by ______ and are atrributed to microscopic ________, which are miniscule vascular outpouchings that occur at 90 degree arteriolar or small penetrating artery branch points.
hypertension; Charcot-Bouchard aneurysms
Typical sites of ICH branch poitns are _____, ______, ____, ____, and _____.
putamen, lobar gray/white jxn, thalamus, pons, cerebellum
______ is characterized by multipel cortical hemorrhages.
Cerebral Amyloid Angiopathy
______ is the MRI sequence most sensitive for detecting old and new blood products.
gradient-echo MRI
T/F ICH often expands in the first few hours and expansion severely worsens prognosis.
T
CN _____ runs with the carotid artery
VI
CN ___, ___, ___ run with the cavernous sinuses.
3, 4, 5
Fronto-pontine pathway travels in the _______ while the POT pontine pathway travels in the ________.
anterior limb of internal capsule vs posterior limb
Corticopontocerebellum Frontopontine pathway
Frontal lobe –> ALIC –> Crus –> Pons –> crossing pontocerebellar pathway –> MCP –> cerebellar cortex + dentate
Corticopontocerebellum POT-pontine pathway
POT –> PLIC –> crus –> pons –> crossing pontocerebellar pathway –> cerebellar cortex + dentate
Corticopontocerebellum output pathway
Purkinje –> dentate –> crossed dentato-rubro-thalamic tract –> through red nucleus –> VL thalamus –> motor cortex
Spinocerebellum Input
somatosensory receptors –> L2-C8 nucleus dorsalis of Clark –> fasciculus gracilis –> nucleus dorsalis of Clark –> dorsal spinocerebellar pathway –> ICP –> cerebellar cortex –> fastigial nuclei
Spinocerebellum Output
Purkinje neurons of fastigial nucleus –> vestibular nucleus –> vestibulospinal –> alpha, gamma motor neurons
Vestibulocerebellum Input
vestibular apparatus –> CN VIII –> ICP –> flocculonodular lobe cortex
Vestibulocerebellum Output
Purkinje cell –> vestibular nerve –> MLF eye movement + –> lateral vestibulospinal pathway –> alpha and gamma motor neurons
The hallmark of cerebellar dysfunction is _____.
ataxia
_____ cerebellar lesions lead to truncal and proximal limb dysfunction.
Midline
Disease affecting the cerebellar hemispheres results in ataxia of _____.
extremities
Nystagmus (jerky) can result from ______ cerebellar lesions.
midline
Disruption of the metrical structure of speech is called _____.
ataxic dysarthria
T/F isolated cerebellar syndromes are rare.
T
Signs of _____ dysfunction are often seen with signs of cerebellar dysfunction.
brainstem –> same blood supply and space
T/F Recovery from cerebellar damage may be rapid; conversely, with slowly progressive damage, a patient can lose a large volume of cerebellum before signs are apparent.
T
Normal tone/transient tone with acute cerebellar damage.
Transient hypotonia
T/F normal tone or hypotonia can occur with chronic cerebellar damage.
T
Appendicular ataxia is maximal at the ______ endpoint of a motor act.
Extreme
Cerebellar lesions cause dysfunction on the ipsilateral/contralateral side of the body.
ipsilateral –> double crossing
Differentiating between sensory and cerebellar ataxia.
Romberg sign present with sensory ataxia
Differentiating between vestibular dysfunction and cerebellar ataxia.
vertigo present with vestibular dysfunction
Differentiating between corticospinal tract disease and cerebellar ataxia.
UMN signs in corticospinal tract lesion
Differentiating between myopathic proximal limb weakness and cerebellar ataxia.
weakness present in myopathy
T/F autoantibodies from ovarian cancer are often directed at the cerebellum.
T –> paraneoplastic cerebellar degeneration
Cerebellar symptoms due to antecedent viral infection.
Post-infectious cerebellitis
Caudal displacement of cerebellar tonsils below foramen magnum.
Chiari I malformation
Chronic ataxia in the cerebellum can be caused by what drugs?
alcohol and phenytoin
Chronic ataxia in the cerebellum can be caused by what drugs?
alcohol and phenytoin
When to consider brainstem as a lesion point.
- patients have cranial nerve symptoms or 2. patients have cerebellar dysfunction
When is brainstem involvement certain.
- crossed hemiparesis or 2. lesion is on hte side of the cranial nerve palsy or ataxia
When should we think about damage AROUND the brainstem?
- multiple cranial nerve involvement or 2. no crossed motor/sensory signs in the extremities
Lesion of the MLF is ipsilateral/contralateral to the eye that doesn’t abduct in INO.
ipsilateral
Left Afferent Relative Pupillary Defect
Eye constricts appropriately when opposite eye is lit but dilates when it is itself lit
Anisocoria
physiologic –> non disease state with differences in pupil size (consistent size difference in light and dark) vs. abnormal
Light stimulation of the pupils produces unilateral/bilateral constriction of the pupils because of 1/2 crosses in ______ area(s).
bilateral; 2 crosses; chiasm and pretectal area (edinger-westphal nucleus)
When you see an afferent pupil defect, you almost always have a ______ problem.
optic nerve
Anisocoria is to do with efferents/afferents.
Efferents
In Horner’s is anisocoria greater in the dark or the light?
dark –> dilation lag
T/F In Horner’s the eye dilates to cocaine.
F
Horner’s Syndrome Localizatoin
1st order –> brainstem; 2nd order –> brachial plexus/lung apex, 3rd order –> carotid dissection
1st order Horner’s
brainstem –> miosis, ptosis, anhidrosis (face, arm, leg)
2nd order Horner’s
brachial plexus/lung apex (e.g. pancoast tumor)-> miosis, ptosis, anhidrosis (face)
3rd order Horner’s
carotid artery dissection–> miosis, ptosis, anhidrosis (upper face)
A lesion of the ciliary ganglion produces a _____ pupil.
tonic
Adie’s tonic pupil
unilaterally large pupil; tonic response to near; segmental reaction of iris; follows ciliary ganglion injury (possible reflexes lost)
Argyll Robertson pupil
poor light response but brisk near target response –> bilateral
3rd nerve palsy is often associated with which aneurysm
posterior communicating artery
Which Horner’s syndrome is painful?
3rd
T/F An afferent pupillary defect may also be seen in chiasmal and optic tract lesions, but not in pathological processes that affect the visual pathway posterior to the lateral geniculate body.
T
T/F
Patients with cataracts and functional visual loss as a cause for their visual loss will not have an afferent pupillary defect.
T/F The most common central cause of Horner’s syndrome is a dorsolateral medullary infarction.
T
T/F Birth trauma and occult neuroblastoma are the most important causes of Horner’s syndrome to recognize in childhood.
T
