Spinal tracts Flashcards
Name two main parts of the spine
-cervical enlargement
-lumbar enlargement
-required to handle the extra info travelling in 2 directions - sensory and motor
Which direction are sensory pathways?
ascending through spinal cord through brain stem into the brain
Which direction are motor pathways?
descending pathways from the brain to skeletal muscles
What is the role of sensory pathways?
carry info from sensory receptors to the brain
conscious- reach cerebral cortex - goes to postcentral gyrus
unconscious- does not reach cerebral cortex goes to cerebellum
What are kinaesthetic receptors?
position and movement of muscle joints
Describe the generic sensory pathway
1- first order neuron- sensory cell body in DRG
2- second order neuron- cell body in dorsal horn or brain stem (axon crosses central line to contralateral side )
3-third order neuron - cell body in thalamus ( thalamus is like the distribution centre )
What is the sensory homunculus?
-somatotopy- representation of sensory info on cortex
the general address is somatosensory cortex post- central gyrus parietal lobe
Describe the spinothalemic pathway/ anterolateral system
-ventral spinothalamic- crude touch
-lateral spinothalamic - pain/temp
-direct pathway - ending up with sensory info being carried to the sensory cortex
Describe the indirect spinothalamic pathway
synapses in areas such as:
-reticular formation
-hypothalamus
-limbic system
also the periaqueductal grey - descending pain modulation
Describe the dorsal column pathway
dorsal white column - column of fibres travelling up posterior part of the spinal cord
-1st order neuron- cell body of DRG
-2nd order neuron in the medulla
-3rd order neuron in cell body in the thalamus
decussation of 2nd order neuron medulla oblongata
What does decussation mean?
the crossing as of nerve fibres especially in the form of an x
Name two components of the dorsal white column
-fasciculus cuneatus- sensory control of upper limb
-fasciculus graclis- sensory contol of lower limb
travel up from the ipsilateral side - 2 of each
What happens when the dorsal column is damaged?
loss of sense of touch, proprioception, vibration on the ipsilateral side
-sensory ataxia
-patient staggers, can’t perceive position or movement of legs
-visual clues help movement
Describe the spinocerebellar pathway
-carries unconcious proprioception signals
-essentially no direct route to motor cortex
Name some effects of spinocerebellar tract damage
-cerebellar ataxia
-clumsy movement
-incoordination of limbs - intention tremor
-wide based reeling gate/ ataxia
-alcoholic intoxication produces similar effects
acute use - enhances GABA inhibitory and suppresses glutamate excitatory. There is a net effect- lack of coordination
What are the main neurons in the motor pathway?
-upper motor neuron
-lower motor neuron- in the ventral grey matter
-often linked with interneurons at the spinal level
Name some generalities of the motor pathway
Neuromuscular junction
skeletal muscle cell
What are the two main types of motor pathway?
pyramidal- direct, conscious
extrapyramidal - indirect, mostly subconscious,UMN in brain stem nuclei
Describe the pyramidal/ direct system
UMN- cortical cell body
often an interneuron
LMN- ventral horn/ ventral root
how many fibres decussate?
-corticospinal
-corticobulbar
90% decussate after pyramids
10% decussate at segmental level
What is the corticobulbar?
control of upper neck and face
LMN spinal cord - ventral spinal root
LMN brain stem- cranial nerves
What is the corticospinal?
carry sensory nerve signals to LMN in spinal cord
Describe extrapyramidal pathways/ unconcious
-UMN in brainstem
-modifies movement- modulatory actions on LMN
-rubrospinal
-tectospinal
-vestibulospinal
-recticulospinal
Describe the rubrospinal tract
-neuronal cell body in the red nucleus
-decussation in the brain stem to the contralateral side
-mainly upper limb- fine motor coordination
-flexors being activated, extensors being inhibited
Describe the tectospinal tract
-decussates in midbrain through pons to cervical spine
-controlling neck/ eye muscles reflexively
-head eye coordination
-visual/auditory feedback
Describe the vestibulospinal tract
UMN in pons associated with vestibular nuclei which receive sensory info on balance, gravity from vestibular apparatus
-ipsilateral projection down to cervical spine to control UMN
-ipsilateral projections down to lumber spine to control things such as balance
Describe the reticulospinal tract
-motor function
-autonomic functions such as CO, respiratory function
-pain modulation
-filtering system controlling posture and locomotor neurons
Free nerve ending location and modality? (unencapsulated)
L- widespread especially in epithelia and connective tissues
M-pain,heat,cold
tactile disk location and modality? (unencapsulated)
L-stratum basale of epidermis
M- merkel, light touch, texture, edges, shapes
hair receptor location and modality? (unencapsulated)
L-around hair follicle
M-hair movement
tactile corpuscles location and modality? (encapsulated)
L-dermal papillae of fingertips, palms, eyelids, lips, tongue
M-light touch, texture - meissners
Krause end bulbs location and modality? (encapsulated)
L-mucous membranes
M-similar to tactile corpuscles
lamellated corpuscles location and modality? (encapsulated)
L-Dermis, joint capsules, some viscera
M-deep pressure, stretch, tickle, vibration
Rufflini corpuscles location and modality?
L-dermis, subcutaneous tissue, joint capsules
M-heavy touch, pressure, stretching of skin, joint movement
Muscle spindles location and modality?
L-skeletal muscle near tendons
M-muscle stretch, proprioreception
golgi tendon organs location and modality?
L- tendons
M-tension on tendons, propioreception
