HUMAN ANATOMY Chapter 15 Chapter 15 Lecture The Nervous System: Fifth Edition Chapter 15 The Nervous System: The Brain and Cranial Nerves Frederic Martini Michael Timmons Robert Tallitsch Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Introduction • The brain is far more complex than the spinal cord. • The brain contains roughly 20 billion neurons. - Excitatory and inhibitory interactions among the extensively interconnected neuronal pools ensure that the response can vary to meet changing circumstances.

Embryology of the Brain Table 15.1 Development of the Human Brain

Fig 15.1

Fig 15.11 White matter Grey matter

Ventricles Fig 4 fluid filled cavities in the brain Lined by ependymal cells 15.2 Contain cerebrospinal fluid

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 arachnoid is subarachnoid space - Network of collagen and elastin fibers (arachnoid trabeculae) - Contains CSF

The Cranial Meninges Figure 15.4b,c Coronal Section

Cerebral Spinal Fluid • Cushions the CNS • Supports the brain-the brains is floating in the CSF • Transport nutrient/wastes etc.

Choroid plexus • Produces CSF 500 ml/day • Composed of ependymal cells and capillaries (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 the brain is from the internal carotid and vertebral 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 Areas of 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 Aqueduct of midbrain Fig or 15.15 Cerebral peduncles 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 the peripheral nervous system that connect to the brain rather than to the spinal cord. - There are twelve pairs of cranial nerves. - Cranial nerves are numbered using Roman numerals. • Each cranial nerve attaches to the brain near the associated sensory or motor nuclei.

1-12 Old 12 pairs of Cranial nerves Owls Fig On 15.21 Tree Tops Are Forever Viewing Green Valleys And 12 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: • Origin: • Passes through: - 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; the inferior oblique muscle; the levator palpebrae superioris 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; palate and tongue (part); motor from motor nuclei of pons

The Trigeminal Nerve (N V) • Passes through: - Ophthalmic branch through superior orbital fissure - Maxillary branch through foramen rotundum - Mandibular branch through foramen ovale • Destination: - Ophthalmic, maxillary, and mandibular branches to sensory nuclei in the pons - Mandibular branch also innervates muscles of mastication

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 stylomastoid foramen

The Facial Nerve (N VII) • Destination: - Sensory to sensory nuclei of pons - Somatic motor: muscles of facial expression - Visceral motor: lacrimal (tear) gland and nasal mucous glands via pterygopalatine ganglion; submandibular and sublingual salivary glands via 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) and hearing (cochlear branch) • Origin: - Receptors of the inner ear (vestibule and cochlea) • Passes through: - Internal acoustic meatus of the temporal bone

The Vestibulocochlear Nerve (N VIII) • Destination: - Vestibular and cochlear nuclei of pons and medulla 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 the tongue, part of the pharynx and palate, the carotid arteries of the neck - Motor from motor nuclei of medulla oblongata • Passes through: - Jugular foramen between occipital and temporal bones

The Glossopharyngeal Nerve (N IX) • Destination: - Sensory fibers to sensory nuclei of medulla oblongata - Somatic motor: • Pharyngeal muscles involved in swallowing - Visceral motor: • Parotid salivary gland, after synapsing in the otic ganglion

The Glossopharyngeal Nerve (N IX) Figure 15.28 The Glossopharyngeal Nerve

The Vagus Nerve (N X) • Primary function: • Origin: - Mixed (sensory and motor) • Origin: - Visceral sensory from pharynx (part), auricle, external acoustic meatus, diaphragm, and visceral organs in thoracic and abdominopelvic cavities - Visceral motor from motor nuclei in the medulla oblongata

The Vagus Nerve (N X) • Passes through: • Destination: - Jugular foramen between occipital and temporal bones • Destination: - Sensory fibers to sensory nuclei and autonomic centers of medulla oblongata - Somatic motor to muscles of the palate and pharynx - Visceral motor to respiratory, cardiovascular, and digestive organs in the thoracic and abdominal 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 medulla oblongata • Passes through: - Jugular foramen between occipital and temporal bones

The Accessory Nerve (N XI) • Destination: - Internal branch innervates voluntary muscles of palate, pharynx, and larynx - External branch controls sternocleidomastoid and 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