Gross Anatomy of the Central Nervous System

Flashcards covering the gross anatomy, subdivisions, meninges, dural supply, brain structures, ventricles, CSF flow, spinal cord features, and clinical conditions of the central nervous system based on the lecture context.

What are the primary components of the Central Nervous System (CNS)?

The brain and the spinal cord.

What are the three layers of meninges surrounding the CNS, listed from outside to inside?

The outer dura mater, middle arachnoid mater, and inner pia mater.

What space lies between the dura mater and arachnoid mater, and what fluid does it contain?

The subdural space, which contains a small amount of serous fluid.

What space separates the arachnoid mater from the pia mater, and what fluid does it contain?

The subarachnoid space, which contains cerebrospinal fluid (CSF).

What are the two dense fibrous tissue layers that form the dura mater?

The outer periosteal/endosteal layer and the inner meningeal layer.

What is the falx cerebri?

A sickle-shaped fold of dura mater formed by the inner meningeal layer that sweeps inwards between the cerebral hemispheres.

Which dural septum forms a crescent-shaped fold between the cerebrum and cerebellum?

The tentorium cerebelli.

What is the function of the diaphragma sellae?

It is a small circular fold of dura mater that forms the roof for the sella turcica, a bone housing and protecting the pituitary gland.

Which meningeal artery is most commonly damaged in head injuries?

The middle meningeal artery.

Which nerves provide sensory supply to the dura mater?

Branches of the trigeminal nerve, vagus nerve, first three cervical nerves ($\text{C1-C3}$), and sympathetic system branches.

Where does the arachnoid mater end inferiorly?

It ends by merging with the dura mater at the level of the $2\text{nd}$ sacral vertebra ($\text{S2}$).

What are arachnoid granulations and where are they most numerous?

Aggregations of arachnoid villi that project into dural venous sinuses to diffuse CSF into the bloodstream; they are most numerous along the superior sagittal sinus.

What is the filum terminale?

A prolongation of pia mater continuing beyond the end of the spinal cord that pierces the arachnoid tube and fuses with the periosteum of the coccyx.

What deep white matter mass connects the right and left cerebral hemispheres?

The corpus callosum.

What are the four lobes of each cerebral hemisphere?

Frontal lobe, parietal lobe, temporal lobe, and occipital lobe.

What primary function is associated with the occipital lobe?

Sight.

What structures compose the diencephalon?

Structures situated around the third ventricle, mainly the thalamus and hypothalamus, along with the pineal gland and optic chiasma.

What is the primary sensory function of the thalamus?

It acts as a relay station for all sensory information (except smell) traveling to the cerebral cortex.

What key physiological functions are regulated by the hypothalamus?

Thermoregulation, hunger and satiety, thirst and water balance, autonomic nervous system control, sleep-wake cycles, emotional responses, and pituitary endocrine functions.

What canal passes through the midbrain to connect the third ventricle to the fourth ventricle?

The cerebral aqueduct (aqueduct of Sylvius).

What are the cerebral peduncles?

Two large bundles of nerve fibers on the ventral aspect of the midbrain containing ascending sensory tracts and descending motor tracts.

What four surface swellings are situated on the posterior aspect of the midbrain?

Two superior colliculi and two inferior colliculi.

What respiratory centers in the pons operate with the medulla oblongata to control respiration?

The pneumotaxic centre and the apneustic centre.

What vital centers are located in the medulla oblongata?

Cardiovascular centre, respiratory centre, and reflex centres for vomiting, coughing, sneezing, and swallowing.

What median strip separates the two hemispheres of the cerebellum?

The vermis.

Which three paired arteries supply arterial blood to the cerebellum?

Superior cerebellar artery (SCA), anterior inferior cerebellar artery (AICA), and posterior inferior cerebellar artery (PICA).

What thin membrane separates the two lateral ventricles of the brain?

The septum pellucidum.

What four components form the blood-brain barrier (BBB)?

Capillary endothelial cells with tight junctions, basement membrane, astrocyte end-feet, and pericytes.

Through what opening does CSF flow from the lateral ventricles into the third ventricle?

The interventricular foramina.

Through what apertures does CSF exit the fourth ventricle into the subarachnoid space?

Two lateral apertures and one median aperture.

Where does the adult spinal cord terminate inferiorly?

At the level of the lower border of the $\text{L1}$ vertebra.

What are the vertebral spans of the cervical and lumbar enlargements of the spinal cord?

The cervical enlargement extends from $\text{C3}$ to $\text{T2}$, and the lumbar enlargement extends from $\text{L1}$ to $\text{S3}$.

How many pairs of spinal nerves are present in humans, categorized by region?

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

What regions are supplied by the ventral and dorsal rami of spinal nerves?

Ventral rami form nerve plexuses to supply limbs and the anterior/lateral body wall; dorsal rami supply deep back muscles and skin of the back without forming plexuses.

What functions are associated with the anterior, posterior, and lateral horns of spinal grey matter?

Anterior horn holds motor control cell bodies, posterior horn processes sensory information, and lateral horn manages autonomic responses.

What causes an extradural (epidural) hemorrhage?

A skull fracture tearing an artery, commonly the middle meningeal artery, leading to bleeding between the skull and dura mater.

What causes a subdural hemorrhage?

Head injury tearing the superior cerebral veins at their entrance into the superior sagittal sinus, between the dura mater and arachnoid mater.

Between which spinal levels is a lumbar puncture performed, and why?

Between $\text{L3-L4}$ or $\text{L4-L5}$ into the subarachnoid space, safely below the termination of the adult spinal cord, to sample CSF.

What clinical significance does the valveless nature of the vertebral venous plexus have?

Its bidirectional flow allows it to act as a collateral venous pathway and facilitates the spread of infections, emboli, and cancer metastases (such as prostate cancer) to the spine or brain.