3.04 Brain and Cranial Nerves 1

Forebrain (structures)

Cerebrum, thalamus, and hypothalamus.

Midbrain (structures/location)

Midbrain, forming the top of the brainstem.

Hindbrain (structures)

Pons, cerebellum, and medulla.

Three major brain regions (external view)

Cerebrum (lobes w/ gyri/sulci), brainstem, and cerebellum.

Brain regions visible in medial view

Diencephalon and midbrain.

Brain regions visible in inferior view

Cerebrum, diencephalon, brainstem, midbrain, and cerebellum.

Embryology Week 4: Primary brain vesicles

Prosencephalon, mesencephalon, and rhombencephalon.

Prosencephalon (Week 4 location/common name)

Superior primary vesicle; the forebrain.

Mesencephalon (Week 4 location/common name)

Middle primary vesicle; the midbrain.

Rhombencephalon (Week 4 location/common name)

Inferior primary vesicle; the hindbrain.

Telencephalon origin and adult structure

Arises from prosencephalon; forms the cerebrum.

Telencephalon neural space

Forms the lateral ventricles.

Diencephalon origin and adult structure

Arises from prosencephalon; forms epithalamus and hypothalamus.

Diencephalon neural space

Forms the third ventricle.

Mesencephalon (Week 5 adult structures)

Forms cerebral peduncles, superior colliculi, and inferior colliculi.

Mesencephalon neural space

Forms the cerebral aqueduct.

Metencephalon origin and adult structures

Arises from rhombencephalon; forms pons and cerebellum.

Metencephalon neural space

Forms the superior part of the fourth ventricle.

Myelencephalon origin and adult structure

Arises from rhombencephalon; forms the medulla.

Myelencephalon neural space

Forms the inferior part of the fourth ventricle.

Neural tube adult fate (margin note)

Forms the central canal and spinal cord.

Secondary vesicles & neural canal development

Fold to form adult regions; neural canal forms named spaces.

Gray matter contents

Motor/interneuron cell bodies, dendrites, telodendria, and unmyelinated axons.

Gray matter location

Forms the outer cerebral cortex.

Cerebral nuclei definition

Deep clusters of neuron cell bodies located within white matter.

White matter composition and location

Myelinated axons; located deep to gray matter in cortex.

White matter examples (notes)

Corpus callosum and internal capsule.

Four protective structures of the brain

Cranium, meninges, CSF, and blood-brain barrier.

Cranial meninges definition

Connective tissue separating the cranium from the brain.

Cranial meninges functions (margin note)

Protect brain, form large veins, contain and circulate CSF.

Pia mater

Thin innermost meningeal layer clinging directly to brain surface.

Arachnoid mater feature

Contains arachnoid trabeculae (web-like fibers).

Dura mater layers

Tough layer with superficial periosteal layer and deep meningeal layer.

Cranial dural septa (dural folds) formation

Formed by meningeal layer extending inward at four cranial cavity locations.

Cranial dural septa function (margin note)

Partition the brain and provide support.

Falx cerebri

Projects into longitudinal fissure; separates left and right cerebral hemispheres.

Tentorium cerebelli (margin note)

Horizontal fold that separates the cerebrum from the cerebellum.

Falx cerebelli

Vertical fold separating the left and right cerebellar hemispheres.

Diaphragma sellae (structure & margin note)

Small septum between pituitary and hypothalamus; forms roof for sella turcica.

Dural venous sinuses formation

Formed where the two dura mater layers separate.

Superior and inferior sagittal sinuses location

Located within superior and inferior margins of falx cerebri.

Confluence of sinuses (margin note)

Junction point where Superior sagittal sinus, Straight sinus, Occipital sinus, and Transverse sinuses sinuses meet.

Transverse sinuses location

Located within posterior border of tentorium cerebelli.

Occipital sinus location (margin note)

Located in posterior vertical border of falx cerebelli.

Foramen magnum

Large skull base opening where vertebral arteries enter.

Vertebral arteries fate (margin note)

Vertebral arteries join to form the basilar artery.

Jugular foramen contents and function

Sigmoid sinus exits here to become internal jugular vein (main drainage).

Jugular foramen position

Anterolateral, first hole relative to foramen magnum.

Carotid foramen contents and position

Internal carotid artery enters (main brain supplier); right in front of jugular.

Foramen spinosum function (margin note)

Passageway through which the middle meningeal artery flows (supplies dura mater). by greater wing of sphenoid.

Transverse sinus groove location

Horizontal groove located on the occipital bone.

Sigmoid sinus groove path (margin note)

S-shaped groove leading from transverse sinus to jugular foramen.

Superior petrosal sinus location

Located along top ridge of petrous temporal bone.

Inferior petrosal sinus location

Located below the petrous temporal bone.

Cavernous sinus location and contents

Located beside sella turcica; internal carotid artery (ICA) flows through.

Sphenoparietal sinus location

Located along the underside of the lesser sphenoid wing.

Lateral ventricles anatomy

Two ventricles (one per hemisphere) separated by septum pellucidum.

Third ventricle location and communication

In diencephalon; communicates with lateral ventricles via interventricular foramen.

Third and fourth ventricle communication (margin note)

Communicate directly through the cerebral aqueduct.

Fourth ventricle location and path

Located between pons and cerebellum; merges with central canal of spinal cord.

Cerebrospinal Fluid (CSF) definition

Clear liquid that circulates in ventricles and subarachnoid space.

CSF Function: Buoyancy

Allows the brain to "float" in CSF.

CSF Function: Protection

Provides a liquid cushion for the brain.

CSF Function: Environmental stability (margin note)

Transports nutrients and removes waste.

Choroid plexus location and function

Located in each ventricle; forms cerebrospinal fluid.

Choroid plexus composition

Composed of ependymal cells and capillaries inside the pia mater.

CSF formation mechanism (margin note)

Blood from capillaries is filtered to form CSF.

Circulation of CSF: Step 1

CSF is produced by the choroid plexus.

Circulation of CSF: Step 2

Flows from lateral ventricle through interventricular foramen into 3rd ventricle.

Circulation of CSF: Step 2 to Step 3 pathway

Flows from third ventricle through cerebral aqueduct to fourth ventricle.

Circulation of CSF: Step 3 exit pathways

Exits fourth ventricle via paired lateral apertures or single median aperture.

Fourth ventricle paired lateral apertures destination

Lead CSF into the subarachnoid space.

Fourth ventricle single median aperture destination

Leads CSF into the central canal.

Circulation of CSF: Step 4

CSF flows throughout the subarachnoid space.

Circulation of CSF: Step 5 drainage

Excess CSF flows into arachnoid villi (granulations) to drain into dural venous sinuses.

Arachnoid villi drainage flow dynamics (margin note)

One-way flow of CSF; blood stays inside the venous sinus.

Circle of Willis: Back source arteries

Two vertebral arteries coming up the neck.

Vertebral arteries cerebellar branch (margin note)

Each vertebral artery gives off a Posterior Inferior Cerebellar Artery (PICA).

Vertebral arteries spinal branch

They give off the anterior spinal artery that runs down spinal cord.

Basilar artery formation

Formed by the merging of the two vertebral arteries.

Basilar artery cerebellar branches

Gives off Anterior Inferior Cerebellar Artery (AICA) and Superior Cerebellar Artery (SCA).

Basilar artery terminal branch (notes/above)

Finally splits into two posterior cerebral arteries (PCA).

Circle of Willis: Front source arteries

Each internal carotid artery (2 ICAs) comes from neck.

Internal carotid artery terminal branches

Splits into Anterior Cerebral Artery (ACA) and Middle Cerebral Artery (MCA).

Posterior communicating artery (PCoA) connections

Links each ICA to PCA on its side, joining front and back.

Anterior communicating artery (ACoA) connections

Links the two anterior cerebral arteries (ACAs), joining left and right.

Main blood supply source: Anterior vs Posterior brain

Anterior source is internal carotid artery; posterior source is basilar artery.

Vertebral artery branches summary

Gives rise to basilar artery and anterior spinal artery.

Arteries above tentorium cerebelli

Posterior cerebral artery (PCA), middle cerebral artery (MCA), and anterior cerebral artery (ACA).

Arteries below tentorium cerebelli

Superior cerebellar artery (SCA), AICA, and PICA.

Connectors in Circle of Willis: Function distinction

PCoA connects front to back; ACoA connects anterior left to right.

Blood-Brain Barrier (BBB) primary function

Regulates what enters the interstitial brain fluid.

Blood-Brain Barrier components

Capillary endothelium, astrocyte perivascular feet, and continuous basement membrane.

Why BBB is reduced in choroid plexus (margin note)

Capillaries must be permeable to allow filtration and make CSF.

Why BBB is reduced in hypothalamus and pineal gland (margin note)

Endocrine hormones require direct access to and from the blood.

Cerebrum (general function)

Location of conscious thoughts and intellectual functions.

Cerebrum (neuronal role)

Contains neurons needed for complex intellectual function.

Cerebrum (hemispheres margin note)

Has a left hemisphere and a right hemisphere.

Cerebrum (structural layers and regions)

Has outer cortex, inner white matter, and cerebral nuclei (deep gray matter).

Cerebrum (surface features)

Surface contains gyri (ridges), sulci (grooves), and deep fissures.