Medulla Spinale (Spinal Cord) Anatomy and Physiology

A comprehensive set of practice flashcards covering the anatomy, topography, tracts, and functional organization of the spinal cord (Medulla Spinalis) based on lecture notes.

What is the general role of the Medulla Spinalis in the Central Nervous System?

It serves as the basal level of the CNS, controlling the entire body except for the head and maintaining the ontogenic segmental organization of the trunk and limbs.

In the context of segmental organization, what is a "neuro-angiosome"?

A local unit where a specific body segment is controlled by its corresponding spinal nerve and metabolically supplied by the blood vessels accompanying that nerve.

What are the anatomical boundaries for the location of the Medulla Spinalis?

It is located within the Canalis vertebralis, extending from the Planum atlanto-occipitalis down to the level of the $L1-L2$ intervertebral disc.

Which structures are responsible for the lateral fixation of the spinal cord within the vertebral canal?

The Ligamenta denticulata, which are formed by the union of the pia mater and arachnoidea mater.

What is the Filum terminale and where does it fix?

It is a fibrous continuation of the pia mater that begins after the spinal cord ends, passes through the dural sac, and fixes at the Hiatus sacralis and Os coccygis.

Name the two major enlargements of the spinal cord and the segments they involve.

Intumescentia cervicalis ($C5-T1$) and Intumescentia lumbosacralis ($L1-S3$), both associated with the innervation of the limbs.

What are the four longitudinal grooves that divide the spinal cord into funiculi?

Fissura mediana anterior, Sulcus medianus posterior, Sulcus anterolateralis, and Sulcus posterolateralis.

Distinguish between the roles of the Radix anterior and Radix posterior.

The Radix anterior is motoric, carrying impulses to effector muscles, while the Radix posterior is sensitive, bringing sensory information to the spinal cord.

How many pairs of spinal nerves are there, and how are they categorized?

There are $31$ pairs: $8$ cervical, $12$ thoracic, $5$ lumbar, $5$ sacral, and $1$ coccygeal.

What is the Cauda equina?

A bundle of nerve roots (low lumbar, sacral, and coccygeal) that descend within the dural sac below the end of the spinal cord ($L1-L2$) before exiting the vertebral column.

Describe the primary function of the Cornu anterius (anterior horn) of the gray matter.

It contains somatic motor neurons whose axons exit through the sulcus anterolateralis to innervate skeletal muscles (somatomotor function).

What is the function of the Cornu lateralis and where is it most prominent?

It has a visceral function (visceromotor and viscerosensor) and is most prominent in the thoracic and upper lumbar segments.

What are Rexed Laminae?

A histological classification system that divides the gray matter into $10$ layers ($I-X$) to identify structural-functional relationships.

What is the significance of the "Gate Control" zone (Laminae $I-II$)?

It acts as a filtering and integration area that can block or modulate signals, such as chronic pain, before they are transmitted to higher CNS levels.

What role does Substantia gelatinosa Rolando (Lamina $II$) play in sensory processing?

It receives impulses from thin, unmyelinated C-fibers (chronic pain, itching) and modulates pain through the release of endogenous analgesics like endorphins.

Which pathway transmits conscious proprioception, and how is it divided in the funiculus posterior?

The medial lemniscal system, divided into the Fasciculus gracilis (Goll) for the lower half of the body and Fasciculus cuneatus (Burdach) for the upper half.

Where does the Tractus spinothalamicus lateralis decussate, and what information does it carry?

It decussates in the Commissura alba at the segmental level and carries information regarding temperature and sharp pain (thermo-algesia).

Which motor tract controls fine voluntary movements and where do most of its fibers cross?

The Tractus corticospinalis lateralis, which contains $90$% of pyramidal fibers that cross at the decussatio pyramidum in the medulla oblongata.

What is the origin and function of the Tractus spinocerebellaris dorsalis (posterior)?

It originates in the Nucleus thoracicus posterior (Clarke's nucleus) between $C8-L3$ and carries unconscious proprioception from the trunk and lower limbs to the cerebellum.

Describe the role of the Tractus rubrospinalis.

An extrapyramidal tract originating in the Nucleus ruber that modifies pyramidal movements and helps maintain balance and coordination.

What reflex is mediated by the Tractus tectospinalis?

Protective motor reflexes in response to sudden visual or auditory stimuli, such as flinching from loud noises or bright lights.

What is the primary function of the Tractus vestibulospinalis lateralis?

It maintains postural balance by activating extensor muscles to provide anti-gravitational tone.

How do the two parts of the Nucleus intermediolateralis differ in function?

The segment from $C8-L2$ is sympathetic (preganglionic neurons), while the segment from $L1-S2$ is parasympathetic (innervating pelvic organs).

List the three essential parts of a spinal reflex arc (arcus reflectorius simplex).

1. Sensitive axis (afferent), 2. Associative segment (interneuron), and 3. Motor axis (efferent).

How does the Formatio reticularis medullae spinalis modulate chronic pain?

By increasing the excitation threshold of pain neurons and facilitating the release of endorphins in the Substantia gelatinosa Rolando.