Lab 1: Gross And Internal CNS I

Question 1

Orientation Rules

Answer 1

Clinical Scan: Ventral is up, dorsal is down and right and left are opposite yours

Neuroanatomical slices: ventral is down, dorsal is up and your right is their right

Question 2

Gross Features of the Spinal Cord

Answer 2

Dorsal Median Sulcus
Ventral Median fissure: look for the anterior spinal artery which runs along this
Dorsal and Ventral rootlets
Denticulate ligaments: attaching spinal cord to the dura mater
Arachnoid and pia mater
Spinal nerve
Dorsal root ganglion 
Conus medullaris
Cauda Equina 
Film Terminale

Question 3

Recognizing Dorsal and Ventral surfaces of Transverse Slice of Spinal Cord

Answer 3

Ventral median fissure: a deep midline cleft in the ventral spinal cord that contains the anterior spinal artery and veins

Dorsal median sulcus: a very shallow midline groove that is continuous with a deeper partition

Entrance of dorsal roots: dorsolateral surface

Reference lines: vertical/horizontal and central canal

Question 4

Internal Subdivisions in Axial Spinal Cord stained slices

Answer 4

Gray matter: an almost wing shaped internal area that contains groups of nuclei

White matter: bundles of ascending and descending fibers peripheral to the gray matter

Central canal: spinal part of the ventricular system. Because cerebrospinal fluid doesn’t circulate through the central canal, it usually become as plugged and is not visible.

Question 5

Zones in Gray Matter Subdivision

Answer 5

Dorsal horn: a dorsal projection of nuclei that process sensory info from afferent fibers. Contains groups of interneurons for local processing of sensory data as well as projection neurons that send axons to higher and lower levels

Intermediate zone: a primitive processing area that contains a network of neurons that process local info for spinal reflexes as well as some neurons that transmit info to higher and lower CNS levels. Continuous with a primitive network in the brainstem called the reticular formation

Ventral horn: a ventral gray matter projection that contains: clusters of interneurons that process motor info en route to motor neurons and MOTOR NUCLEI with somatic motor neurons that send axons via the ventral root to supply skeletal muscle

Question 6

Zones in White Matter Subdivision

Answer 6

Dorsal columns: located between the entrance of dorsal roots and the midline; contain ascending axons that transmit sensory info from discriminative touch and pressure receptors

Lateral column: located between the attachments of the dorsal and ventral roots; contains ascending fibers for pain transmission as well as descending fiber as from the motor cortex for voluntary movement

Ventral column: located between the ventral roots and ventral median fissure; contains descending fibers from the brain that influence motor neurons of the ventral horn

Question 7

Substantia Gelatinosa

Answer 7

A very pale nucleus that forms a cap in the dorsal horn; is involved in processing pain data

FOUND AT ALL SPINAL CORD LEVELS

Question 8

Intermediolateral cell column

Answer 8

A nucleus that extends through levels of T1-L2 only
Forms a pointed lateral projection of the intermediate zone; contains preganglionic sympathetics cell bodies that send axons via ventral roots to sympathetic ganglia and then to visceral structures
Intermediate zone of the sacral spinal cord (S2-4) has a preganglionic parasympathetic nucleus that is not as distinct as the intermediolateral Cell column

Question 9

Clarke’s Nucleus (nucleus Dorsalis)

Answer 9

Occupies the medial part of the base of the dorsal horn between spinal levels T1-L2 and appears in transverse sections as well-defined oval area

Processes unconscious proprioceptive info from muscle spindles and tendon organs and sends it on the cerebellar cortex

Question 10

Medial Motor Nuclei

Answer 10

Nuclei located in the ventral horn at ALL spinal cord levels

Contain motor neurons that supply muscles of the trunk and neck

Question 11

Lateral Motor Nuclei

Answer 11

Nuclei that form a lateral expansion of the ventral horn at the level of cervical (C5-T1) and lumbar (L1-S3) enlargements; contain motor neurons that supply muscles of the limbs

Question 12

Gracile Fascicle

Answer 12

Located in the dorsal columns, adjacent to the midline. This tract transmits discriminative sensory info from the lower half of the body (below T6 level) and is found at EVERY spinal cord level

Question 13

Cuneate Fascicle

Answer 13

Located ONLY at levels C1-T6. Where it’s lateral to the gracile Fascicle; transmits discriminative data from receptors of the UPPER body. A thin septum, the dorsal intermediate septum, separates it from the gracile fascicle

Question 14

Features of a Cervical Spinal Cord Slice (axial)

Answer 14

A large ventral horn containing motor nuclei from both upper limbs (medial and lateral motor nuclei)
Wide dorsal columns that contain both cuneate and gracile fascicles
An intermediate gray that DOESN’T contain an intermediolateral cell column
An ellipsoid shape (due to wide dorsal columns, lateral columns and ventral horn)

Question 15

Characteristics of Transverse spinal cord slice (axial)

Answer 15

A circular shape
Presence of intermediolateral cell column in the intermediate gray zone
Absence of lateral motor nuclei in the ventral horn
Dorsal columns vary

Question 16

Characteristics of a lumbar spinal cord slice (axial)

Answer 16

Thin white matter columns
No intermediolateral cell column
Only a gracile fascicle
Medial and lateral motor nuclei in the ventral horn

Question 17

Cerebellum

Answer 17

Dorsal to the IV ventricle and brainstem
Inferior to the tentorium cerebelli and occipital lobe
Anterior to the occipital bone

Core of white matter with branches like a tree covered with a wrinkled gray cortex (folia)

Question 18

Subdivisions of the Cerebellum (gross)

Answer 18

Vermis: narrow midline region
Hemispheres: large lateral regions (most of the cerebellum)

Question 19

Tonsil

Answer 19

Inferior area of the cerebellar hemisphere that extends medially

Often visible in a sagittal specimen or MR scan

Important for its proximity to cardiorespiratory areas of the medulla

Question 20

Flocculus

Answer 20

Ventral surface of the cerebellar hemispheres.

Lateral to the junction of the pons and medulla

Near 2 cranial nerves (CN VII and VIII)

CN VIII: site of the most common CNS tumor in the posterior cranial fossa (Vestibular schwannoma)