Chapter 15 Lecture

HUMAN ANATOMYFifth Edition

Chapter 15The Nervous System:

The Brain and Cranial NervesFrederic Martini

Michael TimmonsRobert Tallitsch

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Introduction

• The brain is far more complex than thespinal cord.

• The brain contains roughly 20 billionneurons.- Excitatory and inhibitory interactions amongthe extensively interconnected neuronal poolsensure that the response can vary to meetchanging circumstances.

Embryology of the Brain

Table 15.1 Development of the Human Brain

Fig

15.1

Fig

15.11White matter

Grey matter

VentriclesFig

4 fluid filled cavities in the brain

Lined by ependymal cells

Contain cerebrospinal fluid

15.2

Protection and support of the brain

• Bones of the skull

• cranial meninges

• cerebrospinal fluid

• blood-brain barrier

Cranial Meninges

• Protective layers of the brain & spinal cord- Provide physical stability and shock absorption

• Outermost- Dura mater-Tough fibrous layer

• Middle- Arachnoid

• Innermost- Pia mater

The Cranial Meninges

Figure 15.4a Superior Cut away

The Cranial Meninges

Figure 15.3c Midsagittal View

• Deep to arachnoidis subarachnoidspace

- Network ofcollagen andelastin fibers(arachnoidtrabeculae)

- Contains CSF

The Cranial Meninges

Figure 15.4b,c Coronal Section

Cerebral Spinal Fluid

• Cushions the CNS

• Supports the brain-the brains is floating inthe CSF

• Transport nutrient/wastes etc.

Choroid plexus

• Produces CSF 500 ml/day

• Composed of ependymal cells andcapillaries (CSF is very different from plasma)

• Found in each ventricle

• Floor of lateral ventricles (2)

• Roof of 3rd ventricle

• Roof of 4th ventricle

Fig

15.5

CSF circulation

Blood supply to thebrain is from theinternal carotid andvertebral arteries

Blood brain barrier

• Maintained by astrocytes

• Not found in:- the hypothalamus

- Pineal gland

- Roof of 3rd & 4th ventricles

The Cerebrum

Figure 15.8a,b The Cerebral Hemispheres, Superior and Anterior Views

The Cerebrum

Figure 15.8c Posterior View Figure 15.9a Lateral View

Functions of the Cerebrum

Table 15.2 The Cerebral Cortex

Motor and Sensory Areasof the Cerebral Cortex

Figure 15.9b Functional Areas of the Cortex

Central White Matter of the Brain

Figure 15.10a Lateral View Figure 15.10b Anterior View

Basal Nuclei

Figure 15.11b,c Coronal View

The Limbic System

Figure 15.12a Lateral View Figure 15.12b Close up

Sectional View Inside the Brain:The Diencephalon

Figure 15.13a Midsagittal View

Sectional View Inside the Brain:The Diencephalon

Figure 15.13b Coronal Section

The Diencephalon: Thalamus

Table 15.6 The Thalamus

The Mesencephalon

Figure 15.16a Lateral View Figure 15.16c Posterior View

Copora

quadrigemina

Fig

15.15

Aqueduct of midbrainor

Cerebralpeduncles Cerebral aqueduct

The Pons

Figure 15.18 The Pons

The Cerebellum

Figure 15.19a Posterior, Superior Surface

The Cerebellum

Figure 15.19b Sagittal Section of Cerebellum

Fig

15.13

The Cranial Nerves

• Cranial nerves are components of theperipheral nervous system that connect tothe brain rather than to the spinal cord.

- There are twelve pairs of cranial nerves.

- Cranial nerves are numbered using Romannumerals.

• Each cranial nerve attaches to the brainnear the associated sensory or motornuclei.

1-12Old

12 pairs ofCranial

nerves OwlsFig

On15.21

Tree

TopsAre

Forever

Viewing

Green

Valleys

And12 Hills

11

The Olfactory Nerve (N I)

• Primary function:- Special sensory (smell)

• Origin:- Receptors of olfactory epithelium

Figure 15.22 The Olfactory Nerve

The Olfactory Nerve (N I)

• Passes through:- Cribriform plate of ethmoid

• Destination:- Olfactory bulbs

Figure 15.22 The Olfactory Nerve

The Optic Nerve (N II)

• Primary function:- Special sensory (vision)

• Origin:- Retina of eye

• Passes through:- Optic canal of sphenoid

• Destination:- Diencephalon by way of the optic chiasm

The Optic Nerve (N II)

Figure 15.23 The Optic Nerve

The Oculomotor Nerve (N III)

• Primary function:- Motor, eye movements

• Origin:- Mesencephalon

• Passes through:- Superior orbital fissure of sphenoid

The Oculomotor Nerve (N III)

• Destination:- Somatic motor:

• Superior, inferior, and medial rectus muscles; theinferior oblique muscle; the levator palpebraesuperioris muscle

- Visceral motor:• Intrinsic eye muscles

The Oculomotor Nerve (N III)

Figure 15.24 The Oculomotor Nerve

The Trochlear Nerve (N IV)

• Primary function:- Motor, eye movements

• Origin:- Mesencephalon

• Passes through:- Superior orbital fissure of sphenoid

• Destination:- Superior oblique muscle

The Trochlear Nerve (N IV)

Figure 15.24 The Trochlear Nerve

The Trigeminal Nerve (N V)

• Primary function:- Mixed (sensory and motor)

- Ophthalmic and maxillary branches sensory

- Mandibular branch mixed

The Trigeminal Nerve (N V)

• Origin:- Ophthalmic branch (sensory):

• Orbital structures, nasal cavity, skin of forehead,superior eyelid, eyebrow, and part of the nose

- Maxillary branch (sensory):• Inferior eyelid, upper lip, gums, and teeth; cheek;nose, palate, and part of the pharynx

- Mandibular branch (mixed):• Sensory from lower gums, teeth, and lips; palateand tongue (part); motor from motor nuclei of pons

The Trigeminal Nerve (N V)

• Passes through:- Ophthalmic branch through superior orbitalfissure

- Maxillary branch through foramen rotundum

- Mandibular branch through foramen ovale

• Destination:- Ophthalmic, maxillary, and mandibularbranches to sensory nuclei in the pons

- Mandibular branch also innervates muscles ofmastication

The Trigeminal Nerve (N V)

Figure 15.25 The Trigeminal Nerve

The Abducens Nerve (N VI)

• Primary function:- Motor, eye movements

• Origin:- Pons

• Passes through:- Superior orbital fissure of sphenoid

• Destination:- Lateral rectus muscle

The Abducens Nerve (N VI)

Figure 15.2 The Abducens Nerve

The Facial Nerve (N VII)

• Primary function:- Mixed (sensory and motor)

• Origin:- Sensory from taste receptors on anterior two-thirds of tongue

- Motor from motor nuclei of pons

• Passes through:- Internal acoustic meatus of temporal bone,along facial canal to reach stylomastoidforamen

The Facial Nerve (N VII)

• Destination:- Sensory to sensory nuclei of pons

- Somatic motor: muscles of facial expression

- Visceral motor: lacrimal (tear) gland and nasalmucous glands via pterygopalatine ganglion;submandibular and sublingual salivary glandsvia submandibular ganglion

The Facial Nerve (N VII)

Figure 15.26 The Facial Nerve

The Vestibulocochlear Nerve (N VIII)

• Primary function:- Special sensory:

• Balance and equilibrium (vestibular branch) andhearing (cochlear branch)

• Origin:- Receptors of the inner ear (vestibule andcochlea)

• Passes through:- Internal acoustic meatus of the temporal bone

The Vestibulocochlear Nerve (N VIII)

• Destination:- Vestibular and cochlear nuclei of pons andmedulla oblongata

The Vestibulocochlear Nerve (N VIII)

Figure 15.27 The Vestibulocochlear Nerve

The Glossopharyngeal Nerve (N IX)

• Primary function:- Mixed (sensory and motor)

• Origin:- Sensory from posterior one-third of thetongue, part of the pharynx and palate, thecarotid arteries of the neck

- Motor from motor nuclei of medulla oblongata

• Passes through:- Jugular foramen between occipital andtemporal bones

The Glossopharyngeal Nerve (N IX)

• Destination:- Sensory fibers to sensory nuclei of medullaoblongata

- Somatic motor:• Pharyngeal muscles involved in swallowing

- Visceral motor:• Parotid salivary gland, after synapsing in the oticganglion

The Glossopharyngeal Nerve (N IX)

Figure 15.28 The Glossopharyngeal Nerve

The Vagus Nerve (N X)

• Primary function:- Mixed (sensory and motor)

• Origin:- Visceral sensory from pharynx (part), auricle,external acoustic meatus, diaphragm, andvisceral organs in thoracic and

abdominopelvic cavities

- Visceral motor from motor nuclei in themedulla oblongata

The Vagus Nerve (N X)

• Passes through:- Jugular foramen between occipital andtemporal bones

• Destination:- Sensory fibers to sensory nuclei andautonomic centers of medulla oblongata

- Somatic motor to muscles of the palate andpharynx

- Visceral motor to respiratory, cardiovascular,and digestive organs in the thoracic andabdominal cavities

The Vagus Nerve (N X)

Figure 15.29 The Vagus Nerve

The Accessory Nerve (N XI)

• Primary function:- Motor

• Origin:- Motor nuclei of spinal cord and medullaoblongata

• Passes through:- Jugular foramen between occipital andtemporal bones

The Accessory Nerve (N XI)

• Destination:- Internal branch innervates voluntary musclesof palate, pharynx, and larynx

- External branch controls sternocleidomastoidand trapezius muscles

The Accessory Nerve (N XI)

Figure 15.30 The Accessory Nerve

The Hypoglossal Nerve (N XII)

• Primary function:- Motor, tongue movements

• Origin:- Motor nuclei of the medulla oblongata

• Passes through:- Hypoglossal canal of occipital bone

• Destination:- Muscles of the tongue

The Hypoglossal Nerve (N XII)

Figure 15.30 The Hypoglossal Nerve