CNS Protection and Spinal Cord Anatomy

This set of vocabulary flashcards covers the protective structures of the CNS (meninges, CSF, BBB) and the anatomy and functional pathways of the spinal cord as described in the lecture notes.

Pia Mater

The innermost, thin layer of areolar CT that tightly adheres to the brain.

Arachnoid Mater

A delicate web of collagen and elastic fibers located between the dura mater and the pia mater.

Dura Mater

The outermost and toughest layer of the meninges, subdivided into a meningeal layer and a periosteal layer.

Subarachnoid space

The region between the arachnoid and pia mater that contains arachnoid trabeculae and cerebrospinal fluid ($CSF$).

Cranial dural septa

Locations where the dura mater extends into the cranial cavity, including the Falx cerebri, diaphragma sellae, tentorium cerebelli, and falx cerebelli.

Dural Venous Sinuses

Large, blood-filled spaces modified from veins located between the two layers of dura mater that function to drain blood from the brain.

Epidural space

A potential space between the dura mater and the periosteum of the skull; in the spinal cord, it is a real space filled with areolar and adipose CT.

Subdural space

A potential space between the dura mater and the arachnoid mater.

Hematoma

A pooling of blood that can occur in the epidural or subdural potential spaces following injury.

Meningitis

Inflammation of the meninges caused by viral or bacterial infection, characterized by fever, headache, vomiting, and a stiff neck.

Cerebrospinal Fluid ($CSF$)

A clear, colorless fluid produced by the choroid plexus that floats and cushions the brain while transporting nutrients and removing waste.

Choroid plexus

Specialized structures in each ventricle composed of blood capillaries, pia mater, and ependymal cells that produce approximately $500\,mL/day$ of $CSF$.

Arachnoid villi

Projections of the arachnoid mater that extend into dural sinuses to reabsorb $CSF$ into the blood at a rate equal to its production.

Hydrocephalus

A pathological condition involving excessive $CSF$ caused by an obstruction in flow or impaired absorption at the arachnoid villi.

Blood Brain Barrier ($BBB$)

A protective barrier that determines which substances, such as ions, nutrients, and small lipid-soluble molecules, can enter the brain’s interstitial fluid.

Conus medullaris

The tapering inferior border of the spinal cord located at the level of the $L1$ vertebra.

Cauda equina

A group of lumbar and sacral nerve roots that extend inferiorly from the conus medullaris.

Posterior median sulcus

A groove running down the posterior surface of the spinal cord.

Anterior median fissure

A wide groove located on the anterior surface of the spinal cord.

Spinal Nerves

A set of $31$ paired nerves that form when the posterior and anterior roots join, resulting in mixed nerves containing both sensory and motor axons.

Posterior root

The branch of a spinal nerve that houses sensory neurons.

Posterior root ganglion

A swelling on the posterior root that contains the cell bodies of sensory neurons.

Anterior root

The branch of a spinal nerve that houses motor neuron axons.

Lumbar puncture

A procedure performed between $L3$ and $L4$ (or $L5$) to sample $CSF$ from the subarachnoid space.

Posterior horns

Regions of grey matter in the spinal cord that contain the cell bodies and dendrites of interneurons.

Anterior horns

Regions of grey matter in the spinal cord containing the cell bodies and dendrites of somatic motor neurons.

Lateral horns

Regions of grey matter in the spinal cord containing the cell bodies of autonomic motor neurons.

Grey commissure

An unmyelinated connection between the left and right sides of the spinal cord grey matter.

Funiculi

Divisions of white matter in the spinal cord (posterior, lateral, and anterior) subdivided into bundles or tracts.

Decussate

The crossing over of spinal tracts from one side of the body to the other, making them contralateral.

Ipsilateral

Refers to nervous system pathways that do not cross over and remain on the same side of the body.

First order neuron

The initial neuron in a sensory pathway that leads from the sensory receptor to the posterior horn of the spinal cord.

Second order neuron

The neuron in a sensory pathway that extends from the posterior horn to the brain, usually the thalamus.

Third order neuron

The final neuron in a sensory pathway that leads from the thalamus to the somatosensory cortex in the parietal lobe.

Upper motor neuron

A neuron in the direct (pyramidal) motor pathway that leads from the primary motor cortex down the spinal tract.

Lower motor neuron

A neuron located in the ventral (anterior) horn that leads to the skeletal muscle neuromuscular junction ($NMJ$).

Reflexes

Rapid, preprogrammed involuntary responses of muscles or glands to a stimulus that act as survival mechanisms.

Reflex arc

The structural components of a reflex response, typically including a receptor, sensory neuron, CNS/interneuron, motor neuron, and effector.