Chapter 24: Medulla Flashcards
The obex is the part of the fourth ventricle that narrows down to become the _____.
- Central canal
Neurons on the surface of the obex are exposed to the cerebrospinal fluid in the _____.
- 4th ventricle
Neurons on the surface of the obex respond to toxins in the _____ in the 4th ventricle.
- Cerebrospinal fluid
The group of neurons on the _____ that responds to toxins in the cerebrospinal fluid is called the area postrema.
- Walls of the obex
Neurons in the _____ detect toxins in the cerebrospinal fluid.
- Area postrema
Neurons in the area postrema project to the preganglionic parasympathetic neurons in the _____ of the _____ that control the muscles of the stomach.
- Dorsal motor nucleus
- Vagus nerve
When they detect toxins in the cerebrospinal fluid neurons in the area postrema initiate vomiting through their projections to the _____ of the _____.
- Dorsal motor nucleus
- Vagus nerve
The _____ is sometimes called the vomiting center.
- Area postrema
The lateral and anterior spinothalamic tracts carry _____ sensations through the lateral region of the medulla without synapsing.
- Protopathic
Axons in the spinothalamic tracts synapse only in the _____.
- Thalamus
The axons in the _____ and _____ synapse on second order neurons in the nucleus gracilis and nucleus cuneatus in the lower medulla.
- Fasciculus gracilis
- Fasciculus cuneatus
Just as the fasciculus cuneatus is _____ to the fasciculus gracilis, the nucleus cuneatus is _____ to the nucleus gracilis.
- Lateral
- Lateral
The axons of the _____ neurons in the nucleus gracilis run ventrad in wide arcs as internal arcuate fibers.
- Secondary sensory
Internal arcuate fibers from each _____ cross in the midline just dorsal to the pyramids and turn rostrad to form the ventral half of the contralateral medial lemniscus.
- Nucleus gracilis
The axons of the neurons in the left nucleus gracilis form the ventral half of the _____ after they cross the midline.
- Right medial lemniscus
The axons of the neurons in the nucleus gracilis are _____ until they cross the midline.
- Internal arcuate fibers
Internal arcuate fibers make a right angle turn rostrad toward the thalamus when they enter the _____.
- Medial lemniscus
The ventral half of the left medial lemniscus carries _____ information from the _____ extremity to the thalamus.
- Epicritic
- Right lower
Axons of _____ neurons in the nucleus cuneatus run ventrad in wide arcs, cross the midline, and turn rostrad to form the dorsal half of the medial lemniscus.
- Secondary sensory
Axons in the ventral half of the medial lemniscus come from neurons in the _____ and carry epicritic information from the contralateral _____.
- Nucleus gracilis
- Lower extremity
Axons in the dorsal half of the medial lemniscus come from neurons in the _____ and carry epicritic information from the contralateral _____.
- Nucleus cuneatus
- Upper extremity
When axons from the nucleus cuneatus cross the midline they are _____ to axons from the nucleus gracilis.
- Dorsal
Internal arcuate fibers from the nucleus cuneatus must _____ internal arcuate fibers from the nucleus gracilis before crossing the _____.
- Cross
- Midline
In the medulla each medial lemniscus is a vertical ribbon of white matter on the _____ side of a pyramid.
- Dorsal
Tracts are _____; nuclei are _____; but myelinated tracts usually stain black with silver, iron, or osmium, and nuclei usually do not take these metallic stains.
- White matter
- Gray matter
A decussation is a crossing of right and left tracts en route from one level to another. Thus, the crossing of internal arcuate fibers to form the medial lemniscus is the _____ of the medial lemniscus.
- Decussation