Chapter 14: The Brain & Cranial Nerves
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The brain weighs
Males brains are
No correlation exists between
Major landmarks:
 Cerebrum is divided into large paired
o Area of higher mental functions –
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The surface of the hemispheres are folded and covered by neural cortex
o superficial layer of gray matter –
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This cerebral cortex forms a series of elevated ridges
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Gyri are separated by shallow depressions (_______) and deeper grooves (___________)
Hemispheres of the cerebellum lie below the cerebrum
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Cerebellum also covered with neural cortex
o Adjusts movements by comparing incoming signals
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Once the cerebrum is removed, diencephalon can be seen
o Made up of the right and left thalamus
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The hypothalamus, the floor of the diencephalon, is involved with
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The infundibulum connects the hypothalamus with the pituitary gland
o Integrates the nervous system with
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Brain stem includes the mesencephalon, pons, and medulla oblongata
o Mesencephalon contains nuclei that process visual and auditory info and control
the reflexes associated
o Pons connects the cerebellum to the brain stem
o Medulla oblongata connects the spinal cord to the
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Relays sensory info to the hypothalamus and rest of brain and regulate
autonomic functions such as
Ventricles - Expanded hollow chambers
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continuous with each other and the central canal of the spinal chord
- filled with
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lateral ventricles: contained in each cerebral hemisphere and separated by a thin
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third ventricle: exists within the diencephalon and communicates directly with the lateral
ventricles through the
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fourth ventricle: extends from the posterior surface of the pons down to the superior portion
of the medulla oblongata
Protective factors – Skull, meninges, and cerebrospinal fluid (CSF)
Meninges
Dura mater
 outer fibrous layer is fused with the periosteum of the cranial bones
 the space between outer and inner layer (meningeal) contains tissue fluids, blood
vessels and a few large
o created from dural folds
 falx cerebri is a fold that lies in the longitudinal fissure and contain the
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tentorium cerebelli separates and protects cerebellar hemispheres from
the cerebrum above.
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falx cerebelli divide the
Arachnoid
 Middle layer comprised of the arachnoid membrane and arachnoid trabeculae
Pia mater
 Covers all surfaces of the brain anchored by the processes of astrocytes.
Epidural hemorrhage – blood forced between the dura mater and cranium as a result of
damage to meningeal vessels
Subdural hemorrhage – blood below the dura mater that may extend into the arachnoid.
Results from damage to small vein or dural sinus. Symptoms progress slower because of the
lower BP in these vessels
Cerebrospinal Fluid –
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Cushions delicate Neural structures
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Supports the brain –
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Transports nutrients, Chemical messengers, and Waste products –
o CNS function produces changes in the
Formed in the choroid plexus
 Area of specialized ependymal cells and permeable capillaries
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Two extensive folds originate in the roof of the third ventricle
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Produces ~500 ml/day, production keeps pace with removal
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Circulates from the fourth ventricle to the subarachnoid space through two lateral
apertures and a median aperture
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Flows around
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CSF is absorbed into the venus circulation at the arachnoid granulations
o Clusters of fingerlike extensions that
Hydrocephalus –
 Accumulation created pressure on the bran and therefore decreased function
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Results from trauma or more often masses or tumors that block circulation
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In infants, the cranium expands because
Blood Supply
 Neural tissue has a high demand for energy and oxygen
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The brain has a very extensive arterial blood supply from _______________________
___________________________________ and venus return through the ___________
______________ which drain the ________________
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Cerebrovascular disease – disease that disrupts nutrient supply to the brain
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Cerebrovascular accident (CVA) – blood supply is completely cut off to an area of the
brain.
Blood-Brain Barrier
 protective mechanism that helps maintain a
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exists because of tight junctions of epithelial covering capillaries as well as astrocytes
that control permeability of the epithelium
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Neurotransmitters are prevented from passing
Brain regions:
1. Medulla Oblongata
2. Pons (portion of the Metencephalon)
3. Cerebellum
4. Mesencephalon
5. Diencephalon
6. Cerebrum
Medulla Oblongata - MYELENCEPHALON
 most inferior part of brainstem
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Continuous with the spinal cord; blends into spinal cord just above
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central canal of spinal cord continues into medulla where it opens up into the
Three important groups of nuclei
1. Autonomic nuclei controlling visceral activities
a. Reticular fibers - Extend through the medulla into the mesencephalon
b. Reflexively control and adjust HR, strength of cardiac contraction, distribution of
blood flow and set the pace for respiratory movement
2. Sensory and Motor Nuclei of cranial nerves
a. gives rise to Glossopharyngeal (IX), Vagus (X), Accessory (XI), Hypoglossal (XII)
and Vestibulocochlear (VIII)
3. Relay stations along sensory and motor pathways
a. Nucleus gracilis and nucleus cuneatus pass somatic sensory information to the
Thalamus
i. Tracts leaving these nuclei cross over to the other side of the brain
b. A pair of solitary nuclei receives
c. The olivary nuclei relay information to the cerebellar cortex about somatic motor
commands from higher levels
Pons & Cerebellum - METENCEPHALON
A. Pons links the cerebellum with the mesencephalon, diencephalons, cerebrum and spinal
cord
Four major components:
1. Sensory and motor nuclei of cranial nerves V (Trigeminal), VI (Abducens), VII (Facial), and
VIII (partially in medulla as well)
a. Innervate muscles of the jaw, face and extraocular muscles.
2. Nuclei involved with the control of respiration
a. The apneustic and pneumotaxic centers of the reticular formation in the pons
modify the
3. Nuclei and tracts that process and relay information heading to or from the cerebellum
4. Interconnections of longitudinal tracts
a. Cerebral peduncles are connected to transverse fibers (axons) that link nuclei
of the pons to the
B. Cerebellum - autonomic processing center
Two primary functions:
1. Adjusting postural muscles of the body by modifying the activities of motor centers in the
brain stem
a. Coordinates rapid, automatic adjustments that
b. Monitors all
2. Fine tuning of movements controlled at the conscious and subconscious
a. Refines learned movement patterns
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Peduncles (superior, middle, and inferior) link the cerebellum with the brain stem,
cerebrum, and spinal cord
Cerebellar cortex is made up of highly branched Purkinje cells
Ataxia – a disturbance in balance from injury, stroke or toxins
MESENCEPHALON (midbrain)
corpora quadrigemina – pair of sensory nuclei located at the
- superior colliculi receives visual inputs via lateral geniculate nucleus of the thalamus
- reflex movements in response to
- inferior colliculi receives auditory data from nuclei in the medulla and pons
- reflex movements in response to
Reticular Activating System (RAS) – specialized component of the reticular formation that
DIENCEPHALON - (Thalamus, Hypothalamus, Epithalamus)
 Has a vital role in the integration of
1. Thalamus:
a. final relay point for ascending tracts before they go on to the
b. left and right thalamus are separated by
Five major groups of nuclei function to relay information to the basal nuclei and cerebral cortex
1. Anterior nuclei are part of the limbic system involved with
2. Medial group connects emotional centers of the hypothalamus with the frontal lobes to
provide
3. Ventral group nuclei relay motor signals from basal nuclei in the cerebellum and
cerebrum to
4. Posterior nuclei include the lateral and medial geniculate nucleus which
5. Lateral group nuclei affect emotional states by forming feedback loops with the limbic
system and parietal lobes
2. Hypothalamus
a. extends from optic chiasma to mammilary bodies
b. the infundibulum extends inferiorly to connect the hypothalamus to
c. main visceral (autonomic) control center
d. controls HR, pupil size, BP, produces hormones such as ___________ and
______________, regulates thirst and hunger, sex drive, monitors body temp,
and controls Circadian cycles
3. Epithalamus – roof of the diencephalon
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pineal gland – located in the posterior portion; part of the endocrine system that
secretes melatonin
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extensive part of choroid plexus exists here
Limbic System
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complex group of fiber tracts that function to establish emotional states
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found in the limbic lobe of the cerebral hemispheres and outlying areas of the
diencephalons
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responsible for emotional responses;
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hippocampus – nucleus deep to the limbic lobe responsible for
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link between emotional stress and ill health
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limbic system explains why you want to do complex tasks
CEREBRUM (Telencephalon):
 largest region of the brain
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most of the cerebrum is involved in the processing of
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each hemisphere sends information to and receives information from the
5 lobes: frontal, parietal, temporal, occipital, and insula
-named for skull bones that cover then
gyri: elevated ridges; increase the surface area of the brain
sulcus: shallow grooves that separate gyri
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central sulcus divides
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horizontal lateral sulcus separates
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parieto-occipital sulcus separates
fissures: deeper grooves that separate large regions of the brain
- longitudinal fissure divides right and left hemispheres down to the corpus callosum
I. Cerebral White Matter:
Consists largely of myelinated fibers bundles into large tracts
Fibers and tracts classified according to:
1. Commissures:
- gray commsisure
- corpus callosum
2. Association Fibers:
3. Projection Fibers:
II. Basal Nuclei:
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involved with the cycling of movements between starting and stopping, and monitoring
movements executed by the cortex; also the intensity of the movements.
Mostly occurs at the
Masses of gray matter that lie within each hemisphere deep to the floor of the lateral
ventricle
Parkinson’s Disease –
III. Cerebral Cortex: enables us to be aware of ourselves and our sensations, to communicate,
remember, to understand, and to initiate voluntary movement
- Composed of gray matter, contains billions of neurons arranged in
1. Motor Areas: posterior part of frontal lobes that control motor function
A.) Primary Motor Cortex: located in the
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pyramidal cells: large neurons that allow us to control
B.) Premotor Cortex: anterior to the precentral gyrus in the frontal lobe
 controls learned motor skills of
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Frontal eye field: located partially in and anterior to the premotor cortex and
superior to Broca’s area
o voluntary movement of
C.) Broca's Area: (speech center) anterior to the inferior region of the premotor are and
generally exists only in the left hemisphere
2. Sensory Areas: in parietal, temporal, & occipital lobes
A. Primary Somatosensory and Somatosensory Areas
 Primary somatosensory resides in the postcentral gyrus of the parietal lobe
 Identifies
 Somatosensory lies posterior to the primary and has some connection with it
B. Visual Area (Primary Visual Cortex): extreme posterior tip and medial aspect of occipital
lobe
 receives input from
C. Auditory Area (Primary Auditory Cortex): superior margin of temporal lobes
- receives input from
D. Primary Olfactory Area: Small areas of frontal lobe just above the orbits
- receives input from
E. Primary Taste (Gustatory) Cortex: in parietal lobes just deep to the temporal lobes
- receives input from
F. Vestibular (equilibrium) Cortex: possibly located in the posterior part of the insula
- awareness of
3. Association Areas:
- communicate with sensory and motor regions of the cortex
A. Prefrontal Cortex
B. Language areas
C. General interpretation area
Wernicke's area:
D. Visceral Association Area
Lateralization: (split brain concept)
cerebral dominance:
right brain:
left brain:
Electroencephalogram (EEG) –
Seizures -
Cranial nerves: (insert #, know primary function, origin, and destination)
 12 pairs of cranial nerves are located on the ventrolateral surface of the brain stem
Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
Facial
Vestibulocochlear
Glossopharyngeal
Vagus
Accessory
Hypoglossal
Cranial Reflexes