(3) Spinocerebellar pathways Flashcards
summary: posterior/dorsal column medial lemniscus pathway carries what type of sensory information (4)
proprioception
fine touch
pressure
vibration
summary: anterolateral/spinothalamic pathway carries what type of sensory information (5)
crude touch pressure pain temperature itch
what are the basis of these different sensory pathways?
dorsal column and spinothalamic
different types of sensory receptors in skin, joints and muscle
cutaneous receptors do what
mediate sensory information in (sensory) spinal cord pathways
types of cutaneous receptors (4 sensations)
vibration= Pacinian corpuscle
touch= Meissner corpuscle (fine touch), Merkel endings (fine touch), endings around hairs, free nerve endings
pressure= ruffini endings
pain/temp/itch= free nerve endings
2 touch receptors from hairy skin
1) receptors endings wrap around hairs
2) Merkel cell (in basal layer of epidermis)
when skin is deformed there is a change in which receptor
change in merkel cell receptor onto nerve cells, and transmit to spinal cord
where is merkel cell found, responsible for?
- hair and glabrous skin
- responsible for ability to perform fine tactile discriminations with fingertips (2 pt discrimination)
where are meissner corpuscle found
they are encapsulated endings in dermal papillae of hairless skin
- layer of Schwann cells within the capsule
where are Pacinian corpuscles found
subcutaneously over entire body and connective tissue sites
- rapidly adapting
where are ruffini endings found
in dermis and subcutaneously, and other connective tissue sites
- slow adapting
what sensory endings are found in glabrous skin?
fine touch: (M) meissner corpuscle, (Me) Merkel cell
vibration: (PC) Pacinian corpuscle
pressure: (R) ruffini ending
what is 2 point discrimination
minimum distance by which 2 stimuli can be separated and perceived as 2 stimuli
proprioceptors
another way sensory information is mediated in spinal cord pathways
proprioception
perception of the position of parts of the body
proprioceptors are derived from
vibration, touch and pressure receptors in skin and joints, and muscle spindles and Golgi Tendon organs at myotendinous junctions and joints
muscles are supplied with 2 important types of encapsulated receptors
- muscle spindle (unique to muscle)
- Golgi tendon organ (similar to ruffini ending- pressure)
what is the function of muscle spindles in skeletal muscle
relay sensory information of proprioceptors and DETECT MUSCLE LENGTH
- provide info about position of body in space
muscle spindles are…
long, thin, stretch receptors scattered throughout striated muscle in body
muscle spindles consist of…
intrafusal muscle fibers (inside the spindle)
- small muscle fiber with capsule surrounding middle 1/3 of fibers
- ends of intrafusal muscle fibers are attached to extrafusal fibers
(when muscle is stretched, intrafusal fibers also stretched)
golgi tendon organ tracks…
TENSION developed by tendon
how does a golgi tendon organ function
- large diameter sensory fibers enter capsule and branch into fine processes that are inserted among collagent bundles
- tension on capsule squeezes fine processes
- resulting distortion stimulates them
3 unconscious proprioception/sensory pathways carried by spinal cord to cerebellum via ….
posterior/dorsal spinocerebellar tract
anterior/ventral spinocerebllar tract
cuneocerebellar tract
what is the function of the cerebellum
integration center for motor control
9 parts to posterior/dorsal spinocerebellar tract
ascending, sensory, unconscious
1) proprioceptors (muscle spindles, Golgi tendon) in lower leg
2) primary sensory neuron in DRG
3) white matter of spinal cord
4) ascend in fasciculus gracilis (spinal cord)
5) synapse with dendrites of Clarke’s nucleus/nucleus dorsalis (T1-L2/L3)
6) ascend ipsilaterally in posterior spinocerebellar tract (PSCT)
7) caudal pons (lower)
8) inferior cerebellar peduncle
9) cerebellum
origin of posterior/dorsal spinocerebellar tract
clarke’s nucleus
aka nucleus dorsalis
body part –> posterior/dorsal spinocerebellar tract
trunk, lower extremity
remember fasciculus/nucleus gracilis
major inputs posterior/dorsal spinocerebellar tract
mechanoreceptors in muscles, joints and skin
midline crossing posterior/dorsal spinocerebellar tract
NONE
peduncle used to enter cerebellum posterior/dorsal spinocerebellar tract
inferior cerebellar peduncle
10 parts of anterior/ventral spinocerebellar tract
ascending, sensory, unconscious
1) proprioceptors (golgi tendon organs, cutaneous receptors) in lower body
2) primary sensory neuron in DRG
3) axons travel to grey matter of spinal cord
4) synapse with dendrites of spinal border cells (T12- L5)
5) axons of spinal border cells CROSS via anterior white commissure
6) ascend in anterior spinocerebellar tract (ASCT)
7) rostral pons
8) superior cerebellar peduncle
9) cerebellum (synapse)
10) CROSS beck in cerebellum
origin anterior/ventral spinocerebellar tract
spinal border cells
body part–> anterior/ventral spinocerebellar tract
trunk, lower extremity
major inputs anterior/ventral spinocerebellar tract
mechanoreceptors, movement related interneurons
midline crossing anterior/ventral spinocerebellar tract
- spinal cord
- cerebellum
peduncle used to enter cerebellum in anterior/ventral spinocerebellar tract
superior cerebellar peduncle
8 parts to cuneocerebellar tract
ascending, sensory, unconscious
1) proprioceptors (muscle spindles, golgi tendon organ) in upper body
2) primary sensory neuron in DRG
3) ascend in fasciculus cuneatus
4) synpase with dendrites of lateral cuneate nucleus (in lower medulla)
5) ascend in cuneocerebellar tract (CCT(
6) caudal pons (lower)
7) inferior cerebellar peduncle
8) cerebellum
origin cuneocerebellar tract
lateral cuneate nucleus (medulla)
body part –> cuneocerebellar tract
trunk, upper extremity
major inputs cuneocerebellar tract
mechanoreceptors in muscles, joints, skin
midline crossing cuneocerebellar tract
NONE
peduncle used to enter cerebellum in cuneocerebellar tract
inferior cerebellar peduncle
cerebellar peduncles are important for??
circuitry
3 cerebellar peduncles
SCP (superior)= predominant OUTPUT pathway
- anterior spinocerebellar tract
MCP (middle)= connect pons to cerebellum
ICP (inferior)= lower part of pons, predominant peduncle for info flowing INTO cerebellum
lesions to spinocerebellar tracts present as…
ipsilateral loss of muscle coordination
- unlikely damaged in isolation, lesions usually accompanied by injury to descending motor tracts
- cause muscle weakness/paralysis, usually masks loss of muscle coordination
if theres damage to spinocerebellar tracts, likely have damage to which descending pathway?
lateral corticospinal tract
spinocerebellar tract damage component of hemicord lesions
- vibration/pain loss RIGHT side lower body= damage to dorsal columns, loss unconscious proprioceptive info to cerebellum
- pain/temp loss LEFT side lower body= loss of spinothalamic/anterolateral pathway
- motor loss RIGHT side lower body= loss of corticospinal tract, or motor neurons in anterior horn
