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Anatomical Directions Rostral or anterior Head end of four legged animal Caudal or posterior Tail end of four legged animal Inferior or ventral Towards the belly Superior or dorsal Towards the back Figure 2.1 Anatomical Directions. Anatomists use directional terms to name and locate brain structures. Because standing upright puts an 80-degree angle in the human neuraxis, the dorsal surface of the human brain also forms an 80-degree angle with the dorsal spinal cord. (© 2016 Cengage Learning®)
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Functional Neuroanatomy and the Evolution of the Nervous
System
Chapter Two Functional Neuroanatomy and the Evolution of the
Nervous System Anatomical Directions
Rostral or anterior Head end of four legged animal Caudal or
posterior Tail end of four legged animal Inferior or ventral
Towards the belly Superior or dorsal Towards the back Figure 2.1
Anatomical Directions. Anatomists use directional terms to name and
locate brain structures. Because standing upright puts an 80-degree
angle in the human neuraxis, the dorsal surface of the human brain
also forms an 80-degree angle with the dorsal spinal cord. ( 2016
Cengage Learning) Anatomical Directions (contd.)
Figure 2.1 Anatomical Directions. Anatomists use directional terms
to name and locate brain structures. Because standing upright puts
an 80-degree angle in the human neuraxis, the dorsal surface of the
human brain also forms an 80-degree angle with the dorsal spinal
cord. ( 2016 Cengage Learning) Planes of Section Sagittal Coronal
Horizontal Parallel to midline
Divides nervous system front to back Horizontal (axial, transverse)
Divides brain from top to bottom Figure 2.2 Planes of Section.
Anatomists use the horizontal, coronal, and sagittal sections to
view three-dimensional structures as two-dimensional images. ( 2016
Cengage Learning) Planes of Section (contd.)
Figure 2.2 Planes of Section. Anatomists use the horizontal,
coronal, and sagittal sections to view three-dimensional structures
as two-dimensional images. ( 2016 Cengage Learning) Protecting and
Supplying the Nervous System
Meninges Three layers of meninges provide protection Cerebrospinal
fluid Secreted in hollow spaces in the brain knownas ventricles
Circulates through ventricles, subarachnoidspace, and central canal
of the spinal cord Blood supply Brain receives nutrients through
the carotidarteries and vertebral arteries The Skull and Three
Layers of Membrane Protect the Brain
Figure 2.3 (top/left) The Skull and Three Layers of Membrane
Protect the Brain. In addition to the protection provided by the
skull bones, the brain and spinal cord are covered with three
layers of membranes known as meninges. Going from the skull to the
brain, we find the dura mater, the arachnoid layer, and the pia
mater. Between the arachnoid and pia mater layers is the
subarachnoid space, which contains cerebrospinal fluid (CSF). In
the peripheral nervous system (PNS), only the dura mater and pia
mater layers cover the nerves. There is no CSF in the PNS. ( 2016
Cengage Learning) Figure 2.4 (bottom/right) Meningitis Results from
Infection of the Meninges. Viruses and bacteria can invade the
layers of the meninges, causing meningitis. Meningitis causes
headache and stiffness of the neck, which can be followed by
incoherence, drowsiness, coma, and death. This photo shows a fatal
case of meningitis with large areas of pus within the meninges.
(Sebastian Kaulitzki/Shutterstock.com) Cerebrospinal Fluid
Circulation
Figure 2.5 Cerebrospinal Fluid Circulates Through the Ventricles,
Spinal Cord, and Subarachnoid Space. Cerebrospinal fluid (CSF) is
produced by the choroid plexus that lines the walls of the
ventricles. From the lateral ventricles, the CSF flows through the
third and fourth ventricle and into the central canal of the spinal
cord. At the base of the cerebellum, CSF exits into the
subarachnoid space and is reabsorbed by veins near the top of the
head. ( 2016 Cengage Learning) Hydrocephalus Figure 2.6 (left)
Hydrocephalus Results from Blockage in the Circulation of
Cerebrospinal Fluid. This photograph shows a baby born with the
condition of hydrocephalus, which results when the normal
circulation of cerebrospinal fluid (CSF) is blocked. Note the large
size of the babys head, which has expanded to accommodate all of
the CSF. Untreated, hydrocephalus causes intellectual disability,
but, today, shunts installed to drain off the excess fluid can
prevent any further damage to the childs brain. (Barts Medical
Library/Phototake) Figure 2.7 (right) Shunt for Hydrocephalus.
Hydrocephalus in newborns used to be a major cause of intellectual
disability. Contemporary treatment consisting of shunts inserted
into the ventricle that drain excess cerebrospinal fluid (CSF) to
the abdomen or heart has reduced the damage done to the brains of
individuals with this condition. The Brain Has a Generous Supply of
Blood
Figure 2.8 The Brain Has a Generous Supply of Blood. Blood reaches
the brain either through the carotid arteries on either side of the
neck or through the vertebral arteries entering through the base of
the skull.Once in the brain, these arteries branch into the
anterior cerebral artery, and middle cerebral artery, and the
posterior cerebral artery. ( 2016 Cengage Learning) The
Organization of the Nervous System
The central nervous system Brain and spinal cord The peripheral
nervous system All nerves that leave from the brain and spinalcord
and extend to and from all parts of thebody Figure 2.9 The
Organization of the Nervous System. The nervous system has two
major components, the central nervous sytem (CNS), which includes
the brain and spinal cord, and the peripheral nervous system (PNS),
which contains all the nerves that exit the brain and spinal cord.
( 2016 Cengage Learning) The Organization of the Nervous
System
Figure 2.9 The Organization of the Nervous System. The nervous
system has two major components, the central nervous sytem (CNS),
which includes the brain and spinal cord, and the peripheral
nervous system (PNS), which contains all the nerves that exit the
brain and spinal cord. ( 2016 Cengage Learning) The Central Nervous
System The Spinal Cord
Anatomy Extends from the medulla to the first lumbarvertebra 31
spinal nerves (cervical, thoracic, lumbar,sacral, coccygeal) White
matter (nerve fibers); gray matter (cellbodies) Reflexes Patellar
reflex Withdrawal reflex Instructors may want to discuss the
reticular formation at this time. The Anatomy of the Spinal
Cord
Figure 2.10 The Anatomy of the Spinal Cord. The spinal cord is
divided into cervical, thoracic, lumbar, sacral, and coccygeal
segments. The spinal nerves exit either side of the cord between
the surrounding bony vertebrae. ( 2016 Cengage Learning)
Embryological Divisions of the Brain
Table 2.1 | Embryological Divisions of the Brain Structures of the
Brainstem
Figure 2.11 Structures of the Brainstem. (a) This sagittal section
displays many of the important structures found in the brainstem. (
2016 Cengage Learning) Structures of the Brainstem (contd.)
Figure 2.11 Structures of the Brainstem. (b) With the cerebral
hemispheres removed, we can see spatial relationships between the
major structures of the brainstem. The key-to-slice allows us to
view a horizontal section of the medulla and several of the
important structures found at this level of the brain. ( 2016
Cengage Learning) The Central Nervous System: The Hindbrain
Medulla (myelencephalon) Breathing, heart rate, blood pressure
Reticular formation Consciousness, arousal, movement, and pain
Metencephalon Pons: balance, motion sickness Cerebellum Voluntary
movements, muscle tone, balance,speech, motion sickness, executive
functions, andemotional processing The Internal Structure of the
Midbrain
Periaqueductal gray Natural pain management Red nucleus Motor
output pathway Substantia nigra Parkinsons disease Superior and
inferior colliculi Visual and auditory stimuli Figure 2.12 The
Internal Structure of the Midbrain. Important structures in
themidbrain include the superior and inferior colliculi, the
cerebral aqueduct, the periaqueductal gray, the substantia nigra,
and the red nucleus. ( 2016 Cengage Learning) The Internal
Structure of the Midbrain
Figure 2.12 The Internal Structure of the Midbrain. Important
structures in themidbrain include the superior and inferior
colliculi, the cerebral aqueduct, the periaqueductal gray, the
substantia nigra, and the red nucleus. ( 2016 Cengage Learning)
Important Structures in the Brainstem
Table 2.2 Important Structures in the Brainstem The Central Nervous
System The Forebrain
The forebrain is composed of thediencephalon and the telencephalon
Diencephalon Thalamus Receives sensory input Hypothalamus
Regulation of the endocrine system The Thalamus and Hypothalamus of
the Diencephalon
Figure 2.13 The Thalamus and Hypothalamus of the Diencephalon. The
thalamus lies close to the center of the brain, and the
hypothalamus is located rostrally and ventrallyrelative to the
thalamus. Directly below the hypothalamus is the pituitary gland,
which is an important part of the endocrine system. ( 2016 Cengage
Learning) The Central Nervous System The Forebrain (contd.)
Telencephalon Basal ganglia Motor control Parkinsons and
Huntingtons disease; ADHD Limbic sstem Learning, motivated
behavior, and emotion Cerebral cortex Four lobes Sensory cortex,
motor cortex, and associationcortex The Basal Ganglia and the
Limbic System
Figure 2.14 (left) The Basal Ganglia. The basal ganglia include the
caudate nucleus, putamen, globus pallidus, subthalamic nucleus, and
nucleus accumbens. (The subthalamic nucleus and nucleus accumbens
cannot be seen from this point of view). The substantia nigra of
the midbrain is usually considered to be a part of this system. (
2016 Cengage Learning) Figure 2.15 (right) The Limbic System
Participates in Learning and Function. A number of closely
connected forebrain structures are included in the limbic system,
which participates in many emotional, learning, and motivated
behaviors. ( 2016 Cengage Learning) Structures of the Limbic
System
Table 2.3 Structures of the Limbic System The Hippocampus Figure
2.16 (left) The Hippocampus. The hippocampus curves away from the
midline out towards the rostral temporal lobe. This structure plays
important roles in learning, memory, and stress. Figure 2.17
(right) Amygdala Abnormalities Can Lead to Irrational Violence. In
very rare cases, abnormalities of the amygdala are associated with
uncharacteristic, totally irrational violence. Charles Whitman, who
led a previously unremarkable life, killed several family members
and then climbed a clock tower at the University of Texas at
Austin, in He methodically opened fire on people below, killing 15
and injuring 31. Whitman, who was killed by police, was later found
to have a tumor pressing on his amygdala. (Bettmann/Corbis)
Comparative Convolutions of the Cortex
Figure 2.18 Comparative Convolutions of the Cortex. The relative
degree of cortical convolution is positively correlated with the
cognitive abilities of a species. The Layers of the Cerebral
Cortex
Figure 2.19 The Layers of the Cerebral Cortex. The cerebral cortex
covers the outer surface of the brain. Six distinct layers are
apparent in most areas of the cortex. Three different views of
these layers are shown here. The Golgi stain highlights entire
neurons, and the Nissl stain highlights cell bodies. Note the large
pyramid cells shown by the Nissl stain in layer V. The Weigert
stain highlights pathways formed by myelinated axons through the
cortex. Brodmanns Map of the Brain
Figure 2.20 Brodmanns Map of the Brain. Early 20th-century German
neurologist Korbinian Brodmann divided the cerebral cortex into 52
different areas, based on the distribution of cell bodies in each
area. One hundred years after Brodmanns system was first published,
it remains the most widely used system for describing cortical
architecture. ( 2016 Cengage Learning) The Lobes of the Cerebral
Cortex
Figure 2.21 The Lobes of the Cerebral Cortex. The cortex is
traditionally divided into the frontal, parietal, temporal, and
occipital lobes. ( 2016 Cengage Learning) The Corpus Callosum and
the Anterior Commissure
Figure 2.22 The Corpus Callosum and the Anterior Commissure. Two
fiber bundles, the very large corpus collosum and the much smaller
anterior commissure, connect the right and left cerebral
hemispheres. ( 2016 Cengage Learning) Localization of Function in
the Cortex
Frontal lobe Primary motor cortex, cognitive processes Dorsolateral
prefrontal cortex, orbitofrontalcortex Phineas Gage Lobotomies
Brocas area Lateralization of function The Case of Phineas
Gage
Figure 2.23 The Case of Phineas Gage. Mid-19th-century railroad
worker Phineas Gage suffered an accident in which an iron rod was
shot through the frontal lobe of his brain. Although Gage survived,
he was described by his friends as a changed man. Gages case
illustrates the localization of higher-order cognitive functions in
the frontal lobe. (Patrick Landmann/Science Source) Brain Circuits
and the Connectome
The Human Connectome Project Mapping the neural connections within
thebrain Cellular and macro levels of investigation The Peripheral
Nervous System
The cranial nerves Enter and exit the brain directly to serve
theregion of the head and neck The spinal nerves 31 pairs provide
sensory and motor pathwaysto the torso, arms, and legs Mixed nerves
(afferent and efferent) The autonomic nervous system Manages the
vital functions of the bodywithout conscious effort or awareness
The Twelve Pairs of Cranial Nerves
Figure 2.24 The Twelve Pairs of Cranial Nerves. Twelve pairs of
cranial nerves leave the brain directly to carry sensory and motor
information to and from the head and neck areas. The red lines
represent sensory functions, and the blue lines show motor control.
Some cranial nerves are sensory only, some are motor only, and some
are mixed. ( 2016 Cengage Learning) The Structure of the Spinal
Cord
Figure 2.25 The Structure of the Spinal Cord. This cross-section of
the spinal cord shows a number of important anatomical features.
Three layers of meninges surround the cord. The gray matter of the
cord is located in a butterfly shape near the central canal, which
contains cerebrospinal fluid (CSF). The dorsal afferent (sensory)
nerves join the ventral efferent (motor) nerves beyond the spinal
ganglion to form a mixed nerve. ( 2016 Cengage Learning) The
Autonomic Nervous System
The sympathetic nervous system Fight-or-flight system The
parasympathetic nervous system Provides rest, repair, and energy
storage The enteric nervous system Serves the gastrointestinal
tract The endocrine system Hypothalamic control of hormone release
Pituitary gland The Sympathetic and Parasympathetic Nervous
Systems
Figure 2.26 (left) The Autonomic Nervous System. The sympathetic
and parasympathetic divisions of the autonomic nervous system often
have opposite effects on target organs. To carry out their
respective tasks, sympathetic neurons form their first synapse in
the sympathetic chain, whereas parasympathetic neurons synapse on
ganglia close to the target organs. In addition, the systems use
different neurotransmitters at the target organ. ( 2016 Cengage
Learning) The Evolution of the Human Brain and Nervous System
Natural selection and evolution Natural selection favors the
organism with thehighest degree of fitness Evolution of the nervous
system Fairly recent; vertebrates or chordates areanimals with
spinal columns and real brains Evolution of the human brain
Outstanding modern feature is our brain size Brain development
occurred very recently Timeline for the Evolution of the
Brain
Figure 2.28 Timeline for the Evolution of the Brain. When compared
with the entire time scale of evolution, nervous systems represent
a very new development, appearing for the first time in the form of
simple neural nets about 700 million years ago. Advanced brains,
such as the human brain, are more recent still. ( 2016 Cengage
Learning) The Evolution of Chordate Brains
Figure 2.29 (top) True Brains are Found in Chordates. Compared with
invertebrates, such as the Aplysia californica (a type of sea slug)
on the right, chordates have true brains as opposed to ganglia. The
chordate nervous system runs near the dorsal rather than the
ventral surface of the animals body. ( 2016 Cengage Learning)
Figure 2.30 (bottom) Chordate Brains Continued to Evolve. More
complex chordate brains feature increased convolutions and larger
cerebrums and cerebellums. ( 2016 Cengage Learning) Human Brain
Development Proceeded Swiftly
Figure 2.31 Human Brain Development Proceeded Swiftly. Hominin
brains advanced rapidly from those of the early australopithecines,
shown on the left, who had brains about the size of modern
chimpanzees, to Homo erectus (700 cubic centimeters; shown in the
center), to Homo sapiens (1,400 cubic centimeters; shown on the far
right). Brain development then appears to have leveled off. You are
reading this text with essentially the same size brain that has
worked for Homo sapiens for the past 200,000 years. (Australian
Museum)