Quiz 8: Sidman (Ch 44)

Question 1

A useful way to study the brainstem is via cross sections. You saw many cross sections of the brainstem in the preceding chapter. Each level of the brainstem, the medulla, pons, and midbrain, has one or more “representative” cross sections. In each representative cross section, intrinsic structures can be identified. One representative cross section for each level appears below. Based on your knowledge of the external anatomy of the brainstem, label each of the three levels.

Answer 1

Left: Pons
Middle: Midbrain
Right: Medulla

Question 2

The medulla is often represented with several cross sections from top to bottom, a _____al medulla section, a middle sections and a _____al section. Based on your understanding that the _____ medulla has the most in common with the spinal cord and the rostral medulla has the least in common, label each of the three sections below.

Answer 2

rostral; caudal; caudal

Left: Rostral medulla on top right
Middle: Caudal medulla on bottom middle
Right: Mid-medulla on top middle

Question 3

Cross sections through the medulla are easy to identify. The caudal medulla exhibits large pyramids (descending or _____ fibers) on its anterior aspect, while still possessing a CSF-filled _____ canal, as seen in the spinal cord. Label these two structures on the diagram.

Answer 3

motor; central
Central canals from middle circle
Pyramids on bottom middle

Question 4

In the middle of the medulla, the central canal expands and moves _____ to form the 4th ventricle, and a large midline fiber bundle, the medial lemniscus, becomes evident. The medial lemniscus is made of crossed secondary fibers carrying fine touch, conscious proprioception, and vibratory senses from the _____lateral side of the body. These modalities were carried in the _____ columns of the spinal cord. Label the 4th ventricle and medial lemnisci on the diagram.

Answer 4

Posteriorly; contralateral; posterior

4th ventricle on top middle white spot
Medial lemnisci: arrows to both middle shaded areas

Question 5

The _____ medulla also exhibits the 4th ventricle and medial lemniscus; in addition, a prominent fiber bundle connecting it to the cerebellum appears on the lateral aspects- the inferior cerebellum peduncle. Label the 4th ventricle, medial lemniscus, and inferior cerebellum peduncle on the diagram.

Answer 5

Rostral

4th ventricle: Top middle
Medial lemniscus: Shaded middle
Inferior cerebellar peduncle (Light gray, Right shaded)

Question 6

The _____, the middle division of the brainstem, has a unique expansion of its tegmentum (anterior aspect)-the base. The base of the pons is made primarily of many transversally oriented fibers. Label the base and tegmentum of the pons on the following diagram.

Answer 6

pons

Tegmentum (top to middle)
Base (middle to bottom)

Question 7

The most striking feature of the midbrain is the presence of two very large fiber masses on the _____ior aspect-the peduncles, which carry a host of ascending and descending fibers. The 4th ventricle has shrunk in size to form a CSF-filled tube, the cerebral aqueduct. Label the peduncles and the cerebral aqueduct on the diagram.

Answer 7

anterior

Cerebral aqueduct (Top middle circle)
Peduncles (left and right of bottom)

Question 8

Although not necessarily exclusive to a section, the relatively unique characteristics of each section make identification of regions of the brain stem simple; in other words, certain structures are most prominent or first appear in a particular region and therefore serve as useful landmarks. For each structure listed below, identify whether it is a characteristic of the midbrain, pons, or medulla.

Peduncles:
Medial longitudinal fasciculus:
Inferior cerebellar peduncles:
Base:
Pyramids:
Cerebral aqueduct:

Answer 8

midbrain; medulla; medulla; pons; medulla; midbrain

Question 9

Extending the length of the brainstem, which includes the _____, _____, and _____ from superior to inferior, is the reticular formation. The _____ _____ may be conceptualized as the longitudinal core of the brainstem surrounded by tracts and nuclei in much the same way that a hot dog is surrounded by a bun.

Answer 9

midbrain; pons; medulla; reticular formation

Question 10

The _____ _____ is composed of an extensive and poorly organized network of cells and fibers, which given its position in the center of the _____stem, makes it able to receive and project to a huge number of ascending (_____) and descending (_____) tracts and nearby nuclei. Its position allows it to influence such things as consciousness, sleep, musculoskeletal reflexes, and the endocrine and the autonomic nervous systems.

Answer 10

reticular formation; brainstem; sensory; motor

Question 11

Surrounding the reticular formation are the _____ nerve nuclei and the central pathways of their fibers as well as an extensive network of fibers “passing through” the brainstem towards more superior and inferior targets. Encircle the location of the reticular formation on the following diagrams.

Answer 11

cranial

Middle part of three diagrams

Question 12

Within the _____, the caudal-most part of the brainstem, many characteristics of the _____ cord are still evident. Most of the _____ horns of the spinal cord (the motor aspect) move posteriorly towards the central portion of the medulla, while the _____ horns (sensation for the body) move laterally to become associated with the trigeminal system, which mediates _____ for the head. Label the encircled regions on the section to indicate if they are more likely motor areas or sensory areas.

Answer 12

medulla; spinal; anterior; posterior; sensation

Motor on left, Sensory on right (on diagram)

Question 13

The _____ columns, composed of the fasciculus gracilis and cuneatus, feed into their respective nuclei, the nucleus _____ and nucleus _____ in the medulla.

Answer 13

dorsal; gracilis; cuneatus

Question 14

Closer to the midline in the upper sections of the medulla, there appears a pair of medial _____. The _____ lemniscus of each side contains _____ary fibers mediating the dorsal column modalities from the nucleus gracilis (lower limb) and cinematic (_____ limb).

Answer 14

lemnisci; medial; secondary; upper

Question 15

Label the encircled accurate fibers leaving the nucleus gracilis and _____ as they cross to form the _____lateral _____ _____. Label the nucleus gracilis and cuneatus.

Answer 15

cuneatus; contralateral; medial lemniscus

Arcuate fibers: two circles on diagram
Nucleus gracilis: point to right side of middle inner line
Nucleus cuneatus: point to lentil lines on farther right side

Question 16

Further _____, the middle division of the brainstem, the _____, is seen to possess a base region. The base contains a mass of crossing fibers that gives rise to the _____ cerebellar peduncle. In addition to the crossing fibers, the base contains cell bodies-the pontine nuclei- and many _____ing fibers on their way down to the spinal cord.

Answer 16

rostrally; pons; inferior; descending

Question 17

Other features of the pons are continuations of structures seen in the medulla, such as the _____ _____- the ascending fibers that began as the _____ columns of the spinal cord and other pathways passing rostrally to terminate in the _____.

Answer 17

medial lemniscus; dorsal; thalamus

Question 18

From the following list of structures, circle all of the choices that are associated with the posterior or dorsal columns of the spinal cord.

Answer 18

Medial lemniscus; Arcuate fibers; Nucleus gracilis

Question 19

In the midbrain, the _____ ventricle narrows to form the cerebral aqueduct. The cerebral aqueduct is surrounded by a mass of gray matter called the periaductal gray. The cells of the _____ gray have a prominent role in pain modulation. Shade in the periaductal gray and label the cerebral aqueduct on the diagram.

Answer 19

4th; periaductal

Periaductal gray: Shade in middle large circle
Cerebral aqueduct: Point to middle inner circle