Lecture 13- Brain II and Cranial Nerves I

Frontal lobe

1. Motor Cortex: Somatic motor activity 2. Motor Speech Area (Broca's Area): Muscular movement for vocalization 3. Intellectual Functions 4. Personality

Parietal lobe parts

Somatosensory cortex and wernicke area (overlaps temporal love)

Somatosensory cortex

Conscious somatic sensory information

Wernicke area

Speech understanding, speech formulation

The precentral gyrus of the Frontal lobe

is anterior to the central sulcus and associated with somatic motor function

The postcentral gyrus of the Parietal lobe

is posterior to the central sulcus and associated with somatic sensory function

Occipital lobe: visual cortex

processes visual information

Temporal lobe: auditory cortex

process sounds

Temporal lobe: olfactory cortex

process smells

Temporal lobe: wernicke area (overlaps parietal lobe)

Speech understanding, speech formulation

Temporal lobe: equilibrium

associated with ear organs

Insula

Gustatory cortex: Taste center, part of limbic system

The meninges

Connective tissue surrounding the CNS

Meninges examples

Dura mater, arachnoid mater, pia mater

Named spaces are found in between

the meninges

Ventricular system functions (3)

Cerebrospinal fluid (CSF) production, CSF circulation, CSF reabsorption

Ventricular system structures (6)

1. Lateral Ventricles

2. Interventricular foramen

3. Third Ventricle

4. Cerebral Aqueduct

5. Fourth Ventricle

6. Central Canal of Spinal Cord

Choroid plexus if found

in each ventricle and produces CSF

Ependymal cells

filter CSF from blood

Where does CSF flow after the fourth ventricle?

CSF flows inferiorly to the fourth ventricle.

Where does CSF enter the spinal cord?

CSF enters the spinal cord central canal.

How does CSF enter the subarachnoid space?

CSF enters the subarachnoid space via apertures.

What are the types of apertures through which CSF enters the subarachnoid space?

Two lateral apertures and one median aperture.

Subarachnoid space

Is deep to arachnoid mater, which looks a bit like a spider's web

Arachnoid Villi are

subarachnoid space extending into venous sinuses

CSF returns to venous circulation through

arachnoid villi

What is hydrocephaly?

Pathological accumulation of CSF, leading to intracranial pressure.

What causes lack of CSF flow in hydrocephaly?

Lack of ependymal cell cilia.

What is a reason for poor CSF reabsorption in hydrocephaly?

Poor CSF reabsorption through arachnoid villi.

Dural folds

Falx cerebri, tentorium cerebelli

dural venous sinuses

superior sagittal sinus, straight sinus, transverse sinus, sigmoid sinus, cavernous sinus

Epidural hematoma

Within epidural potential space, Blow to the head

Subdural hematoma

Within subdural potential space, Fast, violent rotation

12 cranial nerves are numbered bt

emergence from the brain

• Forebrain to hindbrain

• Rostral to caudal

CN I name

Olfactory

CN II name

optic

CN III name

oculomotor

CN IV name

Trochlear

CN V name

Trigeminal

CN VI name

Abducent

CN VII name

Facial

CN VIII name

Vestibulocochlear

CN IX name

Glossopharyngeal

CN X name

Vagus

CN XI name

Accessory

CN XII name

Hypoglossal

Sensory only CN

CN I, CN II, CN VIII

Motor only CN

CN III, CN IV, CN VI, CN XI, CN XII

Mixed CN

CN V, CN VII, CN IX, CN X

Parasympathetic CN

CN III, CN VII, CN IX, CN X

Cranial Foramina - Internal View - List

Foramina identified on the internal surface of the cranial base. They are listed roughly from Anterior to Posterior within each group

• Transmitting Cranial Nerves

• Cribriform Plate: small ethmoid perforations

• Optic Canal: large round in medial sphenoid

• Superior Orbital Fissure: between lesser and greater sphenoid

wings

• Foramen Rotundum: medium round in greater sphenoid wing

• Foramen Ovale: medium oval in greater sphenoid wing

• Internal Acoustic Meatus: large round in posterior petrous temporal

• Jugular Foramen: space between petrous temporal and occipital

• Hypoglossal Canal: small round at occipital condyle

• Foramen Magnum: very large round in occipital

• Not Transmitting Cranial Nerves

• Foramen Spinosum: small round in greater sphenoid wing

• Foramen Lacerum: space between sphenoid and petrous temporal

Transmitting Cranial Nerves

Cribriform Plate, Optic Canal, Superior Orbital Fissure, Foramen Rotundum, Foramen Ovale, Internal Acoustic Meatus, Jugular Foramen, Hypoglossal Canal, foramen magnum

Cribriform plate

small ethmoid perforations

Optic canal

large round in medial sphenoid

Superior orbital fissure

between lesser and greater sphenoid wings

Foramen rotundum

medium round in greater sphenoid wing

Foramen ovale

medium oval in greater sphenoid wing

Internal acoustic meatus

large round in posterior petrous temporal

Jugular foramen

space between petrous temporal and occipital

Hypoglossal canal

small round at occipital condyle

Foramen magnum

very large round in occipital

Non transmitting cranial nerves

Foramen spinosum, foramen lacerum

Framen spinosum

small round in greater sphenoid wing

Foramen lacerum

space between sphenoid and petrous temporal

cribriform plate CN

olfactory nerve (CN I)

optic canal CN

optic nerve (CN II)

Superior orbital fissures CNs (4)

Oculomotor nerve (CN III), Trochlear nerve (CN IV), Ophthalmic nerve (CN V1), Abducens nerve (CN VI)

Foramen rotundum CN

Maxillary nerve (CN V2)

Foramen ovale CN

Mandibular nerve (CN V3)

Internal acoustic meatus CN (2)

Facial nerve (CN VII), Vestibulocochlear nerve (CN VIII)

Jugular foramen CN (3)

Glossopharyngeal nerve (CN IX), Vagus nerve (CN X), Accessory nerve (CN XI)

Hypoglossal canal CN

Hypoglossal nerve (CN XII)

Cranial nerves that transmit special sensory signals (3)

CN I, CN II, CN III

CN I olfactory nerve special senses

cribriform plate, smell

CN II optic nerve special senses

Optic canal, sight

CN VIII vestibulocochlear nerve special sense

Internal acoustic meatus, hearing and equilibrium

Axons of olfactory nerves pass from

anterior cranial fossa through the cribriform plate

Olfactory nerve neurons pass through

the ethmoid plate into the olfactory bulb where they synapse with interneurons that take the signal down the olfactory tract to the brain.

The optic nerve is a large nerve passing

between the eye and the brain

Some optic nerve neurons

cross over at the optic chiasm, then follow the optic tract through the optic canal of the sphenoid

Optic nerve neurons carrying visual information from the left side of thebody make their way to

the left side of the cerebrum

Some optic nerve neurons cross over at the

optic chiasm, then follow the optic tract to the lateral geniculate body

Two Branches of the vestibulocochlear nerve branch 1

Vestibular branch, cochlear branch

Vestibular branch source

semicircular canals

Vestibular branch function

balance sensation

Cochlea branch source

cochlea

Cochlea branch function

hearing sensation