Download 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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