Exam 2 Flashcards
Dorsal column/medial lemniscus use?
discriminative touch and conscious proprioception
Dorsal column/medial lemniscus pathway
Fasciculus cuneatus or gracilis > spinal cord (dorsal columns) > medulla (cross to the other side of medulla) > medial lemniscus > thalamus > primary somatosensory cortex (areas 3, 1, 2) > secondary somatosensory cortex (areas 5 and 7) > sensory association cortex (areas 39 and 40)
Spinothalamic use?
alert/arousal, temperature, acute pain, conscious
Spinothalamic pathway
Spinal cord (cross spinal cord immediately) > brainstem > thalamus > primary somatosensory cortex (3,1,2) > secondary somatosensory cortex (5,7) > sensory association cortex (39,40)
Spinocerebellar use?
unconscious posture and movement
Spinocerebellar pathway
Spinal cord > medulla > cerebellum (potentially > pons > medulla > medial or lateral vestibulospinal pathways)
Tectospinal use?
unconscious head movement
Tectospinal pathway
optic tract > superior colliculus > tectospinal pathway > reflexive head movement
Pupillary reflex (constricts) Pathway
retina > optic nerve > optic chiasm > optic tract > pretectum > brainstem (midbrain) > CN III > pupil constricts
Pupillary reflex (dilates) Pathway
retina > optic nerve > optic chiasm > optic tract > pretectum > brainstem (pons/medulla) > sympathetic nervous system > pupil dilates
Accommodation reflex Pathway
retina > optic nerve > optic chiasm > optic tract > superior colliculus > cortex magic > superior colliculus > brainstem (midbrain) > CN III > lens change shape and pupil changes size
Reflex Arch Pathway
1) Load is added → GTO and muscle spindles send signal they have been stretched
2) Response → 2 parallel outputs:
○ Alpha motor neurons send signal to muscle fibers to contract the muscle to counteract the stretch
○ Gamma motor neurons send signal to muscle spindles to equally contract as well
3) Result → Now they are the same length and the spindles can sense any new stretch in the muscle = BASIS FOR NORMAL TONE
4) Descending motor control → UMNs act as brake to regulate the LMNs otherwise they would constantly fire resulting in very high tone and eventually spasticity
VOR Pathway
LEFT
physical movement → inertia causes canal fluid (endolymph) to press against the ampula → pulls on the hair cells to activate receptors → utricle → vestibular portion of CN VIII → vestibular nuclei → CN 3 nucleus → relax medial rectus muscles
CN VIII also goes to
↓ ↘
Cerebellum Cranial nerve 6 nucleus → contract lateral rectus muscles
Spinoreticular use?
alerting/arousal to diffuse, aching pain or any sensation that would elicit emotion
Spinoreticular pathway
Dorsal horn of the spinal cord → crosses contralateral right away on the spinoreticular tract → brain stem → tegmentum → hypothalamus → ANS response
↓
Limbic system → cortex
Olivocochlear Output Pathway
superior olivary nucleus > CN VIII > cochlea
Olivocochlear Output Use?
enhances figure-ground discrimination
Reticulospinal use?
general muscle tone (unconscious)
Reticulospinal Pathway
cochlear nuclei > reticular formation > reticulospinal pathway > spinal cord > movement and posture (unconscious)
CN VII Output use?
protects against loud, high frequency sounds
CN V output use?
protects against loud, low frequency sounds
Auditory Pathway
cochlea –> cochlear nuclei –> superior olivary nuclei –> inferior colliculus –> medial geniculate nucleus –> primary auditory cortex (area 41) –> secondary auditory cortex (area 42) –> wernike’s area (Left area 22) –> sensory association cortex (area 39 and 40)
Vestibular portion of CN VIII pathway
Labyrinth > cerebellum
AND
Vestibular Labyrinth > vestibular nuclei > CN III, CN IV, and CN VI (L&R)
Output = VOR
Medial Vestibulospinal pathway
Labyrinth > cerebellum
AND
Vestibular Labyrinth > vestibular nuclei > cervical level of the spinal cord
Output = head and neck posture (not conscious)
Lateral Vestibulospinal pathway
Labyrinth > cerebellum
AND
Vestibular Labyrinth > vestibular nuclei > all levels of spinal cord
Output = axial posture
________ retina fibers cross midline at the optic chiasm
nasal
________ retina fibers remain ipsilateral
temporal
A lesion to the right optic nerve will cause…
total loss of the right visual field (you can still see some of what is on the right side but only what you are picking up with the left visual field – the part that overlaps)
A lesion to the optic chiasm would cause…
bitemporal hemianopsia; loss of peripheral vision (described by patient as tunnel vision)
A lesion to the right optic tract would cause…
contralateral homonymous hemianopsia (loss of the entire left visual field)
A lesion to the upper portion of the optic radiations on the right side would cause…
loss of the lower left visual field (the client might describe how they are running into things or bumping their left shin on the coffee table, but they may not be conscious or aware of this lesion)
What are the different names of the receptors for somatosensory systems?
Pain = nocioception
Temperature = Thermoreception
Touch-pressure = Mechanoreception
Joint position = Proprioception
hyperalgesia
low pain thresholds in receptor or inappropriately increased efficiency of central pain synapses (increased sensitivity to pain)
tactile defensiveness
low touch thresholds, esp. light touch (causes aggression, physical & social withdrawal)
gravitational insecurity
strong emotional response to changes in head position in relation to gravity (elevator jerks when changing floors) – emotional aspect of falling, scared of falling
postural insecurity
over-concern or fear of falling
vertigo
unprovoked sensation of dizziness or movement
Therapeutically, what are strategies with sensory thresholds?
Short-term: Remove stimuli to limit activation
Long-term: Habituate to stimulus; overstimulate system to create performance reserves (you want them to be sure they have extra in case they are in a situation that is abnormally stimulating)
Parallele Processing
Related sensory information is used by different systems for different purposes
more complete view of sensory environment = enhanced performance
Your brain is able to gather as much information as it can by using all of the sensory systems to tell you what is going on
Lateral Vestibulospinal pathway purpose?
balance/posture at all levels
Medial Vestibulospinal pathway purpose?
balance/posture at head and neck (c-spine) levels
