Exam 2 Flashcards
Cranial Nerve Locations
Midbrain: CN III-IV
Pons: CN V-VIII
Medulla: CN IX-XII
Dopamine
-amine neurotransmitter produced in substantia nigra of the brain
-affects motor function, cognition, and behavior, reward seeking behaviors (good for eating, bad for addiction)
-2nd messenger systems
Abnormalities seen in:
-Parkinson’s: not enough dopamine; bradykinesia, treat with precursor
-Schizophrenia: signalling pathways, treat with drugs that prevent binding
Excessive:
-drug abuse by preventing reuptake of presynaptic terminals
Longitudinal Divions of BS
-Basilar
-Tegmentum
-Tectum
Basilar Divison
-ventral
-Descending tracts from cortex
-motor nuceli from substantia nigra, pons, inferior olive
TegmentumDivison
-Dorsal
-reticular formation (arousal)
-sensory nuclei; ascending tracts
-CN V nuclei
-medial longitudinal fasciculus (coordinate eye and head mmt)
Tectum Divison
-midbrain only
-reflexive mmts of eyes and head
-inferior and superior colliculi
Midbrain Divisions
-Basis Pedunculi
-Midbrain Tegmentum
-Tectum
Inferior Colliculi
-info from cochlear to superior colliculi and thalamus
-sound localization; integration of auditory info
Superior Colliculi
-motor and sensory info to orient head and eyes
-visual, auditorry, and somatosensory info
Basis Pedunculi
-Cerebreal peduncles (motor tracts from cortex)
-Substantia Nigra
Midbrain Tegmentum
-ascending tracts
-superior cerebellar peduncle
-red nucleus
-pedunculoponttine nucleus
-CN III and IV
-periaqueductal grey
Pons
-anterior wall of 4th ventricle; anterior to cerebellum
-most ascending tracts pass without synapsing (except corrticopontitne and corticobrainstem)
-Basilar
-Tegmentum
Pons Basilar Division
-descending tracts
-pontine nuclei
-pontocerebellar
Pons Tegmentum Divison
-ascending tracts
-reticular formation
-CN V-VIII nuclei
Upper Medulla
-most CN nuclei
-spinal trigeminal
-inferior olivary nucleus
Inferior Olivary Nucleus
-motor learning, timing, and conttrol of ongoing mmts
-info from cortical and SC then prroject to cerebellum
Lower Medulla
-decussation
-asending tracts pastt posteriorly
Brainstem Blood Supply
-Vertebral A.
-ASA
-PICA
-Basilar
-AICA
-SCA
-PCA
-Pontiene
-Internal auditory A.
Midbrain Blood Supply
-PCA
-Basilar A.
Pons Blood Supply
-Basilar
-Pontiene
-AICA
Medulla Blood Supply
-ASA
-PICA
Brainstem Funcion
-Tracts (lesion: sensory and motor loss both ipsi and contra)
-CN function (lesion: ipsi facial issues)
-Consiousness (RAS, Reticular Formation)
-Vital sign regulation (Leison: BP fluctuation, breathing issues, HR issues)
4Ds of Brainstem Dysfunction
-dysphagia (swallowing)
-Dysarthria (motor production)
-Diplopia (double vision)
-Dysmetria (lack of coordination)
Anteromedial Midbrain Syndrome
-Weber’s Syndrome
-blockage of PCA or Basilar A. (midbrain branches)
Corticospinal: hemiparesis
Occulomotor: ipsi impaired eye mmts
Red nucleus: ataxia; emotional control
Lateral Inferior Pontine Syndrome
-occulsion of AICA; 2nd most common BS stroke
-affects pons
CN VIII Cochlear: ipsi hearling loss
CN VIII Vestib): dysequilibrium; nausea
Horner’s Syndrome: ipsi
CN V: ipsi facial pain
CN VII: decreased tears/saliva; ipsi weakness in face
Antetrolateral Spinothalamic: contra sensation
Bell’s Palsy
-CN VII damage
-flaccidity in ipsi hemiphere of face
-affects upper and lower (cortical is either or)
Horner’s Syndrome
-contricted pupils
-eyelid droop
-dry skin
-SNS issue
Locked-In Syndrome
-basilar artery thrombosis or stenosis affecting ventral pons
Lost
Bilat Corticospinal: paralysis
Bilat Corticobulbar: face paralysis
Bilatt Abducens: not lat eye mmt
Spared
-RAS, vertical gaze
-mimic coma
Medial Medullary Syndrome
-ASA blockage
CN XII: ipsi tongue protrusion
DCML tract: contra loss of sensation
Corticospinal: contra hemiparesis
Lateral Medullar Syndrome
-Wallenberg’s
-Blockage of PICA; mostt common BS stroke
Solitary Nucleus: increase HR
Vestibular Nucleus: balance issues
Vagus N: Increased HR
Trigeminal: facial sensation
Inferior Cerebellar Peduncle: ataxia, coordination
Salivatory nucleus: saliva and tears, dental hygiene
Spinothalamic: contra pain and temp
Descending SNS: ipsi horner’s
Nucleus Ambiguous: swallowing, gag reflex, hoarseness
Mammillary Bodies
-recollective memory
Middle Cerebellar Peduncle
-connects cerebellum to pons
-largest
- contains afferent fibers
Substania Nigra
-production of dopamine
-body movements
-part of basal ganglia
-on midbrain
Cerebral Peduncles
-refining fine motor movements
conversion of proprioceptive information into balance and posture
Inferior Olivary Nucleus
-coordinate signals from SC to cerebellum to regulate coordination
Periaqueductal Grey Matter
-modulation and propagation of pain
Thalamus
-interprets sensation information and perceives it
Diencephalon
-subthalamus
-epithalamus
-Thalamus
-Hypothalamus
Subthalamus/Subthalamic Nuclei
-superior to substantia nigra
-inferior to thalamus
-Lateral to hypothalamus
-functionally a part of basal ganglia
-initiates and suppresses movement
-excitatory input to basal ganglia
Epithalamus
-pineal gland/body biggest in epithalamus
-innervated by SNS
-control carcadian rhythm and glandular secretions
Thalamic Projections
-all projection roject to cortex EXCEPT thalamic reticular nucleus (TRN)
TRN: projects to thalamic nuclei, RF; GABA=inhibitory
Relay Nuclei
-infor from basal ganglia, cerebellum, or sensory sys. to cerebral cortex
-motor, sensation, hearing, vision
Leision
-can disrupt contra sensation (proprioception)
-thalamic pain syndrome
-Lateropulsion/Pusher Syndrome: pushing toward weak side where it is believed to have equilibrium
Association Nuclei
-process memory and emotional info
-connect areas of cortex
-sensory integration
Nonspecific Nuclei
-consiousness, arousal and attention
Cerebellar and Thalamus Pathways
-cerebellum projects through superior cerebellar peduncle to thalamus
-spinocerebellar
-Closed Cerebro-cerebellar-cerebral loop: from lateral cerebellar cortex afferents through middle CP, efferents leave thru superior CP
Hypothalamus
Homeostasis: Vitals, digestion, sleep
Endocrine: growth, metabolism, reproduction
Autonomic control: SNS
Limbic system: emotions
-mammilarry bodies are post. hypothalamus
Hypothalamic Homeostasis Control
-carcadian rhy: light receptors
-appetite
-thirst: osmorrerceptors
-body temp
-sexual development
Hypothalamic Endocrine Contol
-Hypothal to infundibulum to pituitary stalk to pituitary gland
Hypothalamic Limbic Control/Amygdala
-emotional influences on ANS and homeostasis
-Hippocampus > fornix > mammillary bodies > mammilothalamic tract > thalamus > limbic cortex in cingulate gyrus
Pituitary Clinical Implications
-pituitary tumor 10-17% of all intracranial neoplasms
-can put pressure on optic chiasm causing Bitemportal Hemianopia
Posterior Pituitary
-continuous with brain
-release neurohormones
ADH, Oxcytocin
Anterior Pituitary
outgrowth of epthelial tissue
-activated by neurohormones that then release/inhibit specific hormones
GH, TSH, ACTH, LH
Bitemporal Hemianopia
-pituitary tumor puttiing pressure on optic chiasm
-Loss of vision on both sides of visual field
L eye: no left half vision
R eye: no right half vision
Pineal Body
-rest btwn superior coliculi
-part of epithalamus
-secretes melatonin for body’s carcadian rhythm
-modulate onset of puberty
Lateral Geniculate Nucleus
-posterior aspect of thalamus
-relay station for visual info from retina
Medial Geniculate Nucleus
-ventrolateral aspect of thalamus
-major auditory nucleus of thalamus
-directing auditory attention from inf. colliculi
Amygdala
-anterior hippocampus
-center of emotions, behavior and motivation
-process fearful info to detect harm and activate appropriate response
Fornix
-white matter tract connecting to hipocampus
-transmit info from hippocampus to mammilary bodies
Cingulate Gyrus
-limbic system; process emotions and regulate ANS
Septum pellucidum
-partition bettween lateral ventricles
Basal Ganglia
-motor control and adjustments (no direct contact to motor neurons)
-initiate and inhibit movements
-goal-directed
-social behavior
-emotions
Parts of Basal Ganglia
Caudate
Putamen
Caudate+Putamen= Striatum
Anterior/Nucleus Stiatum
Putamen + Globis Pallidus= Lentiform Nucleus
Globis Pallidus Internus
Globis Pallidus Externus
Subthalamic Nucleus
Substantia Nigra
Substantia Nigra
-produces dopamine
-in midbrain
-mood, learning, judgement, descion making
Has
-Substantia nigra compata
Substantia nigra reticularis
Inputs to Basal Ganglia
-From Cerebrum Through Corticostriatal pathways
-From Striatum
-Glutamate; excitatory
-Dopamine; excitatory
-ACH; excitory
-Serotonin; inhibitory
Outputs from Basal Ganglia
-Out of Globus Palliidus Internus
-Out of Substantia Nigra
-GABA; Inhibitory
Motor Loops
-oculomotor loop
-Motor loop
Dorsal striatal pathway
Non-Motor Loops
-Goal-directed behavior loop (prefrontal channel and dorsal striatal pathway)
-social behavior loop (prefrontal channel and dorsal striatal pathway)
-emotion loop (limbic channel and ventral striatal pathway)
Goal-Direct Behavior Loop
- Lateral prefrontal Cortex
- Head of Caudate: descision making, planning and picking actions
- GPi
- Thalamus: linking action chosen by caudate and performing movement
- Lateral Prefrontal Cortex
Deficits: inattention, poor concentration, disorientation, poor short term memory
Social Behavior Loop
- Ventral Prefrontal Cortex
- Head of caudate: social cues, self control, determines irrelevant
- Substantia Nigra Reticularis
- Thalamus
- Ventral Prefrontal Cortex
Deficits: inppulsivity, indifference, temper, risky behaviors
Emotion Loop
- Medial Prefrontal Cortex
- Ventral Striatum: emotions and motivation; links emotional, cognitive and motor systems
- Thalamus
- Medial Prefrontal Cortex
Deficits: L BG stroke causing depression and dull emotions, impaired reward seeking
Oculomotor Loop
- Frontal and Supplementary Eyes Fields
- Body of Caudate: eye motions and spacial attention (rapid eye mmts)
- Substatia Nigra
- Thalamus
- Frontal and Supplementary Eyes Fields
Deficits: poor saccadic eye mmts
Motor Loops
- Motor and Premotor Cortex
- Putamen: motor planning
- Globus Pallidius (both)
- Thalamus
- Motor and Premotor Cortex
Deficits: muscle contractions and force, sequencing
Disinhibition
-2 inhibitory neurons target 1
-2nd inhibitory neuron inhibits the first to allow excitatory activity
-fine tuning movements
Motor Loop Internal Pathways
Stop
Go
No-Go
-all of GPi as output nucleus; inhibits motor thalmus to excite cortical motor areas to excite motor neurons
-cause excessive or insufficient movement
Stop Pathway
-fastest; hyperdirect
Cortex < Glutamate < Subthalamic Nuc < Glutamate < GPi < GABA < Motor Thalamus: inhibit motor programs to stop irrelevant movement
Go Pathway
-direct pathway
-activation disinhibits motor
Cortex < Glutamate < Putamen < GABA < GPi < Dopamine (less) < Motor Thalamus: less inhibition to motor thalamus makes specific mmts to cortex via corticospinal
No-Go Pathway
-indirect pathway
-inhibits unwanted mmt, fine tuning
Cortex < Glutamate < Putamen < Dopamine (inhibits) < GPe < Glutamate (inhibits less) < Subthalamic Nucleus < Glutamate < Gpi < Dopamine (inhibits) < Motor Thalamus
Medium Spiny Neurons
-spiny projections
-GABAergic inhibitory cells in
Striatum
-Putamen’s D1 and D2 bind to Dopamine (made by Substatia Nigra)
D1: Direct pathway (Go); dopamine excites inhibitory in GPi
D2: Indirect pathway (No-go); dopamine inhibits Neurons in putamen and GPe, disinhibiting SN and stimulating GPi
Voluntary Muscle Activity thru Basal Ganglia
-motor thalamus to motor tract cells in cortex
-Glutamate
-corticospinal, corticopontine, corticobrainstem
Postural and Proximal Limb Muscle Activity thru Basal Ganglia
-pedunculopontine nucleus in midbrain to reticulospinal tracts to spinal nerves
-GABA to Glutamate
Walking Activity thru Basal Ganglia
-midbrain locomotor region to retticulospinal tracts to stepping pattern generators
-ACH than Glutamate
Hypokinetic Disorders
-too much BG inhibition
-parkinsons
Hyperkinetic Disorders
-too little inhibition cause
-Huntington’s Disease
-Dystonia
-Tourette’s
Parkinson’s Disease
-decreased dopamine from SN leads to excessive activity of GPi inhibiting motor control
Postural Instability Gait Difficulty (PIGD) Subtype:
-bradykinesia
-hypokinesia (freezing gait, pill rolling, masked face, tremor)
-rigidity
-ANS dysfunction
-Cognitive Dysfunction
Tremor Dominant Subtype:
-Hyperkinetic (resting and activie tremor)
-rigidty
-contipation
-orthostatic hypotension
Huntington’s Disease
-hyperkinetic
-genetic disease causing Cortical, striatum, Putamen progressive degeneration
-90% loss of GABA inhibitory neurons in putamen and caudate so less input to GPe (no-go)
-cause GPi to have Ballistic involuntary, continuous mmts (Chorei-form)
-thalamic neurons can fire randomly
Dystonia
-genetic, nonprogressive, involuntary sustained muscle contractions, abnormal posture and repetitive mmts
-increase during stress or activity
Putamen
-regulate mmts and influence learning
-part of lentiform nucleus with GP
-part of striatum with caudate nucleus
Globus Pallidus Internus
-control conscious and proprioceptive mmts
-cognition and motivation
-output nucleus
-primarily inhibitory
Globus Pallidus Externus
-central hub for motor and non-motor info
-control conscious and proprioceptive mmts
-motivation
-input nucleus
Caudate Nucleus
-ventral striatum with putamen
-planning and execution of mmts, learning, reward, motivation, interaction
Internal Capsule
Anterior: Prefrontal cortex to thalamus and BS fibers
Posterior: Corticospinal, sensory and corticobulbar
Genu: knee of internal capsule
Eye Rectus Muscles
Superior: elevation
Inferior: Depression
Medial: look in
Lateral: look out (Abducens)
Oblique Muscles
-Superior (Trochlear)
-Inferior (Oculomotor)
Pupillary Light Reflex
-Afferent: Optic
Efferent: Oculomotor
-consensual light response
Eye Anatomy
Sclera and Cornea: most anterior
Pupil: controls light into eye
Lens: accommodates for near objects
Choroid: Superficial Layer of blood vessels
Retina: Innermost layer with neurons (rods and cones)
Fovea: in retina, highest visual acuity with smallest field; only cones
Optic Disc: blind spot
Vitreous Humor: jelly substance
Retina
Outer Layer: melanin to decrease light scattering
Inner Layer: phototransduction site
-Photreceptors: Rods (b/w) and Cones (color)
-Bipolar cells: transfer info to ganglion cells
-Ganglion Cells: generate AP as 1st order neuron and synapse with optic nerve
Phototransduction
-release of neurotransmitter by photoreceptors generate AP in ganglion cells (1st order)
-Cones: color, low light sensitivity, small receptive field
-Rods: black and white, large receptive field, high light sensitity, more abundant
Visual Perception
-Ganglion cells (1st order) < optic N. < optic chiasm < optic tract < (2nd order) lateral geniculate body in thalamus < Optic radiation < Primary visual cortex
-imiage is inverted and reversed
Optic Nerve
-ipsilateral nasal (inner fibers) and temporal fibers (outer fibers)
Lesion: ipsi eye blindness
Optic Chiasm
-nasal fibers cross here (inner fibers)
-Temportal fibers stay ipsi
Lesion:
-only temporal fibers
-Bitemporal hemianopsia
- Outer field of vision gone in B eyes
-LE L field gone, RE R field gone
Optic Tract
-Ipsi temporal fibers
-contra nasal fibers
-hemi-visual field
Lesion:
-Homonymous hemianopsia
-contra side of lesion gone in same half of vision in both eyes
- Right lesion, LE L field gone, RE L field Gone
Primary Visual Cortex (Eye lecture)
Cuneus: upper bank; lower quadrant of both eyes
Lingua: lower bank; upper quadrant of both eyes
Visual Association cortex:
-Dorsal Stream: parieto-occippital cortex; motion; localization
-Ventral Stream: occipito-temporal cortex; perception, high resolution and visual acuity, recognition
Eye Movements/Reflexes
Functions
Stabilize Gaze: eye stable during head mmt
-Vestibulo-Ocular Reflex: stabilize images during slow head mmt; eyes stable with head turn in opposite direction to keep stable on retina
-Optokinetic Reflex: vestib info on eye position during head mmt; quick saccades to keep target in eye sight
Movements
-Conjugate: both eyes move in the same direction; both looking right
-Vergence: both eyes move in diff; Convergence (crossing); Divergence (away from midline)
-Saccades: rapid eye mmt to scan, read; align fovea with scene
-Smooth Pursuit: slow tracking mmt of eyes
Eye Movement Control: Brain Stem
-Pontine reticular formation (horizontal gaze center)
-Rostral intersistial Nuc in RF (vertical gaze center)
-Medial longitudinal fasciculus (coordinates both neural circuits)
-CNs
-Vestib N
Eye Movement Control: Forebrain
-initiates accurately shiftitng eyes toward target
Frontal eye field: contra saccades and smooth pursuit
Parieto-Occipital-temporal complex: ipsi smooth pursuit
Superior Colliculus: optic tectum, attention and acuracy of eye mmt in response
Eye Movement Control: Basal Ganglia
-initiation of eye mmt
-oculomotor loop
-prefrontal loop
Eye Movement Control: Cerebellum
-correction of eye mmt
-vestibulocerebellum and spinocerebellum
Lesion to Meyer’s Loop
-top of radiata
-contra superior homonymous quadrantanopsia
- Right lesion, LE top left, RE top left
Lesion to V1
-Opthalamic N (1st branch of Trigeminal)
-Contra homonymous hemianopsia with macular sparing
-Right lesion, LE L field with center spared, RE L field with center spared
Cerebellum Fuction
-adjusts posture and coordinates mmts
-processes proprioceptive info
-compares intended mmt to actual
-make adjustments
-doesn’t cause muscle weakness, just coordination issues
Cerebellar Peduncles
Superior: mostly efferents; projects to motor nuclei of thalamus, red nucleus
-afferents from spinocerebellar
Middle: afferents; from contra pontine from cortex and sup colliculus
Inferior: efferents and afferents;
-afferents: vestibular nuc, inf olivary nuc
-efferent: projectt to vestibulospinal and reticulospinal
Cerebellar Cortical Layers
Molecular: interneurons; most superificial
Perkinjie: middle layer; Perkinjie cell bodies; inhibit nuclei; all cerebellar output goes through perkinjie fibers
Granular: interneurons; Deepest layer
-Mossy Fibers: pons and SC to cerebellum
-Climbing fibers: inferior olivary nuc to cerebellum
Deep Cerebellar Nuclei
Dont eat geasy food
-lat to medial
Dentate
Emboliform
Globose
Fastigial
Functional Unit of Cerebellum
Perkinjie (inhibiory) + Deep nuclear cell (excitatory)
Functional Zones
Vestibulocerebellum (Flocculondular lobe)
Spinocerebellum (vermis and inttermediate zone)
Cerebrocerebellum (Lateral hemisphere)
Vestibulocerebellum (Flocculondular lobe)
-lateral vestibular nuc
-balance, eve, proximal trunk mmts
Spinocerebellum (vermis and inttermediate zone)
-only part of cerebellum receives input directly from SC
-Fastigial nuc (vermis): proximal gross mmts of body limbs, eye and prox trunk
-Interposed Nuc (Intermediate zone): distal limb voluntary mmt
Cerebrocerebellum (Lateral hemisphere)
-dentate nuc
-regulates highly skilled mmts and motor planning
Vertebrobasilar A.
-posterior circulation of brain
-midbrain, pons, medulla
Posterior Inferior Cerebellar A. (Think of location)
-bottom, posterior cerebellum
-tonsils, inferior vermis, inf. peduncle, inf hemisphere
-medulla
Anterior Inferior Cerebellar A.
-front and bottom cerebellum
-middle peduncle, anterior middle cerebellum, flocculus
-pons
Superior Cerebellar A.
-under CN III
-top of cerebellum
-sup and mid peduncles
Posterior Cerebral A.
-posterior cerebrum
-occipital lobe
-Posterior, medial, inferior temporal lobe
-Midbrain
-above CN III
Internal Carotid A.
-anterior circulation of brain
Ophthalmic A.
eyes
Posterior Communicating A.
-connects PCerebralA and ICA
-connects 1 side of ant to post
Anterior Cerebral A.
-medial cerebral hemisphere to parietal lobe
-from ICA
Anterior Communicating A.
-between ant. cerebral A.
Middle Cerebral A.
-lateral cerebral hemisphere
EXCECPT:
-superior and front parietal
-inferior temporal
Vertebral A. Stroke
-prone to shear forces from AA joint from abrupt cervical rotation
-gait issues, ataxia, HA
Basilar A. Stroke
-complete blockage causes death
affects Midbrain (Weber’s Syndrome), pons
-partial: tetraplegia, numbness, ataxia, CN damage, locked in syndrome (only movements)
Anterior Cerebral A. Stroke
-hemiparesis loss to contra side
-personality changes
-lower limb issues
Middle Cerebral A. Stroke
-hemiparesis loss to contra side
-face and upper limb issues
L side: aphasia
R side: spacial relationships, nonverbal communication
Posteror Cerebral A. Stroke
-midbrain issues (thalamic syndrome and Weber’s Syndrome), eye movement issues, cortical blindness (brain cant comprehend vision), ataxia, hemiparesis
Pontine Arteries
-supplies pons
Anterior Inferior Cerebellar A. Stroke
-2nd most common BS stoke
-Lateral Inferior Pontine Syndrome: CN V, VII, VIII, Anteriolateral Spinothalamic issues
Anterior Spinal A. Stroke
-Medial Medullary Syndrome
-CN XII, DCML tract, and Corticospinal
Posterior Inferior Cerebellar A. Stroke
-Most common BS stroke
-Walenberg’s (Lateral Medullary Syndrome): Increased HR, balance issues, facial sensation, secretions, pain and temp issues, swallowing
Inputs of Vestibulocerebellum
-ipsilateral vestibular nuc and visual cortex
-synapses in Flocculonodular lobe
Outputs of Vestibulocerebellum
-project to vestib nuc (posture by vestibulospinal tracts, eye mmts)
Inputs of Spinocerebellum: High Fidelity
-2 neurons ipsi to cerebellum to provide feedback
Posterior Spinocerebellar
-LE
-1st: propprioceptors from LE and trunk to SC FG & Clark’s Nuc
-2nd: Posterior Spinaocerebellar Pathway, ipsi into inf cerebellar ped. to cortex UNCROSSED
Cuneocerebellar
-UE
-1st: propprioceptors from UE and neck to SC FC and synapse to form Cuneocerebellar pathway in medulla, psi into inf cerebellar ped. to cortex UNCROSSED
Inputs of Spinocerebellum: Monitoring System
-internal feedback, monitor spinal interneuron
Anterior Spinocerebellar Tract:
-LE
-TL grey matter, divides and most CROSS at midbrain and then CROSSES AGAIN entering sup CP
-each hemisphere gets input from both; automatic coredinated LE movements
Rostrospinocerebellar Tract:
-UE
-grey of cervical SC to T1, to ipsi cerebellum through inf and sup peduncles
Outputs of Spinocerebellum
Vermis: Perkinjie cells project to deep nuclei; medial motor tracts
Intermediate zone: perkinjie cells project to interposed nuclei; lateral motor tracts; distal muscles of limbs and digits
Inputs of Cerebrocerebellar Circuits
-closed cerebro-cerebello-cerebral loop
-motor planning and timing
-changes in dentate occur before cortex executes movement
-motor and premotor cortices to pontine nuc to lateral cerebellar cortex to dentate nuc to thalamus to cortex
Input: cortex info into pons then CROSS; middle CP into lateral cerebellar cortex
Outputs of Cerebrocerebellar Circuits
Perkinjies of lat cerebellar cortex synapse with dentate; efferents leave sup CP, CROSS, go to thalamus then cortex
Signs of Cerebellar Dysfunction: Everywhere
-coordination but does not affect strength or muscles
-Ataxia
Vermal Ataxia
-trunk
Paravermal Ataxia
-limbs
Signs of Cerebellar Dysfunction: Vestibulocerebellum
Nystagmus: bouncy eye mmtts
-unsteadiness, trunk ataxia, disequilibrium
Signs of Cerebellar Dysfunction: Cerebrocerebellum
Dysarthria: slurred speech
-ataxic finger mmts
Signs of Cerebellar Dysfunction: Spinocerebellum
-Dysarthria: slurred speech
-Scanning/Explosive speech: ataxia of speech; can’t regulate tone or pitch
-Dysdiadochokinesia: rapid mmt issues
-Dysmetria: overshoot or undershoot when moving to a target
-Loss of Check/Rebound: quick removal of resistance creates strong response
-Movement Decomposition: attempting to move 1 joint at a time; compensation
Action Tremor
-shaking limb during mmt
Intention Tremor
-tremor worsens closer to a target
-delays in agonist activity and delay in antagonist brake
Cerebellar Ataxia
-agonsit and antagonist muscles
-EC and EO
-mirror doesnt help
Sensory Ataxia
-DCML
-loss of joint position
-EO helps
-can improve with visual aid
Right Lobe Cerebellum
-language
-executive functions; working mem, muscle control, goal-directed
Left Lobe Cerebellum
-visuospational function
-executive functions; working mem, muscle control, goal-directed
Anterior Lobe Cerebellum
-mediating unconscious proprioception from SC
Posterior Lobe Cerebellum
-initiation, planning and coordination of mmt
-scope of mmt
-GABA
Primary Fissure
-divides ant. and post lobes
Vermis
-midline of cerebellum
-coordinates mmt of central body, posture
-spinocerebellar
Paravermal Area
-mmt of distal limbs
-skilled voluntary mmt
-spinocerebellar
-lateral motor tracts
Dentate Nucleus
-regulates fine control of mmts, cognition, language
-send efferents to contra red nuc or thalamus
-motor planning
Globose Nucleus
-connected to vestib, balance
Emboliform Nucleus
-regulates precision of limb mmts
Interposed Nucleus
Globose+Emboliform= interposed
-eyeblinks and reflexes; agonist-antagoinst pairs
Fastigial Nucleus
-maintain balance, afferent from vermis, interprets body motion
Function of Auditory System
-ear converts acoustic energy (mechanical) into AP
External Ear
-transmits sound waves that vibrate tympanic membrane
Middle Ear
-air filled chamber
Ossicles: malleus, incus, stapes
Muscles: tensor tympani (V3), stapedius (VII)
Internal Ear
-body labyrinth
Auditory Apparatus: cochlea
Vestibular Apparatus: semicircular canals, utricle, saccule
Auditory Apparatus
-Hollow cochlea, coiled and filled with fluid
-basilar membrane vibrates from sounds
-Fluid is moved because of vibration and causes hair cells on Organ of Corti to become bent, causing a mechanical transduction where they are attached to tectorial membrane
-Depolarizes and Activates Cochlear N of CN VIII
Major Auditory Pathways
-Cochlea < Cochlear nuc in medulla < Superior Olive in Pons <Lat lemniscus and RF in Pons < Inferior Colliculi in midbrain < Medial genticulate body in thalamus < Primary auditory cortex (Temporal Lobe)
Peripheral Vestibular System
-Vestibular Apparatus
-Semicircular Canals
-Otolithic Organs
Central Vestibular System
Pathways: vestib ganglion < vestib nuclei
-Medial longitudinal fasciculus
-Vestibulospinal tracts (med/lat)
-Vestibulocolic
-Vestibulothalamocortical
-Vestibulocerebellar
-Vestibulorecticular
Vestibulocerebellum
Vestibulocortex
Vestibib Nuc
Vestibular Apparatus
Semicircular Canals: ant, pos, horizontal
-each with an ampulla
Otolithic Organs: utricle, Saccule
Membranous Labyrinth
-separated by perilymph fluid
-filled with endolymph
-hair receptor cells bend with mmt
Semicircular Canals
-Ampulla that contains a crista with a cupula (gelatanous structure containing hair)
-hairs constanly fire AP when at rest and with head mmts to give information about the body in space
-only actively move during acceleration or deceleration of head
-R and L work recipocally
-L anter and R post are a functional pair
Otolith Organs
Urtricle and Saccule: membranous sac that responds to linear acceleration/decceleration
-have a macula that contains hair cells embedded in a gelatinous mass with microscopic cristals (otoliths) on top
-displacement of otoliths sttimulate neurons
Uricle and saccule: Rotational mmt
Otoliths: Linear mmt
Vestibulo-cervical Reflex
-postural adjustments of head in response to SCC
Vestibulo-Spinal Reflex
-postural tone and adjustments of the body
Medial Longitudinal Fasciculus
-Bilateral connections to extraocular eye muscles and superior colliculus
-Connects eye related CN
Cerebello-Thalamocortical Pathways
-ascending pathway
-lateral and superior vestib colliculi < thalamus < posterior parietal cortex
Primary Somatosensory Cortex
-differentiates basic sensory info (shape, texture, size)
-Post central gyrus and central sulcus
Lesion:
-difficulty with recognizing sensory information
Cortical Layers
Granular cells
Pyramidal cells
Interneurons
-6 layers except for olfactoy and medial temporal
Secondary Somatosensory Cortex
-complex recognition of sensory info from primary and thalamus
-projects to motor and limbic areas
-integration of info, attention and learning memory
-located immediately behind PSC
Lesion:
-Asterognosia, tactile learning, memory
Primary Auditory Cortex
-in lateral fissue and sup. temporal lobe
-allows awareness of intensity of sounds
-Cochlea < inferior col < medial genticulate (thalamus) < auditory cortex
Sedondary Auditory Cortex
-contrasts and classifies sounds and makes/retrieves memories from them
-larger than primary, sup. temporal
Lesion:
-Auditory Agnosia
Primary Visual Cortex
-within calcarine sulcus (occipital to deep)
-differentiates light/dark, shapes, locations, mmts
-Retina < lateral genticulate (thalamus) < cortex
Secondary Visual Cortex
-Analyzes colors and mmts
-project to sup coli (guides visual vixation)
Action Stream: SSC < dorsal to PPC < frontal
-adjust limb mmts
Preception Stream: SSC < ventral to temporal
Vestibular Cortex
-posterior end of lateral vissure in parieto-insular cortex
Parietemporal Association Cortex
-recieves projections from somatosensory cortex and visual sys (highest degree)
-outputs to motor sys for sensory/motor integration
-part of SSC, includes Wernicke’s area
-intelligence, probelm solving, language comprehension, spatial relationship
Dorsolateral Prefrontal Cortex
-self-awareness
-executive functions: planning
-lateral frontal lobe
Ventral and Medial Dorsal Prefrontal Association Cortices
-impulse control
-personality
-Ventral: observable mood and demeanor (Visual Agnosia & Prosopagnosia)
-Medial Dorsal: preception of other’s demeanor and assumptions (Optic Ataxia)
-Medial frontal lobe and inferior frontal lobe
Primary Motor Cortex
-execution of mmt
-controls contra fractionation mmt
-precentral gyrus
Lesion:
-loss of fractionated mmt
-weakness
-dysarthria: muscles for speech
Premotor Cortex
-execution and planning of mmt
-20-30% of corticospinal tact (trunk and shoulder)
-anticipatory postural adjustments
-lateral and anteior to PMC
-attached to Broca’s Area
Lesion:
-speed and automaticity of reaching/grasping
-mmt sequencing
-posture and gait
-Perserveration
-apraxia
Supplemental Motor Area
-motor planning and initiation
-planning bimanual and sequential mmts
-anterior to PMC
Lesion:
-hemiparesis/hemiplegia
-deficits of anti-phase hand mmts
-Perserveration
-apraxia
Agnoasias
-inability to recognize sensory information
Visual Object Agnosia
-cannot recognize objects based on sight
Prosopagnosia
-inability to recognize faces visually
Auditory Agnosia
-cannot recognize object/people from sound
Anosagnosia
-inability to recognize deficits
Astereognosia
-cannot describe object in hand
-need motor function to maniulate object
Optic Ataxia
inability to use visual infor to direct mmts
Hemineglect
-lesion of parietal cortex (usually R), contra neglect
-inability to attend to objects or even own body
-all sensory sys remain intact
Perseveration
-uncontrolled repetition of mmt (mr egg)
Apraxia/Dyspraxia
-motor plannig issues
Ideational Apraxia
-inability to use objects appropriately when sequence is involved
-making coffee, brushing teeth
Ideomotor Apraxia
-unable to complete motor/muscular sequence when commanded
-unbuckling seatbelt
-can be accessed either muscle memory
Magnetic Gait
-always there
-feet glued to the floor
4 As of Cerebral Cortex Disorders
Aphasia, apraxia, agnosia, astereognosis
Basal Ganglia Rules
Cortex= excitatory
Putamen= inhibitory or less excitatory (GABA)
GPi= inhibitory
Subthalamic Nuc= excitatory
