Neurology 2 Flashcards
Somatic sensory neurons in dorsal root ganglion - classifications.
-Touch receptors
-Pain receptors
-Proprioceptors
Explain the process of mechanosensory circuitry - touch sensation. –> i.e., the ascending pathway into spinal cord (vs the descending pathway out of spinal cord - which = motor)
-Touch info = detected by nerve endings in skin - these are afferent neurons - whose cell bodies are found in the dorsal root ganglia
–> so from skin…
-up in through dorsal root ganglia
-into dorsal root of spinal cord
-into dorsal horn of spinal cord
-Synapses in numerous ways:
–> often the focus is on the one going/rising from spinal cord up to medulla = clinically important -> so will synapse in dorsal column nuclei of medulla
-Then a secondary neurone’s axon move out of dorsal column nuclei in through medial lemniscus (of medulla)
-Then rises again to thalamus - where synapses in thalamus (VP nucleus)
-Tertiary neurone’s axon move out thalamus & synapses in primary somatosensory cortex (S1)
-Axon can bifurcate or are single axon
Describe the conscious proprioceptive circuitry - is same as ascending mechanosensory circuitry.
-Muscle tension info from muscles = detected by proprioceptors in subcutaneous tissue
-Afferents of proprioceptors…
-up in through dorsal root ganglia
-into dorsal root of spinal cord
-into dorsal horn of spinal cord
-Synapses in numerous ways:
–> often the focus is on the one going/rising from spinal cord up to medulla = clinically important -> so will synapse in dorsal column nuclei of medulla
-Then a secondary neurone’s axon move out of dorsal column nuclei in through medial lemniscus (of medulla)
-Then rises again to thalamus - where synapses in thalamus (VP nucleus)
-Tertiary neurone’s axon move out thalamus & synapses in primary somatosensory cortex (S1)
-Then motor neuron will pass back to spinal cord - to innervate the intrafusal muscle fibres (type Ia & type II) and golgi tendon organs
–> as these have opposing effects - i.e., when:
*Intrafusal fibres relax
*The GTOs contract (are under tension)
(-Axon can bifurcate or are single axon)
How to determine where lesions to mechanosensory circuitry - based upon clinical examination
Where info goes - what can’t they feel
–> because you will ask them what they can feel & move
Label.
Label the components of the ascending & descending tracts.
REMEMBER - the asc & desc tracts are on both sides of the spinal cord! - only shown on one side for simplicity!
What does somatosensation include?
General sensation: touch, pain, proprioception
