Flashcards in Lecture 3b-ascending pathways Deck (50)
In the ascending pathways, sensory info from receptors comes into the cord via what?
what are their steps after that?
peripheral nerves/spinal nerves/dorsal roots
1. the info participates in spinal reflexes or
2. ascends to the cerebral cortex and
3. ascends to the cerebellum
in the descending pathway, motor commands issued by your brain descend to the cord to synapse wehre?
cord's ventral horn cells
where do tracts live
many tracts have 2 part names, what does the first part tell you? what about the second?
1. tells you the location of the neuronal cell bodies from which these axons originated from (aka cell bodies of origin)
2. tells you the site where they terminate (aka synapse)
whta are the 3 kinds of connections that afferent info make up
1. local reflex connections
2. connections destined for the cerebral cortex (conscious perception)
3. connections destined for the cerebellum (regulation of muscle tone and coordination of muscle function; subconscious)
what is proprioception? what can it be?
either conscious or unconscious
what do conscious sensation reach? via what?
what does unconscoius sensations refer to?
the cerebral cortex via thalamus
unconscious sensations refers to stuff that does not
what are the different subtypes of touch (tactile) stimuli?
2 point tactile discrimination
what is epicritic
what is protopathic
pain and temperature
in the ascending pathway, where does the 1st order neuron always have its cell body in. why?
dorsal root ganglion
-there are no synapses in the DRG
the shortest path to the cerebral cortex is 3 neurons long, what are they?
neuron that crosses the midline
where does each primary afferent neuron have its cell body in?
sensory ganglion (DRG)
-a peripherally directed process ending in skin, muscle, or a joint, and a central process ending in the CNS
primary afferents terminate in the CNS on...
2nd order neurons, which in turn project to 3rd order neurons and so forth.
with few exceptions, the receptive ending, cell body, and central terminals of a primary afferent are all on the...
-central process ends on the side ipsilateral to the cell body
somatic sensory afferents segregate at the margin of the spinal cord.
where do large diameter heavily myelinated fibers enter? and where?
small diamter fibers? and wehre?
medially through dorsal funiculus
laterally through the zone of Lissauer
fasciculus gracilis and cuneatus entering ____ to lissaurer's tract;
-2 pt tactile and proprioceptive info comes in more ______ and is highly myelinated whereas pain and temp is ______ myelinated
what general sensations do the medial lemniscus pathway in the dorsal column carry
"conscious proprioception" from the lower extremity =>eventually lead to cerebral cortex
proprioception (joint position)
2-point tactile discrimination
what is the dorsal column- medial lemniscus pathway (lower extremity)?
1. 1st cell body is DRG enters the cord medially
2. once in dorsal columns (funiculus) rise as fasciculus gracilis
3. FG synpase at nucleus gracilis (2nd CB)
4. 2nd order neuron sneds out fibers (INTERNAL ARCUATE) to arc around and cross the midline to the other side of the body. aka SENSORY DECUSSATION
5. fibers rise as medial lemniscus
6. 3rd order fibers leaving the thalamus as sent through the internal capsule (through its post limb)
7. arrive at the specific place for legs w/in somatosensory area of the parietal cortex
what are mechanoreceptors
pacinian corpuscles (vibration)
meissner's corpuscles (tactile discrimination)
what are proprioceptors
for position sense
gogli tendon worgan
where does tactile sensation start
where does proprioception start out w/
specilized receptors in the muscle spindles or tendons
after leaving the receptors, what is afferent info sent via
large myelinated fast conducting nerves
(same primary afferent as monosynaptic stretch reflex)
where are the central branches of the axons of the primary sensory neurons for discriminative touch and proprioception located
medially located in each rootlet and bifurcate on entering the dorsal funiculus
if epicritic sensation is blocked below/before the decussation, wehre is the clinical deficit to the lesion?
what if it the lesion if above the decussation?
what is romberg sign
loss of conscious proprioception
-ex. walking requires a sense wehere you are in space, if a conscious joint position sense from the lwoer body were damaged and you close your eyes you would sway bc no sense of where you are
what is 2 point discrimination
pt asked to determine whether two points of an instrument are touching them or only 1. most accurate place is at fingertips
what is vibratory sense and deep pressure sense
to test vibratory sense a turning fork is placed against a joint
does FG ever cross over to the other side?