C: Ascending Sensory Pathways 1 Flashcards
What kind of modalities are carried in the spinothalamic pathway? 4
Modalities that are essential to survival:
1) Pain
2) Temperature
3) Some touch
4) Pressure
Modalities carried in the spinothalamic pathway are carried via neurons with what characteristics? How fast is conduction?
Thin, poorly myelinated or unmyelinated fibres
Conduction is slow
What kind of modalities are carried in the dorsal column pathway? 2
Modalities that increase detail:
1) Discriminative touch: 2-point discrimination and vibration
2) Proprioception
Modalities carried in the dorsal column pathway are carried via neurons with what characteristics, how fast is conduction?
Large diameter, heavily myelinated fibres
Fast conduction
General sensory pathways involve how many neurons?
3
A primary, secondary and tertiary
Where is the cell body of the primary neuron in a general sensory pathway located?
Ipsilateral dorsal root ganglion - outside the CNS
On which side does a primary neuron enter the CNS?
Same side as the receptor
Which neuron in a general sensory pathway crosses the midline?
Axon of the secondary neuron
In a general sensory pathway where does the cell body of a secondary neuron reside?
Ipsilateral grey matter of the CNS
In a general sensory pathway cell bodies of the tertiary neuron reside where?
In the contralateral thalamus
Axons of the tertiary neurons in a general sensory pathway project to where?
The somato-sensory cortex
Is synaptic transmission in a general sensory pathway a simple relay?
No, it can be modified by other inputs such as descending pathways
What 2 kinds of circuits can exist in the relaying of sensory information?
1) Diverging circuit - emphasises input
2) Converging circuit - diminishes input
In a spinothalamic pathway where does the axon of the secondary neuron cross the midline?
At the level that it enters the spinal cord - crosses anterior to the canal via the ventral white commissure
How does the axon of a secondary axon in the spinothalamic pathway ascend the spinal cord?
In the spinothalamic tract
Where do the primary and secondary neurons in a spinothalamic pathway synapse?
In the ipsilateral dorsal grey horn at the level of entry to the spinal cord
What is meant by the statement that the spinothalamic tract is somatotypically organised?
Input from a specific sensory receptor will go to a specific region in the spinothalamic tract
What name is given to the spinothalamic tract once it enters the brainstem?
The spinal/lateral lemniscus
Where do primary and secondary neurons synapse in the dorsal column pathway?
In the cuneate and gracile tubercles
Cuneate fascicle carries sensory info from approximately what level?
Above T6
Gracile fascicle carries sensory info from approximately what level?
Below T6
Where are the cell bodies of secondary neurons in the dorsal column pathway located?
In the gracile and cuneate nuclei (within the tubercles)
How do the axons of primary neurons ascend the spinal cord in the dorsal column pathway?
In the ipsilateral cuneate or gracile fascicle
Where are the cell bodies of tertiary neurons located in the dorsal column pathway?
Contralateral thalami
