Ch 19 + 20 - Neuroanatomy

Question 1

the term pyramidal tract refers to fibers in the pyramids on the anterior surface of the __ of the brainstem

Answer 1

medulla

Question 2

as the fibers of the left pyramidal tract descend, most of them __ the midline in the lower medulla and enter the __ tract on the __ side

Answer 2

cross (decussate); lateral corticospinal; opposite (contralateral)

Question 3

As labeled, about 10 to 30% of the pyramidal fibers enter the spinal cord uncrossed as the __ corticospinal tracts arise from cell bodies in the cerebral cortex on the __ side

Answer 3

anterior; left

Question 4

Darken the nerve fibers labeled as ‘A’ over their whole visible length on the diagram. Do all the diagrammed fibers cross the midline within their territory included in the diagram?

Answer 4

no

Question 5

the decussation of the pyramidal tract extends over several millimeters of the junction area between the __ region of the brainstem and the __. On the diagram indicate with an arrow the level where decussation begins

Answer 5

medulla; spinal cord

Question 6

The descending fibers marked “X” are beginning to cross from the __ side to the __ side of the medulla

Answer 6

left; right

Question 7

The pyramidal fibers in level “A” occupy an anterior position in the medulla. By “D: in the lower medulla and upper spinal cord, most of the fibers reach a posterior and lateral position. Between B and C in the pyramidal decussation, the fibers pass from an __ position on one side across the midline in a __ and __ direction

Answer 7

anterior; lateral; posterior

Question 8

If you look at a transverse section of the medulla from an inferior view (looking up from the spinal cord) the left side of the picture represents the left side of the medulla. If you view the same section of the medulla from a superior view (looking down from the midbrain) the left side of the picture represents the __ side of the medulla

Answer 8

right

Question 9

Of the three sections labeled A, B, and C, which one shows fibers of the pyramidal tract decussating from the left to the right side of the medulla? __ Decussating from the right to the left side of the medulla? _ At a level above the pyramidal decussation? __

Answer 9

B;C;A

Question 10

The fibers shown decussating in section A arise mainly in the __ cerebral hemisphere and end in the __ side of the spinal cord

Answer 10

left; right

Question 11

Look at these two sections of the medulla. The more rostral of the two sections is _ Explain

Answer 11

B; Section B does not show the decussation of the pyramidal tract

Question 12

As corticospinal fibers descend, bundles of fibers from one side cross the midline alternately with bundles from the other side so that a given transverse section is likely to show the decussation mainly from one side. On the diagram, fivers crossing the medulla from left to right are shown in levels numbered __ and __. Fibers crossing the medulla from right to left are shown in levels numbered __ and __

Answer 12

4;6;5;7

Question 13

The alternating pyramidal decussations from left to right and right to left give a braided appearance to the __ surface of the lower medulla

Answer 13

anterior

Question 14

In passing from medulla to spinal cord, corticospinal fibers cross the midline in the __ of the __ tract

Answer 14

decussation; pyramidal

Question 15

Corticospinal fibers cross in the pyramidal decussation from the __ surface of the medulla to a __ position in the spinal cord

Answer 15

anterior; posterolateral

Question 16

Label the transition area between the medulla and spinal cord. In the spinal cord, the decussated fivers take up a __ position

Answer 16

posterolateral

Question 17

Corticospinal fibers arise from cells in the surface gray matter of the cortex, pass into the depths of the cortex, and emerge on the anterior surface of the __ region of the brainstem. They pass inferiorly through the pons and again move toward the anterior surface while in the medulla’s __ tract. The fibers then decussate to a __ position inside the cord. Interruption of corticospinal fibers on one side of the brain at the level of the rostral medulla or above is likely to produce paralysis on the __ side of the body

Answer 17

midbrain; pyramidal; posterolateral; opposite

Question 18

Corticospinal fibers on the right side of the top diagram are enriched. Identify the level of each section ( L to R)

Answer 18

Spinal cord; inferior medulla; superior medulla; midbrain

Question 19

We have followed corticospinal fibers that originate in the __ gyrus. Many of the efferent fibers of the pyramidal tract actually arise from cells more widely distributed in the same lobe, the _ lobe

Answer 19

precentral; frontal

Question 20

Most of the efferent fibers of the basal nuclei travel in paths outside of the pyramidal route; hence, the term extra __ motor system is often used for the basal nuclei and their connected structures

Answer 20

extrapyramidal

Question 21

The extrapyramidal system, like the pyramidal system, by definition is a __ system

Answer 21

motor

Question 22

Of the wide range of neurons contributing efferent fibers to the brainstem and spinal cord, much attention has been given to a relatively small population of giant neurons in the precentral gyrus. In honor of their discoverer Betz (1874), these giant neurons are referred to as __ cells

Answer 22

Betz

Question 23

The body is represented on the precentral gyrus as indicated on the diagram. Cells on the most inferior part of the lateral surface of the gyrus, closest to the __ sulcus, influence the __. Over the superior surface and onto the medial side of the precentral gyrus is the representation of the __ limb

Answer 23

lateral; face; lower

Question 24

Movements of the fingers on the opposite side are produced by stimulation of an area on the precentral gyrus __ in size than the area representing the entire thorax plus abdomen

Answer 24

greater

Question 25

An important principle is that the complexity of motor control for a given body part is proportional to the __ of precentral gyrus on which that body part is represented. The same principle applies to sensory representation of body parts on the __ gyrus

Answer 25

area; postcentral

Question 26

In conformity with this principle, the __ is represented by an area larger than that for the rest of the face. If the area of precentral gyrus influencing movements of the toes were as large as the area for the fingers, we might modify the piano and place a keyboard within reach of our __

Answer 26

mouth; toes

Question 27

The cortex is insensitive to pain and can be stimulated directly in human beings. Dr. Harvey Cushing was among the first to describe that movements of different parts of the body are produced on stimulation of different parts of the __ gyrus

Answer 27

precentral

Question 28

Weak electrical stimulation of the superior postcentral gyrus usually leads a conscious human subject to report some sensation localized to the opposite __ limb. Some motor responses may be obtained when the postcentral gyrus is stimulated, but responses are more consistently obtained on stimulation of the __ gyrus. Likewise, sensory responses may be obtained on both sides of the __ sulcus

Answer 28

lower; precentral; central

Question 29

Penfield has drawn a homunculus as represented on the sides of the central sulcus of the human cortex. The distortions of the homunculus emphasize the principle that complexity of function is __ to the __ of the cortex

Answer 29

proportional; area

Question 30

The position as well as the relative size of body parts is distorted on the homunculus. For example, that part of the face represented nearest the neck is not the chin, but the __. On the other side of the neck are cells that influence not the shoulders but the __

Answer 30

forehead; fingers

Question 31

On stimulation of appropriate parts of the precentral gyrus, the opposite arm is raised, or the knee bends. Apparently, no individual muscles but instead coordinated __ of body parts are represented on the cerebral cortex

Answer 31

movements

Question 32

The head is represented in the most inferior parts, the hands are represented more superiorly, and the __ are represented over the superior surface and onto the medial surface of the tow gyri bordering on the __ sulcus

Answer 32

feet; central

Question 33

Fibers line up in topographic sequence as they descend from the cortex. Fibers representing the head lie in the most __ part of the precentral gyrus and in the most __ part of the internal capsule's posterior limb

Answer 33

inferior; anterior

Question 34

Encircle the leg area of the precentral gyrus. Compared to fibers from other parts of the precentral gyrus, fibers from the encircled cells pass through the internal capsule in the most __ position

Answer 34

posterior

Question 35

The linear arrangement of fibers from the precentral gyrus is shown on the diagram. Represented most anteriorly is the __. All of these fibers are in the __ limb of the internal capsule

Answer 35

head; posterior

Question 36

Fibers influencing voluntary motor control of the head and face lie __ to the __ of the internal capsule. Considerable overlap is found in the topographic distribution of efferent fibers from the precentral gyrus. However, the predominant arrangement of these fibers in the internal capsule, from anterior to posterior is __, arm, and __

Answer 36

posterior; genu; head; leg

Question 37

A patient has a stroke that leaves him severely paralyzed in the left leg, mildly weak in the left arm, and unaffected in the left side of the face. His lesion is in the internal capsule on the __ side. The lesion involves primarily the __ part of the __ limb of the internal capsule

Answer 37

right; posterior; posterior

Question 38

This is a transverse section through the __. Label the structures indicated

Answer 38

midbrain

Question 39

Neurons in the left precentral gyrus send axons in the __ internal capsule and the __ basis pedunculi. These fibers influence the __ arm and leg because they decussate at the junction of the __ and __

Answer 39

left; left; right; medulla; spinal cord

Question 40

Fibers from the precentral gyrus lie in the middle __-fifths of the __. The __ is represented most medially, and the legs are represented most __

Answer 40

three-fifths; basis pedunculi; head; laterally

Question 41

Corticospinal fibers labeled "A" originate in the __ part of the precentral gyrus and pass through the __ part of the posterior limb of the internal capsule; fibers labeled __ lie closest to the genu of the internal capsule

Answer 41

superior; posterior; C

Question 42

Fibers arising in the cortex and influencing motor control of the trunk and limbs terminate in the spinal cord (cortico __ fibers) Fibers arising in the cortex and influencing motor control of the head terminate in the brainstem nuclei (cortico __ fibers) An older term for these fibers is corticobulbar, referring to the fact that bulb is an old term for brainstem

Answer 42

corticospinal; corticonuclear

Question 43

Within the middle three-fifths of each basis pedunculi, corticospinal fibers lie in a position __ to fibers supplying the head (__ fibers)

Answer 43

lateral; corticonuclear

Question 44

Since cortico__ fibers influence face and head muscles, they do not pass to the spinal cord but instead terminate at various levels of the brainstem from midbrain inferiorly to __

Answer 44

corticonuclear; medulla

Question 45

In the internal capsule, the predominant arrangement of efferent fibers, from anterior to posterior, is __ arm __. In the internal capsule, the corticonuclear fibers lie __ to corticospinal fibers; in the basis pedunculi, the corticonuclear fibers lie __ to corticospinal fibers

Answer 45

head; leg; anterior; medial

Question 46

The other sectors of the basis pedunculi are occupied mainly by axons that terminate in the pons. The most lateral fibers arise mainly in cell bodies in the __ and __ lobes; the most medial ones arise in the __ lobe.

Answer 46

parietal; temporal; frontal