Term
| Upper motor neuron symptoms |
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Definition
Weakness
Spasticity
Babinski's Sign
Loss of fine voluntary movements |
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Term
| Lower motor neuron symptoms |
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Definition
Weakness or Paralysis
Decreased stretch and withdrawal reflexes
Decreased deep reflexes
Hypotonia
Fasciculations and fibrillations
Severe muscle atrophy |
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Term
Voluntary movements of the body and limbs
-Tract
-Cell type
-Decussation |
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Definition
-corticospinal tract
-Descending axons are from Layer 5 pyramidal cells in the
---Primary motor c.
---Primary somatosensory c.
---Premotor/supplementary c.
-90% pyramidal decussation to lateral funiculus: control more distal muscles
-10% don't decussate and descend in the ventromedial funiculus: control more axial muscles |
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Term
Voluntary movements of the face
-Tract
-Nuclei involved
-Lesion patterns |
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Definition
-Corticobulbar tract
-Synapses on CN V, VII, XII
-Upper face has bilateral innervation from the Cingulate Motor Area
-Lower face has contralateral innvervation from the Primary Motor Cortex
----Cerebral stroke or lesion to the descending tract imparts UMN symptoms to the contralateral lower portion
----Lesion to the facial nerve imparts LMN symptoms to the ipsilateral entire half of the face. (Bell's Palsy) |
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Term
| 5 Upper motor neuron sources and their general movement types |
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Definition
Cortex
--goal directed movement
Red Nucleus
--Gross trunk and shoulder movement
Superior Colliculus
--Orienting towards stimuli
Vestibular Nuclei
--Balance
Reticular Formations
--Posture, locomotion |
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Term
General Cortical layer connection pattern
-Input
-Connections between layers
-Connections between parts of cortex
-Output |
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Definition
Input
--Axons from thalamus and other cortical areas synapse on Layer IV spiny stellate cells
Between Layers
--Layer IV cells make short projections to other layers
Between parts of cortex
--Layer II and III pyramidal cells have long projections to other cortical areas
Output
--Layer V and VI pyramidal cells project to subcortical structures. |
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Term
| 3 categories of Cerebellar Lesion symptoms |
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Definition
1. Hypotonia: diminished resistance to passive limb displacement
2. Ataxia:
-Poor coordination of eye movement
-Poor coordination of walking
-Delayed initiation of movement
-Dysmetria
-Dysdiadochokinesia
-Decomposition of movement
3. Intention Tremor
Also some cognitive deficits |
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Term
Cerebrocerebellum
-Components
-Input
-Output Which Deep Nuclei its Purkinje cells synapse on
-Function |
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Definition
*AKA the Lateral Zone
Input
*Mossy Fibers from Motor Cortex-->Basilar Pons -->MCP (Corticobulbar Tract)
Output
*Dentate Nucleus-->SCP-->VL Thalamus -->Motor Cortex
Note: An anatomical loop to and from the motor cortex
Function
*Motor Planning and coordinate distal musculature such as hands. |
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Term
3 Cortical Layers of the Cerebellum
(Deep to Superficial)
-Cell types
---Excitatory or Inhibitory/N.T. used |
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Definition
Granular
-Granule cells: Glutamate
-Golgi cells: GABA
Purkinje
-Purkinje Cells: GABA
Molecular
-Stellate Cells: GABA
-Basket Cells: GABA |
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Term
2 Fiber inputs to the Cerebellum
-Mossy Fibers
----Origin, target, local control
-Climbing Fibers
----Origin, target, local control |
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Definition
Mossy Fibers
-Come from many sources; excitatory
-Synapse on Deep Nuclei
-Synapse on Granule Cells
----Granule Cells extend parallel fibers to excite Purkinje cells
----Golgi Cells inhibit Granule Cells
Climbing Fibers
-Come from Inferior Olive via contralateral ICP
-Massive excitation on one Purkinje Cell
----Basket and Stellate Cells inhibit Purkinje cellls |
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Term
Spinocerebellum
-Components
-Input
-Output (Which Deep Nuclei its Purkinje cells synapse on)
-Function |
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Definition
Components
*Paravermis and Vermis (AKA intermediate zone)
Input
*Mossy fibers: spinocerebellar tracts-->ICP
Output
*Vermis-->Fastigial Nucleus -->Vestibular Nucleus (Balance) and Pontine Reticular Fibers (Posture)
*Paravermis-->Interposed Nuclei--> Red nucleus (Axial movement)
Function
*Regulating posture and limb movement |
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Term
Vestibulocerebellum
-Components
-Input
-Output Which Deep Nuclei its Purkinje cells synapse on
-Function |
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Definition
Components
*Flocconodular lobe
Input
*Vestibular (Scarpa's) Ganglion and nuclei
*Superior Colliculi
Output
*Purkinje cells directly-->Vestibular Nuclei in the Brain Stem
Function
*Maintain Balance and Coordinate head and eye movement |
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Term
Inputs of the Cerebellar Peduncles
-SCP: 1
-MCP: 1
-ICP: 4 |
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Definition
SCP
-VSCT: from ventral horn superior colliculus
MCP
-Pontocerebellar Tract: via pontine nuclei ?via the corticobulbar tract?
ICP
-Vestibular Nuclei
-Vestibular (Scarpa's) Ganglion
-DSCT: via Clarke's Column
-Climbing fibers from inferior olivary nucleus |
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Term
Outputs of Cerebellar Peduncles
-SCP: 1
-MCP: 0
-ICP: 2 |
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Definition
SCP
-Red Nucleus: from interposed nuclei
-VL Thalamus: from dentate nucleus
MCP
-None
ICP
-Pontine/Medullary Reticular Formations : from fastigial nucleus
-Lateral Vestibular Nucleus
: from floculus/nodulus (direct) and from fastigial nucleus |
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Term
| 4 types of Neural Computations in the Cerebellum |
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Definition
1. Anticipate And Compensate For Force
---Damage/cooling of deep nuclei can cause overcompensation oscillations and intention tremors
2.Cognitively Evaluate Sensory Input
---Increased activity in dentate nucleus when mentally active during movement
3.Motor Learning
---Training to increase or decrease the vestibuloochlear reflex; altered (+/-) ability of Purkinje Cells to inhibit Vestibular Nuclei
4.Classical Conditioning
---Pavlovian association responses |
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Term
Cerebellar Midline Ataxia
-Affected Cerebellar component
-4 Exam components
-3 Hallmarks |
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Definition
*Medial cerebellar disease causes dysfunction in the vestibulocerebellum and spinocerebellum
Exam
* Station, Truncal Stability, Walking, and Tandem Gait
Hallmarks
1.Truncal instability manifested as a titubation tremor
2. Gait ataxia
3. Wide unstable station |
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Term
Cerebellar Appendicular Ataxia
-Site of dysfunction
-6 exam components
-5 Hallmarks |
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Definition
*Cerebrocerebellum dysfunction reuslts in ataxic speech and extremity movements
Exam
1) Finger to nose
2) Rapid alternating movements
3) Heel to shin
4) Rebound and check reflex
5) Deep Tendon Reflexes
6) Speech
Hallmarks: Always IPSILATERAL to the affected hemisphere
1) Scanning dystarthria
2) Intention Tremor
2a) Dysmetria (diff hitting target)
4) Dysdiadochokinesia (breakdown of alt. movements)
5) Hypotonia
6) Hyporeflexi
ALL IPSILATERAL |
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Term
Sensory Ataxia
*Etiology
*Ataxic Symptoms
*Sensory Symptoms |
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Definition
Etiology
*Loss of propioreceptive feedback into the cerebellum usually due to DCML or peripheral nerve disease
Symptoms
*Both appendicular and and wide base gait problems
*Ataxia is exacerbated when eyes are closed--> Romberg sign (note: only tests propioreception, not cerebellar function)
*Position and vibration sense impairment |
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Term
| Cerebellar Ataxia: 4 other causes/traps that can have similar symptoms and their key feature to distinguish them. |
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Definition
1. Sensory ataxia
*Will have loss of proprioreception and vibration sense
*Romberg sign present
2. Vestibular dysfunction
*Vertigo present
3. CST disease: pseudoataxia of distal extremities
*UMN signs present
4. Proximal limb Weakness of thighs and hips
*Psuedoataxic gait, but with weakness |
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Term
| 4 pearls to diagnosing Cerebellar ataxia |
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Definition
1. Appendicular ataxia is always IPSILATERAL TO THE LEASION
2. Appendicular ataxia is maximum at the greatest extent and end point of a motor act
3. Sensory ataxia grows much worse with the eyese closed while cerebellar ataxia rarely does
4. A Romberg test is for position sense and not of cerebellar function. |
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Term
Nerve Conduction Testing findings in
-Demyelination
-Axonal disorder |
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Definition
Demyelinating
*Prolonged distal latency
*Slowed conduction velocity
Axonal disorder
*Reduced motor amplitude |
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Term
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Definition
Sustained muscle contractions causing tiwsting and repetitive movements as well as postural disorders
Exacerbated by voluntary movements |
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Term
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Definition
Low amplitude writhing; usually distal with fingers and toes
Caused by sequential activation of adjacent muscle groups |
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Term
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Definition
Arrhythmic, rapid jerky movements of greater amplitude and erraticism than athetosis
Can resemble fidgetiness when mild |
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Term
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Definition
Much largerer amplitude "flinging" movements than chorea; usually involves proximal muscles
Usually the result of a focal unilateral brain lesion |
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Term
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Definition
Sudden lightning like irregular movements WITH PAUSES between movements which distinguinshes it from tremor
Can be exacerbated by movement |
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Term
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Definition
Regular involuntary oscillations of reciprocally innervated muscles without pauses.
Prominence
Rest: Parkinsons or neuroleptics
Action: Most all other tremors |
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Term
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Definition
Slowness of voluntary movements
Progressive reduction of SPEED and AMPLITUDE with repetition.
Ex: micrographia in PD |
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Term
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Definition
Type of Hypokinesia
Increase in muscle tone during passive movement
Can be CONSTANT/LEADPIPE or RATCHETY/COGWHEEL
Can be brought out by voluntary movement of other body parts (usu. contralateral) Technique is called AUGMENTATION |
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Term
Parkinson's Disease Clinical Features
-3 cardinal motor manifestations
-5 other motor manifestations
-Non-motor symptoms |
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Definition
Cardinal Motor Signs
*Usually more prominent on one side
1. Tremor
2. Cogwheel Rigidity
3. Bradykinesia
Other Motor Signs
1. Postural Instability
2. Shuffling gait
3. Facial Masking
4. Micrographi
5. Reduced arm swing
Autonomic Symptoms
*Constipation*
Hypotension
Incontinence
Drooling
Neuropsychiatric
Depression and apathy
Late Dementia
Sleep disturbance |
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Term
DA replacement for PD
-Biochemistry
-3 Side Effects
-4 Long Term Effects |
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Definition
Biochemistry
-DA can't cross BBB
-L-Dopa can cross BBB and is metabolized to dopamine by DOPA decarboxylase.
-Carbidopa can't cross BBB and inhibits DOPA decarboxylase in the periphery
Side Effects
-Short term nausa, vomiting, and hypertension
Long Term Effects
1) On/Off phenomenon
*The following are due to due much DA
2) Dyskinesia
3) Hallucinations
4) Confusion |
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Term
Blocking DA Metabolism for PD
-Biochemistry
-Useage |
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Definition
Biochemistry
*DA is normall broken down by MAO-B
*SEGELINE is an irreversible inhibitor
Useage
*Mildly effective early on
*Side effects late in disease
*Accentuates side effects of L-Dopa therapy |
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Term
DA Receptor Agonists for PD
-Biochemistry
-Useage |
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Definition
BROMOCRIPTINE and PERGOLIDE
Biochemistry
*Nonselective agoniss of D1 and D2 receptors
*D1 stimulates direct pathway
*D2 inhibits indirect pathway
Useage
* As an adjunct in L-Dopa therapy
* Longer acting helps with "on/off"
*Same side effects as L-DOPA |
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Term
Muscarinic AChR Antagonists for PD
-Biochemistry
-Useage |
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Definition
TRIHEXYPHENIDYL
Biochemistry
*M. AChR activity in the striatum inhibit the direct pathway and stimulate the indirect pathway
*Thus use an antagonist
*M. AChR's are common in periphery as well
Useage
*Infrequently as an adjunct
*Causes sedation, confusion, waste retention |
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Term
Deep Brain Stimulation or Surgical Lesion for PD therapy
-2 targets |
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Definition
Electrically inactivate or lesion the Subthalamic Nucleus (STN) or the Globus Pallidus internal (GPi/MGP).
Either inactivates the indirect pathway |
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Term
Clinical Features of Huntington's Disease
-4 Classic Symptoms
-Late symptoms |
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Definition
Classic Symptoms
Early
1. CHOREA often exacerbated by stress
-dysarthria and dysphagia possibly
2. ATHETOSIS of the hands and fingers
3. GRADUAL MENTAL DECLINE
4. PERSONALITY CHANGES
Late
-Dystonia
-Parkinsonism
-Postural instability |
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Term
Pathophysiology of Huntington's Disease
-Genetics
-Cells/Systems affected |
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Definition
Genetics
*Autosomal Dominant with Anticipation
*Expanding CAG repeat
*Codes for glutamine in huntingtin protein
Cells/Systems
*Selective loss of GABAergic striatal output neurons of the indirect pathway
*Leads to increased inhibition of the STN and thus a decreased indirect inhibitory output
*Thus overactive/unintended movement |
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Term
Symptom treatment in HD
-Chorea in general
-Anxiety induced Chorea
-Psychiatric |
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Definition
Chorea
*Neuroleptics like Halperidol can be used early on
*Eventually accentuate the late parkinsonism and dystonia symptoms
*Benzodiazepines to control anxiety induced chorea
Psychiatric
*Antidepressants and antipsychotics |
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Term
| 3 Neuromodulatory Systems as examples of direct to cortex/thalamic bypasses. |
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Definition
1. RAPHE NUCLEUS: serotonin
2. LOCUS COERULUS: norepinephrine
3. NUCLEUS BASALIS OF MEYNERT: acetylcholine |
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Term
Types of Thalamic Nuclei
-List the 5 major RELAY Nuclei
-DIFFUSE Nuclei example/function
-SUBCORTICAL Nuclei example/functiom |
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Definition
Major Relay Nuclei
*VB, VA/VL, AN, LGN, and MGN
Diffuse Nuclei
*Ex: Intralaminar and midline thalamic
-> widespread cortical synapses and STT input--> set arousal baseline
Subcortical Nuclei
*Ex: Thalamic reticular nucleus
-Doesn't ouput to cortex
-Has both cortical and cerebellar inputs
-Guardian of the thalamic Gateway |
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Term
Ventrobasal (VB) Complex
-Inputs
-Outputs
-Information carried by each |
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Definition
VB= VPL+VPM
Input
*DCML [VPL] Touch, Propio, Vibration
*ALS [VPL] Pain and Temperature
*Trigeminal [VPM] CN V Somatosensory
*Solitary Tract [VPM] Taste
Output
*Somatosensory/postcentral gyrus
*Gustatory cortex [VPM only] |
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Term
Lateral Geniculate Nucleus
-Inputs
-Outputs
-Information carried |
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Definition
LGN
Input
*Optic Tract: vision from retina
Output
* Visual cortex |
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Term
Medial Geniculate Nucleus
-Inputs
-Outputs
-Information carried |
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Definition
MGN
Input
*Inferior Colliculus via inferior brachium: Auditory information
Output
*Primary Auditory Cortex/Heschle's Gyrus |
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Term
VA/VL Thalamic nuclei
-Inputs
-Outputs
-Information carried |
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Definition
Input: Sensory and Motor
*Globus Pallidus Internal
*Substantia Nigra Internal
*Cerebellum via SCP
Output:
*Motor Cortex
*Premotor Cortex |
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Term
Anterior Nucleus (AN)
-Inputs
-Outputs
-Information carried |
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Definition
Input: "Limbic Stuff"
*Mamillothalamic Tract (MB's)
Output
*Cingulate Gyrus |
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Term
Olfactory Pathway
-5 Cortical targets (and beyond) and their functions |
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Definition
*Mitral/Tufted cells are the projection neurons to the cortex
*Ipsilateral, shallow processing, two cell pathway to the cortex without relay of the thalamus
1) Anterior olfactory Nucleus to the contralateral olfactory bulb
*The following all subsequently project to the Frontal Cortex
2) Olfactory tubercule
3) Pyriform Cortex (Olfactory Coding/Perception)
4) Amygdala (Like/Dislike) --> Hypothalamus
5) Entorhinal Cortex --> Hippocampus (Memory) |
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Term
Olfactory Coding in Epithelium (Level 1)
-Transduction
-Odorant Receptors
-Combinatorial Coding |
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Definition
Transduction
*Common G Protein pathway
Odorant Receptors
*Single OSN expresses only one of a 1000 different receptors on its cilia
Combinatorial Coding
*One receptor can bind many odorants with different affinities
*One odorant can bind to many receptors with different affinities
*This allows QUALTIY and INTENSITY to be encoded by a COMBINATION of multiple OSN's. |
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Term
Olfactory Coding in the Bulb (Level 2)
-Synaptic Organization-->Spatial/temporal Coding
-Lateral/Self Inhibition-->Sharpening |
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Definition
Synaptic Organization
*The axons of multiple OSN's with identical receptors converge as neuropils to a single glomerulus
*Multiple mitral tufted cells send their signal primary dendrite to a single glomerulus
*Thus the bulb inherits the combinatorial coding of the neuroepithelium as a spatial coding map
*This spatial coding map is bilaterally symmetric.
*Temporal coding as well
Lateral/Self Inhibition
*Lateral inhibition via granule and periglomerular cells
*Self inhibition by the M/T cells
*Sharpens the receptive field causing a modified response pattern from that occuring in the OSN's |
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Term
Olfactory Coding in the Cortex (Level 3)
-Location
-Synthesis |
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Definition
Pyriform cortex
*Only three layer instead of six
*Extensive connections with other cortical regions
Synthesis
*M/T cells from a single glomerulus project diffusely throughout the pyriform cortex
*Neural maps are created for each odor (a mix of odorants)
*At this level odor perception is synthetic; the are irreducible entities. Discrete compounds cannot be detected |
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Term
Gustatory Pathway
-Tongue to Brainstem
-Brainstem to Thalamus
-Thalamus to Cortex |
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Definition
IPSILATERAL!
Taste cells-->primary gustatory afferent nerve fibers--> CN 7/9/10-->synapse on solitary nucleus in the medulla-->ascend the solitary tract-->synapse on VPM--> relayed to the ipsilateral primary gustatory cortex (anterior insula and frontal operculum) |
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Term
Gustatory Coding by Taste Cells (Level 1)
-Transduction
-Receptor expression/labeled lines |
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Definition
Transduction receptors
*Salt: Na+ opens gated Na+ channels
*Sour: 1) H+ enters cation channels
2) H+ blocks K+ efflux
*Sweet/Umami/Bitter : G-protein linked receptor
Expression/Labeled Lines
*Each Taste Cell expresses multiple taste receptors
*However, they are each tuned to one modality-->labeled lines |
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Term
| Gustatory coding in the afferent fibers |
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Definition
*Single fiber can respond, to multiple stimuli in varying degrees, but responds best to a single stimulus
*Each fiber is innervated by a population of taste cells with a distinct set of response specificities
*Specific "tastes" are encoded by patterns of activity in the entire fiber population or by activation of different, but overlapping sets of fibers. |
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Term
| Jim White's Corticospinal Tract -Path of the tract in the brainstem -Position in the brainstem -Note about CBT and CPT |
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Definition
| Path of the Tract *Motor Cortex-->Posterior limb of the internal capsule-->Cerebral Peduncle (Midbrain)-->Basis Pontis (Pons)-->Pyramid (Medulla)-->Pyramidal decussation (Cervico-medullary Junction) Position *Runs ventromedially throughout the entire brainstem Note: CBT (UMN's) courses with the CST to innervate LMN's in cranial nerve nuclei. (Also synapses on sensory relay nuclei and the reticular formation CPT courses with CST and CBT to synapse on nuclei in the basal pons which project axons through the contralateral MCP's into the cerebellar hemispheres |
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Term
| Path of the Tract *Motor Cortex-->Posterior limb of the internal capsule-->Cerebral Peduncle (Midbrain)-->Basis Pontis (Pons)-->Pyramid (Medulla)-->Pyramidal decussation (Cervico-medullary Junction) Position *Runs ventromedially throughout the entire bra |
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Definition
| Somatotopic Orientation of CST fibers *Prior to pyramidal decussation Arm Medial. Legs Lateral, *In the spinal cord: Legs medial(exit last), Arms lateral(exit first) Somatotopic Orientation of DCML *Spinal Cord (DC): Legs Medial (enter first), Arms Lateral (enter last) *After Med. Decussation (ML) to as arcuate fibers : Arms Medial, Legs Lateral Somatotopic Orientation of ALS *Immediate decussation thus Legs Lateral (Enter First) and Arms Medial(Enter last) all the way through the spinal cord and brainstem |
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Term
| Jim White's Other descending motor tracts Brainstem pathways and synapses of *Lateral Motor System -Corticospinal Tract (not covered here) -Rubrospinal Tract |
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Definition
| RST *Red Nucleus-->immediate tegmental decussation-->runs with the CST through the brainstem and cervical spinal cord |
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Term
| Jim White's Other descending motor tracts Brainstem pathways and synapses of *Medial Motor System (Postural) -Uncrossed Corticospinal Tract (not covered) -Vestibulospinal Tract -Reticulospinal Tract -Tectospinal Tract |
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Definition
| Which of these has bilateral innvervation? VST *Lateral/Medial Vestibular Nuclei (Pons/Rostral Medulla)-->respective paths through Brainstem (MLF?)-->Ventral Funiculi (spinal cord)-->bilateral innvervation of LMN in the medial Anterior Horn RST *Pontine/Medullary Reticulary formation-->respective paths through Brainstem-->Ventral Funiculi (spinal cord)-->????? innvervation of LMN in the medial Anterior Horn TST *Superior Colliculus (Midbrain)-->respective paths through Brainstem-->Ventral Funiculi (spinal cord)-->????? innvervation of LMN in the medial Anterior Horn |
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Term
| Jim White's Desceding Hypothalamic Fibers -General Path through Brainstem and Spinal Cord -Path of Sympathetic Innervation Pathway of Face Scalp and Orbit |
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Definition
| Entirely Ipsilateral innervation; remains lateral. Pathway *Hypothalamus-->descending hypothalamic fibers-->course with STT in ALS-->Synapse in brain stem and the lateral horn of spinal cord with Preganglionic sympathetic and parasympathetic neurons--> Important for this test is the sympathetic innervation to the face scalp and orbit *-->synapse with preganglionic sympathetic neurons at T1 level-->white rami--> up the paravertebral sympathetic chain ganglia--> thru I. Cervical ganglion-->synapse on Post.G.S.N in superior cervical ganglion--> P.G.S.N travel up external carotid artery Lesion gives ipsilateral Horner's Syndrome: see Dr. Galetta |
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Term
| Jim White's tricks to locate oneself in Brain Stem Cross sections -Midbrain -Rostral Pons -Caudal Pons |
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Definition
| Midbrain *Colliculi and Cerebral Aqueduct -Cerebral Peduncles -CN's III and IV Rostral Pons *4th Ventricle -CN V entry and exit -CN V Motor Nucleus and Chief Sensory Nucleus (ALS like) Caudal Pons -4th Ventricle -CN's VI, VI, VII ( Motor eff's loop around nucleus of VI before exit) |
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Term
| Jim White's tricks to locate oneself in Brain Stem Cross sections -Rostral Medulla -Caudal Medulla |
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Definition
| Rostral Medulla *Olive -4th Ventricle -CN's IX, X, and XII Caudal Medulla *Pyramidal decussation of CST *Dorsal Column Nuclei (UMN cell bodies) *DCML UMN's decussating as internal arcuate fibers into ML |
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Term
| Jim White's Brainstem CN Nuclei Columns -What CN nuclei and what level of B.S. -Symptoms of a lesion Motor Columns -Medial Motor Column -Middle Motor Column -Lateral Motor Column |
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Definition
| Medial Motor Column: All the strictly motor CN's -Midbrain: *Oculomotor/III: External Strabismus, possible ptosis, possible parasympathetic (E.W.) defects *Trochlear/IV: ?Contralateral? S.O. deficit causing diplopia from unnaposed extorsion; patient will tilt head AWAY from the side of the lesion to compensate -Caudal Pons: *Abducens/VI: LR dysfunction causing internal strabismus Note: Located near facial nerve loop and in the PPRF |
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Term
| Mechanical portion of sound transduction -Middle Ear Mechanics -Inner Ear Mechanics |
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Definition
| Middle Ear: Impedance Matching: Air-->Fluid *Tympanic membrane vibrates from air pressure waves *Causes ossicle vibration *Stapes vibration opens the round window and transmits vibration down the 3 fluid filled scala and back out through the round window Inner Ear: Frequency to Place Translation: Tonotopic Organization *Reissner's membrane transmits vibration into scala media and causes displacement of the basilar membrane *Basilar membrane has a stiffness/impedance gradient *Stiffness is lowest at base-->high frequencies *Stiffness is highest at apex-->low frequencies *Local displacement of basilar membrane thus shearing force on specific hair cells allows frequency spectral decomposition of complex sound |
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Term
| Gating spring hair cell transduction physical-->electrical |
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Definition
| Physical portion *Local Stereocilia bundles attached to the tegmental membrane are bent by local shearing force *Stereocilia attached to hair bundles by tip link which gets stretched *Stretched tip link pulls opens the K+ channel on a force dependent scale of open probability causing signal intensity to be proportional to positive displacement |
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Term
| Auditory Neurons -Sound Intensity Coding -Frequency Coding |
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Definition
| Intensity *Single Hair cell innervates multiple nerve fibers which each have different thresholds to cover a range of 0-100 decibels Frequency: the Periodicity Principle *Single auditory neurons can't fire fast enough to reflect sound frequency *Single Hair cells innervate multiple AN's at shifted but same intervals which collectively can sum to reflect the sound frequency |
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Term
| Central Auditory Processing Pathways -Dorsal Cochlear Nucleus -Superior Olivary Nucleus (MSO and LSO) -Superior Colliculus and Medial Geniculate Nucleus -Auditory Cortex |
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Definition
| DCN: Complex tuning *Ipsilateral input *Tonotopic organization is maintained *Lateral inhibition allows edge sharpening further selectivity of frequency and intensity Superior Olivary Nucleus: Position *First Binaural Input *Medial cells compute location by TIMING differences in the arrival pattern from both ears: EE cell *Lateral cells compute location by INTENSITY differences from ipsilateral excitatory input and contralaterl ihibitory input: EI cell Inferior Colliculus and MGN: Common Relays *Tonotopic organization maintained *Contralateral DCN (Complex Tuning) and LSO (Intensity) Input *Ipsilateral MSO (Timing) Input *Ipsilateral ouput--> Medial geniculate nucleus--> Auditory Cortex Auditory Cortex: Integration of everything 1. Iso Frequency Strips 2. Tonotopic organization maintained 3. Alternating EI and EE sensitive bands |
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