Ascending Tracts Flashcards
What type of signals do ascending tracts carry? Which direction do they travel?
sensory signals up the spinal cord
What is the name of the first neuron? What does it do?
first order neurondetects a stimulus and transmits a signal to the spinal cord or brainstem
What is the name of the second neuron? What does it do?
second order neuroncontinues up to the thalamus
What is the name of the third neuron? What does it do?
third order neuroncarries the signal to the sensory region of the cerebral cortex
What are the axons of these neurons called?
the first, second, or third order neuron fibers
What prefix normally is with the tract? Whatroot follows it?
spinoa root that denotes the location of its fibers in the brain
What type of signals foes gracile fasciculus carry?
carries signals from the mid-thoracic and lower parts of the body (vibration, visceral pain, deep and discriminative touch, and proprioception)
What is the gracile fasciculus joined with? By what?
the cuneate fasciculusT6
What does gracile fasciculus consist of?
first order neuron fibers that travel up the spinal cord
Where does the gracile fasciculus end?
the gracile nucleus in the medulla oblongota
What is proprioception?
non-visual sense of the position and movements of the body
What is discriminative touch?
touch whose location one can precisely identify
What type of signal does cuneate fasciculus carry?
sensory signals originating from the upper limbs and chest
What joins the cuneate fasciculus and where?
the gracile fasciculusT6
Where does the cuneate fasciculus end?
the cuneate nucleus in the medulla oblongata
In the medulla, what happens between the gracile fasciculus and the cuneate fasciculus?
decussate and form the medial leminscus
What is the medial leminscus?
a tract of nerve fibers that leads the rest of the way up the brainstem to the thalamus
Where do 3rd order fibers go in the cuneate fasciculus?
they go from the thalamus to the cerebral cortex
What happens to the signal because of the decussation of the gracile fasciculus and the cuneate fasciculus?
the signals go the contralateral cerebral hemisphere of the origin
What type of signal does the spinothalamic tract carry?
pain, temp, pressure, tickle, itch, and light/crude touch
Where do the first order neurons end in the spinothalamic tract?
the posterior horn of the spinal cord near the point of entry
What happens after the first order neuron ends in the spinothalamic tract?
the 2nd order neuron synapses, which decussate and form the contralateral ascending spinothalamic tract until the thalamus
What does the third order neuron do in the spinothalamic tract?
continue from thalamus to the cerebral cortex
Why do the sensory signals arrive in the cerebral hemisphere contralateral to their origin?
because of decussation
What type of signals does the spinoreticular tract carry?
pain resulting in tissue injury
Where do the 1st order neurons enter in the spinoreticular tract?
the posterior horn
What happens with the 2nd order neuron in the spinoreticular tract?
the 1st order neuron immediately synapse with the 2nd order neurons after they enter the posterior horn and they decussate to the opposite anterolateral system, ascend cord, and end in the reticular formation
What is the reticular formation?
a loosely organized core of gray matter
What happens with the 3rd order neurons in the spinoreticular tract?
continue from pons to the thalamus
What do the 4th order neurons do in the spinoreticular tract?
complete the path from the thalamus to the cerebral cortex
What tracts form the anterolateral system?
the spinothalamic and the spinoreticular tracts
What signals do the posterior and anterior spinocerebellar carry?
proprioceptive signals from limbs and trunk to the cerebellum
Where do the 1st order neurons originate in the posterior and anterior spinocerebellar tracts? Where do they end?
muscles and tendons the posterior horn of the spinal cord
What do 2nd order neurons do in the posterior and anterior spinocerebellar tracts?
send their fibers up the spinocerebellar tracts and end in the cerebellum
What do the fibers do in the posterior and anterior spinocerebellar tracts?
the posterior fibers travel up the ipsilateral side of the spinal cord, and the anterior fibers cross and travel up the contralateral side, but cross back into the brainstem
What do the posterior and anterior spinocerebellar tracts provide the cerebellum?
feedback needed to coordinate muscle action