Chapter 7 Body Systems
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Transcript Chapter 7 Body Systems
Chapter 13
Central Nervous
System
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Mosby items and derived items © 2007, 2003 by Mosby, Inc.
Coverings of the Brain
and Spinal Cord
Two protective coverings:
Outer covering is bone
Inner covering is the meninges
continues
inside the spinal cavity beyond the end of the
spinal cord
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Coverings of the Brain
and Spinal Cord
Meninges
3 membranous layers
Dura
mater
strong, white fibrous tissue
outer layer of meninges and
inner periosteum of the
cranial bones
Arachnoid
mater
delicate, cobwebby layer
between the dura mater and
pia mater
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Coverings of the Brain
and Spinal Cord
Meninges
3 membranous layers (cont.)
Pia
mater
innermost, transparent layer
adheres to the outer surface of the brain and spinal cord
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Cerebrospinal Fluid
Functions
Provides a supportive, protective cushion
Reservoir of circulating fluid, which is monitored by the brain to
detect changes in the internal environment
Fluid spaces
Cerebrospinal fluid— found around the brain and spinal cord
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Cerebrospinal Fluid
Fluid spaces (cont.)
Ventricles— fluidfilled spaces within
the brain; four
ventricles within the
brain
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Spinal Cord
Structure of the spinal cord
Oval cylinder that tapers slightly from above
downward
Two bulges, one in the cervical region and
one in the lumbar region
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Spinal Cord
Structure of the spinal cord (cont.)
Nerve roots
Fibers
Carry sensory information into the spinal canal
Fibers
of dorsal nerve root
of ventral nerve root
Carry motor information out of the spinal cord
Interneurons are located in the spinal cord’s gray matter
core
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Ventral (anterior)
nerve root
Dorsal (posterior)
nerve root
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Spinal Cord
Structure of the spinal cord (cont.)
Gray matter
Consists predominantly of
cell bodies of interneurons
and motor neurons
In transverse section, looks
like an H
White matter
Surrounds the gray matter
consists of a large bundle of
axons divided into tracts
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Spinal Cord
Functions of the spinal cord
Provides conduction routes to and from the brain
Ascending tracts (sensory)— conduct impulses up the
cord to the brain
Descending tracts (motor)— conduct impulses down
the cord from the brain
Bundles
of axons compose all tracts
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Spinal Cord
Functions of the spinal cord (cont.)
Important
ascending
(sensory) tracts = BLUE
crude touch, pain, and
temperature
pressure
discriminating touch and
conscious kinesthesia
(proprioception)
subconscious
kinesthesia
touch related to visual
reflexes
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Spinal Cord
Functions of the spinal cord (cont.)
Important descending (motor) tracts
voluntary movements on opposite
side of the body
voluntary movements on same side of body
maintain posture during movement
transmit impulses that coordinate body movements and
maintenance of posture
head and neck movements during visual reflexes
coordination of posture and balance
Spinal
cord—
reflex center for all spinal reflexes
reflex centers are located in the gray matter of the
cord
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The Brain
Structures of the brainstem
Medulla oblongata
Lowest part of the brainstem
Composed of white matter and a network of gray and
white matter called the reticular formation
Nuclei— clusters of neuron cell bodies located in the
reticular formation
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The Brain
Structures of the brainstem (cont.)
Pons
Located
above the medulla and below the midbrain
Composed
of white matter and reticular formation
Midbrain
Located
above the pons and below the cerebrum; forms the
midsection of the brain
Composed
conduct
Red
of white tracts and reticular formation
impulses between the midbrain and cerebrum
nucleus and substantia nigra (“black matter”)
clusters of cell bodies of neurons involved in muscular
control
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The Brain
Functions of the brainstem
Performs sensory, motor, and reflex functions
Nuclei in medulla— contain reflex centers
Of primary importance— cardiac, vasomotor, and
respiratory centers
Nonvital reflexes— vomiting, coughing, sneezing,
etc.
Pons— help regulate respiration
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The Brain
Structure of the cerebellum
Gray matter makes up the cortex, and white matter
predominates in the interior
Cerebellum has numerous sulci (groove) and delicate,
gyri (raised areas)
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The Brain
Functions of the cerebellum
coordinates movements to produce the intended action
General functions
produce skilled movements by coordinating the activities of
muscles
maintains balance
Controls posture
smooth movements and make movements efficient and
coordinated
Processes sensory information
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Stand Up!
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The Brain
Diencephalon
Located between the cerebrum and the midbrain
Consists of several structures: thalamus, hypothalamus, pineal
gland, and several others
Thalamus
Dumbbell-shaped mass of gray matter made up of many nuclei
plays role in processing auditory and visual input
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The Brain
Thalamus (cont.)
Serves
as a major relay station for sensory impulses
on their way to the cerebral cortex
Performs the following primary functions:
Two parts for sensations:
conscious recognition of the crude, less critical
sensations of pain, temperature, and touch
Neurons relay all kinds of sensory impulses, except
possibly olfactory, to the cerebrum
emotions by associating sensory impulses with feeling of
pleasantness and unpleasantness
arousal mechanism
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The Brain
Diencephalon (cont.)
Hypothalamus
lies
beneath (hypo) the thalamus
Small but functionally important area of the brain,
performs many functions of greatest importance for
survival and enjoyment
Links mind and body
Links nervous system to endocrine system
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The Brain
Hypothalamus (cont.)
Summary
of hypothalamic functions
Regulator and coordinator of autonomic activities
Major relay station between the cerebral cortex and lower
autonomic centers
crucial part of the route by which emotions can express
themselves in changed bodily functions
maintaining water balance
arousal mechanism
regulating appetite
maintaining normal body temperature
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The Brain
Diencephalon (cont.)
Pineal gland
Involved
in regulating the body’s biological clock
Produces melatonin as a “timekeeping hormone”
Melatonin is made from the neurotransmitter serotonin
Melatonin levels increase when sunlight is absent and
decreases when sunlight is present, thus regulating the
circadian (daily) biological clock (Figure 13-15)
Melatonin is the “sleep hormone”
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The Brain
Structure of the cerebrum
Cerebral cortex
Largest
and uppermost division of the brain
consists of right and left cerebral hemispheres
each hemisphere is divided into four lobes:
Frontal lobe
Parietal lobe
Temporal lobe
Occipital lobe
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The Brain
Cerebral cortex (cont.)
Cerebral cortex— outer surface made up of six
layers of gray matter
Gyri— raised areas
Sulci— shallow grooves
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The Brain
Cerebral cortex (cont.)
Fissures—
deeper grooves, divide each cerebral
hemisphere into lobes
Central sulcus— groove between frontal and parietal
lobes
Lateral fissure— groove between temporal lobe below
and parietal lobes above
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Structure of the cerebrum
Basal nuclei (or cerebral nuclei)
Basal nuclei— islands of gray matter located deep
inside the white matter of each hemisphere
Unsure of exact function but important in regulating
voluntary motor functions, especially repetitive actions
Example: maintaining posture, walking
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The Brain
Functions of the cerebral
cortex
Certain areas of
cortex have certain
functions
Transverse
gyrus— auditory
area
Occipital lobe—
visual areas
Precentral gyrussomatic motor
Postcentral gyrussomatic sensory
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The Brain
Functions of the cerebral cortex (cont.)
Sensory functions of the cortex
Cortex contains a “somatic sensory
map” of the body
Senses send information to primary
sensory areas, as well as to other
parts of the brain
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The Brain
Motor functions of the cortex
For normal movements to occur,
many parts of the nervous system
must function
Precentral gyrus
primary somatic motor area
controls individual muscles
Secondary motor area (premotor)
in the gyrus immediately anterior
to the precentral gyrus
activates groups of muscles
simultaneously
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The Brain
Integrative functions of the cortex
Consciousness
State of awareness of one’s self,
one’s environment, and other
beings
Depends on excitation of
neurons from the reticular
formation
Two about reticular activating
system:
Functions as the alert
system for the cerebral
cortex
Its functioning is crucial for
maintaining consciousness
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The Brain
Integrative functions of the cortex (cont)
Language
Ability to speak and write words AND ability to
understand spoken and written words
Left cerebral hemisphere contains speech centers in
approximately 90% of the population
FYI: Explains Broca’s and Wernicke’s area
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The Brain
Integrative functions of the cortex (cont.)
Emotions
Limbic system— also known as the “emotional brain”
hippocampus
Have primary connections with other parts of the
brain, such as thalamus, amygdaloid nucleus, and
hypothalamus
FYI:
removal of hippocampus causes inability to recall
new info
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The Brain
Integrative functions of the cortex (cont)
Memory
One of the major human mental activities
Cortex is capable of storing and retrieving both
short- and long-term memory
Temporal, parietal, and occipital lobes are among
the areas responsible for short- and long-term
memory
Cerebrum’s limbic system plays a key role in
memory
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The Brain
Right
and left hemispheres of the cerebrum specialize in
different functions
Both sides communicate with each other to accomplish
complex functions
Left hemisphere is responsible for:
Language functions
Dominating control of certain hand movements
Right hemisphere is responsible for:
Auditory
Tactual perception
Perceiving and visualizing spatial relationships
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Cycle of Life:
Central Nervous System
The development and degeneration of the CNS is the
most obvious functional change over the life span
Development of the brain and spinal cord begins
in the womb
Lack of development in the newborn is evidenced by
lack of:
Language- both speech and reading
Comprehension of spatial relationships
Complex motor skills- walking
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Cycle of Life:
Central Nervous System
Complex functions develop by adulthood
Late adulthood— tissues degenerate
Profound degeneration— unable to perform complex
functions
Milder degeneration— temporary memory lapse or
difficulty with complex motor tasks
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The Big Picture: The Central
Nervous System and the Whole
Body
Central nervous system
ultimate regulator of the body
essential to survival
Able to integrate bits of information from all over the
body, make sense of them, and make decisions
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