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)