Flashcards: The Nervous System (Anatomy 2)

Ganglia: Collections of nerve cell bodies in the PNS

Nuclei: Collections of nerve cell bodies in the CNS

Nerves: Collections of axons in the PNS

Tracts: Collections of axons in the CNS

Forebrain: Cerebrum and diencephalon

Midbrain

Hindbrain: Pons, medulla oblongata, and cerebellum

Largest area of the brain, divided into two cerebral hemispheres (longitudinal fissure)

Conscious thought processes and intellectual function

Memory storage, processing, and retrieval

Regulation of skeletal muscle contraction (conscious and subconscious)

Connected by the corpus callosum

Surface layer: Cortex (gray matter - neuronal cell bodies)

Inner layers: White matter (neuronal axons)

Innermost: Deep nuclei (gray matter - diencephalon)

Coordinates complex somatic motor patterns

Maintains balance via postural muscles

Refines learned movement patterns

Midbrain

Pons

Medulla oblongata

Processes and relays information between the cerebrum and cerebellum

Contains reflex centres for respiratory and cardiovascular functions

Houses cranial nerve nuclei

Continuation into the spinal cord

Thalamus: Relay and processing centre

Hypothalamus: Involved in hormone production and emotional control

Continuation of the brainstem into the vertebral column through the foramen magnum.

Runs through the vertebral/spinal canal.

Initiates at the foramen magnum and terminates at L1.

Covered by meninges (dura mater, arachnoid mater, and pia mater).

Cervical enlargement: Provides sensory and motor innervation to the upper limbs.

Lumbar enlargement: Provides sensory and motor innervation to the lower limbs.

A collection of nerve roots descending below the conus medullaris.

Performed below L1 to avoid damaging the spinal cord.

Inserted into the subarachnoid space to collect cerebrospinal fluid (CSF).

Needle passes through skin, subcutaneous tissue, supraspinous ligament, interspinous ligament, and ligamentum flavum.

Avoids the conus medullaris; targets the cauda equina.

Originates from dorsal (sensory) and ventral (motor) spinal roots.

Main branches:

Dorsal ramus: Innervates muscles and skin of the back.

Ventral ramus: Forms plexuses and innervates limbs and anterior body wall.

Autonomic components: Sympathetic and parasympathetic fibres for visceral control.

Contains nerve cell bodies, dendrites, and synaptic contacts (synapses).

Shaped like a butterfly or an "H."

Divided into:

Posterior (dorsal) horn: Receives sensory input.

Anterior (ventral) horn: Contains motor neurons.

Lateral horn: Present in T1-L2/3 and S2-S4 segments; contains autonomic neurons.

Posterior (dorsal) horn: Sensory processing.

Anterior (ventral) horn: Motor output.

Lateral horn: Autonomic function (only in specific segments).

Made of myelinated axons.

Contains ascending and descending nerve fibers.

Organized into columns (funiculi):

Posterior funiculus

Lateral funiculus

Anterior funiculus

Columns are further subdivided into tracts that carry specific signals.

Ascending tracts: Transmit sensory information to the brain.

Descending tracts: Transmit motor commands from the brain to the body.

Posterior (dorsal) median sulcus: Shallow groove on the posterior side.

Anterior (ventral) median fissure: Deep groove on the anterior side.

Central canal: Runs through the center of the spinal cord, contains cerebrospinal fluid.

Funiculi (columns): Bundles of nerve fibers organized for specific functions.

Dura mater: Outermost, tough fibrous layer.

Arachnoid mater: Middle, web-like layer.

Pia mater: Innermost, delicate layer adhering to the spinal cord.

The dura mater surrounds the spinal cord and nerve roots, forming the dural sac.

The arachnoid mater lines the dura mater and encloses the subarachnoid space containing cerebrospinal fluid (CSF).

The pia mater is directly adhered to the spinal cord and nerve roots, anchoring them to the coccyx via the filum terminale.

The meninges protect the spinal cord and provide a cushion for nerve roots.

Compression occurs when nerve roots are pressed against the dura mater due to herniated discs, tumors, or inflammation.

Can lead to pain, numbness, or motor deficits depending on the affected nerve root.

Delivers medication (e.g., anesthetics, steroids) into the epidural space outside the dura mater.

Commonly used for pain relief during labor or to treat chronic back pain.

The needle does not penetrate the dura mater.

Used to obtain cerebrospinal fluid (CSF) for diagnostic tests or to administer medications.

Performed between L3-L4 or L4-L5 vertebrae to avoid damaging the spinal cord (ends at L1-L2).

Needle passes through:

Skin and subcutaneous tissue.

Supraspinous and interspinous ligaments.

Ligamentum flavum.

Epidural space.

Dura mater and arachnoid mater into the subarachnoid space.

Iliac crests: Imaginary line connecting the crests crosses L4.

L3-L4 or L4-L5 intervertebral space: Safe region below the spinal cord termination.

Patient positioned in lateral decubitus (side-lying) or sitting position.

The space between the dura mater and the walls of the vertebral canal.

Contains fat and venous plexuses, and is the site for epidural anesthesia.

The space between the arachnoid mater and pia mater.

Contains cerebrospinal fluid (CSF), which cushions the spinal cord.

Extends from the foramen magnum to the S2 vertebral level.

Continues as separate sheaths for each dorsal and ventral root, becoming continuous with the epineurium of spinal nerves.

Extends to the S2 vertebral level, closely associated with the dura mater.

Covers the spinal cord and continues as the filum terminale to the coccyx.

Anchors the spinal cord to the coccyx, providing stability.

A thin filament extending from the conus medullaris to the coccyx.

Composed of:

Pia mater.

Surrounding continuation of the central canal.

Some neural elements.

Forms a separate sheath for each dorsal and ventral root.

Extends over the dorsal root ganglion (DRG) posteriorly.

Becomes continuous with the epineurium of the spinal nerve.

The conical termination of the spinal cord.

Located at the L1-L2 intervertebral space in adults.

The dura mater extends over the spinal nerve roots.

It transitions into the epineurium, the outer connective tissue covering of peripheral nerves.

A thin ridge of pia mater on each side of the spinal cord.

Made up of 21 pointed projections of pia mater extending laterally.

Extends from the foramen magnum to the L1 vertebra.

Anchors the spinal cord within the duramater.

Limits the movement of the spinal cord within the duramater.

Cerebrospinal fluid (CSF)

Also known as the subdural (potential) space.

Classified as a potential space.

The space outside the dura mater.

Filled with semiliquid fat and a venous plexus.

A needle is used to collect a sample of cerebrospinal fluid from the subarachnoid space.

Spinal cord.

At the lower border of the L1 vertebra or the L1-L2 intervertebral disc.

The highest point of the iliac crest (L4).

The needle is inserted one or two spaces above this level.

A sensory or motor disturbance caused by pathology of a nerve root.

Intervertebral disc herniation.

Osteophytes.

Spinal stenosis.

Trauma.

Contains motor and sensory fibers.

Divides into anterior and posterior ramus.

Somatic motor to intrinsic back muscles.

Somatic sensory to the skin of the back.

Motor (efferent neurons):

Somatic: Muscles.

Visceral: Organs (autonomic nerves).

Sensory (afferent neurons):

Somatic: Skin.

Visceral: Organs (e.g., visceral peritoneum).

In the dorsal root ganglia.

Somatic motor to muscles of the trunk and limbs.

Somatic sensory to the skin.

There are 31 pairs of spinal nerves.

8 Cervical

12 Thoracic

5 Lumbar

5 Sacral

1 Coccygeal

Spinal nerves emerge from the intervertebral foramina before traveling to their destination.

A dermatome is a skin area supplied by the sensory fibers of a single nerve root.

A myotome is a group of muscles primarily innervated by the motor fibers of a single nerve root.

The patterns are relatively consistent due to the development of the limbs.

The neuronal body of the autonomic component is located in the lateral horn.

Preganglionic sympathetic fibers travel through the ventral root (efferent) and are responsible for carrying signals from the spinal cord to the sympathetic ganglia.

White ramus communicans (pre-ganglionic): Connects the spinal nerve to the sympathetic ganglia.

Grey ramus communicans (post-ganglionic): Connects the sympathetic ganglia to the spinal nerve.

The visceral sensory fibers are located in the dorsal root (afferent).

Divide the cranial cavity into freely communicating spaces.

Contain subdivisions of the brain.

Restrict the rotatory displacement of the brain.

The Falx Cerebri lies in the midline between the two cerebral hemispheres.

It is a reflection of the dura mater that separates the cerebral hemispheres.

The Diaphragma Sellae is a small circular fold of dura.

It allows the passage of the infundibulum (pituitary stalk).

The Falx Cerebelli projects forward between the cerebellar hemispheres.

It is another reflection of the dura mater.

The Tentorium Cerebelli roofs over the posterior cranial fossa.

It covers the upper surface of the cerebellum.

It supports the occipital lobes of the cerebral hemispheres.

The Tentorial Notch is an opening in the tentorium cerebelli.

It allows the passage of the midbrain.

The Falx Cerebri is a vertical fold of dura mater.

It is located in the median longitudinal fissure, separating the two cerebral hemispheres.

It extends from the crista galli (anteriorly) to the internal occipital protuberance (posteriorly).

Contains the superior sagittal sinus along its superior margin and the inferior sagittal sinus along its inferior margin.

Superior Sagittal Sinus

Inferior Sagittal Sinus

Straight Sinus

The Tentorium Cerebelli is a tent-like fold of dura mater.

It lies between the cerebrum and cerebellum.

It is pulled up by its attachment to the Falx Cerebri.

It has attached and free margins.

The Falx Cerebelli is a small fold of dura mater located along the internal occipital crest.

It contains the occipital sinus.

The Diaphragma Sellae is a circular fold of dura mater that covers the hypophyseal fossa.

It is pierced by the infundibular stalk of the pituitary gland.

The intercavernous sinus is contained within the Diaphragma Sellae.

The dura mater is sensitive to stretching, which forms the anatomical basis for headaches.

Damage to the middle meningeal artery can lead to an extradural (epidural) hematoma.

The arachnoid mater is a thin, avascular layer located between the pia mater and dura mater.

It is a loosely applied layer, with projections that allow structures to pass through the subarachnoid space.

The subarachnoid space contains cerebrospinal fluid (CSF).

CSF is produced by the choroid plexus in the brain ventricles.

It flows through the ventricular system and exits the fourth ventricle to enter the subarachnoid space.

CSF is absorbed back into the dural venous sinuses through arachnoid granulations, providing buoyancy to the brain, thereby protecting it from mechanical forces.

Arachnoid granulations are bulbous projections of the arachnoid mater found in venous sinuses like the superior sagittal sinus.

They allow excess CSF to drain from the subarachnoid space into the venous sinuses.

These granulations contain smaller structures called arachnoid villi (finger-like projections).

The tips of arachnoid villi have perforations that facilitate communication between the subarachnoid space (where CSF is located) and the venous sinuses.

This process helps regulate CSF pressure and maintains fluid balance in the central nervous system.

Location: Situated between the periosteal and meningeal layers of the dura mater.

Tributaries: Receive tributaries (smaller veins) from the brain, skull bones, the orbit, and the internal ear.

Key Fact: Venous sinuses play an essential role in venous drainage from these regions.

Characteristics:

Very thin walls.

No valves.

Function:

Veins emerge from the brain and lie in the subarachnoid space.

They pierce the arachnoid mater and the meningeal layer of the dura mater.

Drain into the cranial venous sinuses.

Key Fact: The lack of valves in these veins allows for bidirectional flow under certain conditions.

Superior Cerebral Veins:

Pass upward over the lateral surface of the cerebral hemisphere.

Empty into the superior sagittal sinus.

Superficial Middle Cerebral Vein:

Drains the lateral surface of the cerebral hemisphere.

Runs inferiorly in the lateral sulcus.

Empties into the cavernous sinus.

Deep Middle Cerebral Vein:

Drains the insula.

Joins the anterior cerebral vein and striate veins.

Forms the basal vein.

Basal Vein:

Joins the great cerebral vein.

Drains into the straight sinus.

Superior Sagittal Sinus

Inferior Sagittal Sinus

Straight Sinus

Transverse Sinus

Sigmoid Sinus

Sphenoparietal Sinus

Cavernous Sinus

Inferior Petrosal Sinus

Superior Petrosal Sinus

Occipital Sinus

Sigmoid Sinus

Transverse Sinus

Located in the middle cranial fossa

Contains the internal carotid artery

Related to cranial nerves 3, 4, 5 (1st and 2nd divisions), and 6

Important for venous drainage of the brain