Flashcards in Ascending Sensory Pathways Deck (66)
What does somatosensory mean?
Relating to a sensation that can occur anywhere in the body (e.g. pain), rather than localised at one organ (e.g. sight).
-I.e. senses other than 5 senses
What are the 2 groups of somaesthetic modalities?
-Modalities that are essential to survive
-Modalities that increase detail
What sort of modalities are essential to survive?
Pain, temperature, some touch & pressure.
What fibres carry modalities that are essential for survival?
Thin, unmyelinated fibres.
-relatively slow conduction
What sort of modalities increase detail?
-Discriminative touch (2-point and vibration)
What fibres carry modalities that increase detail?
Large, very myelinated fibres.
What is proprioception?
The body's ability to sense movements in joints and joint positions.
What is the general mechanism of proprioception?
Golgi tendons/muscle spindles sense degree of tension/stretch in muscles >> CNS.
What is a pseudounipolar neuron?
Sensory neuron in PNS with a single stalk that splits into 2 processes.
(1 >> periphery, 1 >> spinal cord)
What is a nucleus?
Collection of cell bodies in the CNS.
What is a ganglion?
Collection of cell bodies in the PNS.
-e.g. dorsal root ganglion
How many neurons do general sensory pathways consist of?
Where do the cell bodies of sensory 1* neurons in the PNS reside?
Dorsal root ganglion.
Where do the cell bodies of sensory 1* neurons in the CNS reside?
Cranial nerve nuclei.
Where do 1* neurons synapse?
In the CNS (spinal cord/brain) on the same side as they entered the cord (ipsilateral).
Which neuron crosses the midline?
Where do 2* neuron cell bodies reside?
In ipsilateral grey matter in the CNS.
What happens to 2* neurons once they cross the midline?
They ascend to the thalamus.
-VPL nucleus (from body)
-VPM nucleus (from face)
Where do 3* cell bodies reside?
In the thalamus.
Where do the 3* axons project?
3* axons project to the somatosensory area of the post-central gyrus.
-Contralateral 1* neuron origin
What does somatotopic mean?
-area of body >> specific point on post-central gyrus
Are general sensory pathway somatotopic?
Is synaptic transmission from 1*, 2* and 3* neurons a simple relay? Give 3 examples.
No, can be modified by other inputs.
-e.g. diverging circuit, converging circuit, descending pathways
What is a diverging circuit?
One pre-synaptic neuron stimulates a response in multiple post-synaptic neurons. Increases the amount of info to CNS, and allows brain signals to travel to various locations of the body.
What is a converging circuit?
Several pre-synaptic neurons stimulate one post-synaptic neuron. Focuses information.
What is the general pathway of sensory information to the face?
Sensory stimulus >> 3 neurons >> thalamus (VPL/VPM) >> post-central gyrus.
Which arteries in the medial hemisphere supplied by?
Anterior cerebral arteries.
What are the main ascending and descending fibre tracts? (4)
What are the major ascending tracts? (2)
-Dorsal column pathway