THE NERVOUS SYSTEM

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• THE NERVOUS SYSTEM

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Divisions of the nervous system
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Protection of the Brain The Cranial Meninges

• Cranium is covered with protective membranes
  meninges
• Cranial meninges are continuous with spinal
  meninges
• 3 layers 1. outer, fibrous dura mater forms
  sheets (falx) that separate the cerebrum and the
  cerebellum into the hemispheres and the
  cerebellum from the cerebrum
• comprised of an outer endosteal layer and and
  inner meningeal layer
• 2. middle arachnoid mater avascular layer
• -named for the spider-like struts (trabeculae)
  that connect the arachnoid to the underlying pia
  mater
• 3. inner, thin pia mater vascular connective
  tissue
• -makes direct contact with brain tissue
• -cells of the pia mater are impermeable to the
  passage of many substances
• -this membrane is pierced by tiny capillaries
  that nourish the brain tissue arise from the
  larger capillaries that travel within the dura
  mater

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• large spaces for the circulation
• of blood can be found between the
• two dural layers sinuses
• e.g. superior sagittal sinus
• also large veins run through the
• subarachnoid space
• e.g. cerebral veins

-there are spaces between these membranes A.
subarachnoid space between the arachnoid and
pia maters -for the circulation of CSF B.
subdural space between the arachnoid and the
dura mater C. epidural space between the
dura mater and the vertebral canal in the
spinal column
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Medical Application

• Pathology
• There are three types of hemorrhage involving the
  meninges
• Epidural bleeding is rapid because it is usually
  from arteries, which are high pressure.
• Epidural bleeds from dural arteries can grow
  until they reach their peak size at six to eight
  hours post injury, spilling from 25 to 75 ml of
  blood into the epidural space
• the bleeding strips the dura from the inside of
  the skull, causing an intense headache.
• the bleeding is usually restricted to defined
  locations as its expansion stops at skull's
  sutures, where the dura mater is tightly attached
  to the skull.
• Bleeding into the epidural space in the spine may
  also cause epidural hematoma. These may arise
  spontaneously (e.g. during childbirth, or as a
  rare complication of anaesthesia (such as
  epidural anaesthesia)
• bleeding is likely to be venous.
• may present as pain, muscle weakness, or bladder
  and bowel dysfunction.
• estimates vary from 1 per 10,000 to 1 per 100,000
  epidural anaesthetics
• A subarachnoid hemorrhage is acute bleeding under
  the arachnoid it may occur spontaneously or as a
  result of trauma.
• A subdural hematoma is located in a separation of
  the arachnoid from the dura mater.
• subdural bleeding usually results from tears in
  veins that cross the subdural space.
• This bleeding often separates the dura and the
  arachnoid layers.
• Subdural hemorrhages may cause an increase in
  intracranial pressure (ICP), which can cause
  compression of and damage to delicate brain
  tissue.
• the blood may be aspirated surgically to remove
  the mass and reduce the pressure it puts on the
  brain
• The hematoma is neurosurgically evacuated through
  a burr or craniotomy.
• The diagnosis of epidural hematoma requires a
  patient to be cared for in a facility with a
  neurosurgeon on call to decompress the hematoma
  if necessary and stop the bleed by ligating the
  injured vessel branches.

subarachnoid hemorrhage
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Protection of the Brain CSF

• CSF 80 to 150 mL of clear, colorless liquid
• replaced completely up to three times per day
• glucose, proteins, lactic acid, urea, ions
• made by specialized cells in the lateral
  ventricles choroid plexus
• networks of capillaries in the walls of the
  ventricles
• covered by ependymal cells (epithelial) cells)
  that filter the blood plasma and produce CSF by
  secreting it
• these cells are capable of allowing passage of
  certain substances from the blood through them
  into the CSF inhibit the passage of others
• continually circulates ventricles of the brain
  and central canal to subarachnoid space
• functions
• 1. Chemical protection provides an optimal
  chemical environment for neuronal signaling
• 2. Mechanical protection acts as a shock
  absorber, preventing direct physical contact
  between brain tissue and the bones of the cranium
  or vertebral canal
• 3. Circulation allows the exchange of nutrients
  and waste products between the blood and nervous
  tissue

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Flow of CSF
-CSF forms in the choroid plexi of the lateral
ventricles and flows into the 3rd ventricle
through the interventricular foramina -the 3rd
ventricle adds to the CSF volume -the CSF then
flows into the 4th ventricle via and cerebral
aqueduct (passes through the midbrain)
contributes more volume -then enters the
subarachnoid space via openings in the 4th
ventricle called apertures -also enters the
central canal of the SC -circulation is driven by
ciliary action and pressures provided by the
blood and gravity 10 mm Hg
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Circulation of the CSF

• CSF is gradually reabsorbed into the
• blood through fingerlike projections
• into the dural venous sinuses arachnoid
• granulations
• -absorbed at about 20ml/hr which equals
• its rate of formation

• interfering with the drainage of CSF
• into the subarachnoid space can result
• in accumulation of CSF in the ventricles
• CSF pressure rises hydrocephalus
• (implantation of a shunt lateral ventricle
• into the superior vena cava or abdomen)

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Blood-Brain Barrier (BBB)

• within the body the capillaries are sites of
  exchange between materials in the blood and the
  ECF filtration of the blood plasma by capillary
  cells helps form the ECF
• most locations within the body, this exchange is
  very free
• the capillary walls are formed of a single layer
  of cells endothelium
• the cells are joined loosely and are connected by
  numerous gap junctions and pores between the
  cells
• this allows for an easy diffusion of many plasma
  components (except large plasma proteins) between
  the cells themselves
• so even small changes in blood plasma contents
  can dramatically effect the ECF composition
• however, in the brain, the capillary cells are
  careful as to what is filtered out of the blood
• the cells of the endothelium are very tightly
  linked together
• the cells are joined by tight junctions to
  restrict the flow of materials among them and
  through them into the ECF surrounding the brain
• so materials must directly passage the cells
  themselves to contribute to the ECF
• so the passage of things like glucose, amino
  acids, ions are carried through the cells by
  carrier proteins
• But lipid-soluble materials and gases (oxygen)
  can cross easily through the PM of the
  endothelial cells
• so transport between the cells is Anatomically
  Prevented and transport through the cell is
  Physiologically Restricted BBB
• role of astrocytes in the BBB 1. signal the
  capillaries to get tight
• 2. participate in the transport of some ions like
  K

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The blood supply to the brain

• Arterial blood reaches brain via internal
  carotid, vertebral arteries
• Venous blood leaves via internal jugular veins

-transient ischemic attacks (TIA) no permanent
neurologic damage -temporary cerebral
dysfunction caused by impaired blood flow to the
brain -dizziness, weakness, blurred vision,
slurred speech, paralysis -persists from 5 to
50 minutes -caused by emboli (blood clots),
atherosclerosis
-cerebral vascular accident (CVA)
stroke -affects 500,000 people per year -third
leading cause of death -permanent cerebral
dysfunction caused by impaired blood flow to the
brain -sudden onset of symptoms -caused by
cerebral hemorrhage (anuerysm), blood clot,
atherosclerosis -treatment rapid
administration of clot-dissolving drugs (e.g.
tPA) if stroke is caused by a clot
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Neuronal Organization
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Neural Organization Pathways

• A neural pathway is comprised of centers/cell
  bodies and tracts

• Sensory pathway
• Ascending
• Information from sensory receptors to CNS
• Motor pathway
• Descending
• Information from CNS to skeletal muscle or glands
• Direct pathways cause precise, voluntary
  movements
• Indirect pathways result in involuntary
  movement (from brain stem)

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Figure 15.1 Major Divisions of the Brain
Major Regions of the Brain
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Major Regions of the Brain
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Major Regions and Landmarks

• Cerebrum largest portion
• -left and right cerebral hemispheres divided by
  the longitudinal fissure
• -connected by the corpus callosum
• -folded into ridges and grooves grooves sulci
• -sulci divide the cerebrum into lobes
• -ridges gyri (gyrus)

• Central sulcus
• Frontal and parietal lobes

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Major Regions and Landmarks
-outer layer of the cerebrum cerebral
cortex -area for specific processing of
sensation, -area of voluntary movement, speech,
all thought processes

• motor and sensory areas
• e.g. primary visual, auditory gustatory areas
• e.g. primary motor area (precentral gyrus)
  controls voluntary contractions
• -plus association areas for integration and
  analysis of incoming info help in making of
  decisions

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The Cerebrum

• -cerebrum is comprised of
• 1. white matter - neurons with
• long, myelinated axons
• -organized into tracts
• Association tracts conduct
• impulses between gyri within
• a hemisphere
• Commisural tracts connects
• gyri in one hemisphere to
• others in the other hemisphere
• corpus callosum
• anterior commisure
• posterior commisure
• C. Projection tracts tracts that connect
• cerebrum to the lower parts of the
• CNS (e.g. Thalamus, brainstem)
• 2. gray matter outer edge of the
• cerebrum cerebral cortex (2-4 mm

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Basal Ganglia

• -nuclei found deep within the cerebrum
• - links to the midbrain
• - receives input from the cortex provides
  output to the motor areas of the cortex via the
  thalamus
• -integrates motor commands
• -regulates the initiation termination of
  muscle mve.
• -also functions to anticipate body movements
  controls subconscious contraction of skeletal
  muscle
• comprised of the
• 1. striatum
• caudate nucleus activity occurs prior to eye
  movements
• putamen precedes or anticipates body movements
• nucleus accumbens
• 2. globus pallidus regulates muscle tone for
  movements
• 3. claustrum
• 4. substantia nigra high concentration of
  dopanergic neurons
• 5. subthalmic nucleus

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Basal Ganglia

• comprised of the
• 1. striatum planning and modulation of movement
• also involved in cognitive function
• secretes the neurotransmitters ACh and GABA
• caudate nucleus controls mve of arms and legs
  when walking
• activity in this area occurs prior to eye
  movements
• also involved in learning and memory
• language comprehension
• falling in love
• obsessive compulsive behavior
• putamen precedes or anticipates body movements
• involved in reinforcement learning
• projects neurons to the premotor area of the
  cortex via the GP and thalamus
• also considered part of the lenticular nucleus
  (putamen globus pallidus claustrum)
• nucleus accumbens
• 2. globus pallidus regulates muscle tone for
  movements
• prepares the body for walking
• once moving the CN and P provide the pattern
  for the rhythm of trunk and limbs
• 3. claustrum thin strip of gray matter between
  the putamen and insula

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Medical application Basal Ganglia
-damage to the basal ganglia -results in
uncontrollable, abnormal body movements -muscle
rigidity may develop and tremors -Parkinson
neurons that extend from the substantia nigra
to the caudate nucleus and putamen
degenerate -loss of dopamine releasing
neurons increase in muscle tone and
stiffness -Huntington - hereditary
disorder -caudate nucleus and putamen
degenerate with loss of neurons that release
GABA or ACh -spasmatic muscle contractions and
loss of mental status
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Integrative Functions and the Reticular
Activating System

• integrative function of the cerebrum
• processing of sensory information (analysis and
  storage) and making a decision
• includes sleep and wakefulness, learning and
  memory, emotional responses
• wakefulness/sleep role of the RAS
• 24 hr cycle called circadian rhythm
• established by the hypothalamus and epithalamus
• transition between the states of sleep and
  wakefulness is controlled by the RAS
• portion of the cerebral cortex that is activated
  upon sleep arousal
• when active transmission of signals to many
  areas of the cortex both directly and via the
  thalamus general increase in cortical activity
• arousal awakening from sleep
• stimulation of the RAS by touch, pressure,
  pain, light
• no input by olfactory receptors!!
• stimulation of cholinergic neurons that release
  AcH
• sleep state of altered consciousness from which
  you can be arouse
• exact function is still unknown
• two components NREM and REM
• NREM four stages
• REM 3 to 5 episodes per 7 to 8 hour sleep
  period (10-20 minutes)
• regulated by many areas of the brain
  hypothalamus, forebrain, medulla oblongata

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Integrative Functions

• learning and memory
• learning the ability to acquire new information
• no completely satisfactory explanation
• memory the process by which information that is
  acquired through learning is stored and retrieved
• role for long-term potentiation (LTP) enhances
  transmission at the hippocampus after a period of
  high-frequency stimulation
• role for glutamate binds NMDA glutamate
  receptors on post-synaptic neurons
• different categories of memory
• 1. immediate ability to recall ongoing
  experiences, provides perspective to the present
  time so we know where we are and what we are
  doing
• 2. short-term temporary ability to recall
  information - seconds to minutes old
• e.g. look up a phone number and then dial it a
  few seconds later
• hippocampus, mamillary bodies of the hypothalamus
  and the anterior and medial nuclei of the
  thalamus
• 3. long-term transfer of short-term into a more
  permanent type
• last from days to years
• e.g. use the telephone number enough stored
  permanently
• role for the basal ganglia, cerebral cortex and
  cerebellum
• http//www.nlm.nih.gov/medlineplus/memory.html
• http//en.wikipedia.org/wiki/Anterograde_amnesia
• http//en.wikipedia.org/wiki/Retrograde_amnesia

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Medical Application Alzheimers Disease -loss
or reasoning, memory -11 of population over 65
(4 million people) -unknown cause thought to be
genetic factors environmental
lifestyle -neuronal plasma membranes contain a
protein amyloid precursor protein
(APP) abundant in presynaptic axon
terminals -cleavage of APP yields a secreted
product sAPPa that is secreted by
the presynaptic terminals normally -if APP is
cleaved at the wrong site beta-amyloid -two
forms of beta-amyloid are possible based on
cleavage site the longer form (Ab40) is
harmless -but the form Ab42 10 of the cleaved
b-amyloid aggregates to form plaques and is
neurotoxic -underlying causes for Ab plaque
formation remain unknown -about 15 of cases
appear to have a genetic link familial
Alzheimers -mutations in 3 genes prenisilin-1,
-2 and APP lead to early onset forms (less the
15 of all cases) prenisilins cleave
APP -mutations in these genes can shift the
balance of b-amyloid to the harmful form, -so
can age -also mutations in gene coding for
apolipoprotein E (ApoE) a protein that helps
transport cholesterol in the blood -may account
for 85 of the cases late-onset
Alzheimers -mutated genes for apoE apoE4 may
increase risk of development -may predispose you
to Ab plaque formation, or may hasten the onset -
?????
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Medical Application Alzheimers Disease

• -brain abnormalities
• 1. loss of ACh releasing neurons from the
  nucleus basalis (below
• the globus pallidus)
• 2. beta-amyloid plaques
• 3. neurofibrillary tangles
• -plaque central core of b-amyloid, surrounded
  by degenerating nerve endings
• the plaques attract microglia inflammatory
  reaction against the plaque, including the
  secretion of toxic chemicals that harm
  bystander neurons
• -tangles bundles of abnormal filaments that
  accumulate in the cell
• bodies of the affected neurons
• probably form in response to the formation of Ab
  plaques bind to the neurons and alter
• the proper formation of the neurons cytoskeleton
  production of tangles
• the Ab plaques are also thought to lead to
  excessive influx of Ca ions which kills the cells
• hippocampal neurons (long-term memory) seem to be
  vulnerable
• -treatments drugs that inhibit
  acetylcholinesterase improve alertness by
  increasing Ach signaling in the brain
• e.g. Donepezil only ones currently approved
  (Aricept)
• may improve the symptoms they dont slow the
  degeneration

http//en.wikipedia.org/wiki/AlzheimerAcetylcholi
nesterase_inhibitors
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Major Regions and Landmarks

• Diencephalon
• includes the hypothalamus, thalamus, epithalamus
  and subthalamus
• thalamus 80 of the diencephalon
• paired oval masses of gray matter organized into
  nuclei, interspersed with white matter
• joined by the intermediate mass (gray matter) in
  about 70 of brains
• major relay station for most sensory impulses
  from the SC, brain stem
• crude perception of pain, heat and pressure
  (refined in cerebrum)
• transmits motor information from cerebellum to
  the cerebrum
• relays nerve impulses to and from different areas
  of the cerebrum
• seven major groups of nuclei !!!

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Thalmic nuclei

• reticular
• pulvinar
• geniculate medial and lateral
• anterior
• medial
• ventral lateral, posterior and anterior
• lateral posterior and dorsal

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• hypothalamus
• -Emotions, autonomic functions, hormone
  production
• -mamillary bodies serve as relay stations for
  reflexes related to eating
• -supraoptic and preoptic nuclei that in hormone
  secretion (ADH) and body temp
• -major functions
• 1. control of the ANS integrates signals from
  the ANS (regulated smooth and cardiac muscle
  contraction)
• major regulator of visceral activities (heart
  rate, food movements, contraction of bladder)
• 2. produces hormones connects with pituitary to
  regulate its activity

3. regulates emotional and behavioral patterns
rage, aggression, pain and pleasure sexual
arousal 4. regulates eating drinking
hypothalamus contains a thirst center which
responds to a rise in osmotic pressure in the
ECF (dehydration) 5. controls body temperature
monitors temp of blood flowing through the
hypothalamus
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Hypothalmic nuclei

• mamillary bodies
• supraoptic
• preoptic
• dorsomedial
• ventromedial
• anterior hypothalmic
• posterior hypothalmic
• paraventricular
• suprachiasmatic
• arcuate

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• epithalamus consists of the pineal gland and
  habenular nuclei
• -pineal gland part of the endocrine system
• -secretes the hormone melatonin
• -increased secretion in dark
• -promote sleepiness and helps set the
  circadian
• rhythms of the body (awake/sleep period)
• subthalamus works with the cerebrum and
  cerebellum to control body
• movements
• -majority is made of the subthamic nuclei
• -sends efferent connections to the caudate
  nucleus and putamen,
• to the medial and lateral nuclei of the thalamus
  and to the red
• nucleus and substantia nigra of the midbrain
• -also receives afferent connections from the
  substantia nigra

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Major Regions and Landmarks
BRAIN STEM

• Medulla oblongata
• continuation of the SC that forms the inferior
  part of the brain stem
• relays sensory information and controls automatic
  motor functions
• where the SC and MO meet - 90 of the axons from
  the right side of the SC cross over to the left
  side of the MO and vice versa decussation
• white matter contains sensory/ascending and
  motor/descending tracts
• some of the white matter form bulges called
  pyramids white tracts that connect the cerebrum
  to the SC
• contains several nuclei also that regulate
  autonomic functions - reflex centers for
  regulating heartbeat and BP (cardiovascular
  center), respiration (respiratory center), plus
  vomiting, coughing, sneezing, hiccuping and
  swallowing
• nuclei in the posterior part are associated with
  sensations of touch, proprioception, pressure and
  vibration

-associated with 5 pairs of cranial
nerves VIII IX X XI XII
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-nuclei -reflex centers e.g.
cardiovascular respiratory 1. inferior
olivary part of the olive -relay impulses from
proprioceptors to the cerebellum joint and
muscle position 2. gracile ascending sensory
tracts from SC synapse here -relayed to the
thalamus by postsynaptic neurons 3. cuneate
ascending sensory tracts from SC synapse
here -relayed to the thalamus by postsynaptic
neurons -white matter pyramids
-injury to the medulla hard blow to the back of
the head or upper neck can be fatal -damages the
medullary rhythmicity area of the respiratory
center (disrupts pattern of breathing) -non-fatal
injury paralysis and loss of sensation,
irregular breathing and heart rate
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BRAIN STEM

• Pons
• bridge
• - e.g. connects brain stem to the cerebrum via
  bundles of axons
• - superior to the medulla and anterior to the
  cerebellum
• consists of nuclei (cell bodies in gray matter)
  and tracts
• somatic and visceral motor responses
• Pontine nuclei control voluntary movements that
  originate in the cerebral cortex and are relayed
  through the pons into the cerebellum
• Pneumotaxic area controls breathing (with
  medulla)
• Apneustic area controls breathing (with
  medulla)

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BRAIN STEM

• Midbrain (Mesencephalon)
• relay station between the cerebrum and the spinal
  cord
• extends from the pons to the diencephalon
• sends motor tracts to the SC, medulla and pons
  conducts sensory tracts to the thalamus
• anterior portion contains a pair of white tracts
  cerebral peduncles
• conduct impulses from the cerebrum to the SC,
  pons and medulla
• posterior portion tectum
• white matter tracts cerebellar peduncles
• four round elevations colliculi
• reflex centers for visual activities (tracking,
  scanning) pupillary reflex, shape of the lens
• reflexes that mediate movements of the eyes, head
  and neck - the startle reflex
• relays impulses from hearing receptors to the
  thalamus

• -generates involuntary somatic motor responses
• release of dopamine from substantia nigra
  (nuclei) - loss of these neurons Parkinsons
• red nuclei forms synapses with cerebellum to
  coordinate muscle movements

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Midbrain nuclei

• colliculi superior and inferior
• red nuclei
• substantia nigra
• white matter tracts cerebral peduncles,
  cerebellar peduncles

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• Cerebellum
• divided into hemisphere with lobes - like the
  cerebrum
• anterior and posterior lobes
• involuntary motor activities
• evaluates and coordinates motor activities
  initiated by the cerebrum and corrects problems
  by sending info back to the cerebrum
• regulate posture balance
• has a superficial layer of gray matter called the
  cerebellar cortex - like the brain
• deep to the gray matter are tracts of white
  matter arbor vitae
• also has nuclei cerebellar nuclei (origin of
  neurons that connect the cerebellum to the brain
  and SC)
• connected to the brain stem by three cerebellar
  peduncles
• inferior sensory information from the inner ear
  and body proprioceptors
• middle carry commands for voluntary movements
  that originated into the cortex into the
  cerebellum for coordination
• superior connects to the red nuclei and the
  nuclei of the thalamus

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Medical application Ataxia

• damage to the cerebellum
• blindfolded people cannot find the tip of their
  nose
• also changed speech patterns due to incoordinate
  speech muscles
• abnormal walking or balance
• alcohol overdose also suppresses the activity of
  the cerebellum

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The Limbic System
corpus callosum

• called the emotional brain
• group of structures that surround the brain stem
• involved in olfaction and memory
• emotion anger, fear, happiness
• associated with specific responses behavioral
  patterns
• basic behavioral patterns
• -preparing for attack, laughing, crying, blushing
• also includes sexual behaviors for the
  continuation of the species
• connects with the hypothalamus to regulate these
  behaviors
• main components
• 1. limbic lobe rim of cerebral cortex on the
  medial surface of
• each hemisphere includes the hippocampus
  (memory)
• 2. dentate gyrus
• 3. amygdala stimulation - rage
• 4. olfactory bulbs
• 5. septal nuclei
• 6. mammillary bodies of the hypothalamus

cingulate gyrus
anterior thalmic nuclei
hypothalmic nuclei
fornix
olfactory tract
mamillary body
amygdala
parahippocampal gyrus
hippocampus
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Limbic system

• main components
• 1. limbic lobe rim of cerebral cortex on the
  medial surface of each hemisphere includes the
  hippocampus (parahippocampal gyrus), the
  cingulate gyrus, the insula and the dentate gyrus
• hippocampus is located within the dentate gyrus
  and is surrounded by the parahippocampal gyrus
• cingulate gyrus is located above the corpus
  callosum
• insula located within the lateral sulcus that
  separates the temporal lobe from the parietal
  lobe
• 2. amygdala integration center between the
  limbic system, cerebrum and various sensory
  systems
• stimulation rage
• fear recognition
• social interaction
• recognition of familiar objects, facial
  expression
• interpretation of facial expressions
• 3. olfactory bulbs
• 4. septal nuclei
• 5. mammillary bodies of the hypothalamus
• 6. fornix - tract of white matter that connects
  the hippocampus to the hypothalamus
• fibers end at the mammillary bodies
• 7. hypothalmic nuclei
• other areas include the anterior nuclear group of
  the thalamus and the reticular system within the
  brain stem

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I - Olfactory II - Optic III - Oculomotor IV-Troch
lear V - Trigeminal VI - Abducens VII -
Facial VIII - Acoustic IX - Glossopharyngeal X -
Vagus XI - Accessory XII - Hypoglossal
-cranial nerves 12 pairs -considered part of
the peripheral nervous system (PNS) -olfactory
optic contain only sensory axons sensory
nerves -remaining are either motor or mixed
nerves both motor and sensory axons some say
my mother bought my brother some bad beer, my my
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Spinal Cord

• length in adults 16 to 18 inches
• Cervical and lumbar enlargements
• cervical C4 to T1, nerves to and from upper
  limbs
• lumbar T9 to T12, nerves to and from lower
  limbs
• Tapers to conus medullaris
• filium terminale arises from the CM - extension
  of the pia mater that anchors the SC to the
  coccyx
• 31 segments each with
• Dorsal root ganglia
• Sensory neuron cell bodies
• Pair of dorsal roots
• Pair of ventral roots

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Spinal Meninges

• Specialized membranes
• Provide physical stability and shock absorption
• Three layers
• Dura mater dense irregular CT
• continuous with the brains DM
• above it is the epidural space
• Arachnoid continuous with brain
• above it is the subdural space
• below is the subarachnoid space
• avascular
• Pia mater connective tissue
• collagen and elastin bundles
• well vascularized

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• The Pia Mater
• Innermost meningeal layer
• Bound firmly to underlying tissue
• Denticulate ligaments bind pia mater to the
  arachnoid

-spinal tap under local anesthetic -long needle
is inserted into the subarachnoid space and CSF
is withdrawn or antibiotics or anesthetics are
given -given between L3 L4 or L4 L5
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Histology of the Spinal Cord

• Central gray matter
• Contains cell bodies of neurons and glial cells
  unmyelinated axons
• Gray matter projections are horns
• Peripheral white matter
• Myelinated and unmyelinated axons
• Tracts or columns

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Organization of Gray Matter

• Posterior gray horns
• Somatic and visceral sensory nuclei
• Anterior gray horns
• Somatic motor control
• Lateral gray horns
• Visceral motor neurons
• Gray commissures
• Axons of interneurons crossing cordated and
  unmyelinated axons

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Organization of White Matter

• Six columns (funiculi)
• Anterior, lateral and posterior white columns
• Contain tracts
• Ascending tracts relay information from spinal
  cord to brain
• Descending tracts carry information in the
  opposite direction

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• Spinothalamic tract
• pain, temperature, deep pressure crude touch
• Posterior columns
• proprioception, discriminative touch, two-point
  discrimination, pressure and vibration
• Direct pathways (corticospinal corticobulbar)
• precise, voluntary movements
• corticobulbar cerebral cortex to brain stem and
  out via cranial nerves to muscles of head and
  neck
• corticospinal also called the pyramidal tracts
  (lateral and anterior)
• cerebral cortex to spinal cord and out to
  voluntary muscles (synapses with lower motor
  neurons in the ventral gray horn)
• Indirect pathways (rubrospinal, vestibulospinal)
• programming automatic movements, posture muscle
  tone, equilibrium coordination of visual
  reflexes
• rubrospinal alternate route for voluntary
  movements of arms and legs
• red nucleus of midbrain through the lateral
  column
• vestibulospinal