Low Yield (for those who want to get a 260 on STEEP) Flashcards
What are the cortical syndromes associated with PCA occlusion?
- P2: cortical and temporal lobe signs
- Contra homonymous hemianopia with macular sparing
- Acute disturbance in memory if lesion reaches hippocampus
WDescribe the pathway of pupillary constriction reflex.
HSV infection affects?
Temporal and inferior frontal lobes
What is the neural circuit of smooth pursuit eye movement?
Retinal Image -> Ret Ganglion Cells -> LGN -> Visual Cortex -> Reticular Form -> CN III
What is the input, output and function of the vestibulocerebellum?
Input - Vestibular
Output - vestibular
Function - VOR and postural
What are the arrows pointing to and what symptoms could appear if damage were to occur to these areas?
Superior cerebellar peduncle contains?
mostly efferent fibers, sending impulses to thalamus and spinal cord, with relays in the red nuclei; afferent fibers from the ventral spinocerebellar tract enter here
How is temperature info conveyed to the hypothalamus? Which nucleus of the hypothalamus senses temperature
Somatosensory system - temperature sensitive afferents
neurons in anterior nucleus of hypothalamus sense temp
What are the general characteristics of the parietal cortex (Areas 5 & 7)?
- Parietal cortex influences movements related to “extrapersonal space”
- Defined as the space external to the body but within reach for exploration
- Using arm and hand movements
- General function in motor control is selective attention to objects of motivational interest
What is the vestibulo-postural reflex seen in the post-rotational component
In a pt who was previously spinning to the right (decel to right/ accel to left)
- Subject will fall to the right – opposite the direction of acceleration
- Increased left CN VIII firing -> Increased firing of vestibulospinal neurons
- Causes excitation of extensors on left -> Extension
- Decreased right CN VIII firing -> Decreased firing of vestibulospinal neurons
- Causes inhibition of extensors on right -> Flexion
What are symptoms of lesions of the cerebrocerebellum?
What is the pupillary dilation reflex (startle, arousal)?
What are the common syndromes associated with blockage of the posterior cerebral artery?
What is the general pattern for the flow of information in the primary motor cortex
General pattern of information flow: basal ganglia + cerebellum + parietal cortex –> SMA and premotor cortex –> primary motor cortex –> corticospinal output to motoneurons.
What are the VOR effects in post-rotational component?
In a patient who was previously spinning right (decel righ/accel left)
- Slow conjugate eye movements to the right followed by nystagmus to the left
- Increased left CN VIII firing ⇒ Increased Med Vestibular Nuc firing
- Caused decreased left CN VI and decreased right CN III
- Decreased right CN VIII firing à Increased Med vestibular Nuc firing
- Causes increased right CN VI and increased left CN III
Results in nystagmus to opposite direction results as a reflex
Lesions of the superior colliculus tend to have?
Less accurate voluntary saccades
What are the limbic system nuclei of the thalamus? (2)
Medial Dorsal – part of the “drive” pathway between the amygdala, nucleus acumbens and orbitofrontal cortex
Anterior nucleus – part of the Papez memory circuit
What is the input, output, and function of the basolateral pathway of amygdala?
-Functions: reaction to sensory information, comparisons to previous memories and information, decision making and conscious response formation
- Input: neocortical sensory association cortex (temporal lobe)
- Output: orbitofrontal cortex, dorsomedial thalamus, nucleus acumbens, hypothalamus
Area 7 specifically has the function of?
- controls eye movements
- Neurons issue commands to the frontal eye fields for eye movements to achieve and maintain fixation of objects of interest in extrapersonal space
- Neurons include: saccade related, smooth pursuit related and fixation related
Area 5 specifically has the function of?
- controls arm movements
- Neurons issue commands to motor cortex for manual exploration of objects of interest in extrapersonal space
What are the motor system nuclei of the thalamus? (2)
VL – relays basal ganglia and cerebellar info to motor and premotor cortex feed forward system to smooth out movements
VA – relays basal ganglia info widespread areas of frontal cortex - projects to the frontal eye fields and premotor cortex
What is the mechanism by which the ampullae (semicircular canals) detech angular acceleration?
- Hair cells are located in ampullae on a ridge of tissue called the crista ampullaris
- Stereocilia are embedded in the cupula, a tall glycoprotein matrix mass
- Cupula is deflected by fluid flowing through the canal when the head turns
- Results in bending of stereocilia
What are the symptoms seen with a unilateral labyrinthectomy?
Imbalance of input from the semicircular canals due to the high tonic background firing rate present in the unaffected side (elicits both a vestibulo-ocular and vestibulo-postural reflex)
- Fall towards the side of the lesion
- Nystagmus away from the side of the lesion
What occurs in a bilateral vs unilateral ACA occlusion?
What is the neural mechanism of VOR eye movements?
Vestibular Hair Cell -> CN VIII -> Vestibular Nucleus -> Oculomotor Nucleus -> CN III
Area 5 specifically has the function of?
- controls arm movements
- Neurons issue commands to motor cortex for manual exploration of objects of interest in extrapersonal space
Where do the neurohypophyseal system and tuberoinfundibular system project? What endocrine functions are mediated by these systems?
What are the two basic types of nystagmus and how is each evoked?
Nystagmus from rotation (post-rotational phase of Barany Chair Test)
Internuclear opthalmoplegia - results from lesion of medial longitudinal fasiculus, MLF (young adults: due to MS; older adults: occlusion of basilar artery)
- Inability rotate the eyes medially (adduct) due to interruption of abducens interneurons that transmit signals to CN III for contraction of medial rectus in the MLF
- Affects all horizontal eye movements (VOR, saccades, pursuit) except convergence
- Will cause images on contralateral side to be horizontally displaced, producing diplopia
- Abducting eye often shows nystagmus
Fill this in
Describe the major structures of the auditory system
What is the underlying fault in neural circuitry for Huntington’s Disease?
- Caused by loss of the GABA neurons projecting from striatum to Gpe
- GPe is disinhibited, allowing neurons to fire at a higher rate, suppressing STN
-Suppressed STN disinhibits thalamic nuclei, causing hyperkinesia
What are the characteristics of the Purkinje Cell?
Primary Output
Form inhibitory, GABA-ergic synapses
Have a high tonic firing rate
Cell bodies in Purkinje cell layer
Dendrites fan out with axons projecting ipsilaterally to deep cerebellar nuclei (spinocerebellum, cerebrocerebellum) as well as vestibular nucleus cells (vestibulocerebellum)
Describe the central auditory pathway.
What is the role of the corticobulbar tract?
face region of sensorimotor cortex ⇒ cranial nerve nuclei thru posterior limb of IC and middle portion of crus cerebri
What are the two main types of cilia found in the vestibular hair cell. How does their relationship to one another affect the firing rate of the vestibular hair cell?
Stereocilia (multiple small cilia) and Kinocilium (single long cilium)
When stereocilia are displaced towards the kinocilium, the rate of CN VIII firing increases above the basal level as a result of depolarization of the vestibular hair cell increasing synaptic vesicle release
When stereocilia are displaced away from the kinocilium, the rate of CN VIII firing decreases as a result of hyperpolarization of the vestibular hair cell decreasing synaptic vesicle release to CN VIII
What are the characteristics of normal VOR?
Use: maintain fixation on a stationary object by moving the eyes in the opposite direction relative to head movement (acceleration)
No fluctuation in firing of purkinje cells
What are the 3 tracts in the lateral column of the white matter of the spinal cord? What do they control?
lateral corticospinal tract, rubrospinal tract, and lateral reticulospinal tract
-Skilled voluntary movements
What is the general pattern for the flow of information in the primary motor cortex
General pattern of information flow: basal ganglia + cerebellum + parietal cortex –> SMA and premotor cortex –> primary motor cortex –> corticospinal output to motoneurons.
What are the characteristics of the vestibulospinal tract?
Originates from vestibular nuclei
Primarily lateral vestibular nucleus (Dieters’ nucleus)
Terminates mainly on interneurons and motorneurons in anterior horn, mainly on ispilateral side
Plays role in facilitating anti-gravity muscles in order to maintain an erect posture
Which regions of the hypothalamus play a role in feeding behavior? What are their effects?
Ventromedial nucleus - satiety stimulation (stimulation reduces food intake, lesions produce overeating and obesity)
Lateral nuclei - feeding center (stimulation produces eating, lesion produce anorexia)
What is the effect of turning the head rightward on the firing of the right and left horizontal semilunar canals?
Effect of Rightward Head Rotation
- *Right** Horizontal Canal: endolymph bends cilia TOWARD the kinocilium –> Excitation
- Left* Horizontal Canal: endolymph bend cilia AWAY from the kinocilium –> Inhibition
What is the neural circuit of smooth pursuit eye movement?
Retinal Image -> Ret Ganglion Cells -> LGN -> Visual Cortex -> Reticular Form -> CN III
What are the symptoms seen with a unilateral labyrinthectomy?
Imbalance of input from the semicircular canals due to the high tonic background firing rate present in the unaffected side (elicits both a vestibulo-ocular and vestibulo-postural reflex)
- Fall towards the side of the lesion
- Nystagmus away from the side of the lesion
What are the two factors involved in the spinocerebellum that allows it to act as comparator in the ongoing correction of movements?
- Monitoring the course of a movement –––> spinocerebellar tracts
- Monitoring the command for movement (i.e., the desired movement) –––> pontocerebellar input from motor cortex.
- Issuing an error correction based on the difference between the intended and actual movement
How does the hypothalamus play a role in the circadian rhythm?
Suprachiasmatic nucleus; input from retinal ganglion cells containing melanopsin; project to SCN at chiasm
Regulates core body temp; ACTH levels, slow wave sleep; skin temp
What is the effect of turning the head rightward on the firing of the right and left horizontal semilunar canals?
Effect of Rightward Head Rotation
- *Right** Horizontal Canal: endolymph bends cilia TOWARD the kinocilium –> Excitation
- Left* Horizontal Canal: endolymph bend cilia AWAY from the kinocilium –> Inhibition
What is the process of the pupillary dilation reflex (dim light)?
Lesions of the Basal Ganglia affect limbs on the?
Contralateral side
Here’s why:
The projections from BG to cortex are uncrossed.
The projection from motor cortex to spinal cord is largely crossed.
What is the Cerebellar Circuit for canceling the VOR?
- Collaterals of CN VIII enter the cerebellum as mossy fibers
- Mossy fibers excite granule cells
- Granule cells bifurcate into parallel fibers
- Parallel fibers excite Purkinje cells
- Purkinje cells inhibit vestibular nucleus cells
- Cancels the opposing inhibitory input from CN VIII afferents
-Result: no VOR
What are the lenticulostriate arteries and what is the importance of them?
What are the sensory system nuclei of the thalamus? (5)
Lateral geniculate nucleus (primary visual pathway)
Medial geniculate nucleus (primary auditory pathway)
VPL (body) and VPM (head) (primary somatosensory pathway)
VPMpc (primary gustatory pathway)
Medial dorsal (primary olfactory pathway)
What are the efferent connections of the hypothalamus?
Decending autonomic control - from paraventricular nucleus
Mamillothalamic tract - papez circuit, to anterior n. thalamus
Reciprocal connections
Type of pathology of TM?
Cholesteatoma
Pars Flaccida
Benign skin cyst caused by longterm trapping of skin cells in retraction pocket
What is the jaw jerk reflex and what is it mediated by?
What is the pathway of the Dopamine NT system?
Substantia nigra and Ventral Tegement
Basolateral - Ventral Teg - Nucleus Acc - Orbitofrontal cortex
What are the two basic types of nystagmus and how is each evoked?
Nystagmus from rotation (post-rotational phase of Barany Chair Test)
Internuclear opthalmoplegia - results from lesion of medial longitudinal fasiculus, MLF (young adults: due to MS; older adults: occlusion of basilar artery)
- Inability rotate the eyes medially (adduct) due to interruption of abducens interneurons that transmit signals to CN III for contraction of medial rectus in the MLF
- Affects all horizontal eye movements (VOR, saccades, pursuit) except convergence
- Will cause images on contralateral side to be horizontally displaced, producing diplopia
- Abducting eye often shows nystagmus
What are the 4 tracts in the ventral column of the white matter of the spinal cord? What do they control?
Vestibulospinal tract, Ventral reticulospinal tract, ventral corticospinal tract, and tectospinal tract
-Adjustment of proximal muscles and posture
What is the origin of the Reticulospinal tract?
Originates from reticular formation of medulla and pons
What will be the symptoms of a superior division stroke of the MCA?
- Occurs after the bifurcation of the M1 segment of MCA
- Superior division supplies lateral surface of frontal and parietal lobes above the lateral sulcus
- Deficits resulting from stroke:
- Postcentral Gyrus: contra hemisensory deficit with sparing of leg and foot
- Precenral Gyrus: contra hemiparesis with sparing of leg and foot
- Broca’s Area: expressive aphasia if stroke in dominant (left) hemisphere
- Frontal Eye Fields: ipsi deviation of head/eyes
-No impairment of alertness
What are the key points of the VOR?
Sinusoidal head rotation modulates 8th nerve afferent activity in a sinusoidal pattern. For example, head acceleration to the right activates 8th nerve afferents on the right.
This activity produces a proportional sinusoidal modulation of the firing rate of vestibular nuclear cells.
This activity is imposed on oculomotoneurons to produce an eye movement equal in magnitude but opposite in direction to the head movement.
The circuit through the cerebellum is switched off.
Anxiety has what type of neurotransmitter profile?
Decreased serotonin and increased noradr
What are the neurosurgical treatments of PD?
-Pallidotomy
Deep Brain Stimulation. Targets: GPi and Subthalamic Nuclei. Advantage over lesioning techniques in that it doesn’t involve destruction of part of the brain
Both pallidotomy and DBS result in reduction of GPi output, reducing the inhibition of the thalamic nuclei
Damage to th entorhinal cortex will do what?
-Damage to the entorhinal cortex will prevent new memories from forming, but will not affect retrieval of memories previously moved to long term storage
How do opoids affect dopamine?
Modulation of dopamine via GABA
What are the VOR effects in post-rotational component?
In a patient who was previously spinning right (decel righ/accel left)
- Slow conjugate eye movements to the right followed by nystagmus to the left
- Increased left CN VIII firing ⇒ Increased Med Vestibular Nuc firing
- Caused decreased left CN VI and decreased right CN III
- Decreased right CN VIII firing à Increased Med vestibular Nuc firing
- Causes increased right CN VI and increased left CN III
Results in nystagmus to opposite direction results as a reflex
What are the characteristics of syndrome of neglect?
- Caused by lesions in parietal cortex
- Results in inability to respond to stimuli on the contralateral side of body or in the contralateral visual field
- Characteristics:
- Neglect of contralateral arm and objects in contralateral visual field
- Apraxia: difficulty manipulating objects
- Astereognosis: failure to recognize objects placed in hand
- Errors in accuracy of arm movements
- Difficulty performing discrete finger/hand movements requiring visual cues
Bilateral lesions will produce bilateral deficits, and tend to be more severe
What is the sequence by which sound wave entering the ear result in 8th nerve activity?
Describe the central gustatory pathway
- CN VII, IX, X ⇒ Solitary Nucleus (Medulla) ⇒ VPM (Thalamus) ⇒ Lateral Cortex
- Taste is represented both ipsilaterally and contralaterally in the brain
What is the input, output, and function of the central pathway of amygdala?
-Functions: autonomic responses (gut, HR, etc)
- Input: viscerosensory relay nuclei (e.g. solitary nucleus)
- Output: hypothalamus and brainstem ANS nuclei
What are the characteristics of the Rubrospinal tract?
- Originates in red nucleus
- -Receives input from the contralateral deep cerebellar nuclei and motor cortex bilaterally
- Travels in lateral column to terminate on interneurons in spinal cord
-Largely crossed
-Controls distal limb muscles
- -Stimulates flexors
- -Inhibits extensors
What is the input, output and function of the spinocerebellum?
Input - Vestibulospinal cerebellar/Spinocerebellar
Output - Fastigal/ INterspersed
Function - ongoing error correction
Which fibers are contained in the internal capsule?
Area 7 specifically has the function of?
- controls eye movements
- Neurons issue commands to the frontal eye fields for eye movements to achieve and maintain fixation of objects of interest in extrapersonal space
- Neurons include: saccade related, smooth pursuit related and fixation related
What is the vestibulo-postural reflex seen in the post-rotational component
In a pt who was previously spinning to the right (decel to right/ accel to left)
- Subject will fall to the right – opposite the direction of acceleration
- Increased left CN VIII firing -> Increased firing of vestibulospinal neurons
- Causes excitation of extensors on left -> Extension
- Decreased right CN VIII firing -> Decreased firing of vestibulospinal neurons
- Causes inhibition of extensors on right -> Flexion
What are neural mechanisms behind saccadic eye movements– voluntary and reflexive?
Voluntary Saccades
-Frontal Eye Field (Area 8) -> Superior Colliculus -> Reticular Formation -> CN III
Reflex Saccades (in response to a novel visual stimulus – like a flash of light)
-Retinal Ganglion Cells -> Superior Colliculus -> Reticular Formation -> CN III
What occurs in opthalmic artery stroke?
- Ophthalmic artery is a branch off of the ICA
- Supplies: retina, optic nerve, glove, orbit, frontal scalp, and frontal/ethmoid sinuses
- Deficits due to occlusion:
- -Ipsi blindness
- -Painless
- -Amaurosis Fugax: transient blindness as clot moves and restores blood flow
What happens in an internal carotid artery stroke?
Both ventral and lateral reticulospinal tracts do what?
- Both tracts act primarily on extensors to modulate spinal reflex activity
- Pontine: stimulates
- Medullary: inhibits
What is the use of suppression of the VOR by Vestibulocerebellum?
maintain fixation on a moving object by keeping eyes stationary in head as it moves
Which parts of the hypothalamus coordinated the body’s response to changes in temperature? Warm or cold?
Response to warm: Anterior nucleus
Response to cold: Posterior nucleus
What are the general characteristics of the parietal cortex (Areas 5 & 7)?
- Parietal cortex influences movements related to “extrapersonal space”
- Defined as the space external to the body but within reach for exploration
- Using arm and hand movements
- General function in motor control is selective attention to objects of motivational interest
What is the mechanism by which the saccule and utricle detect changes in linear acceleration (gravity)?
- Stereocilia embedded in gelatinous glycoprotein matrix filled with otoliths
- Otoliths (calcium carbonate crytsals) shift during linear acceleration
- Results in bending of stereocilia
What are the characteristics of outer hair cells?
-Change the stiffness of the basilar membrane
-Damage changes thresholds and
- Organized in three rows
- Modulate sensory transduction by IHCs
- Synapse with efferent fibers from the brain
- Originating in superior olivary nucleus
- Amplify the transduction of quiet sounds and attenuate the transduction of loud sounds
- Can create otoacoustic emissions
How does Parkinson’s Disease affect the normal functions of the BG (direct and indirect pathway)?
-Normally: Direct Path: disinhibits thalamic nuclei to allow motor output. Indirect Path: inhibits thalamic nuclei to inhibit motor output
Dopamine activates the direct pathway and inhibits the indirect pathway.
In Parkinson’s disease, the loss of dopaminergic input by the SNc most significantly affects motor output via the indirect path:
- Loss of inhibition from SNc
- STN can excite GPi/SNr
- GPi/SNr can inhibit thalamic nuclei
- Cortical motor output is suppressed
What is the difference between leptins and Ghrelins?
- Leptins: produced in adipose tissue and reduce appetite
- Ghrelins: Produced in gastric mucosa stimulate appetite
What are the characteristics of the Tectospinal tract?
- Originates from superior colliculus in the midbrain
- Travels in the ventral column, primarily crossed and terminates on interneurons and motoneurons in cervical spinal cord
- Plays role in reflexive control of neck muscles in response to visual stimuli
- More developed in other animals
Draw out the basic circuitry and neurotransmitter of the basal ganglia (include direct and indirect pathways)
Direct pathway: By inhibiting the GPi/SNr, it can no longer inhibit the thalamus. Thus, the thalamus is disinhibited and motor output occurs
Indirect Pathway: By stimulating the GPi/SNr, inhibition of thalamus occurs. Thus, thalamus does not excite the cortex, no output
What does the anterior choroidal artery serve?
Serves optic tract, inferior portions of the posterior limb of internal capsule, thalamocortical radiations of posterior limb and strucutres of temporal lobe
What are the characteristics of syndrome of neglect?
- Caused by lesions in parietal cortex
- Results in inability to respond to stimuli on the contralateral side of body or in the contralateral visual field
- Characteristics:
- Neglect of contralateral arm and objects in contralateral visual field
- Apraxia: difficulty manipulating objects
- Astereognosis: failure to recognize objects placed in hand
- Errors in accuracy of arm movements
- Difficulty performing discrete finger/hand movements requiring visual cues
Bilateral lesions will produce bilateral deficits, and tend to be more severe
Describe the wave displacement of the basilar membrane at the base and apex. Relate this to stiffness and frequency.
- Wave produced by stapes at oval window moves from base to apex of the basilar membrane
- Stiffness of the membrane differs along its length
- -Base: narrow and stiff
- -Apex: wide and flexible
-Amplitude of displacement at a given location of the membrane depends on the frequncy
- -Base: high frequencies (stiff membrane ⇒ requires more energy to displace)
- -Apex: low frequencies (flexible membrane ⇒ requires less energy to displace)
What is the input, output and function of the cerebrocerebellum?
Input - cerebral cortex
Output - dentate
Function - planning and programming
How is Rhabdovirus transported?
Intra-axonal transport
What are the key points of suppression of the VOR?
Head movement still produces activation of the right horizontal semicircular canal 8th nerve afferents and this activity is transmitted to the brainstem.
The circuit involving 8th nerve afferent collaterals to the cerebellum is switched on producing a proportional sinusoidal modulation of Purkinje cells.
The inhibitory activity of Purkinje cells impinges on cerebellar nuclear cells almost simultaneous with the excitatory activity arriving from 8th nerve afferents.
These two inputs to the vestibular nucleus cell cancel each other, that is, inhibitory potentials from Purkinje cells cancel excitatory potentials from 8th nerve afferents.
The firing rate of vestibular nucleus cells remains unchanged (unmodulated).
What is the input, output, and function of the corticomedian pathway of amygdala?
-Functions: sexual behavior, feeding, appetite
- Input: olfactory bulb and piriform cortex
- Output: septum and hypothalamus
What is a P1 syndrome?
-Infarction typically in ipsi subthalamus and medial thalamus and in ipsi cerebral peduncle/midbrain
- -Can cause Weber’s Syndrome (Medial Midbrain)
- -Ipsi oculomotor ophthalmoplegia
- -Contra hemiplegia
-Can also cause Thalamic Syndrome (Dejerine-Roussy) if the Thalamogeniculate A is occluded
- -Contra hemisensory loss; burning pain in affected area
- -Hemiparesis, hemiballismus, choreoathetosis
- -Intention tremor
- -Ataxia
Draw a chart comparing the Normal neural circuity and a Parkinson’s Patient.
How does MDMA work?
MAT inhibition
What will the symptoms be of an inferior division stroke of the MCA?
- Occurs after the bifurcation of the M1 segment of MCA
- Inferior division supplies: lateral surface of the temporal lobe below the lateral sulcus
- Deficits resulting from stroke:
- -Wernicke’s: receptive aphasia, if stroke in dominant (left) hemisphere
- -Visual Radiations/ Primary Visual Cortex:
- -Superior quadrantanopsia or homonymous hemianopsia depending on stroke size
- -Left visual neglect, when in NON-dominant (right) hemisphere
-Agitation and confused state may result with stroke to NON-dominant hemisphere
Where are the sensory cell bodies for CN VII, IX, and X?
VII - geniculate
IX - inferior petrosal
X - nodose
