Flashcards in Exam #6: Review Deck (61):
What are the functional differences between nuclear bag and nuclear chain fibers? What types of nerve fibers are associated with these two structures?
- Velocity of length change (dynamic)
- Change in length (static)
Why do UMN lesions result in hypertonia?
- Loss of presynaptic inhibition of muscle spindle afferents (from UMN lesion)
- Allows the slow and/or sustained muscle stretch reflex to elicit continual muscle contraction
In the vestibular system, what is the result of stereocilia movement toward the kinocilium? What about away?
What are the two most common etiologies of positional vertigo?
2) Viral Labyrinthitis
What are the central connections of the vestibular labyrinth?
- Flocculonodular lobe of the cerebellum
- Vestibular nuclei
What are the four projections of the vestibular nuclei?
1) MLF to EOM (vestibulo-ocular reflexes)
2) Lateral vestibulospinal tract
3) Medial vestibulospinal tract
4) Higher centers
What two pathways are implicated in decerebrate posturing?
Lateral vestibulospinal tract
Pontine reticulospinal tract
****Both facilitate the motor neurons of the extensor muscles
What is the difference between the lateral & medial vestibulospinal tracts?
- Medial descends only to the throacic spinal cord & mediates reflex head movements in response to vestibular stimuli
- Lateral descends the length of the spinal cord & facilitates extension
What is the function of the reticulospinal system?
- Anticipatory postural adjustments
- Activating locomotion and controlling its speed
What is the function of the colliculospinal tract? What is the alternate name for this tract? Where does is project from/ to?
- Also called the "Tectospinal tract"
- Superior colliculus-->cervical spine
- Reflex head movements in response to visual stimuli
What is the vestibulocollic reflex?
Head righting reflex in response to vestibular input i.e. in the absence of visual input
What is the cervicocollic reflex?
Head righting reflex in response to proprioceptive inputs from the cervical spine
Describe the position of a patient with an asymmetric neck reflex?
- Arm & leg of one half of body extended
- Arm & leg of opposite half flexed
- Head rotated toward extended side
What are the specific boundaries of a lesion that will cause decerebrate posturing?
- Below the red nucleus (caudal)
- Above the lateral vestibular nucleus (rostral)
Generally, this is the upper pons/ lower midbrain
What is the major landmark used to describe the lesion that causes decorticate posturing?
Supratenorial i.e. above the tenorium cerebelli
What is gamma rigidity?
- Gamma motor neuron excitation
- Contraction of intrafusal fibers
- Stimulation of Ia afferents
- Contraction of muscle via alpha motor neurons
What is the treatment for severe CP?
Dorsal Rhizotomy i.e. selectively cutting some of the Ia fibers (dorsal lumbar nerves) to damped down excessive gamma rigidity that is part of the CP pathology
What is the Bordmann area for the motor cortex? Premotor cortex? Supplementary motor cortex? Frontal eye fields?
Frontal Eye Fields= 8
What is the function of the premotor area? What would a lesion to the premotor area cause?
Planning related to external stimuli/ visually guided stimuli e.g. reaching & grasping
- The ability to perform such tasks would be diminished
What is the function of the supplementary motor area? What would a lesion to the supplementary motor area cause?
Function: planning in regards to:
1) Internal acts
2) Sequential actions
3) Coordinating both sides of the body
4) Anticipatory adjustments
- Defects in the above abilities AND difficulty initiating/ suppressing movements
Where would a vascular lesion be to involve the premotor cortex vs. the supplementary motor cortex?
What are the ipsilateral consequences of Brown-Sequard Syndrome?
1) Anesthesia at the level of hemisection
3) Babinski sign
4) Deficits in the DC/ML pathway i.e. vibration, proprioception, touch
What is the contralateral consequence of Brown-Sequard Syndrome?
Spinothalamic pathway damage= deficit in pain & temperature
Draw the functional divisions of the cerebellum. Labal the deep cerebellar nuclei associated with each functional region. Label the UMN or LMN projection of each functional division.
What are the manifestations of a lesion to the spinocerebellum?
3) Intention tremor
4) Pendular reflexes
What are the manifestations of a lesion to the cerebrocerebellum?
1) Delay in starting & stopping movement
3) Impairment in sequenced movements
What are the manifestations of a lesion to the vestibulocerebellum?
2) Cerebellar nystagmus (up & down beat nystagmus)
3) Defects in smooth eye movements
Draw the direct and indirect loops of the basal ganglia. Label the NTs & primary areas of pathology of PD, Huntington's Disease, & Hemiballismus.
Draw the four major functional loops of the basal ganglia.
What brain region is associated with REM sleep?
Reticular Activating System
What NT is primarily associated with REM sleep?
What NTs are associated with wakefullness?
What brain region produces NE associated with wakefulness?
What brain region produces 5-HT associated with wakefulness?
Pontine Raphe Nucleus
What brain region produces Histamine associated with wakefulness?
What brain region produces Orexin/Hypocretin associated with wakefulness?
List the six symptoms of Prefrontal Lobe Syndrome.
1) Personality changes
2) Planning deficits
4) Frontal release signs
5) Lack of ambition
6) Akinetic mutism
What is the difference between abulia and akinetic mutism?
Abulia= loss or impairment in the ability to perform voluntary actions & make decisions
Akinetic mutism= patient does not move or speak despite being awake
Review the Costanzo table on the type of information carried by different never fiber types.
Outline the steps of auditory transduction.
1) Sound waves
2) Vibration of organ of Corti
3) Bending of cilia in Scala Media
4) Change in K+ conductance to cause depolarization & hyperpolarization
5) Oscillating receptor potential i.e. cochlear microphonic
6) Glutamate release
7) Action potential
Outline the pathway of auditory input.
2) CN VIII
3) Dorsal & ventral cochlear nuclei (medulla)
4) Lateral lemniscus
5) Inferior colliculus
6) Medial geniculate nucleus of thalamus
7) Auditory cortex
What is efferent control?
This is a mechanism of the auditory system to sharpen the frequency
How do we know if the sound comes from the right or left?
- Certain auditory neurons compare loudness of sound arriving in each ear
- Other neurons compare time of arrival
What are the typical causes of conductive deafness?
Fibrosis from OM
OM w/ effusion
Damage to DM
What are the typical causes of sensorineural deafness?
What is is BAER?
Brainstem auditory evoked potentials
What is a response or tone-click hearing test?
- Most human ears cont. emit one or more pure tones
- A click can cause the emission of tones
- Clinically, hearing loss >30 dB will cause a patient NOT to emit these tones
*****Note that this test is done routinely to test for congenital deafness in newborns
What is audiometry?
This is the headphone test of hearing that you're familiar with from visits to the doctor's office
Where is the primary auditory cortex?
What is binocular disparity? What is the function of binocular disparity?
- Binocular disparity is the difference in image location of an object seen by the left and right eyes, resulting from the eyes' horizontal separation (parallax).
- Brain uses this to extract depth information from the two-dimensional retinal images in stereopsis
What is stereopsis?
Perception of depth and 3-dimensional structure
What is the difference between scotopic and phototopic vision?
What is propagnosia?
Inability to recognize faces
What is the function of the pretectal area in vision?
Pupillary and lens reflexes
What is the function of the dorsal visual stream?
Motion & position of objects
What is the function of the ventral visual stream?
High level object recognition
Outline the afferent pathway for taste information.
1) Cranial nerve
3) VPM of the Thalamus
4) Insular & frontal taste cortices
What are WDRs?
These are the spinothalamic neurons located in Lamina V--they receive noxious & non-noxious input
Vs. "nociceptive specific" neurons located in lamina I, II, & III of the spinothalamic tract
How does the amygdala interact with the hypothalamus to produce behavior?
What is the Ventral Tegmental Area (VTA)?