The Spinal Cord and Periphery Flashcards
what are the three columns of white matter?
posterior, lateral & anterior.
what does each column of white matter contain?
various bundles (tracts) of axons.
are ascending pathways sensory or motor?
sensory
are descending pathways sensory or motor?
motor
what are the three important tracts
Corticospinal/ pyramidal tract
Posterior/ dorsal column
Lateral spinothalamic tract
function of Corticospinal/ pyramidal tract
carries motor impulses from motor cortex to skeletal muscles
function of Posterior/ dorsal column
carries touch, tactile localisation, vibration sense, proprioception
function of Lateral spinothalamic tract
pain and temperature
where does the pathway start for CORTICOSPINAL/PYRAMIDAL TRACT
starts from the motor cortex (Area 4)
what are the characteristics of ascending spinal tracts pathways?
There are 3 neurons between peripheral receptor and cortex.
how does the posterior/dorsal column work?
1st order neuron ends by synapsing with the cell body of the 2nd neuron. This is situated in the lower part of the medulla.
2nd order neuron crosses over (decussates) in the medulla.
The third order neuron starts from the thalamus and axons pass through the IC and radiate to the post-central gyrus (Area 2,1,3)
where does the first order neuron enter in the lateral spinothalamic tract?
into the grey matter and ends at the same level.
why do the 2nd order neurons cross over in the lateral spinothalamic tract?
to reach the lateral column and is now called lateral spinothalamic tract
where does the 2nd order neuron end in the lateral spinothalamic tract?
thalamus and 3rd order passes through IC, radiation to reach post-central gyrus
what is a reflex?
involuntary stereotyped pattern of response brought about by a sensory stimulus.
action of the stretch reflex?
Tendon stretched
Intrafusal muscle fibres stimulated
Sensory neuron activated
Monosynaptic reflex arc
Polysynaptic reflex arc to inhibitory interneuron
Muscle contraction
5b.Reciprocal innervation
action of the flexor reflex
Pain stimulus
Sensory neuron activated
Polysynaptic reflex arc
Flexion and withdrawal from noxious stimulus
4b.Crossed extensor response to contralateral limb (only in weight bearing limbs)
why is the stretch reflex important?
controlling muscle tone and posture
why is the flexor reflex important
Flexor reflex helps protect the body from painful stimuli
what mediates reflexes?
lower motor neurones
If LMN is not affected in a UMN lesion that causes paralysis then what happens to reflexes?
Reflexes are exaggerated in UMN lesions!!
what do upper motor neurone do to muscle tone?
increases tone
what does lower motor neuron do to muscle tone?
causes flaccidity
what does a L UMN lesion at IC cause?
R sided paralysis
Hyper-reflexia
Increased tone
what does a L UMN lesion at upper cervical spinal cord cause?
L sided paralysis
Hyper-reflexia
Increased tone
what does a L LMN lesion cause?
L sided paralysis
Absent reflexes
Flaccid
what does a Lesion of the UMN above the decussation cause
contralateral spastic paralysis and hyperreflexia
what does a Lesion of the UMN below the decussation cause
ipsilateral spastic paralysis and hyperreflexia
what does a Lesion of the LMN cause
ipsilateral flaccid paralysis and arreflexia
what is motor neurone disease?
Group of diseases affecting the lower motor neuron in the ventral horn of spinal cord.
The neuron dies and as a result muscle supplied by it atrophies.
Progressive, incurable disease.
does all sensory information need to be sent to the brain for decisions to be made?
no, in instances where an immediate response is needed, the spinal cord can make these decisions
