Chapter Four
Anatomy of the Nervous
System
Starring…
Your Brain
Research Methods
Injection of dye into blood allows CAT
(computerized axial tomography) scanner to
take images of the brain
 Intentional brain damage
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points to behavioral impairment, e.g., damage to
Broca’s area associated with inability to speak
intense magnetic field temporarily inactivates area
electrode or chemicals used to damage specific area
but, brain damage may not solely produce behavior;
impairment may be due to many factors
Figure 4.1 Computerized axial tomography (CT scanning). (a) A person’s head is
placed into the device and than a rapidly rotating source sends x-rays through the head while
detectors on the opposite side make photographs. A computer than constructs an image of
the brain. (b) A CT scan of a normal human brain. (Source: Dan McCoy/Rainbow).
Research Methods cont.

Brain stimulation
 can
evoke sensations, e.g., flashes of light
 less intense magnetic fields stimulate an area
 injected chemicals stimulate specific receptors
 but, sensations are in isolation and behaviors
depend on coordination across brain areas
Research Methods cont.
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Recording brain activity
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identifies area of brain associated with behavior
PET (positron emission tomography) detects
radioactive chemicals absorbed by most active cells
rCBF (regional cerebral blood flow) measures
increased blood flow by monitoring inert radioactive
chemical
fMRI (functional magnetic resonance imaging) detects
release of oxygen in active cell - replaces PET and
rCBF
but, brain is always active and interpreting changing
activity is a challenge
also, different people use different areas for same
task
New Brain Research; CNN
Today: Biological Psychology,
Volume I
Research Methods cont.
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Correlating brain anatomy with behavior
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extensive practice on string instrument correlated
with enlarged area of brain receiving sensations from
left hand
experienced taxi drivers have enlarged area of
hippocampus related to spatial memory
Albert Einstein had one area of brain larger than
normal and had unusually high ratio of glia to
neurons
Caution: samples are small & correlation is not
causation
Structure of the Vertebrate
Nervous System
CNS: brain & spinal cord
 PNS: nerves outside brain &spinal cord

 somatic:
nerves that convey messages from
sense organs to CNS & from CNS to muscles
and glands
 autonomic: set of neurons that control heart,
intestines, & other organs
 sympathetic:
arousal, “fight or flight”, emergency
 parasympathetic: “relax and digest”, nonemergency
Figure 4.5 The human nervous system. Both the central nervous system and
the peripheral nervous system have major subdivisions. The closeup of the brain
shows the right hemisphere as seen from the midline.
Anatomical Terms for Directions

Road map of nervous system uses
technical terms to describe a three
dimensional structure
 basic
terms include, e.g., ventral, dorsal,
lateral and medial
 permits clear communication among
investigators
Figure 4.6 Terms for anatomical directions in the nervous system. In four-legged
animals dorsal and ventral point in the same direction for the head as they do for the rest of
the body. However, human’s upright position has tilted the head relative to the spinal cord, so
the dorsal and ventral directions of the head are not parallel to the dorsal and ventral
directions of the spinal cord.
The Spinal Cord
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Bell-Magendie Law:
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the entering dorsal roots carry sensory info to brain
and,
the exiting ventral roots carry motor info to muscles
and glands
Dorsal root ganglia: clusters of neurons outside,
but near, the spinal cord on dorsal roots carrying
sensory info
 Cut the spinal cord and brain loses motor control
over parts of body served by that segment and
below

Figure 4.7 Diagram of a cross section through the spinal cord.
The dorsal root on each side conveys sensory information to the spinal
cord; the ventral root conveys motor commands to the muscles.
Autonomic Nervous System

Sympathetic: prepares body for arousal
 increased
breathing, increased heart rate,
decreased digestive activity
 form chain of ganglia just outside spinal cord
 act as a single system; in “sympathy” with
one another
 short preganglionic axons and long
postganglionic axons both release
norepinephrine
Autonomic Nervous System cont.

Parasympathetic: facilitates vegetative,
nonemergency responses by the body’s organs
increases digestive activity, activities opposing
sympathetic system
 consists of cranial nerves and nerves from sacral
spinal cord
 long preganglionic axons extend from the spinal cord
to parasympathetic ganglia close to each internal
organ
 shorter postganglionic fibers then extend from the
parasympathetic ganglia in the organs; release
acetylcholine
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The Hindbrain (rhombencephalon)
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Medulla: controls vital reflexes, e.g., breathing, heart
beat
Pons: area where many axons cross from one side of the
brain to the other
Reticular formation: controls motor areas of the spinal
cord; output to cerebral cortex increasing arousal and
attention
Raphe system: sends axons to much of the forebrain,
increasing or decreasing the brain’s readiness to respond
Cerebellum: controls movement, balance and
coordination
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damage impairs timing and difficulty shifting attention between
auditory and visual stimuli
The Midbrain (mesencephalon)
Tectum (“roof”): includes superior colliculus and
inferior colliculus, important routes for sensory
information
 Tegmentum (”covering, carpet”) includes:
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nuclei for third and fourth cranial nerves (eye
movements)
parts of reticular formation
extensions of the pathways between the forebrain
and the spinal cord or hindbrain
Substantia nigra gives rise to dopamine path
that deteriorates in Parkinson’s disease
Figure 4.12 The human brain stem. This composite structure
extends from the top of the spinal cord into the center of the forebrain.
The pons, pineal gland, and colliculi are ordinarily surrounded by the
cerebral cortex.
The Forebrain (prosencephalon)
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Cerebral cortex: outer portion of brain
Thalamus: center of forebrain and relay station for
sensory info to/from cerebral cortex (except olfactory)
Hypothalamus: small area with widespread connections
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damage here affects sexual behavior temperature regulation,
fighting, feeding, activity level
sends messages to attached pituitary gland, altering release of
hormones into bloodstream
Limbic system borders the brain stem and mediates
eating, drinking, sexual activity, anxiety and aggression
Figure 4.14 The limbic system is a set of subcortical structures
that form a border (or limbus) around the brain stem.
The Forebrain cont.
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Basal ganglia: includes caudate nucleus,
putamen, globus pallidus
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Basal forebrain
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many connections with frontal cortex, where
planning, memory and emotional expression arise
here the nucleus basalis is key part of brain’s system
for arousal, wakefulness, and attention (intermediary
between hypothalamus and cerebral cortex)
Hippocampus
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located between thalamus and cerebral cortex
critical for the formation of new memory
connected to the hypothalamus by the fornix
Figure 4.18
Figure 4.18 The basal ganglia. The thalamus is in the center, the
basal ganglia are lateral to it, and the cerebral cortex is on the outside.
(Source After Nieuwenhuys Voogd & vanHuijzen, 1988)
Cerebral Spinal Fluid and the
Ventricles

Cerebral spinal fluid assists in cushioning
the brain
 fills
the central canal, channel in the center of
the spinal cord
 fills the ventricles, four cavities within the
brain
 fills space between brain and meninges
(membranes that surround the brain and
spinal cord)
 meningitis is inflammation of meninges
Cerebral Spinal Fluid and the
Ventricles cont.
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Cerebral spinal fluid is clear fluid similar to
blood plasma
 formed
in choroid plexus
 flows from lateral to third to fourth ventricle
to central canal or between meninges
 reabsorbed in arachnoid apace between
meninges and brain and spinal cord
Cerebral Spinal Fluid and the
Ventricles cont.

Hydrocephalus is blockage of flow of CFS
 increases
pressure on the brain
 in infants this spreads the skull bones and is
associated with mental retardation
Figure 4.20 The cerebral ventricles. (a) Diagram showing positions of the
four ventricles. (b) Photo of a human brain, viewed from above, with a horizontal
cut through one hemisphere to show the position of the lateral ventricles. Note
that the two parts of this figure are seen from different angles. (Source: After
Woolf, 1991)
Cerebral Cortex
Contains grey matter, the outer surface of
cerebral hemispheres
 White matter is formed by axons
extending inward from cortex
 Neurons from each hemisphere
communicate with each other through the
corpus callosum and anterior commissure
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Cerebral Cortex cont.
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Contains six distinct layers of cells parallel
to surface of cortex (laminae I - VI)
a
layer may be missing in a region, e.g.,
lamina IV is absent from the motor cortex
 lamina V is thickest in motor cortex

Organized into columns of cells
arranged perpendicular to the laminae
 cells within a given column have similar or
related properties, e.g., may all respond to
touch on palm of hand or foot
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Lobes of Cortex
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Occipital lobe: posterior end of cortex
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contains primary visual cortex
damage in one hemisphere causes blindness in
opposite visual field
Parietal lobe: between occipital lobe and the
central sulcus
contains the primary somatosensory cortex which
receives touch sensation, muscle-stretch and joint
position information
 postcentral gyrus includes four bands of cells; two
receive light-touch information, one receives deeppressure and one a combination of both
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Lobes of Cortex cont.
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Temporal lobe: lateral portion of each
hemisphere, near the temples
 essential
for understanding spoken language
 contributes to perception of movement and
face recognition
 damage may lead to Külver-Bucy syndrome

Frontal lobe extends from the central
sulcus to the anterior limit of the brain
 primary
motor cortex controls fine movements
 prefrontal cortex important for working
memory, delayed response tasks, planning of
appropriate behavior for context
How Do the Parts Work Together

A brain area functions like a word in a
sentence
 damage
the amygdala and diminish fear
(delete a word and you lose something)
 but, fear intensifies with pain and diminishes
with a trusted friend (a word has richer
meaning in context)
 no single brain area where information is
integrated
How Do the Parts Work Together
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Unified experience emerges from
“binding” of separate parts
 Simultaneous
areas
neural activity may bind brain
recognition of Mooney faces produced gamma
waves 30-80/second in various brain areas
 when cat sees and hears bird it has synchronized
neural activity in occipital, parietal, and frontal
areas
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 Einstein’s
brain had larger than normal inferior
parietal cortex, an area known to bind
different aspects of perception, e.g., damage
prevents binding color to shape
How Do the Parts Work Together
cont.
But, why does synchronous activity
produce binding?
 Overall, the cerebral cortex serves to
elaborate sensory material
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