Download Cerebral Cortex

The Central Nervous System
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Objectives
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Describe the functions of the different areas
of the brain.
Distinguish between different types of
memory and describe the roles of different
brain regions in memory.
Describe the location of the hypothalamus
and explain the significance of this region.
Explain the role of the medulla in the control
of visceral functions.
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Objectives
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(continued)
Explain the role of the basal nuclei and
cerebellum in motor control.
Describe the structures involved in a
reflex arc.
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CNS
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Consists of:
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Brain.
Spinal cord.
Receives input from
sensory neurons.
Directs activity of motor
neurons.
Association neurons
(interneurons) maintain
homeostasis in the
internal environment.
Figure 8-1
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Cerebrum
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Largest portion of brain
(80% mass).
Responsible for higher
mental functions.
Corpus callosum:
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Major tract of axons that
functionally interconnects
right and left cerebral
hemispheres.
Figure 8-6
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Cerebral Cortex
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Frontal lobe:
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Anterior portion of each
cerebral hemisphere.
Precentral gyri:
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Contains upper motor
neurons.
Involved in motor control.
Body regions with the
greatest number of motor
innervation are represented
by largest areas of motor
cortex.
Figure 8-7
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Parietal Lobe
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Primary area
responsible for
perception of
somatesthetic
sensation.
Body regions with
highest densities of
receptors are
represented by largest
areas of sensory
cortex.
Figure 8-7
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Cerebral Cortex
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Temporal:
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Contain auditory centers that receive sensory
fibers from cochlea.
Interpretation and association of auditory and
visual information.
Occipital:
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(continued)
Primary area responsible for vision and
coordination of eye movements.
Insula:
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Implicated in memory encoding.
Integration of sensory information with visceral
responses.
Coordinate cardiovascular response to stress.
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Epilepsy
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Jeremey is a 15 year old male high school football
player who was tackled during practice. Jeremey
became very angry and fell to the ground with
sudden onset of unconsciousness. His body stiffened
with arms and legs extended. He did not breathe for
about 10 seconds, then began violent rhythmic
muscular contractions accompanied by
hyperventilation.
Jeremey awoke in a confused state in ER. About an
hour later he experienced a second seizure.
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Epilepsy
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General term for the primary condition that causes
seizures.
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Is not a diagnosis but a symptom.
Conditions in which no underlying correctable cause
for the seizure is found.
Incidence: 20-70/100,000
Seizure activity demands 250% increase in ATP.
02 consumption increases 60%.
Cerebral blood flow increase 250%.
Glucose and 02 already depleted.
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Epilepsy
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Epileptic seizures:
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Partial:
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Simple:
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Without impairment of consciousness.
Complex:
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Seizures beginning locally, involving neurons unilaterally
Have a local focal onset, usually originating from cortical
brain tissue.
Impaired consciousness.
Involve neurons bilaterally, do not have a focal onset and
originate from subcortical or deeper brain focus.
Generalized:
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Seizures bilaterally symmetric, without local onset.
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Epilepsy
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Pathophysiology:
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Plasma membrane is more permeable.
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May be due to abnormalities in K+ or Ca++ conductance.
Defects in GABA inhibitory system.
Abnormality in N-methyl-D- aspartate receptor.
Neuronal discharge spreads to adjacent neuronal tissue.
Tonic:
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Epileptic focus is a group of neurons that evidence a
paroxysmal depolarization shift and sudden changes in
membrane potential.
Muscle contraction with increased muscle tone.
Loss of consciousness.
Clonic:
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Alternating contractions and relaxations of muscles.
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Electroencephalogram (EEG)
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Measures synaptic
potentials produced
at cell bodies and
dendrites.
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Create electrical
currents.
Used clinically do
diagnose epilepsy
and brain death.
Figure 8-10
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EEG Patterns
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Alpha:
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Recorded from parietal and occipital regions.
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Person is awake, relaxed, with eyes closed.
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Beta:
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Strongest from frontal lobes near precentral gyrus.
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Produced by visual stimuli and mental activity.
Evoked activity.
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13-25 cycles/sec.
Theta:
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Emitted from temporal and occipital lobes.
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Common in newborn.
Adult indicates severe emotional stress.
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10-12 cycles/sec.
5-8 cycles/sec.
Delta:
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Emitted in a general pattern.
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Common during sleep and awake infant.
In awake adult indicate brain damage.
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1-5 cycles/sec.
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EEG Sleep Patterns
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2 types of EEG
patterns during
sleep:
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REM (rapid eye
movement):
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Dreams occur.
Low-amplitude, highfrequency oscillations.
Similar to
wakefulness (beta
waves).
Non-Rem (resting):
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High-amplitude, lowfrequency waves
Figure 8-11
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Basal Nuclei (basal ganglia)
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Masses of gray matter
composed of neuronal
cell bodies located deep
within white matter.
Contain:
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Corpus striatum:
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Caudate nucleus.
Lentiform nucleus:
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Putman and globus
pallidus.
Functions in the control
of voluntary
movements.
Figure 8-12
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Cerebral Lateralization
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Cerebral dominance:
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Specialization of one
hemisphere.
Left hemisphere:
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More adept in language
and analytical abilities.
Damage:
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Severe speech
problems.
Right hemisphere:
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Most adept at
visuospatial tasks.
Damage:
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Difficulty finding way
around house.
Figure 8-14
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Language
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Broca’s area:
 Involves articulation of speech.
 In damage, comprehension of speech in unimpaired.
Wernicke’s area:
 Involves language comprehension.
 In damage, language comprehension is destroyed.
 Speech is rapid without any meaning.
Angular gyrus:
 Center of integration of auditory, visual, and somatesthetic
information.
 Damage produces aphasias.
Arcuate fasciculus:
 To speak intelligibly, words originating in Wernicke’s area
must be sent to Broca’s area.
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Broca’s area sends fibers to the motor cortex which directly
controls the musculature of speech.
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Emotion and Motivation
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Hypothalamus and limbic
systems.
Limbic system:
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Forebrain nuclei and fiber
tracts that form a ring
around the brain stem.
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Center for basic emotional
drives.
Closed circuit (Papez circuit):
 Fornix connects
hippocampus to
hypothalamus, which
projects to the thalamus
which sends fibers back to
limbic system.
Figure 8-16
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Emotion and Motivation
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Areas or the hypothalamus and limbic system are
involved in feelings and behaviors.
Aggression:
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Hypothalamus (feeding and satiety centers).
Sexual drive and behavior:
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Amygdala and hypothalamus.
Feeding:
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Amygdala and hypothalamus.
Fear:
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(continued)
Hypothalamus and limbic system.
Goal directed behavior (reward and punishment):
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Hypothalamus and frontal cortex.
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Memory
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Short-term:
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Medial temporal lobe:
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Memory of recent events.
Consolidates short term into long term
memory.
Hippocampus is critical component of
memory.
Acquisition of new information, facts
and events requires both the medial
temporal lobe and hippocampus.
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Long-Term Memory
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Consolidation of short-term memory into long-term
memory.
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Requires activation of genes, leading to protein synthesis and
formation of new synaptic connections.
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Cerebral cortex stores factual information:
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Altered postsynaptic growth of dendritic spines in area of
contact.
Visual memories lateralized to left hemisphere.
Visuospatial information lateralized to right hemisphere.
Prefrontal lobes:
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Involved in performing exact mathematical calculations.
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Complex, problem-solving and planning activities.
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Long-Term Potentiation
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Type of synaptic learning.
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Synapses that are 1st
stimulated at high
frequency will subsequently
exhibit increased excitability.
Postsynaptic changes:
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Glutamate binds to NMDA
and AMPA receptors.
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Opens Ca2+ and Na+
channels.
Presynaptic changes:
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Ca2+ causes, release of
NO from postsynaptic
neuron.
NO acts as a retrograde
messenger, causing release
of NT in bouton.
Figure 8-17
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Thalamus
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Thalamus:
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Composes 4/5 of the diencephalon.
Forms most of the walls of the 3rd ventricle.
Acts as relay center through which all sensory information
(except olfactory) passes to the cerebrum.
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Lateral geniculate nuclei:
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Medial geniculate nuclei:
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Relay visual information.
Relay auditory information.
Intralaminar nuclei:
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Activated by many sensory modalities.
Projects to many areas.
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Promotes alertness and arousal from sleep.
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Hypothalamus
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Contains neural centers for hunger, thirst, and
body temperature.
Contributes to the regulation of sleep,
wakefulness, emotions, sexual arousal, anger,
fear, pain, and pleasure.
Stimulates hormonal release from anterior
pituitary.
Produces ADH and oxytocin.
Coordinates sympathetic and parasympathetic
reflexes.
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Pituitary Gland
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Posterior pituitary:
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Stores and releases
ADH (vasopressin)
and oxytocin.
Anterior pituitary:
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Regulates secretion
of hormones of other
endocrine glands.
Figure 11-12
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Midbrain
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Contains:
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Corpora quadrigemina:
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Superior colliculi:
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Inferior colliculi:
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Composed of ascending and descending fiber tracts.
Substantia nigra:
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Relay centers for auditory information.
Cerebral peduncles:
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Involved in visual reflexes.
Required for motor coordination.
Red nucleus:
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Maintains connections with cerebrum and cerebellum.
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Involved in motor coordination.
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Hindbrain
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Metencephalon:
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Pons:
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Surface fibers connect to
cerebellum, and deeper fibers
are part of motor and sensory
tracts.
Contains several nuclei
associated with cranial nerves
V, VI, VII.
Contains the apneustic and
pneumotaxic respiratory
centerss.
Cerebellum:
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Receives input from
proprioceptors.
Participates in coordination of
movement.
Necessary for motor learning,
coordinating different joints
during movement, and limb
movements.
Figure 8-23
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Hindbrain
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(continued)
Myelencephalon (medulla oblongata):
 All descending and ascending fiber tracts between spinal
cord and brain must pass through the medulla.
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Vasomotor center:
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Controls autonomic innervation of blood vessels.
Cardiac control center:
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Nuclei contained within the medulla include VIII, IX, X, XI, XII.
Pyramids:
 Fiber tracts cross to contralateral side.
Regulates autonomic nerve control of heart.
Regulates respiration with the pons.
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Reticular Formation
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Reticular Formation:
 Complex network of nuclei and nerve fibers within
medulla, pons, midbrain, thalamus and
hypothalamus.
 Functions as the reticular activating system (RAS).
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Non specific arousal of cerebral cortex to incoming
sensory information.
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Alzheimer’s Disease
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Gertie is a 76 year-old female shopping for groceries
with her daughter. Gertie became separated from
her daughter. She was aimlessly wandering the
aisles when an employee asked if she could help her.
Gertie become angry and combative when the
employee tried to assist her. Her daughter, hearing
the commotion found her mother, and tried to calm
her down. The two left the store without the
groceries.
Vivian, her daughter immediately took her to ER.
She tested positive for memory difficulty on the
Geriatric Depression Scale.
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Alzheimer’s Disease
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Gradual onset and continuing decline in cognitive
function.
Most common dementia for the elderly.
Incidence: 4 million in US
Risk factors:
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Increasing age
Female gender
Genetics:
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Presenilin gene on chromosome 1, 14
Epsilon 4 allele on chromosome 19
Head trauma
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Alzheimer’s Disease
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Pathophysiology:
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Abnormal amyloid beta proteins
Oxygen radicals
Excess glutamate and aspartate
ICF excess [Ca++] cause cell protein denaturiation
Neurofibrilary tangles
Neritic plaque
Degeneration of cholinergic neurons
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Alzheimer’s Disease
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Clinical manifestations:
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Insidious onset
Forgetfulness increasing over time
Memory loss
Deteriorating ability for problem solving
Judgment deteriorates
Behavioral changes
Labile
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Reflex Arc
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Unconscious motor response
to a sensory stimulus.
Stimulation of sensory
receptors evokes APs that
are conducted into spinal
cord.
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Synapses with association
neuron, which synapses with
somatic motor neuron.
Conducts impulses to muscle
and stimulates a reflex
contraction.
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Brain is not directly involved.
Figure 8-28