The Central Nervous System Part 2- Diencephalon, Midbrain, and Hindbrain + Cranial & Spinal Nerves

Question 1

Where does the spinal cord start and extend to?

Answer 1

Extends from the level of the foramen magnum of the skull to the first lumbar vertebra.

Question 2

Where do you find white matter in the spinal cord?

Answer 2

On the outside, gray matter is on the inside.

Question 3

How is the gray matter in the spinal cord arranged?

Answer 3

First, it is interior, deep to the white matter. It is arranged in the shape of an “H” with two dorsal (posterior) horns and two ventral (anterior) horns.

Question 4

Where are ascending and descending fiber tracts found in the spinal cord?

Answer 4

In the white matter.

Question 5

How would you name an ascending tract?

Answer 5

Usually starts with the prefix spino- and ends with the name of the brain region where the spinal cord fibers first synapse.

Question 6

How would you name a descending tract?

Answer 6

Begin with a prefix that denotes the brain region that gives rise to the fibers and end with the suffix -spinal

Question 7

Sensory/Afferent tracts are which tracks in the white matter of the spinal cord?

Answer 7

Ascending Tracts

Question 8

Motor/Efferent tracts are which tracks in the white matter of the spinal cord?

Answer 8

Descending Tracts

Question 9

What types of impulses does the anterior spinothalamic tract carry?

Answer 9

Carries impulses conveying the sense of touch and pressure, and synapses to the thalamus. From there it relays to the cerebral cortex.

Question 10

Another name for Pyramidal Tracts?

-Where does it start and descend to?

Answer 10

Corticospinal Tracts–begin in the cerebral cortex and descend the spinal cord.

Question 11

What are proprioceptors?

Answer 11

Muscle and Joint Receptors

Question 12

Ascending fiber tracts convey sensory information from what receptors?

Answer 12

Cutaneous Receptors
Proprioreceptors
Visceral Receptors

Question 13

Where are the two places that sensory modalities decussate?

Answer 13

Medulla Oblongata and Spinal Cord.

Question 14

What are the two major groups of descending fiber tracts that originate in the brain?

Answer 14

The Pyramidal Tracts (aka Corticospinal Tracts) &

Extrapyramidal Tracts

Question 15

What is “pyramid” associated with?

Answer 15

Medulla

Question 16

Which descending tracts descend directly, without synaptic interruption, from the cerebral cortex to the spinal cord?

Answer 16

Pyramidal Tracts

Question 17

The cell bodies that contribute ~ 80%-90%fibers to the pyramidal tracts are located primarily in what region? Where do the other ~10% come from?

Answer 17

The larger portion of the cell bodies that contribute fibers to the pyramidal tracts are located primarily in the precentral gyrus.
The remaining 10% are located in the supplementary motor complex.

Question 18

What is the precentral gyrus?

Answer 18

The primary motor cortex

Question 19

Where is the Supplementary Motor Complex?

Answer 19

Located in the superior frontal gyrus, just anterior to the “leg” region of the primary motor cortex.

Question 20

What’s the difference between the lateral and anterior corticospinal tracts?

Answer 20

Lateral Corticospinal Tracts: Make up ~80-90% of the pyramidal tracts and decussate in the PYRAMIDS of the MEDULLA OBLONGATA. From there they descend as the lateral corticospinal tracts.
Anterior Corticospinal Tracts: Remaining UNCROSSED fibers form and descend as the anterior corticospinal tracts, which then decussate in the SPINAL CORD.

Question 21

What is the result of decussation of descending fibers?

This helps Corticospinal tracts be primarily concerned with what kind of movement?

Answer 21

The right cerebral hemisphere controls the musculature on the left side of the body, and vice versa fr the L hemisphere and right side of the body.
–Corticospinal tracts are primarily concerned with the control of fine motor movements that require dexterity.

Question 22

What damage to the skilled motor activity of the hands would expect with someone with lesions in the left-hemisphere parietal lobe? Why?

Answer 22

These pts. often have impaired skilled motor activity of both hands, this has lead scientists to believe the left hemisphere has more control in the skilled motor control of both hands.
Why: L hemisphere appears to control the left hand indirectly, via projections to the right hemisphere through the corpus callosum.

Question 23

Where do extrapyramidal motor tracts originate?

Answer 23

In the brain stem

Question 24

The extrapyramidal motor tracts are largely controlled by the motor circuit structures of what areas?

Answer 24

Corpus Striatum–caudate nucleus, putamen, and globus pallidus.
as well as Substantia Nigra and the Thalamus.

Question 25

Walk through the breakdown of the Basal Nuclei

Answer 25

Basal Nuclei is divided into two sections Corpus Striatum and Claustrum.
Corpus Striatum is then divided into the Caudate Nucleus and Lentiform Nucleus.
Lentiform Nucleus is divided into Putamen and Globus Pallidus.

Question 26

How does the cerebellum influence motor activity without its own descending tracts?

Answer 26

It influences motor activity only INDIRECTLY by it’s effects on the vestibular nuclei, red nucleus, and basal nuclei, which send axons to the reticular formation)