Chapter 8
Central Nervous System
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CNS Functions
• Communication and coordination system in
the body
• Seat of intellect and reasoning
• Communicates with the endocrine system
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Divisions
• Central nervous system includes the brain
and spinal cord
• The peripheral nervous system consist of 12
pairs of cranial nerves and 31 pairs of spinal
nerves
• Autonomic nervous system includes the
sympathetic and parasympathetic systems
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The Nerve Cell
• Called the neuron
– Transmits messages from one cell to another
• Nucleus, cytoplasm, and cell membrane
• Dendrites
• Axons (only one per cell)
– Neurilemma or myelin sheath
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Figure 8-1 Two types of neurons
showing cell body, axon, and
dendrite: (A) efferent (motor)
neuron, (B) afferent (sensory)
neuron
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Nervous Tissue/Cells
• Neuroglia
– Astrocytes, microglia, oligodendrocytes and Schwann
cells
• Neurons
– Sensory or afferent
– Motor or efferent
– Associative or interneurons
• Membrane excitability
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Synapse
• When messages go from one cell to the
next cell
• Synaptic cleft
– The space between the axon of one nerve cell and the
dendrites of another
• Neurotransmitters
– Chemical substances that make it possible for messages
to cross the synapse to a target receptor
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Effects of Aging
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Slowing nerve conduction
Loss of brain size
Slowing of reaction time
Changes in sleep patterns
Important to continue physical and mental
activity to stimulate nerve cells, blood flow
and neurotrophin production
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The Brain (1 of 2)
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Weighs about 1,400 grams or 3 pounds
100 billion neurons
Meninges and cerebrospinal fluid
Without oxygen, brain damage occurs
within 4–8 minutes
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The Brain (2 of 2)
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Cerebrum
Diencephalon
Cerebellum
Brain stem
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Figure 8-5 A cross section showing the major parts of the brain:
cerebrum, cerebellum, diencephalon, and brain stem
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Memory
• Storage of old and new information
• Role of the hippocampus of the limbic
system
• Short- or long-term memory
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Coverings of the Brain
• Dura mater
– Outer that lines the inside of the skull
• Arachnoid mater
– Middle layer, resembles a fine cobweb
• Pia mater
– Inner layer, covers the brain, consists of blood vessels
(called the choroid plexus) and connective tissue
• Cerebrospinal fluid
– Acts as a shock absorber and a source of nutrients
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Ventricles of the Brain
• Four lined cavities filled with cerebrospinal
fluid
• Choroid plexus helps with the production of
cerebral spinal fluid
• 1st and 2nd
– Right and left lateral ventricles
• 3rd and 4th
– Third is connected to the two lateral ventricles vis the
interventricular foramen
– The 3rd and 4th are connected via a narrow canal called
the cerebral aqueduct
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Cerebrospinal Fluid (CSF)
• Formed inside the four ventricles
• Transports nutrients to and removes
metabolic waste products from the brain
cells
• Blood-brain barrier
– Selectively permeable
– Consist of choroid plexus capillaries
• Lumbar puncture
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Cerebrum
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Largest part of the brain
Weighs about 2 pounds
Cerebral cortex (gray matter)
Two hemispheres and longitudinal fissure
Fissures (deeper) and sulci (shallow)
Gyri or convolutions (elevated ridges
between the sulci)
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Five Major Fissures
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Longitudinal fissure
Transverse fissure
Central fissure
Lateral fissure
Parieto-occipital fissure
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Figure 8-8 Lateral view of the brain
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Cerebral Functions
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Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe
Limbic lobe or system
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Figure 8-9 (A) The parts of the brain
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Figure 8-9 (B) Areas of brain function
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Diencephalon
• Located between the cerebrum and the
midbrain
• Thalamus
– Relay station for incoming and outgoing nerve impulses
• Hypothalamus
– Considered to be the “brain” of the brain
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Hypothalamus (1 of 2)
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Autonomic nervous control
Cardiovascular control
Temperature control
Appetite control
Water balance
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Hypothalamus (2 of 2)
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Manufacture of oxytocin
Gastrointestinal control
Emotional state
Sleep control
Mind-over-body experiences
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Cerebellum
• Located behind the pons and below the
cerebrum
• Right and left cerebellar hemispheres
connected by vermis
• Gray matter on the outside and white matter
on the inside
• Communicates with the rest of the CNS by
three pairs of tracts called peduncles
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Cerebellar Function
• Maintenance of balance
• Maintenance of muscle tone
• Coordination of muscle movements
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Brain Stem
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Midbrain
Pons
Medulla oblongata
Pathway for ascending and descending
tracts
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Spinal Cord
• Begins at foramen magnum of the occipital
bone
• Ends at the second lumbar vertebrae
• 31 pairs of spinal nerves
• Protected by meninges and other tissues
• White and gray matter
• Functions
– Carry messages from the sensory neurons to the brain
for interpretation, then carry the response back through
the motor neurons to muscles and glands
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Disorders (1 of 3)
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Meningitis
Encephalitis
Epilepsy
Cerebral palsy
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Disorders (2 of 3)
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Poliomyelitis
Hydrocephalus
Parkinson’s disease
Essential tremor
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Disorders (3 of 3)
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Multiple sclerosis
West Nile virus (WNV)
Dementia
Alzheimer’s disease
Tumors
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Brain Injuries
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Hematoma
Concussion
Coup and contrecoup injury
Spinal cord injuries
– Quadriplegia
– Paraplegia
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Headaches
• Tension
• Migraine
• Cluster
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