Chp. 14 The Brain
They are not all alike
1
The Brain Introduction
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The other organ of the CNS
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The “supercomputer” of the
body
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Cellular activities of brain neural
tissue are responsible for the
above functions
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Primary integration center
Carries out motor, sensory,
association, and higher order
functions
Personality, emotions, and
dreaming
Learning, memory, planning, social
judgement, and language are
considered some higher order
functions
We know very little about
2
Major Brain Landmarks
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Rostral (toward the forehead) and caudal (toward the spine)
are commonly used, and used differently depending on the
reference point
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Anterior/posterior and superior/inferior are still acceptable and I
prefer these terms
Main regions are the brainstem, cerebrum, and cerebellum
3
Major Brain Landmarks Continued
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The cerebrum makes up 83% of brain
volume and is divided into two lateral
hemispheres
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Cerebral hemispheres possess many
folds called gyri (plural), which are
separated by grooves called sulci
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Gyrus and sulcus – singular
Cerebellum is the second largest
portion of the brain at 10%
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50% of the brain’s neurons though!!
Separated rostrally (superiorly) by a
transverse cerebral fissure
Also possess folds (folia) and sulci
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Brain stem is comprised of medulla
oblongata, pons, midbrain, and
diencephalon (caudally to rostrally)
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Brain is often described as looking like
a mushroom
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Brainstem is the stalk while the cerebrum
is the cap
4
Gray and White Matter Organization
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From Chapter 12 of BI 231, recall what
structures comprise gray matter
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What structures comprise white matter?
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Called cortex which means bark or rind
All three regions of the brain possess
collections of gray matter called nuclei
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Why does it appear white?
Gray matter of cerebrum and cerebellum
is primarily superficial
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Why does it have a gray appearance
Neuron cell bodies with chromatophilic
substance (Nissl bodies)
Deep and completely surrounded by white
matter
White matter is found everywhere else
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Arranged in bundles of axons called tracts
(fasciculi) as in spinal cord
Specific types of brain tracts discussed
later
5
Cranial Meninges
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Neural tissue is quite delicate
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Meninges, along with cranial
bones, CSF, and brain barrier
system protect the brain
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Same three layers as spine
with similar function
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Mostly continuous with spinal
meninges
One major difference is that
cranial dura mater consists of
two layers
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Periosteal layer is next to inner
layer of compact bone of
cranial bones
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No epidural space in cranium
Meningeal layer forms falx
cerebri, tentorium cerebelli,
and falx cerebelli
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Is also continuous with spinal
meninges, as where periosteal
layer is not
6
Cranial Meninges Continued
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Two dura mater layers form dural sinuses in
areas where they separate
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Main one is the superior sagittal sinus
Transverse sinus is another large one
Contains venous blood that drains into internal
jugular veins
7
Meningitis
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What does the suffix “-itis” mean??
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Primarily affects young people, typically
three months to two years
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Can be bacterial, viral, or fungal
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Often enter through nose or throat
Bacterial is usually more dangerous and
caused by Streptococcus, Escherichia, Listeria, and
Neisseria
Viral usually resolves in one to two weeks
Infection can spread from arachnoid and
pia mater to nervous tissue
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Can result in fatal cerebral edema and
hemorrhaging
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Lumbar puncture used to collect CSF for
diagnosis
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Drowsiness, intense headache, stiff neck,
8
vomiting, rash (in some),
photophobia,
phonophobia, and high fever
The Central Cavity
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Series of hollow spaces and tubes within the
brain that is continuous with the central canal of
spine
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One large lateral ventricle in each cerebral
hemisphere
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Third ventricle
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Deep inside diencephalon
Connects to fourth ventricle via cerebral aqueduct,
which runs through the midbrain
Fourth ventricle
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Separated medially by septum pellucidum
Connect to third ventricle via interventricular
foramina
Between posterior pons and anterior cerebellum
Continuous with central canal
Each ventricle contains one choroid plexus
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Collection of capillaries covered with ependymal
cells
Ependymal cells also line other parts of central
9
Cerebrospinal Fluid
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100 – 160ml of clear liquid present
in central cavity, central canal, and
subarachnoid space
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Ependymal cells of choroid
plexuses, lining central cavity, and
subarachnoid space produce it
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Produced from blood plasma, which
is modified by ependymal cells
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More sodium and chloride
Less potassium, calcium, and protein
Many functions:
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Increases brain buoyancy, reducing
weight of brain from 3lbs to 50g
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Uninfected
CSF
Infected
CSF
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Weight of brain would otherwise kill
neural tissue
Absorbs shock when skull is hit
Transports gases, wastes, and
nutrients
Maintains appropriate environment
for action potentials
10 to thermoregulate
Even helps brain
Cerebrospinal Fluid Circulation
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500ml CSF produced per day
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Produced and drained at same rate
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Capillaries of choroid plexuses are fenestrated
(porous), and thus, lots of blood plasma reaches
the surrounding ependymal cells
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Ependymal cells refine blood plasma to produce
CSF, which they then secrete into the central
cavity and subarachnoid space
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Cranial blood pressure pulses and ependymal cilia
cause CSF to circulate
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CSF leaves central cavity and enters
subarachnoid space
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Through two lateral apertures and one median
aperture in walls of fourth ventricle
CSF enters superior sagittal sinus
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Space formed between the two layers of cranial dura
mater
Arachnoid granulations (collections of arachnoid villi)
allow CSF to drain into superior sagittal sinus
11
12
Hydrocephalus
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Occurs when too much CSF is
produced, tube of central cavity
becomes blocked, or not enough CSF
drains across arachnoid granulations
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Interventricular foramen blockage is
most common
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Caused by tumor, inflammation
(such as meningitis), injury,
hemorrhage, or developmental
malformation
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Pressure inside central cavity
increases, and fluid compresses
brain tissue, killing neurons
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Entire head can enlarge in infants
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Inserting a tube into central cavity
and connecting to a vein in neck,
abdomen, or subarachnoid space in
order to drain corrects this
13
Cranial Blood Flow
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Internal carotid arteries deliver blood to
brain
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O2 and glucose deprivation causes syncope
within 10 seconds, and neuronal death
within 4min
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Lysosomes release contents
Starts positive feedback loop that kills even
more neurons
Cerebral arterial circle (circle of Willis)
provides redundant blood flow to brain
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Brain receives roughly 15% of blood supply,
and uses 20% of glucose and O2
Allows for alternate routes of flow in case there
is a blockage
Blood returns to venous circulation and
leaves head via internal jugular veins
14
Brain Barrier System (BBS)
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System of two barriers between fluid compartments
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Protects brain by regulating passage of materials from blood into tissue
fluid of brain nervous tissue, and from blood into the CSF
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Bacteria, viruses, antibiotics, and cancer drugs have a hard time crossing
Glucose, water, O2, CO2, alcohol, nicotine, caffeine, and anesthetics cross easily
Important to understand BBS when prescribing medications
Blood-brain barrier (BBB) regulates passage of materials from blood
plasma into neural tissue
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Blood-brain barrier (BBB)
Blood-CSF barrier
Capillaries in brain tissue have endothelium with tight junctions so that materials
must pass through endothelial cells (transcellularly), instead of between cells
(paracellularly)
Perivascular feet of astrocytes also contribute
Blood-CSF barrier regulates passage of materials from blood plasma into
central cavity
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Comprised of tight junctions between ependymal cells of choroid plexuses
Not present at ependymal cells of rest of central cavity and canal, so that wastes
15
can diffuse from nervous tissue into CSF
16
Circumventricular Organs
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Small collections of tissue surrounding third and fourth
ventricles
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Have homeostatic roles
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Don’t worry about most of the specific names, but they are:
area postrema, posterior pituitary gland, median eminence,
organum vasculosum laminae terminalis (OVLT), subfornical
organ, pineal gland, and subcommissural organ
Delivering sensory information regarding blood osmolarity,
glucose levels, temperature, and pressure
Play a role in hormonal regulation
Highly permeable capillaries – weak spots in BBS
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Allows protein-hormones in and out of brain tissue
Also allows HIV, some other viruses and bacteria, a way
into brain tissue
17
Brain Stem Gray and White Matter
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Central canal of spinal cord is
surrounded by gray matter
while white matter is superficial
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Formed as a result of neural tube
and is filled with CSF
Central canal is continuous with
the central cavity
As proceed rostrally, gray
matter surrounds central cavity
in brain stem
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Doesn’t completely surround
ventricles
White matter is still superficial
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Brainstem also possess
scattered nuclei
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18 locations, and
Recall the names,
functions of the spinal cord
The Brainstem
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Consists of the medulla
oblongata, pons, midbrain, and
diencephalon (caudal to rostral)
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Each structure about an inch long
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Structurally more complex than
spinal cord, but not as complex as
cerebrum and cerebellum
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Central cavity surrounded by gray
matter
White matter contains tracts
Other nuclei embedded within
white matter (spine lacks this)
No cortex
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Crucial link between rest of brain
tissue, and spine
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Also contains nuclei for 10 of the
12 pairs of cranial nerves
19
20
Medulla Oblongata
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Commonly referred to as
medulla
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Most inferior portion of
brainstem
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Continuous with spinal cord
but slightly wider
All sensory and motor
communication between brain
and spinal cord must travel
through medulla
Two bulges of white matter
called pyramids located on
anterior aspect
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Contain corticospinal tracts descending fibers from
primary motor cortex of
cerebrum
21
Medulla Oblongata Continued
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Sensory information
ascends posterior medulla
via the gracile and cuneate
fasciculi
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Most sensory fibers
decussate at some point
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Fasciculus also known as??
First order fibers synapse at
respective nuclei…nucleus
gracilis and cuneatus
Second order fibers leave
nuclei and decussate at
medial lemniscus of the
medulla, and synapse at
thalamus
Either in spinal cord or
brainstem
Understand the implications
of crossing over in loss of
sensory and/or
motor
22
function in the event of a
Medulla Oblongata Continued
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Inferior olivary nuclei are relay
stations between brain/spinal
cord, and cerebellum
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Olives are bulges on lateral
aspects of medulla
Thus, medulla plays a role in
equilibrium
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Medulla also serves the body’s
life support system
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Contains important nuclei that
regulate heart rate, blood
vessel diameter, and
respiratory rate via the ANS
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Cardiac center, vasomotor
center, and respiratory centers,
respectively
These nuclei belong to the
reticular formation
(more on
23
this later)
Medulla Oblongata Continued
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Cochlear nucleus for hearing is in
the medulla
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Signals arrive via cochlear branch
of vestibulocochlear nerve (VIII)
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Spinal gating of pain is in part
dependent on chemicals released
by reticular formation neurons of
the medulla (more on this with
chapter 16)
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The glossopharyngeal, (IX), vagus
(X), accessory (XI), and
hypoglossal (XII) nerves all start
or stop here
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Specific functions of these nerves
(and thus, medullary function)
discussed later
24
Pons
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Bulbous structure of brain
stem, just rostral (superior)
to medulla
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Major communication center
consisting mostly of tracts
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Middle cerebellar peduncles
are transverse tracts that
connect cerebellum to pons
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Name means “bridge”
Inferior cerebellar peduncles
pass through pons and
connect medulla and
cerebellum
Superior cerebellar peduncles
connect midbrain and
cerebellum
Also contains respiratory
nuclei which work with
medulla oblongata
25
to
regulate respiration
Pons Continued
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Contains nuclei of
trigeminal (V), abducens
(VI), facial (VII), and
vestibulocochlear (VIII)
nerves
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Many functions as a result
of cranial nerves
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Vestibular nucleus of VIII
Trigeminal nerve arises
from anterior pons
Other three arise from
anterior groove between
pons and medulla
Specifics discussed later
Urinary nuclei are located
26
27
Midbrain
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Rostral to pons, caudal
to diencephalon
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Ventral aspect contains
tracts called cerebral
peduncles
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Descending (motor)
fibers that go from
primary motor cortex to
superior cerebellar
peduncles of pons
Signals go on to
cerebellum
Components of
reticular formation
also
28
found in midbrain
Midbrain Continued
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Contains two pairs of sensory
nuclei on dorsal aspect
collectively called the corpora
quadrigemina
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One pair of superior colliculi
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Visual reflex centers that
coordinate head and eye
movements when we visually
track an object
Allow us to blink
Also causes one to turn head in
response to movement
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Visual startle reflex
One pair of inferior colliculi
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Relay auditory sensory info to
thalamus
Important in startle reflex when
hear loud noise
29
Midbrain Continued
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Cerebral aqueduct passes through
midbrain
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Nuclei for oculomotor (III) and
trochlear nerves (IV); functions
discussed later
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Red nucleus is found in cerebral
peduncles and contains lots of
blood vessels and thus iron
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Fibers leaving nucleus go to
cerebellum and help to smooth out
fine motor movements
Substantia nigra is dark because it
contains melanin
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Produces precursor to dopamine, and
dopamine inhibits the thalamus and
basal nuclei
This prevents unwanted muscle
contractions
Degeneration of these neurons has
implications in Parkinson disease
30
Reticular Formation
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Numerous, small, scattered nuclei in
medulla, pons, midbrain, and
hypothalamus that have motor and
sensory functions
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Fibers leaving some nuclei form the
reticulospinal tracts of the spine, which
adjust balance, posture, and muscle tone
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Cardiac, vasomotor, and respiratory nuclei
are part of the reticular formation
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Reticular formation nuclei also have
sensory functions
● Send visual and auditory info to
cerebrum, along with visual,
equilibrium, and proprioceptive signals
to cerebellum
● Reticular formation nuclei and fibers
participate in spinal gating of pain
signals
31
Reticular Activating System
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Reticular activating system (RAS) is
the group of reticular formation
nuclei that play role in wakefulness
and alertness
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Many stimuli result in sensory
signals along RAS:
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Stimulation of RAS nuclei causes
them to release orexin, which
causes thalamus to become more
active
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Position of head and limbs, visual and
auditory cues, pain, pressure, touch,
and mental activities
Not olfaction!!
More action potentials reach cerebral
cortex
Implications of orexin in narcolepsy
Damage to results32in coma, or a
state of unconsciousness without
Cerebellum
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Name means “small brain”
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Second largest part of brain at 10% of brain mass but
contains 50% of brain neurons
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Inferior to occipital lobes of cerebrum and dorsal to
pons/medulla
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Vermis is a sagittal constriction that separates into left
and right cerebellar hemispheres
33
Cerebellum Continued
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All input arriving goes to its
cortex of gray matter
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Folds of which are called folia
that are separated by sulci
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Arbor vitae (“tree of life”) is
tree-like pattern of white
matter than connects to
cerebellar peduncles of pons
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Each hemisphere has four
deep nuclei, and all output
from cerebellum arises from
these
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Purkinje cells are large
neurons lined up near
junction of cerebellar gray
and white matter
34
Cerebellum Continued
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Cerebellum receives information from
several sources
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Proprioceptive info from spine reaches
cerebellum via inferior cerebellar peduncles
Information from motor cortices, eyes, and
inner ear reach cerebellum via middle
cerebellar peduncles
Purkinje cells compare motor
performance with sensory information,
and if motor performance does not
match the intent, they send action
potentials to deep nuclei of
cerebellum
35
Cerebellum Continued
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Cerebellum next sends motor signals via superior
cerebellar peduncles to two destinations:
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Skeletal muscles to smooth out and improve coordination of
movements
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Also sends signals to motor association area to improve
muscle memory
Cerebellar functions in general:
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Receives proprioceptive, visual, and equilibrium sensory
information
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Provides blueprint for movement to motor areas
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Results in smooth and coordinated skeletal muscle
movements, along with proper posture and balance
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Some spatial perception of 3D objects and interpreting
textures of objects by feel alone
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Timekeeping and rhythm
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Some roles in hearing and language, such as judging
between pitches of sound
Damage to or alcohol can impair cerebellar
36
Diencephalon
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Everything between the fornix and the midbrain, and is composed of the thalamus,
hypothalamus, and epithalamus
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Thalamus makes up 80% of diencephalon
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Two egg-shaped halves, the left and right thalamus
Mostly gray matter that contains at least 23 nuclei
Third ventricle situated medial to the two halves
Thalamic functions:
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Relay station primarily for almost all general and special sensory info travelling to cerebral cortex
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Damage to causes improper routing of sensory action potentials
Filters sensory information
Memory and emotions through participation in the limbic system
Motor control by communicating with cerebral cortex, cerebellum, and basal nuclei
37
Thalamic Nuclei Groups
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Know basic functions of various
groups of nuclei
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Limbic system discussed later
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Prefrontal cortex is in charge of
most higher-order functions
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Somesthetic means “general
senses” and association areas
discussed later
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Postcentral gyrus interprets
general sensory information
38
Diencephalon Continued
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Hypothalamus is located inferior to thalamus and forms
the floor of the third ventricle
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Mostly gray matter and like the thalamus contains a
great deal of nuclei
39
Diencephalon Continued
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Maintains homeostasis of almost all body systems
through regulation of the endocrine system and
autonomic nervous system (ANS)
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Is the “master endocrine gland”
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Produces two important hormones that get stored in
posterior pituitary
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Monitoring of body temperature and activation of
physiological mechanisms for thermoregulation
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Communicates with pontine and medullary nuclei to
regulate ANS functions such as heart rate, blood
vessel diameter, and respiration
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Part of the limbic system and plays a role in
memory, emotions, and “drives”
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Thirst, hunger, and satiation centers are here
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Sleep and circadian rhythm
40
Know infundibulum, anterior/posterior pituitary, optic chiasma, anterior
nucleus, arcuate nucleus, mammillary nuclei (bodies), paraventricular
nucleus, preoptic nucleus, suprachiasmatic nucleus, and supraoptic
nucleus
41
The Cerebrum
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Formed from two cerebral hemispheres
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83% of brain mass
You already know the name of the groove that separates
left from right
Comprised of three primary portions:
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Cerebral cortex
White matter
Basal nuclei
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Deep gray matter located near lateral ventricles
Major functions:
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Processing motor and sensory information
Emotions
Personality
Higher order functions such as learning, memory, planning,
42
and language
Lobes of the Cerebrum
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Certain sulci divide the cerebral hemispheres into
the following lobes:
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A central sulcus separates the frontal and parietal lobe
on each hemisphere
Lateral sulcus separates each temporal lobe from the
parietal and frontal lobes
Parieto-occipital sulcus separates each parietal lobe
from its neighboring occipital lobe
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Lobes are named according to overlying cranial
bones
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Frontal lobe functions in voluntary movement,
memory, planning, emotion, mood, social
43
judgment, and aggression
Central
Sulcus
Parietooccipital
Sulcus
Lateral
Sulcus
44
Lobes of the Cerebrum Continued
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Parietal lobe functions in perception of general
sensation (somatic and visceral), perception of
gustation (taste), and some vision association
(processing)
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Occipital lobe functions in vision perception and visual
association
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Temporal lobe functions in hearing, olfaction, language,
and some visual association
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A deep lobe, known as the insula can be seen by
retracting the lateral sulcus or cutting part of the
temporal lobe away
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Not much is known about, but proposed roles
45 in
understanding language, gustation, and risk-taking
46
Cerebral White Matter
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Deep to cortex
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Tracts of myelinated
fibers, along with glial
cells
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Commissural tracts allow
two hemispheres to be
linked
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Corpus callosum is largest
collection of commissural
tracts
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Association tracts
connect different parts of
same hemisphere
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Projection tracts connect
cortex to47lower CNS
48
The Cerebral Cortex
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Superficial layer of gray matter (2-3 mm
thick) over entire cerebrum
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High degree of folding provides three times
more surface area than if cerebrum were
smooth, and allows skull and brain to be
smaller
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Already know definitions of gyri and sulci
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Where the majority of the processing power
of cerebrum is
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Possesses pyramidal cells, which are
multipolar neurons
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Axons leave cerebral cortex and synapse with
neurons in other parts of CNS
Stellate cells have dendrites that project
short distances in all directions
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Anaxonic and info travels locally in any
direction
Saves lots of space because
doesn’t require
49
large numbers of unidirectional neurons
Limbic System
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Your emotional brain
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Collection of nuclei and gyri located medially and deep within
cerebrum
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One per hemisphere
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Loop-pattern consisting of cingulate gyrus, hippocampus, and
amygdala, among others
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Emotions such as pain, pleasure, affection, anger
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Also plays a role in formation of memories, especially olfactory
memory
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Nucleus accumbens is a gratification (reward) center, and
amygdala plays a role in aversion (fear)
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Neurons of hippocampus have some ability to undergo mitosis!
50
51
Basal Nuclei
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Three collections of gray
matter surrounded by white
matter of cerebrum
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Lateral to thalamus
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Globus pallidus, putamen,
and caudate nucleus
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Regulate initiation and
termination of movements,
suppressing unwanted
movements, and regulate
muscle tone
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Communicates with
substantia nigra of midbrain
● Implications in Parkinson
52Disease already discussed
Integrative Brain Functions
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Many portions of the brain
participate in multiple functions
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The brain has “systems” within it
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Integrative functions we will cover:
sleep, cognition (association),
memory, sensation, motor control,
and language
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Various research mechanisms for
studying the brain:
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Positron emission tomography (PET) is
where use of radioactively labeled
glucose by a tissue is measured
Functional magnetic resonance
imaging (fMRI) measures increased
blood flow to an area of brain due to
increased astrocyte activity
Electroencephalography measures
brain waves
53
54
Cognition
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Cognition - mental processes by which we gain and
use knowledge
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Judgment, reasoning, personality, sensory perception,
thinking, memory, and imagination
Most of brain (about 75%) is association areas where
sensory and motor information is integrated
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Most of cerebral cortex
Damage to these association areas (as in brain
lesions due to cancer, stroke, or trauma) affects
cognition
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Parietal lobe damage can result in contralateral neglect
syndrome, where the patient becomes unaware of one half
of their body
Temporal lobe damage can result in agnosia (inability to
recognize objects) or prosopagnosia (inability to recognize
faces)
Frontal lobe damage can cause personality problems, such
Phineas Gage
•
Accidental lobotomy occurred in
Vermont in 1848
•
Powder tamper working on
railroad
•
Tamping rod shot through medial
aspect of both frontal lobes
• Damaged his prefrontal cortex
(also called frontal association
area)
• Crucial in planning, moral
judgment, and emotional
control
•
Personality change to an
“irreverent, profane and fitful
person”
Learning and Memory
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Learning is gaining new skills and/or information
through experience or instruction
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Memory is the storage and retrieval of information
one has learned
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Brain lesions or trauma can result in aterograde
amnesia (unable to store new information) or
retrograde amnesia (recall things prior to the
injury)
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Forgetting things is as equally important as
remembering
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Occurs in –part during consolidation of REM sleep
Hanging on to trivial info harms reading
comprehension and produces difficulty deciphering
57
what details are important, and which are
not
Memory Continued
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Structures involved in memory:
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Association areas of cerebral cortex for
sensory/motor/higher order function
Hippocampus of limbic system for long-term memory
Amygdala of limbic system for emotional memories
Cerebellum for learning motor skills
Conversion of short-term to long-term memory is
known as long-term potentiation (LTP)
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Number of dendritic branches at a synapses may
increase
Number and size of axon terminals may increase
Release of more neurotransmitter, sometimes constant
Changes in gene expression and up/down-regulation of
receptors
58
59
Functional Organization of Cerebrum
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Sensory areas
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Motor areas
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Involved in your conscious awareness of a sensation, your
perception
Apply to general (somatic and visceral) and special senses
In general, posterior half of cerebrum
Control your voluntary movements
In general, anterior cerebrum
Association areas
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Found all over and work with sensory and motor areas
Responsible for (examples):
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Your memory of a particular smell
Recognizing a friend’s face
Muscle memory as a result of practicing a sport
60
Primary Somatosensory Cortex
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Also called the primary sensory
cortex
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Posterior to the central sulcus
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Receives general sensory
information such as pain,
pressure, touch, vibration, and
temperature
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Perception of the stimulus occurs
here
Somatic and visceral sensation
Impulses arrive at thalamus
typically through trigeminal
nerves or spinothalamic tracts
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Postcentral gyrus
Go to postcentral gyrus from
thalamus
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Sensory info from special sense
Sensory Homunculus
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A map of the cortical
region where a sensory
signal from a specific
general receptor arrives
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Proportional to how
many receptors are
located in that body part
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Face on homunculus
appears huge because
there are many more
receptors
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Thus, larger portion of
the cortex is devoted to
sensations of the face
and hands
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Somatosensory Association Area
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Just posterior to post-central gyrus
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We make sense of what it is we are feeling here and
memories of general senses stored here
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Examples – kinesthetic memories, memories of pain,
temperature changes, etc.
Special Sensory Areas
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Vision
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Primary visual cortex is at the posterior occipital lobe
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Visual association area is at the anterior occipital,
posterior parietal, and inferior temporal lobes
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Receives visual signals and perception of image occurs here
Interpretation of what we are looking at
Ability to recognize objects and faces
Hearing
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Primary auditory cortex is at the superior temporal
lobe and insula
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Where perception of sounds occurs
Auditory association area is also on superior temporal
lobe
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Memories of sounds, recognizing voices, remembering songs
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you’ve heard, etc.
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Special Sensory Areas Continued
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Taste
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Primary gustatory cortex is located at inferior portion of
post-central gyrus and part of anterior insula
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Association area for gustation is the orbitofrontal cortex at
the anterior/inferior frontal lobe
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Also acts as association area for olfaction, and even takes into
account visual signals
Memories of the smells, tastes, and appearances of different
foods are stored and recalled from here
Smell
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Primary olfactory cortex is primarily at the medial temporal
lobe
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Perception of taste molecules
Perception of odorant molecules
Orbitofrontal cortex is the association area for olfaction
What about equilibrium?
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Motor Association Area
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Also called the premotor area (cortex)
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Posterior half of the frontal lobe
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Comes up with a blueprint for an intended
movement and sends to the primary motor cortex
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Correct neurons fire at the appropriate rate and in
the appropriate sequence
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“Muscle memories” such as playing an instrument
or typing stored here
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Primary Motor Cortex
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Also called primary
motor area and is at
the precentral gyrus
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Long axons of these
upper motor
neurons synapse
with lower motor
neurons in brain
stem and spinal cord
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Lower motor
neurons control
skeletal70muscle
Motor Homunculus
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Motor homunculus depicts
which body regions are
controlled by which collections
of upper motor neurons
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Size of the cortical area and
homunculus pictures (face,
hands, etc.) is proportional to
the number of motor units
that innervate a region
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Different muscles have
different numbers of motor
units and different numbers of
fibers per unit
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More motor units equals fine
control
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Language
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Speaking, understanding
words, reading, signing, and
writing are all important to
language
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Wernicke area is located
just posterior to lateral
sulcus, usually on left
hemisphere
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Crucial to recognition of
spoken and written words
Produces a plan for what we
intend to say and sends to
Broca area
Broca area is found on the
inferior prefrontal cortex,
on the same hemisphere as
Wernicke area
●
Generates the motor
blueprint for the facial and
laryngeal
72muscles used to
speak
Aphasia
• Aphasia—any language deficit from lesions in same hemisphere
(usually left) containing the Wernicke and Broca areas
• Nonfluent (Broca) aphasia
• Lesion in Broca area
• Slow speech, difficulty in choosing words, using words that only approximate
the correct word
• Fluent (Wernicke) aphasia
• Lesion in Wernicke area
• Speech normal and excessive, but uses senseless jargon
• Cannot comprehend written and spoken words
• Anomic aphasia
• Can speak normally and understand speech, but cannot identify written
words or pictures
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