Central Nervous System (CNS) and the Brain

4.2 Biology- Anatomy & Physiology

Central and Peripheral Nervous Systems (CNS and PNS)

The 2 Nervous System Structures

The Brain

A Complex Mass of Nerve, Connective, & Epithelial Tissue

Cerebrum, Diencephalon, Cerebellum, & Brainstem

The 4 Anatomical and Functional Regions

Cerebrum

Largest region & occupies most of the space in the cranial cavity; split into 2 cerebral hemispheres (left & right) & each hemisphere are made up of lobes

Diencephalon

Pair of oval-shaped structures deep into the cerebrum; protruding laterally in the lateral ventricles, then meets medially encapsulating the 3rd ventricle; it contains multiple nuclei and is dubbed as the gateway to the cerebral cortex

Cerebellum

Second largest region of the brain; located inferior to the cerebrum but posterior to the brainstem. It consists of a left & right cerebellar hemispheres

Brainstem

A long structure that extends inferiorly from the diencephalon; 10 of the 12 cranial nerves originate from here; it is made up 3 sections/parts/regions: the superior midbrain, the middle round-shaped pons, & inferior medulla oblongata

Cerebrum

Structure A

Diencephalon

Structure B

Cerebellum

Structure D

Brainstem

Structure C

Fissures

Deep grooves/furrows, usually separating bigger parts of the brain.

Sulci

Shallow grooves found in the cerebrum

Gyri

Folds found in the cerebrum; think of a gyro sandwich which is folded

Gyri; Sulcus; 2 Sulci; Gyrus

It takes two _ to form a _ & _ are found on each side of a _.

Cranial Gray Matter

Located superficial in the cerebrum & cerebellum; they are mainly composed of neuron cell bodies, dendrites & synapses- surrounds white matter

Cerebellar & Cerebral Cortexes

Superficial layer on both the cerebrum & cerebellum

Nuclei

Deep masses of gray matter; surrounded by white matter

White Matter

Lies deep to the gray matter & is mainly composed of bundles of axons/tracts.

Cranial Meninges

A set of 3 connective tissue membranes surrounding the brain and spinal cord

Dura Mater

Tough layer protecting the brain; made up of 2 layers

Periosteal Layer

Outer layer surrounding the cranial bones, equivalent to periosteum

Function of the Meningeal Layer

Function: Surrounds and Supports Dural senses that drain deoxygenated blood from the brain

Meningeal Layer

inner layer facing other meninges, extends from the vertebral canal and has 3 structures

Falx Cerebri

In Meningeal Layer; Separates cerebral hemisphere in longitudinal fissure

Tentorium Cerebelli

Separates each Cerebellar Hemisphere; located in the transverse fissure

Falx Cerebelli

Separates each cerebellar hemisphere; located inferiorly to the cerebellum

Subdural Space

A potential space found below the dura mater and above the arachnoid mater; can be opened if needed for brain bleeds etc.

Dural Sinuses

Formed by the dura mater and collects deoxygenated blood and CSF

Arachnoid Mater

Second Layer resembling a spider web; contains the Arachnoid Granulations

Arachnoid Granulations

tree-like protrusions piercing through the dura mater that reabsorbs CSF into the Dural Sinuses

Pia Mater

very thin and delicate layer that closely follows every contour of the brain

Ventricles

A system of fluid filled cavities; lined with a spongy mass of capillaries

Choroid Flexus

Spongy Mass of Capillaries found in ventricles

Cerebrospinal Fluid

Clear and Colorless fluid following in the ventricles; derived from plasma and serves to protect the brain by allowing it to float in the insulating fluid of the CSF

500mL per day

How much CSF is produced by the ependymal cells lining the choroid plexus found in each ventricle and pathways

Functions of the CSF

Buoyancy; Protection; Chemical Stability

Buoyancy in the CSF

allows the brain to attain considerable size without being impaired by its own weight

Protection in the CSF

protects the brain from striking the cranium when the head is jolted in CSF

Chemical Stability in the CSF

rinses metabolic wastes from the nervous tissue and regulates its chemical environment

Lateral Ventricles

forms an arch with anterior, posterior, and inferior horns in the right and left hemispheres

Interventricular Foramen

Inferior to the anterior horn; connects lateral ventricles to the 3rd ventricle

3rd Ventricle

Below the corpus callosum and within the medial part of the thalamus

Cerebral Aqueduct

In midbrain; connects the 3rd and 4th ventricles

4th Ventricle

between the pons and cerebellum

Central Canal and Apertures

near the medulla oblongata; drains CSF into the subarachnoid space

Subarachnoid Space

Space that surrounds the brain and spinal cord, located below the arachnoid mater

Arachnoid Granulations

Reabsorbs CSF into the Dural Sinuses

Lateral Ventricle (image)

Anterior Horn (image)

Interventricular Foramen (image)

Third Ventricle (image)

Cerebral Aqueduct (image)

Fourth Ventricle (image)

Central Canal (image)

Apertures Anterior View (image)

Inferior Horn Anterior View (image)

Posterior Horn (image)

Inferior Horn Lateral View (image)

Apertures Later View (image)