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.
Major Landmarks of the Brain
I-Cerebrum
BRAIN
II- Brain Stem
III- Cerebellum
Foramen magnum
Spinal cord
Major Landmarks of the Brain
II- Brain Stem
1- Diencephalon
a-Thalamus
I- Cerebrum
b- Hypothalamus
C- Epithalamus
2- Midbrain
d- Cerebral
peduncles
e- Corpora
quadrigemina
a
c
b
d
3- Pons
4- Medulla
oblongata
BRAIN
e
III- Cerebellum
Foramen magnum
Spinal cord
Left
Right
hemisphere hemisphere
I- The Cerebrum
Central
sulcus
Gyrus
Gyrus
Frontal lobe
Precentral
gyrus
Gyri
Frontal lobe
Frontal lobe
Precentral
gyrus
Central
sulcus
Parietal lobe
Parietal lobe
Insula
Postcentral
gyrus
Lateral
sulcus
Occipital Occipital
lobe
lobe
Longitudinal fissure
It separates the right
and left hemispheres
Postcentral
gyrus
Parietal lobe
Temporal
lobe
Occipital
lobe
Cranial Meninges
Skull
Arachnoid villus
Dura mater:
Periosteal layer
Meningeal layer
Arachnoid mater
Pia mater
Superior sagittal
sinus (contains
blood)
Subarachnoid
Space (contains
CSF)
Falx cerebri (in longitudinal
fissure only)
Ventricles and Cerebrospinal Fluid
Lateral ventricles
Interventricular
foramen
Third
ventricle
Cerebral
aqueduct
Fourth ventricle
Central canal
Septum It separates the lateral
pelucidum 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
Lateral apertures They connect the
Medial aperture
Central canal
fourth ventricle with
the sub- arachnoid
space
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.
Functional regions of the Cerebral Cortex
Primary motor cortex
The neurons send signals for
precise, finely coordinated limb
movements (contralateral)
Primary somesthetic It contains the primary
somatosensory cortex for
cortex
touch, pain and
temperature.
Somesthetic It interprets the sensory
association information to making
cognitive sense of it
area
Wernicke area
Motor association
area
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 area
It generates a motor
program for all the muscles
of speech
It recognizes faces and
other familiar objects
Primary
visual cortex
Prefrontal cortex
It receives visual signals
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 gustatory
cortex
It receives gustatory
(taste) signals
Primary
auditory cortex
Auditory
association area
It receives auditory signals
It recognizes the signals received as spoken
words, a familiar piece of music, a voice, etc.
II- The Brain Stem
Thalamus
1- Diencephalon
Thalamus
Hypothalamus
Epithalamus
Epithalamus
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.
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
Median
section
II- The Brain Stem
2- Midbrain
Corpora quadrigemina
Cerebral peduncles
Corpora quadrigemina:
Superior culliculi
They mediate visual
attention and visually
tracking moving objects.
Inferior culliculi
They mediates the
reflexive turning of the
head in response to a
sound
Cerebral peduncles
Median section
They contain the substantia nigra, a motor center
that relays inhibitory signals preventing unwanted
movements.
Degeneration of the neurons of the substantia nigra
leads to the muscle tremor of Parkinson’s disease.
II- The Brain Stem
3- Pons
4- Medulla oblongata
Pons
It connects the two hemispheres
of the cerebellum
Medulla oblongata
Posterolateral
view
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)
Median
section
III- The Cerebellum
Functions:
1- It monitors muscle contractions and
coordinates postural muscles
2- It aids in motor coordination to produce
smooth movements
Cranial and Spinal Nerves
Spinal Nerves
Cranial Nerves
1- Olfactory nerve (I)
Cervical plexus
2- Optic nerve (II)
Brachial plexus
3- Oculomotor nerve (III)
4- Trochlear nerve (IV)
5- Trigeminal nerve (V)
6- Abducens nerve (VI)
Thoracic nerves
7- Facial nerve (VII)
8- Vestibulocochlear nerve (VIII)
9- Glossopharyngeal nerve (IX)
Lumbar plexus
10- Vagus nerve (X)
11- Accessory nerve (XI)
Sacral plexus
12- Hypoglossal nerve (XII)
Coocygeal plexus
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.
Oculomotor nerve (III)
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.
Trochlear nerve (IV) Motor. It innervates the superior oblique muscle of the eye.
Mixed. It provides sensory innervation to the face, and motor innervation
Trigeminal nerve (V) to the muscles of mastication.
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)
Sensory. It provides for the senses of hearing and equilibrium.
Glossopharyngeal
nerve (IX)
Mixed. It provides motor innervation to the muscles of pharynx, and sensory
for taste to the posterior third of the tongue.
Vagus nerve (X)
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).
Hypoglossal nerve (XII)
Accessory nerve (XI)
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Motor. It innervates the muscles that move the tongue.
Motor. It innervates the muscles that move the head and neck (trapezius,
sternocleidomastoid).