1. Lecture # 21: The Brain and Cranial Nerves
(Chapter 14)
Objectives:
1- Name the major regions of the brain and give the functions of each.
2- Name the three coverings of the central nervous system and give the characteristics, location, and function of each.
3- Give the functions of cerebrospinal fluid and explain its formation, circulation, and resorption.

2. Major Landmarks of the Brain
I-Cerebrum
II- Brain Stem
III- Cerebellum
Foramen magnum
Spinal cord

3. Major Landmarks of the Brain
II- Brain Stem
BRAIN
1- Diencephalon
I- Cerebrum
a-Thalamus
b- Hypothalamus
C- Epithalamus
2- Midbrain
d- Cerebral
peduncles a c
e- Corpora
quadrigemina b e d
3- Pons
III- Cerebellum
4- Medulla oblongata
Foramen magnum
Spinal cord

4. I- The Cerebrum Frontal lobe Frontal lobe Parietal lobe Insula
Right hemisphere
Left hemisphere
Central sulcus
Precentral gyrus
Postcentral gyrus
Gyrus
Gyri
Frontal lobe
Frontal lobe
Precentral gyrus
Parietal lobe
Central sulcus
Insula
Postcentral gyrus
Lateral sulcus
Temporal lobe
Occipital lobe
Parietal lobe
Occipital lobe
Longitudinal fissure
It separates the right and left hemispheres

5. Functional regions of the Cerebral Cortex
Primary motor cortex
(Precentral gyrus)
It contains the primary somatosensory cortex for touch, pain and temperature.
Primary somesthetic or somatosensory cortex
(Postcentral gyrus)
The neurons send signals for precise, finely coordinated limb movements (contralateral).
It interprets the sensory information to making cognitive sense of it.
Somesthetic
association area
Motor association
area
Wernicke area (Temporal lobe)
It is where neurons plan a program for the contraction of muscles required for an action such as dancing, typing or speaking.
It is responsible for the recognition of spoken and written language.
Visual association
area
Broca’s area
(Frontal lobe)
It recognizes faces and other familiar objects.
It generates a motor program for all the muscles of speech.
Primary visual cortex
(Occipital lobe)
It receives visual signals.
Prefrontal cortex (Frontal lobe)
It gives us a sense of our relationship to the rest of the world, enabling us to think about it and to plan and execute appropriate behavior.
Primary auditory cortex (Temporal lobe)
It receives auditory signals.
Primary gustatory cortex
(Insula)
Auditory
association area
It receives gustatory (taste) signals.
It recognizes the signals received as spoken words, a familiar piece of music, a voice, etc.

6. Cranial Meninges Skull Dura mater: Arachnoid mater Pia mater
Arachnoid villus
Dura mater:
Periosteal layer
Superior sagittal
sinus (contains blood)
Meningeal layer
Arachnoid mater
Subarachnoid
Space (contains CSF)
Pia mater
Falx cerebri (in longitudinal
fissure only)

7. Ventricles and Cerebrospinal Fluid
Lateral ventricles
Interventricular foramen
Third ventricle
Cerebral aqueduct
Fourth ventricle
Central canal

8. Interventricular foramina (foramina of Monro)
Septum pelucidum
It separates the lateral ventricles
Interventricular foramina (foramina of Monro)
They communicate the lateral ventricles with the third ventricle
Cerebral aqueduct
It communicates the third ventricles with the fourth ventricle
They connect the fourth ventricle with the sub- arachnoid space
Lateral apertures
Medial aperture
Central canal

9. The Flow of Cerebrospinal Fluid
CSF is secreted by choroid plexus in each lateral ventricle.
CSF flows through
Interventricular foramina
into third ventricle.
Choroid plexus in third
ventricle adds more CSF.
CSF flows down cerebral
aqueduct to fourth ventricle.
Choroid plexus in fourth
ventricle adds more CSF.
CSF flows out two lateral apertures
and one median aperture.
CSF fills subarachnoid space and
bathes external surfaces of brain
and spinal cord.
At arachnoid villi, CSF is reabsorbed
into venous blood of dural
venous sinuses.

10. II- The Brain Stem 1- Diencephalon Thalamus Epithalamus Hypothalamus
It contains the pineal gland that helps regulate the sleep-wake cycle
1- It is the “gateway to the cerebral cortex” – nearly all sensory input to the cerebrum passes by way of synapses in the thalamic nuclei, filters information on its way to cerebral cortex
2- It is involved in emotional functions
Hypothalamus
1- Hormone secretion. It controls anterior pituitary gland.
Median section
2- It is the major integrating center for the autonomic nervous system
3- Thermoregulation
4- Hunger center
5- Thirst center that monitors osmolarity of the blood

11. II- The Brain Stem 2- Midbrain Corpora quadrigemina:
Cerebral peduncles
Corpora quadrigemina
Corpora quadrigemina:
Superior culliculi
They mediate visual attention and visually tracking moving objects.
Inferior culliculi
Cerebral peduncles
They mediates the reflexive turning of the head in response to a sound
They contain the substantia nigra, a motor center that relays inhibitory signals preventing unwanted movements.
Median section
Degeneration of the neurons of the substantia nigra leads to the muscle tremor of Parkinson’s disease.

12. II- The Brain Stem 3- Pons 4- Medulla oblongata Pons Medulla oblongata
It connects the two hemispheres of the cerebellum
Medulla oblongata
Median section
It contains:
1- Cardiac center (regulates the rate and force of heartbeat)
2- Vasomotor center (regulates blood pressure)
3- Respiratory centers (regulates the rhythm and depth of breathing)
Posterolateral view

13. III- The Cerebellum Functions:
1- It monitors muscle contractions and coordinates postural muscles
2- It aids in motor coordination to produce smooth movements

14. Cranial and Spinal Nerves
Cranial Nerves
Cervical plexus
1- Olfactory nerve (I)
2- Optic nerve (II)
Brachial plexus
3- Oculomotor nerve (III)
Thoracic nerves
4- Trochlear nerve (IV)
5- Trigeminal nerve (V)
6- Abducens nerve (VI)
7- Facial nerve (VII)
8- Vestibulocochlear nerve (VIII)
Lumbar plexus
9- Glossopharyngeal nerve (IX)
10- Vagus nerve (X)
Sacral plexus
11- Accessory nerve (XI)
12- Hypoglossal nerve (XII)
Coocygeal plexus

15. Extrinsic muscles of eyes Tongue Head
Three are sensory nerves: Olfactory nerve (smell), optic nerve (vision), and vestibulocochlear nerve (hearing and equilibrium)
Four are mixed nerves: Trigeminal nerve, facial nerve, glossopharyngeal nerve, and vagus nerve.
Five are motor nerves: Oculomotor nerve, trochlear nerve, abducens nerve, hypoglossal nerve, and accessory nerve.
Extrinsic muscles of eyes
Tongue
Head
Olfactory bulb
Optic chiasm
Olfactory tract
Optic nerve (II)
Sensory. It provides for the sense of vision.
Motor. It innervates four of the six extraocular muscles that move the eyes, the muscle that open the eyelid, the muscle that constricts the pupil, and the muscle that changes the shape of the lens for accommodation.
Oculomotor nerve (III)
Motor. It innervates the superior oblique muscle of the eye.
Trochlear nerve (IV)
Mixed. It provides sensory innervation to the face, and motor innervation to the muscles of mastication.
Trigeminal nerve (V)
Motor. It innervates the lateral rectus muscle of the eye.
Abducens nerve (VI)
Mixed. It provides motor innervation to the muscles of facial expression, and sensory innervation to taste to the anterior two thirds of tongue.
Facial nerve (VII)
Vestibulocochlear nerve (VIII)
Glossopharyngeal nerve (IX)
Sensory. It provides for the senses of hearing and equilibrium.
Vagus nerve (X)
Hypoglossal nerve (XII)
Mixed. It provides motor innervation to the muscles of pharynx, and sensory for taste to the posterior third of the tongue.
Accessory nerve (XI)
Mixed. It provides sensory fibers to skin of head and to the pharynx. It provides motor fibers to muscles of speech and swallowing. It innervates most of thoracic and abdominal viscera (parasympathetic nervous system).
Motor. It innervates the muscles that move the tongue.
Motor. It innervates the muscles that move the head and neck (trapezius, sternocleidomastoid).
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16. 1- Sensory 2- Motor General Sensory Trigeminal (V) Special Senses Face
Olfaction (smell)
Olfactory (I)
Vision (sight)
Optic (II)
Equilibrium (balance) and Hearing
Vestibulocochlear (VIII)
Facial (VII)
Glossopharyngeal (IX)
Gustation (taste)
2- Motor
Muscles of facial expression
Facial (VII)
Muscles of mastication
Trigeminal (V)
Motor
Muscles of the eyes
Oculomotor (III), Abducens (VI), Trochlear (IV)
Muscles of the tongue
Hypoglossal (XII)
Muscles that move the head and neck
Accessory (XI)
Taste to the posterior third of the tongue
Muscles of pharynx
Glosso (tongue)
Glossopharyngeal (IX)
Hypoglossal (XII)
Muscles of tongue