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

Sensory and motor pathways Flashcards by HARRY RICHARDSON

2 main somatosensory pathways

Lateral spinothalamic tract

Dorsal columns tract

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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.

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cranial nerves sense

Vision
Taste
 Smell
 Hearing
 Balance
 Touch on face

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spinal nerves sense

pain 
touch 
pressure 
temp
proprioception 
vibration

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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

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is the thalamus the common relay station?

yes

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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

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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

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What does the lateral spinothalamic tract carry

pain, temp and course touch

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what does the dorsal columns tract carry

proprioception , vibration, pressure and fine touch

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where dose the LSTtract decussate

spinal level

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where does the DCTract decussate

medulla

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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

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Anterior spinal artery syndrome

Anterior 2/3 damage to spinal cord- sudden loss of supply AVN
Loss of pain sensation and temperature

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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)

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What cranial nerve carries somatosensory information from the head and the neck

trigeminal nerve - sends to thalamus via trigemini-thalamic tract

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Consequence of irritating the trigemini-thalamic tract

contralateral face pain

also trigeminal neuralgia - sneosry fibres irritated

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Where does the UMN go between

motor cortex and spinal cord

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Where does the LMN go between

spinal cord and the muscles

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Are cranial nerves UMN or LMN

LMN because the UMN synapses in the brianstem

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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

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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

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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