Chapter 14 Outline - An Introduction to the Brain and Cranial Nerves
Learning Outcomes
 14-1 Name the major brain regions and ventricles, and describe the locations and
functions of each.
 14-2 Explain how the brain is protected and supported, and discuss the formation,
circulation, and function of cerebrospinal fluid. Identify the CSF pathway starting with
the choroid plexus. Describe the structure and functions of the blood-brain barrier and
the blood – CSF barrier
 14-3 Identify the main components and functions of the medulla oblongata.
 14-4 List the main components of the pons, and specify the functions of each.
 14-5 List the main components of the cerebellum, and specify the functions of each.
 14-6 List the main components of the midbrain, and specify the functions of each.
 14-7 List the main components of the diencephalon, and specify the functions of each.
 14-8 Identify the main components of the limbic system, and specify the locations and
functions of each.
 14-9 Identify the major anatomical subdivisions and functions of the cerebrum, and
discuss the origin and significance of the major types of brain waves seen in an
electroencephalogram.
 14-10 Describe representative examples of cranial reflexes that produce somatic
responses or visceral responses to specific stimuli.
 Describe what may result when various areas of the brain have been damaged/are not
functioning properly. Identify areas of brain injury based on description of injury
symptoms (Focus on examples given in class or on application handouts).
 Be able to answer questions similar to clinical scenario application questions.
Chapter 14 Outline - An Introduction to the Brain and Cranial Nerves
I.
14-1 An Introduction to Brain Structures and Functions
A. Major Brain Structures and Functions
Structure
Cerebrum
Cerebellum
Diencephalon
Midbrain
Pons
Medulla oblongata
Description
 Divided into L and R hemispheres
 Gyri = elevated ridges
 Sulci = shallow depressions
 Fissures = deeper grooves
 Covered by layer of gray matter =
cerebral cortex
 Divided into L and R hemispheres
 Covered by layer of gray matter =
cerebellar cortex
 Provides structural and functional link
between cerebral hemispheres and
brain stem
 3 divisions: Epithalamus, thalamus
and hypothalamus
 Pituitary gland connects to
hypothalamus via a stalk known as
the infundibulum
 Aka mesencephalon
 Found between diencephalon and
pons
 Pons means “bridge”
 Connects cerebellum to brain stem
 Connects brain to spinal cord
Basic Functions
Controls higher mental functions,
such as conscious thought, intellect
and memory
Coordinates repetitive body
movements







Thalamus: relays/processes
sensory information
Hypothalamus: involved with
hormone production, emotion
and autonomic function
Processes sight, sound and
associated reflexes
Maintains consciousness
Involved in somatic and
visceral motor control
Relays information to
thalamus/brain stem
Regulates autonomic
functions such as heart rate,
blood pressure and digestion
B. Ventricles of the brain
1. Neurocoel: fluid filled internal cavity within developing brain
2. Neurocoel expands during embryonic development to form chambers =
ventricles
a. 2 lateral ventricles separated by septum pellucidum
b. Third ventricle communicates with lateral ventricles via interventricular
foramen
c. Fourth ventricle connects to third ventricle via cerebral aqueduct, also
narrows to join central canal of spinal cord
3. Ventricles lined with ependymal cells
4. CSF circulates from ventricles/central canal into subarachnoid space
Chapter 14 Outline - An Introduction to the Brain and Cranial Nerves
II.
14-2 Protection of the Brain
A. Physical Protection of the Brain
1. Bones of the cranium
2. Cranial meninges
a. Have three layers
i.
Pia mater

Innermost layer

Sticks to surface of brain

Anchored by astrocytes

Accompanies cerebral BVs as they penetrate surface of
brain to reach internal structures
ii.
Arachnoid mater

Covers brain providing smooth surface (no folds)

Subarachnoid space separates arachnoid and pia mater,
where CSF circulates
iii.
Dura mater

2 layers – outer layer fused to periosteum of cranial
bones

Outer and inner layer separated by gap where fluids
and BVs are located

Dural folds:
 Inward folding of inner layer of dura mater
 Provides additional stabilization and support
(seatbelt)
 Three largest are falx celebri (separates cerebral
hemispheres), tentorium cerebelli (protects
cerebellar hemispheres), falx cerebelli
(separates cerebellar hemispheres)

Dural sinuses: large collecting veins within dural folds,
includes superior/inferior sagittal sinus and transverse
sinus
Chapter 14 Outline - An Introduction to the Brain and Cranial Nerves
b. Are continuous with spinal meninges
c. Protect the brain from cranial trauma (head injury resulting from
impact with another object)
d. Meninges and Clinical Applications
i.
Cranial trauma = head injury resulting from impact with another
object (example: concussion)
ii.
Bleeding in cranial cavity can result in:
 Epidural hemorrhage
 cranial artery breaks and blood is forced between dura
mater and cranial cavity = in pressure = distortion of
brain tissue = loss of consciousness
 Cranial vein break = delay in symptoms; fatal if not
treated
 Subdural hemorrhage: blood enters inner layer of dura
mater from small vein/dural sinuses; delay in symptoms
 Pool of blood forming outside of damaged vessel =
subdural hematoma
3. Cerebrospinal Fluid (CSF)
a. Surrounds all exposed surfaces of CNS
b. Interchanges with interstitial fluid of brain
c. Functions of CSF
i.
Shock absorption/protection
ii.
Cushion brain structures
iii.
Transport nutrients, chemical messengers and waste products
d. Formation of CSF
i.
Occurs in choroid plexus
ii.
Specialized ependymal cells secrete and adjust CSF
iii.
Circulation of CSF

Ependymal cells secrete CSF in choroid plexus

CSF circulates through ventricles/central canal

CSF reaches subarachnoid space and flows around
brain, spinal cord and cauda equine

CSF fluid is absorbed into venous circulation at
arachnoid granulations and returns to choroid plexus
Chapter 14 Outline - An Introduction to the Brain and Cranial Nerves
iv.
Hydrocephalus (aka “water on the brain)

Occurs when too much reabsorption of CSF in infants

Can be caused by genetics, trauma, meningitis, tumor
or hemorrhage
B. Biochemical Isolation - Blood–brain barrier (BBB)
1. Blood Supply to the Brain
a. Supplies nutrients and oxygen to brain
b. Delivered by internal carotid arteries and vertebral arteries
c. Removed from dural sinuses by internal jugular veins
2. Blood–Brain Barrier (BBB)
a. Isolates CNS neural tissue from general circulation
b. Formed by network of tight junctions prevents diffusion of most
materials
c. Only lipid-soluble compounds (O , CO ), steroids, and prostaglandins
2
2
can diffuse into interstitial fluid of CNS
d. Astrocytes control blood–brain barrier by releasing chemicals that
control permeability
3. Blood–CSF Barrier
a. Formed by special ependymal cells
b. Surrounds capillaries of choroid plexus
c. Limits movement of compounds transferred
d. Allows chemical composition of blood and CSF to differ
4. Four Breaks in the BBB
a. Portions of hypothalamus
i.
Secrete hypothalamic hormones and allows for their diffusion
into circulation
b. Posterior lobe of pituitary gland
i.
Secretes hormones ADH and oxytocin and allows for their
release into circulation
c. Pineal gland
i.
Pineal secretions released into circulation
d. Choroid plexus
i.
Where special ependymal cells maintain blood–CSF barrier
Chapter 14 Outline - An Introduction to the Brain and Cranial Nerves
5. BBB and blood-CSF barrier Clinical Applications
a. Some substances freely move between blood – brain or blood – CSF,
while others do not
b. Important in choosing appropriate medicine for treatment of disease
c. Example: bacterial meningitis cannot be treated by antibiotic
tetracycline because it cannot break through barriers so other
antibiotics must be explored
III.
14-3 The Medulla Oblongata
A. Includes three groups of nuclei
Nuclei
Function
•
Receive inputs from cranial nerves, cerebral cortex, and brain stems
•
Output controls two major groups of reflex centers
•
Cardiovascular centers: adjust HR, blood flow
•
Respiratory rhythmicity centers: set pace for respiratory movements
Sensory/Motor of Cranial
•
Associated with five of the cranial nerves
Nerves
•
Provide motor commands to muscles of pharynx, neck, back and
Autonomic
visceral organs of thoracic/peritoneal cavities
Relay Stations
•
Pass somatic sensory info to thalamus
•
Receive visceral sensory info
•
Relay info regarding somatic motor commands to cerebellar cortex
Chapter 14 Outline - An Introduction to the Brain and Cranial Nerves
IV.
14-4 The Pons
A. Associated with 4 of 12 cranial nerves
B. Includes four components
Component
Function
Sensory/Motor Nuclei of Cranial Nerves
•
Innervate jaw, face, eye muscles and
sense organ of internal ear
Nuclei involved with respiration
•
Monitor activity of respiratory
rhythmicity center
Nuclei/tracts that process/really info to and from
cerebellum
•
Links cerebellum w/ brain stem,
cerebrum, spinal cord
Ascending, Descending, Transverse Tracts
•
Carry sensory/motor info
V.
14-5 The Cerebellum
A. Two main functions
1. Adjust postural muscles of body (proprioceptive information)
2. Programming/fine tuning conscious and subconscious movements
B. Vermis: separates hemispheres of cerebellum
C. Cerebellar peduncles: link cerebellum to brain stem, cerebrum, spinal cord
D. Cerebral cortex:
1. gray matter
a. Purkinje cells
i.
Large, branched cells in cerebellar cortex
ii.
Receive input from 200,000 synapses
2. White matter
a. Arbor vitae - “tree of life”
b. Contains branching white matter
E. The Cerebellum and Clinical Applications
1. Ataxia
2. Disturbance in muscle coordination
3. Severe cases = inability to sit or stand without assistance
4. Caused by: trauma, stroke, drugs (alcohol)
VI.
14-6 The Midbrain
A. Corpora Quadrigemina: pairs of sensory nuclei which process visual and auditory
sensations
Chapter 14 Outline - An Introduction to the Brain and Cranial Nerves
VII.
14-7 The Diencephalon
A. Integrates sensory info with motor output at subconscious level
B. Epithalamus (roof)
1. contains pineal gland
2. Pineal gland secretes melatonin which is important to regulation of day-night
cycles
C. The Thalamus: Relay sensory information to basal nuclei and cerebral cortex of
cerebrum and to cerebellum
D. The Hypothalamus
1. Mamillary bodies
a. Process olfactory sensations
b. Control reflex movements such as eating, chewing, licking and
swallowing
2. Eight Functions of the Hypothalamus
a. Provides subconscious control of skeletal muscle
b. Controls autonomic function
c. Coordinates activities of nervous and endocrine systems
d. Secretes two hormones
i.
Antidiuretic hormone (ADH): restricts water loss by kidneys
ii.
Oxytocin (OT; OXT): stimulates smooth muscle contractions of
uterus, mammary glands and prostate
VIII.
e. Produces emotions and behavioral drives
i.
The feeding center (hunger)
ii.
The thirst center (thirst)
f. Coordinates voluntary and autonomic functions
g. Regulates body temperature
h. Controls circadian rhythms (day–night cycles)
14-8 The Limbic System
A. Functional grouping along border of cerebrum and diencephalon that:
1. Establishes emotional states
2. Links conscious functions of cerebral cortex with autonomic functions of brain
stem
3. Facilitates memory storage and retrieval
Chapter 14 Outline - An Introduction to the Brain and Cranial Nerves
B. Components of limbic system
1. Nuclei, hypothalamus and mammillary body of diencephalon
2. Corpus callosum: links two cerebral hemispheres
3. Fornix: connects hippocampus and hypothalamus
4. Hippocampus: important in storage/retrieval of long term memories
IX.
14-9 The Cerebrum
A. Is the largest part of the brain
B. Controls all conscious thoughts and intellectual functions
C. Processes somatic sensory and motor information
D. Parts of the Cerebrum
1. Cerebral cortex = gray matter
2. White matter
a. Deep to basal cortex
b. Found around basal nuclei
c. Contains fibers which connect various parts of the brain
3. Lobes = divisions in brain (frontal, parietal, occipital, temporal)
4. The Basal Nuclei
a. Masses of gray matter embedded in white matter of cerebrum
b. Direct subconscious control of skeletal muscle tone and coordinate
learned movement patterns
5. Activities inhibited by dopamine
a. Parkinson’s = decrease in dopamine secreted = impact to basal nuclei
functions
Chapter 14 Outline - An Introduction to the Brain and Cranial Nerves
6. Motor and Sensory Areas of the Cortex
Area
Function
Primary motor cortex
Voluntary control of skeletal muscle
Primary sensory cortex
Conscious perception of touch, pressure, pain, vibration, taste and
temp
Visual cortex
Conscious perception of visual stimuli
Auditory cortex
Conscious perception of hearing
Olfactory cortex
Conscious perception of smell
Association areas
Integrate/process sensory data
Process/initiate motor activities
Chapter 14 Outline - An Introduction to the Brain and Cranial Nerves
7. Integrative Centers
a. Located in lobes and cortical areas of both cerebral hemispheres
b. Receive info from association areas
c. Direct complex motor or analytical activities
Center
Function
Prefrontal cortex

Integrates information from sensory association areas
and performs abstract intellectual functions (i.e.
predicting consequences of possible responses)
General interpretive area
(Wernicke’s area)



Receives info from all sensory association areas
Only in one hemisphere
Integrates sensory information and coordinates access
to visual/auditory memories
Speech center (Broca’s area)

Regulates patterns of breathing and vocalization
needed for normal speech
Brodmann areas


Patterns of cellular organization in cerebral cortex
Correspond to various association areas and
integrative centers
8. Hemispheric Lateralization
a. Functional differences between L and R hemispheres
b. Each performs certain functions that are not ordinarily performed by
the opposite hemisphere
c. Left Hemisphere controls:
i.
Reading, writing, math
ii.
Decision making
iii.
Speech and language
d. The Right Hemisphere relates to:
i.
Senses
ii.
Recognition (faces, voice inflections)
E. Monitoring Brain Activity
1. Electroencephalogram (EEG)
a. Monitors brain activity
b. Typical brain waves
i.
Alpha waves: occur in brains of healthy, awake adults resting
with eyes close
Chapter 14 Outline - An Introduction to the Brain and Cranial Nerves
ii.
Beta waves: occur during intense concentration, stress,
psychological tension
iii.
Theta waves: occur during sleep in normal adults, children,
frustrated adults
iv.
Delta waves: seen during deep sleep, infants and awake adults
when tumor, vascular blockage, inflammation has caused
damage
2. Pacemaker mechanism
a. Synchronizes electrical activity between hemispheres
b. Brain damage can cause desynchronization resulting in:
i.
Seizure
 Is a temporary cerebral disorder
 Changes the electroencephalogram
 Symptoms depend on regions affected
X.
14-10 Cranial Reflexes
A. Monosynaptic and polysynaptic
B. Involve sensory and motor fibers of cranial nerves
C. Clinically useful to check cranial nerve for brain damage
D. Examples:
Reflex
Type
Stimulus
Action
Corneal
Somatic
Contact with
cornea
Blinking
Auditory
Somatic
Loud noise
eye/head movement
Direct light/Consensual light
Visceral
Light
Constriction of pupil