Download Chapter 11 - Central Nervous System

Chapter 11 -Central Nervous System
PROTECTION – Bones, membranes, fluid
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Meninges -3 membranes around the brain and spinal cord
• Dura Mater
• Arachnoid Mater
• outermost attached to periosteum
• middle, thin net-like layer
• tough fibrous connective tissue
• subarachnoid space contains CSF
• forms dural sinuses
• arachnoid granulations function?
• Pia Mater - very thin delicate layer
• falx cerebri, falx cerebelli,
tentorium cerebelli)
• clings to brain convulsions
• contains many nerves and blood vessels
PROTECTION – Spinal Cord
Meningeal arrangement like brain except
• dura mater is not attached to vertebrae
• epidural space - filled with adipose and loose CT
 CSF fills the subarachnoid space and central canal
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Cerebral Spinal Fluid
(CSF)
Total volume 150ml; 500 ml
secreted daily to replace the
circulating 150 ml.
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Made and circulated by ependymal cells
of the choroid plexus in the ventricles
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Nutritive and protective; helps
maintain stable ion concentrations in
CNS
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Circulation – surrounds the
brain and spinal cord
BRAIN - Cerebrum largest
brain portion
100,000,000,000 neurons
Cerebral hemispheres connected by corpus callosum
 Divided into lobes named for bones that cover them
 Internal lobe – Insula
 Convolutions are made up of
• sulci - shallow groove
• central sulcus
• lateral sulcus
• fissure - deep groove
• longitudinal fissure
• transverse fissure
 Composition
• white matter - bundles of
myelinated axons -(tracts)
• gray matter - cell nuclei and unmyelinated axons
• cerebral cortex -"gray matter“
• nuclei- "basal ganglia"
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Cerebral Cortex “Gray Matter”
outer portion of the cerebrum
conscious integrated behavior "gray matter“
 motor, sensory and associative behavior
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• Precentral gyrus -motor area
• voluntary motor impulses
• anterior to central sulcus
• Postcentral gyrus -cutaneous
sensory area
• receives sensory information
• posterior to central sulcus
• Associative Areas
• integrates motor and
sensory areas to --• provide memory, reasoning,
verbalization, judgment
Basal ganglia
Caudate, Putamen, Globus pallidus nuclei
gray matter deep in the cerebral white matter
relays skeletal motor impulses from primary motor cortex
 relies on dopamine to inhibit and tame these impulses
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Ventricles - lateral, third,
cerebral aqueduct, fourth
interconnected cavities within cerebrum and brain stem
 filled with CSF
 continuous with central canal in spinal cord
 CSF secreted by choroid plexuses
 lined with ependymal cells
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Diencephalon
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Thalamus - relays sensory information to cortex
• except smell
• directs and inhibits sensory info
• third ventricle between two halves
• optic tracts, optic chiasm, mammary bodies
• Hypothalamus - regulates homeostasis of
• heart rate and bp
• body temperature
• water and electrolyte balance
• hunger and body weight
• digestive movement and secretions
• sleep-wake cycles - pineal gland
• endocrine function
• infundibulum
• posterior pituitary
Brainstem
pathway for fiber tracts to and from the
cerebrum, also houses many cranial nerves
Midbrain- between diencephalon and pons
• Corpora quadrigemina- visual and auditory
reflex center (nuclei)
• Cerebral peduncles- fiber tracts (white matter)
• a and b separated by cerebral aqueduct
 Pons - bulging portion
• major fiber tract cross section
• pneumotaxic area (regulates breathing rate)
 Medulla oblongata - connect to spinal cord
• autonomic reflex centers for homeostasis
• Cardiac Center
• Vasomotor Center
• Respiratory Center
• Vomiting, swallowing, coughing
• Hypothalamus relays impulses through medulla
• Olive - connects to Cerebellum
• Fourth ventricle
• Decussation of Pyramids - Corticospinal tracts
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Cerebellum
arbor vitae - pattern of white and gray matter
 vermis connects hemispheres
 cerebellar cortex – gray matter
 Coordinates voluntary muscle movements
• inferior peduncle receives proprioception
• middle peduncle receives desired motion from cerebrum
• cerebellum integrates a and b
• superior peduncle sends out coordinated information
 Skilled movements, posture, equilibrium
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Functional Brain systems - integrations
throughout the brain
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Limbic System - emotional brain
• diencephalon, basal ganglia, frontal and temporal cerebrum,
olfactory, amygdala
• pleasure, anger, fear, sorrow
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Reticular Formation - wakeful brain
• brain stem, major tracts to and from the cerebrum and cerebral nuclei
• suppressed by seratonin, darkness, alcohol
• injury causes coma
Aging Brain
Secrets of Healthy Aging
Gross structure
of the spinal cord
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length about 17 inches
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starts at foramen magnum
tapers to a point (conus medullaris)
at L1- L2
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31 segments 31 nerves
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Cervical and lumbar enlargements
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Note cauda equina and filum terminale
Cross-sectional Anatomy
of the Spinal Cord
Extensions
 Gray matter -interneuron and motor
• ventral root - motor nerve axons
neuron cell bodies
• dorsal root - sensory nerve axons
• Dorsal horn - sensory nerve entrance
• ganglion- a bundle of cell
• Lateral horn - T1 to L1 - sympathetic
bodies outside CNS
• Ventral horn - motor nerve exit
• dorsal root ganglia - contains
 Spinal nerve -fusion of dorsal root & ventral root
cell bodies of sensory neurons
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Cross-sectional Anatomy
of the Spinal Cord (cont.)
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White matter (columns)- nerve tracts
• myelinated interneuron axons
• named funiculi - posterior, lateral, anterior
• provide a 2-way system of communication
• ascending tracts located posteriorly
(sensory)
• Spinothalamic
• Spinocerebellar
• Fasciculus gracilis and cuneatus
• descending tracts (next page)
Spinal Tracts (cont.)
Descending tracts located
anteriorly (motor)
• Corticospinal
• Reticulospinal
• Rubrospinal
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General characteristics of tracts
• Pairs cross at some point
• Consist of 2-3 neurons
• Exhibit somatotrophy
Reflex arc - nerve pathway
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Uses of reflexes
• to insure proper transmission of a
nerve impulse
• to prevent tissue damage
Reflex
automatic, subconscious
responses to stimuli
Parts of a reflex pathway
• receptor
• sensory neuron (afferent)
• interneuron (associative)
• motor neuron (efferent)
• effector (muscles and glands)
Characteristics of a Reflex
examples
involves 2-3 neurons
 involuntary response
 does not involve the brain
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• knee-jerk
• Withdrawal
• cross-extensor
• superficial reflex - Babinski sign
References
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Web Sites on Brain
Web Sites on Spinal Cord
Hole's Online Learning Center - try Test Yourself