Sensory and motor pathways Flashcards
2 main somatosensory pathways
Lateral spinothalamic tract
Dorsal columns tract
what does somatosensory mean
a sensation that can occur anywhere in the body
( pressure, pain and temp) in contrast to one localised at a sense organ.
cranial nerves sense
Vision Taste Smell Hearing Balance Touch on face
spinal nerves sense
pain touch pressure temp proprioception vibration
How main neurones do sensory neurones involve ?
3
1st order - soma in dorsal root ganglion
2nd- soma in spinal cord
3rd - soma in the thalamus
is the thalamus the common relay station?
yes
Lateral spinothalmic tract all 3 neurones
- 1st order neurone enters in dorsal root with soma in dorsal root ganglion. Synapses here 2nd order – ascends in lateral spinothalamic tract on opposite side – soma in spinal cord - 3rd order – soma in the thalamus – takes information to the cortex
Dorsal columns tract
soma in the DRG – enters the DC on the ipsilateral side
- Synapses and crosses in the medulla – 2nd order neurone with soma in the medulla
- 3rd order neurone synapses and has soma in the thalamus, sending signals to the cortex
What does the lateral spinothalamic tract carry
pain, temp and course touch
what does the dorsal columns tract carry
proprioception , vibration, pressure and fine touch
where dose the LSTtract decussate
spinal level
where does the DCTract decussate
medulla
What is Brown sequard syndrome
A lesion in the spinal cord which results in weakness or paralysis on one side of the body and loss of sensation on the other. Due to STtract and corticospinal tract injuries - unilateral
Anterior spinal artery syndrome
Anterior 2/3 damage to spinal cord- sudden loss of supply AVN
Loss of pain sensation and temperature
Syringomyelia
Fluid filled cyst within the spinal cord- central
spinothalamic tract affected first
Pain/temp loss bilaterally
( 2nd order neurone is affected as they cross the spinal cord)
What cranial nerve carries somatosensory information from the head and the neck
trigeminal nerve - sends to thalamus via trigemini-thalamic tract
Consequence of irritating the trigemini-thalamic tract
contralateral face pain
also trigeminal neuralgia - sneosry fibres irritated
Where does the UMN go between
motor cortex and spinal cord
Where does the LMN go between
spinal cord and the muscles
Are cranial nerves UMN or LMN
LMN because the UMN synapses in the brianstem
What and where is the motor cortex
region of the cerebral cortex involved in planning and control and execution of voluntary muscles.
zoned by blood supply. Blockage of ones of these arteries will affect relevant motor distrutions
What does the anterior cerebral artery supply
medial part which is the leg and waist part of the motor cortex
if drooping is seen then it is a stroke until proven otherwise
what does the medial cerebral artery supply
supplies the hand and face, if drooping is seen then it is a stroke until proven otherwise
How far does the spinal column go down to
Spinal column goes down to Coccyx 1
Where does the spinal cord finish
spinal cord finishes at L1-2
Lateral cortico spinal tract pathway
What percentage of motor movement does it control
UMN starts in motor cortex and crosses in the medulla(pyramids)
synapses with LMN in grey matter of anterior horn on contralateral side
- 85% of movement
- If lost, there is a greater affect
anterior corticospinal tract
starts in the cortex and decussates at exit level in the spinal cord
motor nerve moves down passed the thalamus and enters the anterior corticospinal tract
- Fine movements, not a big deal to lose
Whee does the LCST decussate
medulla
Where does the ACST decussate
exit level in spinal cord
what area does the ACST supply
neck and upper limbs and upper limbs
What is a motor unit
a motor neurone and all the muscle fibres it innervates - all or nothing manner
function of muscle spindles
Muscle spindles allow for control – special sensory organ in muscles detecting when the muscle fibre stretches
- When the opposite muscle is stretched it contracts to control the movement
- When the tendon is hit the muscle contracts to control the stretch – lower motor neurone pathology when it is tapped and doesn’t move enough
- When the tendon hit causes exaggerated movement – upper motor neurone could be affecte
What is clonus
involuntary muscle contractions
A 95 year old presents with a reduced conscious level and weakness. CT scan showed an acute bleed from the middle cerebral artery.
Which of the following features would be present on examination?
Presence of clonus, upgoing plantar reflexes, hypertonia, hyperreflexia
If a person has increased muscle spasticity(contracted) and tone, increased clonus and upping bainski reflex
UMN
if a person has decreased muscle tone so relaxed and flaccid and decreased clonus and downgoing reflexes
LMN
C4 injury
paralysis below neck , quadriplegia
C6 injury
partial paralysis of arms , hand and lower body
T6 injury
below the chest paralysis
L1 injury
below the waist paralysis
What is Spondylosis
narrowing of the c5 nerve root – common in elderly, can cause problems
What is Myositis
autoimmune attack of muscle – measured by listening to muscle
causes weakness and tiredness
hypertonia
too much muscle tone so that arms or legs, for example, are stiff and difficult to move.
hyperreflexia
overactive or overresponsive reflexes
how does the motor pathways split control in terms of percentage between the two major tracts
Anterior corticospinal – 15% ish of motor control
- Lateral corticospinal – 85% ish of motor control
the lateral corticospinal tract decussates high in the pyramids where does the anterior CST decussate
low in the spinal cord
the ACST supplies the neck and upper limbs where does the LCST supply
all spinal levels
The lateral CST does most motor functions what does the Anterior CST do
fine movements such as and especially the hands
what neurone does a stretch reflex use
interneurone
the efferent impulses which cause contraction of the stretched muscle that resits the stretch also do what
inhibit contraction of the antagonistic muscle
A stretch reflex is also called
rapid monosynaptic reflex
do nociceptors have bare nerve endings
yes
what are the 2 types of pain conduction
Fast response
Slow response
Fast response to pain uses what fibres
Adelta fibres are large and myelinated up to 10m/sec - sharp stabbing pain
slow response to pain uses what fibres
Slow response - Cfibres small and unmyelinated 1.2m/sec - aching, burning pain
are local anaesthetics proton acceptors
yes they are bases
