Ascending Sensory pathways 1 Flashcards
What are somaesthetic pathways?
perception of bodily sense - pain, temperature, touch and position
What is a spinothalamic pathway?
responds to pain, temp and some touch
What is a dorsal column pathway?
responds to fine, precise touch, vibration and position.
What is proprioception?
position awareness
What two things does the somaesthetic pathway involve?
- body
- perception
From where are different types of modalities of information carried to the brain in the somaesthetic pathway? (4)
- Skin
- Mucus membranes
- Joints
- Muscles
How is each modality detected in somaesthetic pathway?
specific sensory receptors/ specialised nerve endings
What 2 groups does somaesthetic modalities fall into?
- Essential for survival - Spinothalamic pathway
2. That increase detail - Dorsal column pathway
What modalities are essential to survival?
pain, temperature, some touch and pressure
What types of fibres are modalities that are essential for survival/spinothalamic pathway carried?
thin, small diameter, poorly myelinated or unmyelinated fibres
What is conduction like in modalities that are essential for survival/ spinothalamic pathway?
slow
What modalities increase detail/ dorsal column pathway?
2 point discrimination and vibration, proprioception
What type of fibres carry modalities that increase detail/ dorsal column pathway?
large diameter, heavily myelinated
What is conduction like in modalities that increase detail/ dorsal column pathway?
fast
Which side of the central gyrus of the brain is information from the right side sensed?
left central gyrus
How many neurones are involved in the general sensory pathway?
3 neurone chain
What is in the thalamus?
VPL - ventral posteral nucleus/ Posterior ventral nucleus
What is the 1st order neurone?
- pseudo unipolar cell body
- in sensory ganglion
- DRG
- centre is ipsilateral
What is the 2nd order neurone?
- axon crosses midline
- ascends to ventral posterior nucleus in thalamus
What is the 3rd order neurone?
- axon projects to post central gyrus - parietal lobe
Where do the cell bodies of the 1st order neurons reside in?
dorsal root ganglia (PNS)
Where do the cell bodies of 2nd order neurons reside in?
CNS ipsilateral gray matter
Where do axons of the 2nd order neurone cross and what do they ascend to?
crosses the midline
ascend to thalamus
Where do the cell bodies of 3rd neurone reside in and where do the axons project to?
thalamus
axons project to somatosensory cortex
What pathways are somatotopic?
sensory pathways
How can synaptic transmission from 1st, 2nd and 3rd neurone be modified?
- neurones not simple relay
- modified by other inputs - descending pathways or convergence/divergence
What is the medial surface of the brain’s hemisphere supplied by and what can damage result in?
Anterior cerebral artery
damage to certain features on somatotopic map on post-central gyrus
What is a converging circuit?
several presynaptic neurons that stimulate a single postsynaptic neuron
What is a diverging circuit?
a single presynaptic neurone stimulating several post-synaptic neurone
What are the two major types of fibre tracts?
ascending fibre tracts
descending fibre tracts
Is the dorsal column ipsilateral or contralateral?
ipsilateral
What information does the dorsal column interpret?
joint position sense and vibration sense
When does the dorsal column cross the midline?
- won’t cross immediately
- crosses over at the medulla
Is the spinothalamic pathway ipsilateral or contralateral?
contralateral
When does the spinothalmic pathway cross the midline?
immediately
In spinothalamic pathway where does the synapse cross over the midline?
at a very specific place
In the spinothalamic pathway where is the 1st neurone cell body?
In dorsal root ganglia
How and where does the 1st neurone contact the 2nd neurone in the spinothalmic pathway?
Fibres ascend 1-2 segments then contacts in dorsal grey horn
Where does the second neurone cross the midline in the spinothalamic pathway?
in ventral white commissure
In the spinothalamic tract where does the 2nd neurone fibres ascend to?
thalamus
Where does the spinothalamic tract change it’s name?
At the levels of the brainstem
Spinal lemiscus
Where is the 1st neurone cell body in the dorsal column pathway?
Dorsal root ganglion
Where do the 2nd neurone cell body ascend?
In one of the ipsilateral dorsal column
Where does the gracile fascicle run?
whole length of the spinal cord
Where does the cuneate fascicle run?
above T6 only
In the dorsal surface on the brain stem what receives ascending sensory tracts from the spinal cord and what are these a part of?
medulla
- the dorsal column pathway
What types of sensations does the dorsal column pathway pick up?
discriminatory touch
position sense
Where does the 1st neurone ascend to synapse with the 2nd neuron in the dorsal column pathway?
The cuneate or gracile nucleus
Where does the 2nd neurone cross the midline in the dorsal column pathway?
internal arcuate fibres
Where to the fibres in the dorsal column pathway ascend in and to?
Medial lemniscus to thalamus
What is somatotopically organised?
medial leminiscus - collection of fibres that pass through the brainstem
Which hemisphere do both pathways project to?
to the opposite hemisphere
Where do fibres carrying pain an temperature travel in the cord? (spinothalamic pathway)
Contralaterally
Where do fibres carrying pain and temperature (spinothalamic pathway) cross?
at the level of the spinal cord entry
Where do fibres carrying discriminative touch and proprioception travel?
ipsilateral in the cord
How many neurons does the dorsal column and spinothalamic pathway use?
3 neurons
Examples of different modalities
- temp
- pain
- pressure
