Sensory Pathways Flashcards
what are the categories of sensory receptors?
mechanoreceptors
thermoreceptors
photoreceptors
chemoreceptors
nociceptors
where do Aalpha afferent fibers conduct signals from?
proprioceptors in muscle spindles and golgi tendon organs
where do Abeta afferent fibers conduct signals from?
non-noxious mechanoreceptors
what are the three major somatosensory tracts?
dorsal column medial lemniscal pathway
spinothalamic tracts
spinocerebellar tracts
what does a first-order neuron in a conscious pathway do?
delivers sensations to the CNS
where does the paleospinothalamic tract project to?
higher cortical areas (amygdala) to coordinate emotional aspect of pain
where does the spinomesencephalic tract project to?
periaqueductal gray
where does the spinoreticular tract project to?
reticular formation
what provides sensory innervation of the head?
all three branches of the trigeminal nerve (CN V)
external ear: CN VII, IX, X, spinal nerves C1 and C2
what controls the muscles of mastication?
proprioceptive afferents and motor efferents of the trigeminal
when does the vestibular system maintain balance?
forward movement
head rotation
tilting of the head or trunk
what are the compartments of the membranous labyrinth?
semicircular canals (3)
macula: utricle and saccule
firing is _____________ in the direction of the head movement
increased
where are cell bodies of bipolar vestibular neurons found?
within vestibular ganglion
where do some fibers from the optic nerve cross?
optic chiasm
where are olfactory receptors?
olfactory epithelium in upper nasal cavity
where do axons from the vomeronasal organ project to?
accessory olfactory bulb
what is the only sensory input with direct cortical innervation?
olfaction
what makes up superficial sensation?
touch
temperature
pain
what is part of deep sensation?
proprioception
deep muscle pain
vibration
where do Adelta fibers conduct signals from?
noxious mechanoreceptors for quick, intense pain
what are the classic pain receptors?
nociceptors with C fibers
what type of fibers are in the dorsal column medial lemniscal pathway?
Aalpha and Abeta
what does the dorsal column medial lemniscal pathway conduct?
superficial sensation
which fibers do the spinothalamic tracts utilize?
Adelta
C fibers
how many neurons do conscious pathways require?
at least 3
what is the path of the dorsal column medial lemniscal pathway?
dorsal horn, ascend ipsilaterally
synapse caudal medulla
ascend to contralateral thalamus via medial lemniscus
thalamus to ipsilateral somatosensory cortex
lesions above the medulla will have signs that are on the ___________ side with conscious proprioception
contralateral
what information do the spinothalamic tracts carry?
deep pressure
sharp pain
temperature
why can pain caused by spinal nerve or cord damage in spinothalamic tracts be difficult to localize?
numerous interneurons, collaterals, and bilateral projections
what are the indirect spinothalamic tracts?
paleospinothalamic
spinoreticular
spinomesencephalic
what tracts are involved in unconscious proprioception?
spinocerebellar tracts
where do the trigeminal touch, pain, and temperature pathways synapse?
pontine (touch) or spinal (pain and temperature) trigeminal nuclei
what helps to maintain normal jaw function with unilateral damage?
bilateral projections to and from muscles of mastication
where are hair cells concentrated?
ampulla
if there is a lesion on one side, what do the hair cells do?
decrease firing on that side
what bends the cilia of hair cells in the macula?
gravity
damage to which areas would impact the visual pathway and the pupillary light reflex?
optic nerve
optic chiasm
optic tract
what are the secondary sensory neurons of the olfactory system?
mitral cells
where does the vomeronasal organ project to?
accessory olfactory bulb
where is olfactory information transmitted to?
olfactory cortex
amygdala
hippocampus
what types of fibers do spinal nerves contain?
both afferent and efferent fibers
lesions below the medulla will have signs that are on the ___________ side with conscious proprioception
ipsilateral
what is the trigeminal lemniscus?
where most fibers of the trigeminal (CN V) cross to synapse in the contralateral thalamus
what is a lesion on one side of thee semi-circular canals interpreted as?
decreased activation on that side
