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7
The Nervous System
PART B
PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University
ESSENTIALS
OF HUMAN
ANATOMY
& PHYSIOLOGY
EIGHTH EDITION
ELAINE N. MARIEB
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
The Reflex Arc
 Reflex – rapid, predictable, and involuntary
responses to stimuli
 Reflex arc – direct route from a sensory
neuron, to an interneuron, to an effector
 All reflex arcs have 5 elements (#ed below)
Figure 7.11a
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Simple Reflex Arc
Figure 7.11b–c
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Types of Reflexes and Regulation
 Autonomic reflexes
 Smooth muscle regulation
 Heart and blood pressure regulation
 Regulation of glands
 Digestive system regulation
 Somatic reflexes
 Activation of skeletal muscles
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Central Nervous System (CNS)
 CNS develops from the embryonic neural
tube
 The neural tube becomes the brain and
spinal cord
 The opening of the neural tube becomes
the ventricles
 Four chambers within the brain
 Filled with cerebrospinal fluid
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Regions of the Brain
 Cerebral hemispheres
 Diencephalon
 Brain stem
 Cerebellum
 Adult brain weighs a little over 3 pounds
Figure 7.12b
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Cerebral Hemispheres (Cerebrum)
 Paired (left and
right) superior
parts of the brain
 Include more than
half of the brain
mass
Figure 7.13a
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Cerebral Hemispheres (Cerebrum)
 The surface is
made of ridges
(gyri) and
grooves (sulci)
Figure 7.13a
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Lobes of the Cerebrum
 Fissures (deep grooves) divide the cerebrum
into lobes
 Single deep fissure (longitudinal fissure)
separates the cerebral hemispheres
 Surface lobes of the cerebrum named for the
cranial bones that lie over them
 Frontal lobe
 Parietal lobe
 Occipital lobe
 Temporal lobe
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Lobes of the Cerebrum
Figure 7.13b
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Specialized Areas of the Cerebrum
Figure 7.13c
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Specialized Areas of the Cerebrum
 Somatic sensory area – receives impulses
from the body’s sensory receptors (pain,
coldness, light touch)
 Located in the parietal lobe posterior to
central sulcus
 Left side of the sensory cortex receives
impulses from the right side of the body
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Specialized Areas of the Cerebrum
 Primary motor area – sends impulses to
skeletal muscles
 Located in the frontal lobe anterior to the
central sulcus
 Axons of these motor neurons form the
corticospinal or pyramidal tract, which
descends to the cord
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Specialized Areas of the Cerebrum
 Broca’s area – involved in our ability to speak
 Located at the base of the precentral gyrus
 Located in only one hemisphere (usually
the left)
 Damage to this area causes inability to say
words properly – know what you want to
say but can’t vocalize
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Sensory and Motor Areas of the Cerebral
Cortex
Figure 7.14
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Specialized Areas of the Cerebrum
 Cerebral areas involved in special senses
 Gustatory area (taste)
 Parietal lobe – corner of the central &
lateral sulcus
 Visual area
 Posterior part of the occipital lobe
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Specialized Areas of the Cerebrum
 Auditory area
 In the temporal lobe bordering the
lateral sulcus
 Olfactory area
 Deep inside the temporal lobe
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Specialized Areas of the Cerebrum
 Interpretation areas of the cerebrum
 Speech/language region
 Junction of the temporal, parietal, &
occipital lobes
 Allows one to sound out words
 Usually in only one cerebral
hemisphere
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Specialized Areas of the Cerebrum
 Language comprehension region
 Frontal lobes
 Word meanings
 General interpretation area
 Temporal, parietal, & occipital lobes
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Specialized Areas of the Cerebrum
Figure 7.13c
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Layers of the Cerebrum
 Gray matter
 Outer layer
(cerebral cortex)
 Composed
mostly of neuron
cell bodies
 Highly ridged
(convoluted) –
gives more
surface area for
neurons
Figure 7.13a
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Layers of the Cerebrum
 White matter
 Fiber tracts
(bundles of
nerve fibers)
inside the gray
matter
 Carry impulses
to & from
cerebral cortex
Figure 7.13a
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Layers of the Cerebrum
 Example: corpus
callosum
connects cerebral
hemispheres
allowing for
communication
*Important because
some of the
critical functional
areas are in only
one hemisphere
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Layers of the Cerebrum
 Basal nuclei (basal
ganglia) – internal
islands of gray matter
 Help regulate
voluntary motor
activities by
modifying
instructions sent
to the skeletal
muscles by the
primary motor
cortex
Figure 7.13a
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Diencephalon
 Sits on top of the brain stem
 Enclosed by the cerebral hemispheres
 Made of three parts
 Thalamus
 Hypothalamus
 Epithalamus
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Diencephalon
Figure 7.15
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Thalamus
 Surrounds the third ventricle
 The relay station for sensory impulses upward
to the sensory cortex
 Transfers impulses to the correct part of the
cortex for localization and interpretation by
the neurons
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Hypothalamus
 Under the thalamus
 Important autonomic nervous system center
 Helps regulate body temperature
 Controls water balance
 Regulates metabolism
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Hypothalamus
 An important part of the limbic system
(emotions)
 The pituitary gland hangs from the anterior
floor of the hypothalamus by a slender stalk
 Regulates the pituitary gland
 Produces 2 of its own hormones
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Epithalamus
 Forms the roof of the third ventricle
 Houses the pineal body (an endocrine gland)
 Includes the choroid plexus – forms
cerebrospinal fluid
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Brain Stem (size of a thumb)
 Attaches to the spinal cord
 Parts of the brain stem
 Midbrain
 Pons
 Medulla oblongata
 Provides pathway for ascending &
descending tracts
 Basal nuclei of brain stem control breathing
& blood pressure
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Brain Stem
Figure 7.15a
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Midbrain
 Mostly composed of tracts of nerve fibers
 Has two bulging fiber tracts –
cerebral peduncles – convey ascending &
descending impulses
 Has four rounded protrusions –
corpora quadrigemina
 Reflex centers for vision and hearing
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Pons (“bridge”)
 The bulging center part of the brain stem
 Mostly composed of fiber tracts
 Includes nuclei involved in the control of
breathing
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Medulla Oblongata
 The lowest part of the brain stem
 Merges into the spinal cord
 Includes important fiber tracts
 Contains important control centers
 Heart rate control
 Blood pressure regulation
 Breathing
 Swallowing
 Vomiting
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Reticular Formation
 Diffuse mass of gray matter along the brain
stem
 Involved in motor control of visceral organs
 Reticular activating system plays a role in
awake/sleep cycles and consciousness
*Damage to this area can result in permanent
unconsciousness (coma)
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Reticular Formation
Figure 7.15b
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
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