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The Brain and
Cranial Nerves
Major Parts of the Brain
1. Brain stem – continuous with spinal
cord
 Midbrain
 Pons
 Medulla Oblongota
Major Parts of the Brain
2. Cerebellum – Posterior to brain stem
Major Parts of the Brain
3. Diencephalon – superior to the brain
stem
 Thalamus
 Epithalamus
 Hypothalamus
 Subthalamus
Major Parts of the Brain
4. Cerebrum – largest part of the brain
supported by the diencephalon and brain
stem
Brain Stem
1. Medulla Oblongata
 Continuous with spinal cord
 Contains both motor and sensory tracts
Brain Stem / Medulla
 Contains portrusions of white matter
called called pyramids
Brain Stem / Medulla
 The crossing of pyramids result in
neurons in the left cerebral cortex
controlling skeletal muscles on the right
side of the body and neurons in the right
cerebral cortex controlling skeletal
muscles on the left side
Brain Stem / Medulla
 There are reflex centers for regulation of
heart rate, respiratory rate,
vasoconstriction, swallowing, vomiting
Brain Stem / Pons
 Superior to the medulla
 Helps control breathing
 It relays nerve impulses related to
voluntary skeletal movements from the
cerebral cortex to the cerebellum
Brain Stem / Midbrain
 Extends from the pons to the
diencephalon
 Cerebral Peduncles, superior colliculi,
and inferior colliculi located here
Brain Stem / Midbrain
 Cerebral Peduncles – contain major
motor tracts
Brain Stem / Midbrain
 Superior colliculi – help with reflex head
turning in response to visual stimuli
 Responsible for the pupillary reflex and
accomodation reflex (adjusts shape of
lens for far versus close vision)
Brain Stem / Midbrain
 Inferior coliculi – helps with reflex head
turning in response to auditory stimuli
 Reflex center for startle reflex
Cerebellum
 Vermis - central constricted area
 Cerebellar hemispheres – lateral lobes
Cerebellum
 Cerebellar cortex – superficial layer of
the cerebellum made up of gray matter
Cerebellum
 Arbor Vitae – Deep to the gray mater
made up of tracts (White Matter)
Cerebellum
 Main function – Regulates posture and
balance
Diencephalon / Thalamus
 A pair of oval masses of grey matter,
organized into nuclei, with interspersed
tracts of white matter
Diencephalon / Thalamus
 Intermediate mass – Joins the right and
left halves of the thalamus
Diencephalon / Thalamus
 Surrounds the third ventricle
Diencephalon / Thalamus
 It registers conscious recognition of pain,
temp., light touch, and pressure.
 You need your cerebral cortex to
understand the nature of the pain.
Diencephalon /
Hypothalamus
 Inferior to the thalamus
Diencephalon /
Hypothalamus
 Mammillary bodies – serve as reflexes
related to the sense of smell
Diencephalon /
Hypothalamus
 Infundibulum – Connects the pituitary
gland to the hypothalamus
Diencephalon /
Hypothalamus
 Axons from the paraventricular and
supraoptic nuclei form the
hypothalamohypophyseal tract extends
through the infundibulum to the posterior
pituitary
Diencephalon /
Hypothalamus
 Functions
 Control of the ANS
 Production of hormones
 Regulation of emotional and behavioral
patterns
 Regulation of eating and drinking
 Control of body temperature
Diencephalon /
Epithalamus
 Superior and posterior to thalamus
Diencephalon /
Epithalamus
 Pineal Gland – It secretes the hormone
melatonin.
Diencephalon /
Subthalamus
 Below the thalamus
 Helps control body movements
Circumventricular Organs
 Part of the diencephalon called CVOs
that can monitor chemical changes in the
blood because they lack a blood-brain
barrier
Circumventricular Organs
 Part of the hypothalamus, the pineal
gland, and the pituitary gland
Circumventricular Organs
 Thought to be the site of entry into the
brain of HIV.
Cerebrum
 Largest part of the brain
Cerebrum
 Cerebral cortex is composed of grey
matter
 The deep grooves are called fissures
 Shallower grooves are called sulci
Cerebrum
 Beneath the cortex lies cerebral white
matter
Cerebrum
 Longitudinal fissure separates it into right
and left halves
Cerebrum
 The corpus callosum (a bundle of white
fibers) connects it internally.
Cerebrum
 Each cerebral hemisphere is separated
into four lobes (frontal, parietal, temporal,
and occipital)
Cerebrum
 White matter is under the cortex and
consists of myelinated axons running in
three principle directions
Cerebrum
 Association fibers connect and transmit
nerve impulses between gyri in the same
hemisphere
Cerebrum
 Commissural fibers connect gyri in one
cerebral hemisphere to the
corresponding gyri in the opposite
hemisphere
Cerebrum
 Projection fibers transmit impulses from
the cerebrum to other parts of the brain
and spinal cord
Cerebrum
 Basal ganglia are paired masses of grey
matter internally located in each cerebral
hemisphere
Cerebrum
 The Basal Ganglia function in controlling
muscular movements
Cerebrum
 Huntington’s disease is a hereditary
degenerative disorder of the basal nuclei.
 Patients may suffer from abrubt, jerky,
almost continuous movements called
chorea
Cerebrum
 Limbic System found in the cerebral
hemispheres and diencephalon
Cerebrum
 It functions in emotional aspects of
behavior and memory, and is associated
with pleasure and pain
 We tend to remember things associated
with strong emotions. (Think back to the
events you remember from early
childhood. What emotions pop up?)
Lobes of the Cerebrum
 Central Sulcus – Separates the frontal
lobe from the parietal lobe
Lobes of the Cerebrum
 Precentral gyrus – immediately anterior
to the central sulcus
Lobes of the Cerebrum
 Postcentral gyrus – Located immediately
posterior to the central sulcus
Lobes of the Cerebrum
 Lateral cerebral sulcus – Separates the
frontal lobe from the temporal lobe
Parieto-occipital sulcus
 Separates the parietal lobe from the
occipital lobe
Blood-Brain Barrier (BBB)
 Prevents passage of many substances
from blood into brain tissue
Blood-Brain Barrier (BBB)
 Endothelial cells of brain capillaries are
sealed together by tight junctions
Blood-Brain Barrier (BBB)
 Processes of astrocytes press up against
the brain capillaries and only allow
certain substances to pass from the
blood to neurons
Blood-Brain Barrier (BBB)
 Glucose (water soluble) crosses the BBB
via active transport
Blood-Brain Barrier (BBB)
 Other water soluble substances such as
creatinine, urea, and most ions cross
slowly
Blood-Brain Barrier (BBB)
 Proteins and antibiotics cannot cross
Blood-Brain Barrier (BBB)
 Lipid soluble substances such as oxygen,
carbon dioxide, alcohol, and most
anesthetic agents cross easily
Protective coverings of
the Brain
1. Cranium
2. Cranial Meninges – continuous with the
spinal meninges
Protective coverings of
the Brain
Cranial Meninges made up of;
Dura Mater – outer
Arachnoid Mater – middle
Pia Mater – inner
Protective coverings of
the Brain
 Subarachnoid space – between the
arachnoid mater and pia mater which
contains cerebrospinal fluid
Protective coverings of
the Brain
 Three extensions of the dura mater
separate parts of the brain
Protective coverings of
the Brain
1. Falx Cerebri – Separates the two
hemispheres
Protective coverings of
the Brain
2. Falx Cerebelli – Separates the two
hemispheres of the cerebellum
Protective coverings of
the Brain
3. Tentorium Cerebelli – Separates the
cerebrum from the cerebellum
Cerebrospinal Fluid
 Clear colorless liquid
Cerebrospinal Fluid
 Protects the brain and spinal cord against
physical and chemical injuries
Cerebrospinal Fluid
 Caries glucose, oxygen, and other
chemicals from blood to neurons and
neuroglia
Cerebrospinal Fluid
 Circulates through cavities in the brain
and spinal cord and in the subarachnoid
space of the brain and spinal cord
CSF-filled cavities within
Brain
1. Lateral Ventricles – Within each
hemisphere of the cerebrum
CSF-filled cavities within
Brain
2. Third Ventricle – A narrow cavity along
the midline superior to the hypothalamus
and between the R. and L. halves of the
thalamus
CSF-filled cavities within
Brain
3. Fourth Ventricle – between the brain
stem and the cerebellum
Circulation of CSF
 CSF is formed by filtration from networks
of capillaries called choroid plexuses
(found in the ventricles) and in the brain
tissue
Circulation of CSF

1.
2.
3.
4.
5.
It circulates through the;
Lateral ventricles
Third ventricle
Cerebral aqueduct
Fourth ventricle
Then down through the central canal
and around the brain (subarachnoid
space)
Circulation of CSF
 Most of the fluid is absorbed by the
arachnoid villi
Sensory Areas
 Sensory Areas of the cerebral cortex are
concerned with the reception and
interpretation of sensory impulses
Sensory Areas
 Primary Somatosensory area – located in
the postcentral gyrus
Sensory Areas
 Primary Somatosensory Area – Localizes
exactly the points of the body where
sensations originate
Sensory Areas
 Primary Visual Area – located in the
occipital lobe and receives impulses that
convey information for vision
Sensory Areas
 Primary Auditory Area – located in the
superior part of the temporal lobe
Sensory Areas
 Primary Auditory Area – Helps you
interpret pitch, rhythm, and loudness of
speech
Sensory Areas
 The primary gustatory area – it receives
impulses for taste and is located in the
parietal lobe
Sensory Areas
 Primary Olfactory Area – Located in the
medial aspect of the temporal lobe and
receives impulses for smell
Motor Areas
 Govern muscular movements
Motor Areas
 Primary Motor Area – is in the precentral
gyrus
Motor Areas
 Primary Motor Area - It has cell bodies of
neurons that descend to the cord
Motor Areas
 Broca’s Area – Is located in the frontal
lobe close to the lateral cerebral sulcus
and is the motor speech area
Association Areas
 Association areas are concerned with
complex integrative functions such as
memory, emotions, reasoning, will,
judgement, personality traits, and
intelligence
Association Areas
 Wernicke’s Area – Is a broad region in
the temporal and parietal lobes
Association Areas
 Wernicke’s Area – Responsible for
understanding language, but it may be
more involved in sounding out unfamiliar
words.
Aphasia
 Aphasia is the inability to use or
comprehend words due to injury to the
association or motor speech areas
Aphasia
 Receptive Aphasia – You have problems
with comprehension but your own
language is ok
Aphasia
 Expressive Aphasia – You may
comprehend language but your speech
does not make any sense
Cranial Nerves
 Twelve pairs of cranial nerves originate
from the brain
Cranial Nerves
 Some cranial nerves (I, II, VIII) contain
only sensory fibers and are called
sensory nerves
Cranial Nerves
 The rest are mixed nerves because they
contain both sensory and motor fibers