Lecture 3: Development of the Dorsal Columnar System Flashcards
How many spinal nerve pairs are there (name number in each division of spinal column)?
8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccylgeal pair
What are the conus medullar is and caudal equina respectively
terminal tapered portion of the cord at level L2, caudal equine is coral and ventral ROOTs of lumbar, sacral and cooccygeal nerves
What is meant by topographic organization of the white and gray matter
the body part, sensory surface or muscles innervated represent an orderly pattern, divided into layers/ groups (Lamina of Rexed)
Name the 4 divisions of the grey matter of the spinal cord?
dorsal horn, ventral horn, lateral horn and commissure
Name the areas of white matter in the spinal cord (mostly ascending and descending axons/tracts).
dorsal (posterior) funiculus (divided into fasiculus); lateral funiculus; ventral (anterior) funiculus
Under the general organization of the spinal cord, neurons and interneurons are situated with ____-____ topography with cells dealing with axial musculature (medial) and distal muscles (lateral), flexors are more dorsal and extensors are more ventral.
medio- lateral
What is a funiculus?
a large group of nerve fibers located in a particular area (also used is tract for nerve fibers in a funiculus with a similar function, origin, destination and course)
What types of fibers/sense does the dorsal column system carry?
alpha beta axons of the DRG carrying touch, vibration and conscious proprioception which branch to the dorsal horn and send a funiculus to the brainstem on the same side
What is a fasciculus?
a smaller group of nerve fibers with similar function or origin
Are alpha beta axons myelinated? What is their conduction speed and diameter relatively speaking.
are myelinated, large diameter axons with pretty fast conduction velocity
Name 5 types of receptors used by the dorsal column and whether they are capsulated or not.
unencapsulated: merkels’s, hair receptors; encapsulated: meissner’s corpuscle, pacinian corpuscle and ruffini corpuscle
Name the depth and modality of meissner’s corpuscles
it is a surface receptor with rapid adaption and small receptive field, carrying info about light touch, texture low and low frequency vibes
Name the depth and modality of merkel’s cells
surface receptor with slow adaption and small receptive field, relays information on light touch and pressure
Name the depth and modality of pacinian corpuscles.
they are deep receptors with rapid adaption and large receptive field relaying info on deep pressure and high frequency vibes
Name the depth and modality of ruffini endings.
a deep receptor with slow adaption and large receptive field relaying info about deep pressure and stretch
Name the depth and modality of hair follicle receptors.
they are deep with rapid adaption and a small receptive field the relay information based on hair follicle movement
Joint receptors that run in the dorsal column include these types of receptors
type 1 golgi like (position and movement); type 2 ruffini (position and velocity) and type 3 (pressure)
Is two point discrimination greatests where meissners and merkels are concentrated or evenly spaced?
best where concentrated
Which portion of the dorsal column runs along the faciculus gracilis?
T7 and below axions run in the faciculus
What protion of the dorsal column runs int eh faciculus cuneatus?
T6 and above run in the cuneatus (more lateral)
Cutting the the dorsal column at any spinal level will cause loss of touch, vibration, conscious proprio below the lesion on the _______ side.
ipsilateral side (neuron axons come in from the DRG and ascend in the column on the same side up to the brain stem)
Fasciculus cuneatus axons synapse in the nucleus ________ and the fsciculus gracilis axons synapse in the nucleus ______
nucleus cuneatus and nucleus gracilis respectively
Nucleus fibers in the dorsal column cross the midline as _____ fibers and form the ascending group of axons called the _______
arcuate fibers; medial lemniscus
Medial lemniscus fibers synapse where in the thalamus?
ventral posteriolateral thalamic nucleus (VPL)
VPL axons continue on to what part of the brain?
the somatosensory cortex
What carries dorsal column sensory information from the head?
trigeminal nerve CN V
Where does the trigeminal nerve synapse in the thalamus?
ventral posterior medial thalamic nucleus (then continues on to the somatosensory cortex)
What is the basis of phantom limb sensation
sprouting of nearby axons into the denervated area of the cortex cause sensation input form other areas that gets mis-interpreted as sensation from missing limb
What is a rhomberg sign
if you sway while standing with your eyes closed that is a positive rhomberg sign which is connected to feedback from joints and vestibular system (if you sway with your eyes open, its most likely a cerebellar or vesicular problem)
What is a L’hermitte’s sign?
if you maximally bend your neck forward, a positive sign would be getting electric-like sensations in your lower extremities which can be due to ectopic firing of damaged nerves that are stretched.
What is agraphethesia?
inability to recognize a form drawn on the skin
What is asterognosia?
inability to recognize a familiar object simply by touch
Where are the cell bodies of the 1st and 2nd neuron in the dorsal column system located?
1st (DRG) 2nd (dorsal column nuclei- nucleus gracilis or cuneatus)…. 3rd neuron is in the thalamus that runs to the primary somatosensory cortex
