King Ch 8, Pt II - Pain Flashcards
What type of fibers transmit superficial pain sensations?
Thinly myelinated A-III (A-delta) fibers
These fibers have a diameter of 2–6 µm.
Through what pathway are superficial pain sensations conducted to the brain?
Through the spinothalamic tract
This pathway is specific for superficial pain.
What type of fibers are responsible for transmitting deep pain?
Unmyelinated C fibers
These fibers have a diameter of about 0.3–1.3 µm.
Which pathways carry deep pain sensations to the cerebral cortex?
Ascending reticular formation and spinothalamic tract
These pathways are less specific than those for superficial pain.
What tract transmits temperature sensation?
The spinaothalamic tract
Some touch fibers also travel in the ventral part of this tract.
Where is the cell location of neuron 1 in the spinothalamic tract?
Dorsal root ganglion
In the head, it is in an equivalent cranial nerve ganglion.
What occurs when the axon of neuron 1 enters the dorsal horn?
It gives off short branches making synapses and connects with interconnecting neurons
Some branches synapse with the reticular formation.
What is the location of neuron 2 in the spinal cord?
Dorsal horn
This neuron decussates and ascends in the spinothalamic tract.
What happens to the axon of neuron 2 at the level of the pons?
It blends with the medial lemniscus
This arrangement allows pathways of superficial pain and temperature to share the medial lemniscus.
What is the anatomical arrangement of the spinothalamic tract in humans?
Second neuron decussates and assembles somatotopically
Sacral fibers are positioned laterally and cervical fibers medially.
How does the spinothalamic pathway in domestic mammals differ from that in humans?
It may be more bilateral, diffuse, and multisynaptic
This difference complicates the classification of the pathway.
From where does the spinocervical tract arise, and where does it project to?
It arises from cutaneous receptors and joins the medial lemniscus
This tract is involved in touch, pressure, and some superficial pain sensations.
Where does neuron 3 of the spinocervical tract project?
To the ventral group of thalamic nuclei
The axon then decussates and synapses with neuron 4.
What distinguishes the modalities transmitted by the spinocervical tract in cats from those in humans?
The spinocervical tract is small or absent in humans
There may be an inverse relationship between the two tracts’ development.
