Title: BIOLOGY 2401 ANATOMY
1BIOLOGY 2401ANATOMY PHYSIOLOGYPART ICHAPTER
12 13
- The Brain and the Cranial Nerves
2REGIONS AND ORGANIZATION OF THE BRAIN
- The basic parts of the brain are as follows
- The cerebrum
- The diencephalon
- The brain stem
- The cerebellum
- The brain is organized into groupings of cell
bodies (the gray matter) and fibers (the white
matter). - The cerebrum the cerebellum contain gray matter
on the outer edges w/white matter below this
surface. - While the diencephalon brain stem are filled
with internal pockets of gray matter w/white
matter around them
3THE CEREBRAL HEMISPHERES
- More than 80 of brains weight is the cerebrum.
- The cerebrum is divided into different regions by
fissures sulci (singular, sulcus) - The upfoldings are called gyri.
- There are four major lobes or areas on each
hemisphere - The frontal lobe
- The parietal lobe
- The occipital lobe
- The temporal lobe
4VIEW OF THE CEREBRUM
5Other parts
- The diencephalon
- The thalamus
- The hypothalamus
- The epithalamus
- The brain stem
- The midbrain
- The pons
- The medulla oblongata
- The cerebellum
6PROTECTION OF THE BRAIN
- The brain spinal cord are a very delicate set
of organs which are easily damaged by pressure or
blows. - The CNS is protected by a set of structures
- The cranium spinal column vertebrae
- The meninges
- The cerebrospinal fluid
- The blood brain barrier
7THE MENINGES
- The meninges are a set of 3 connective tissue
layers that surround the brain and spinal cord. - The dura mater toughest outermost
- The arachnoid mater middle layer containing
most major blood vessels and cerebrospinal fluid. - The pia mater inner most layer with fine blood
vessels.
8VIEW OF THE MENINGES
9CEREBROSPINAL FLUID
- CSF is found within and all around the brain to
protect it and make it more buoyant. - CSF is produced from blood plasma.
10VENTRICLES OF THE BRAIN
11CRANIAL NERVES
- 12 major nerves leave the brain before the spinal
cord - These are part of the Peripheral Nervous System
(PNS) - They are numbered I-XII
12CRANIAL NERVES
- I. Olfactory
- II. Optic
- III. Oculomotor
- IV. Trochlear
- V. Trigeminal
- Ophthalmic
- Maxillary
- Mandibular
- VI. Abducens
- VII. Facial
- VIII. Vestibulocochlear
- IX. Glossopharyngeal
- X. Vagus
- XI. Accessory
- XII. Hypoglossal
13 14Cranial Nerve I Olfactory
- Functions solely by carrying afferent impulses
for the sense of smell
15Cranial Nerve II Optic
- Arises from the retina of the eye
- Functions solely for vision
- Exits through optic canal
16Cranial Nerve III Oculomotor
- Functions in raising the eyelid, directing the
eyeball, constricting the iris, and controlling
lens shape - Exits through superior orbital fissure
17Cranial Nerve IV Trochlear
- Primarily a motor nerve that directs the eyeball,
- Exits through the superior orbital fissure
18Cranial Nerve V Trigeminal
- Composed of 3 divisions ophthalmic (V1),
maxillary (V2), and mandibular (V3) - Fibers run via the superior orbital fissure (V1),
the foramen rotundum (V2), and the foramen ovale
(V3) - Conveys sensory impulses from various areas of
the face (V1) and (V2), and supplies motor fibers
(V3) for mastication
19Cranial Nerve V Trigeminal
20Cranial Nerve VI Abducens
- Fibers enter the orbit via the superior orbital
fissure - Primarily a motor nerve innervating the lateral
rectus muscle (abducts the eye) - Exits through the superior orbital fissure
Figure VI from Table 13.2
21Cranial Nerve VII Facial
- Motor functions include facial expression, and
the transmittal of autonomic impulses to lacrimal
and salivary glands - Sensory function is taste from the anterior
two-thirds of the tongue - Exits through the internal acoustic meatus and
the stylomastoid foramen
22Cranial Nerve VII Facial
23Cranial Nerve VIII Vestibulocochlear
- Sensory fibers arise from the hearing and
equilibrium apparatus of the inner ear - Two divisions cochlear (hearing) and vestibular
(balance) - Exits through the internal acoustic meatus
24Cranial Nerve IX Glossopharyngeal
- Mixed nerve with motor sensory functions
- Motor innervates part of tongue pharynx, and
provides motor fibers to the parotid salivary
gland - Sensory fibers conduct taste and general
sensory impulses from the tongue and pharynx - Exits through the jugular foramen
25Cranial Nerve X Vagus
- The only cranial nerve that extends beyond the
head and neck the wanderer - The vagus is a mixed nerve
- Most motor fibers are parasympathetic fibers to
the heart, lungs, and visceral organs - Its sensory function is in taste
- Exits through the jugular foramen
26Cranial Nerve X Vagus
27Cranial Nerve XI Accessory
- Primarily a motor nerve
- Supplies fibers to the larynx, pharynx, soft
palate - Innervates the trapezius and sternocleidomastoid,
which move the head and neck - Exits through the jugular foramen
28Cranial Nerve XI Accessory
29Cranial Nerve XII Hypoglossal
- Innervates muscles of the tongue, which
contribute to swallowing and speech - Exits through the hypoglossal canal
30Practice Questions
31- Which of the following cranial nerves is not
involved with the eye? - Oculomotor
- Trochlear
- Optic
- Abducens
- Trigeminal
32- Which of the following cranial nerves is purely
sensory? - Accessory
- Vagus
- Trigeminal
- Optic
- Hypoglossal
33- Which of the following cranial nerves has a name
that means "the wanderer"? - Vestibulocochlear
- Glossopharyngeal
- Trochlear
- Trigeminal
- Vagus
34- Cranial nerves are formed by fusion of sensory
and motor roots. True False
35- Nerves are either sensory or motor but not
both. True False
36- The cranial nerves serve structures only in the
head and neck. True False