Transcript 12 - Brazosport College

Human Anatomy & Physiology
Ninth Edition
CHAPTER
12
The Central
Nervous
System:
Part 3 –CSF,
BBB, CVA
© Annie Leibovitz/Contact Press Images
© 2013 Pearson Education, Inc.
Brain Video
• Neurotransmitters – Noradrenalin,
serotonin, dopamine and endorphins
Cerebrospinal Fluid (CSF)
• Composition
– Watery solution formed from blood plasma
• Less protein and different ion concentrations than
plasma
– Constant volume
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Cerebrospinal Fluid (CSF)
• Functions
– Gives buoyancy to CNS structures
• Reduces weight by 97%
– Protects CNS from blows and other trauma
– Nourishes brain and carries chemical signals
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Choroid Plexuses
• Hang from roof of each ventricle; produce
CSF at constant rate; keep in motion
– Clusters of capillaries enclosed by pia mater
and layer of ependymal cells
• Ependymal cells use ion pumps to control
composition of CSF and help cleanse CSF
by removing wastes
• Normal volume ~ 150 ml; replaced every 8
hours
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Figure 12.24b Formation, location, and circulation of CSF.
Ependymal
cells
Capillary
Connective
tissue of
pia mater
Wastes and
unnecessary
solutes absorbed
Section
of choroid
plexus
Cavity of
ventricle
CSF formation by choroid plexuses
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CSF forms as a filtrate
containing glucose, oxygen,
vitamins, and ions
(Na+, Cl–, Mg2+, etc.)
Figure 12.24a Formation, location, and circulation of CSF.
Slide 1
4
Superior
sagittal sinus
Arachnoid villus
Choroid plexus
Subarachnoid space
Arachnoid mater
Meningeal dura mater
Periosteal dura mater
1
Interventricular
foramen
Third ventricle
Right lateral ventricle
(deep to cut)
3
Cerebral aqueduct
Lateral aperture
Fourth ventricle
Median aperture
Central canal
of spinal cord
(a) CSF circulation
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Choroid plexus
of fourth ventricle
2
1 The choroid plexus of each
Ventricle produces CSF.
2 CSF flows through the ventricles
and into the subarachnoid space via
the median and lateral apertures.
3 CSF flows through the
subarachnoid space.
4 CSF is absorbed into the dural
venous sinuses via the arachnoid villi.
Figure 12.25 Hydrocephalus in a newborn.
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Blood Brain Barrier
• Helps maintain stable environment for
brain
• Separates neurons from some bloodborne
substances
• Composition
– Continuous endothelium of capillary walls
– Thick basal lamina around capillaries
– Feet of astrocytes
• Provide signal to endothelium for formation of tight
junctions
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Figure 11.3a Neuroglia.
Capillary
Neuron
Astrocyte
Astrocytes are the most abundant CNS neuroglia.
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Blood Brain Barrier: Functions
• Selective barrier
– Allows nutrients to move by facilitated diffusion
– Metabolic wastes, proteins, toxins, most drugs, small
nonessential amino acids, K+ denied
– Allows any fat-soluble substances to pass, including
alcohol, nicotine, and anesthetics
• Absent in some areas, e.g., vomiting center and
hypothalamus, where necessary to monitor
chemical composition of blood
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Homeostatic Imbalances of the Brain
• Traumatic brain injuries
– Concussion—temporary alteration in function
– Contusion—permanent damage
– Subdural or subarachnoid hemorrhage—
may force brain stem through foramen
magnum, resulting in death
– Cerebral edema—swelling of brain
associated with traumatic head injury
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Blood Flow to the Brain
• Brain requires more blood flow and
oxygen
• Receives 15 – 20% of body’s blood flow
• Uses 15 – 20% of body’s oxygen
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Mickey Dufilho
Figure 19.22b Arteries of the head, neck,
and brain.
Ophthalmic artery
Basilar artery
Vertebral artery
Internal
carotid artery
External
carotid artery
Common
carotid artery
Thyrocervical
trunk
Costocervical
trunk
Subclavian
artery
Axillary
artery
Branches of
the external
carotid artery
• Superficial
temporal artery
• Maxillary artery
• Occipital artery
• Facial artery
• Lingual artery
• Superior thyroid
artery
Larynx
Thyroid gland
(overlying trachea)
Clavicle (cut)
Brachiocephalic
trunk
Internal thoracic
artery
(b) Arteries of the head and neck, right aspect
Figure 19.22d Arteries of the head, neck,
Anterior
Cerebral arterial
and
Frontalbrain.
lobe
circle
(circle of Willis)
Optic chiasma
• Anterior
communicating
artery
• Anterior
cerebral artery
• Posterior
communicating
artery
• Posterior
cerebral artery
Basilar artery
Middle
cerebral
artery
Internal
carotid
artery
Mammillary
body
Temporal
lobe
Pons
Occipital lobe
Vertebral artery
Cerebellum
Posterior
(d) Major arteries serving the brain (inferior view, right side
of cerebellum and part of right temporal lobe removed)
Figure 19.22c Arteries of the head, neck,
and brain.
Homeostatic Imbalances of the Brain
• Cerebrovascular accidents (CVAs or strokes)
– Ischemia
• Tissue deprived of blood supply; brain tissue dies, e.g.,
blockage of cerebral artery by blood clot
– Hypoxia
• condition in which inadequate oxygen is available to tissues
– Hemiplegia (paralysis on one side), or sensory and
speech deficits
– Transient ischemic attacks (TIAs)—temporary
episodes of reversible cerebral ischemia
– Tissue plasminogen activator (TPA) is only
approved treatment for stroke
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Homeostatic Imbalances of the Brain
• Degenerative brain disorders
– Alzheimer's disease (AD): a progressive
degenerative disease of brain that results in
dementia
• Memory loss, short attention span, disorientation,
eventual language loss, irritable, moody, confused,
hallucinations
• Plaques of beta-amyloid peptide form in brain
– Toxic effects may involve prion proteins
• Neurofibrillary tangles inside neurons kill them
• Brain shrinks
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Homeostatic Imbalances of the Brain
• Parkinson's disease
– Degeneration of dopamine-releasing neurons
of substantia nigra
– Basal nuclei deprived of dopamine become
overactive  tremors at rest
– Cause unknown
• Mitochondrial abnormalities or protein degradation
pathways?
– Treatment with L-dopa; deep brain
stimulation; gene therapy; research into stem
cell transplants promising
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Homeostatic Imbalances of the Brain
• Huntington's disease
– Fatal hereditary disorder
– Caused by accumulation of protein huntingtin
• Leads to degeneration of basal nuclei and cerebral cortex
• Initial symptoms wild, jerky "flapping"
movements
• Later marked mental deterioration
• Treated with drugs that block dopamine effects
• Stem cell implant research promising
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Brain Video
• Shows effects of stroke and repair
• Formation of new synapses
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Mickey Dufilho
Physiology of Addiction
• Definition
• Psychological or Physiological?
• Kinds of addictions?
7/2/2012
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Day in the Life of Nicotine Junkie
• 1 st Cigarette/chew of
the day
– Nicotine = ACh
– Stimulates release of
hormones Epi and NE
– Lasts 30 min
• 2nd, 3rd, 4th cig/chew
– Stimulates release of
hormone cortisol
– Then NT dopamine
and glutamate
– Lasts 30 min
7/2/2012
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Why is Nicotine Addictive?
• ↓ ACh
• ↑ # Nicotinic of
Receptors
• So what?
7/2/2012
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Physiology of Depression
• Definition
• Psychological or Physiological?
• Causes?
– Environmental and neurotransmitters
7/2/2012
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Physiology of Depression
• ↓ in NE and/or
Serotonin
• Due to?????
• Treatment – dual
approaches
– MAO Inhibitors
(monoamine oxidase)
– Tricyclic
antidepressants
– SSRI (serotonin
specific reuptake
inhibitors)
7/2/2012
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What about anxiety?
• What system creates anxiety?
• Treatment
– Valium (diazepam), Ativan (lorazepan), Xanax
• Rohypnol – date rape drug is in the same
family of drugs as Valium, Ativan
• Barbiturates (penobarbital) bind to GABA
receptor – opens chloride channels which
cause hyperpolarization
7/2/2012
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