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Summary Introduction to clinical neuropsychology
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Introduction to clinical neuropsychologyChapter 2 | The structure of the central nervous system
Human nervous system is divided into…
1. Central nervous system (CNS)
2. Peripheral nervous system (PNS)
3. Autonomic nervous system (ANS)
ANS = General activation; emergency response;
specialized system formed from components emotion
of both CNS and PNS
PNS Carries information from receptors distributed
around the body into CNS + back to effectors
• Generally: communication between
spinal cord and periphery
• Cranial nerves = specialized part
dealing with neck, head and special
senses
Damage = can (partly) be regenerated
CNS Carries information outward to effectors in
muscles and glands
Damage = permanent
Terminology
Rostral Toward the head
Caudal Toward the tail
Dorsal Toward the back
Ventral Toward the belly
Lateral Toward the side
Medial Toward the midline
Anterior Toward the front
Posterior Toward the back
Superior Above
Inferior Below
1 2
,The environment of the CNS
Spinal cord =
CNS = composed of brain and spinal cord; contained within bony case of the skull and spinal composed of a series of layers (each layer related to a spinal vertebra);
column in which it’s further protected by several membranes (= meninges): spinal nerve roots at each layer (one ventral, one dorsal pair) link PNS to CNS;
1. Dura mater = “hard mother” each relates to identifiable region (= dermatomes) on surface of the body;
2. Arachnoid layer = “like a spider’s web” Carries motor info down from the brain out to the body + receives sensory info
3. Pia mater = “soft mother”
Reflexes:
1/5 of blood pumped by the heart are used by the brain. Sensory information enters at one layer and links directly in a reflex arc to a motor nerve, which
then exists back out to PNS (simplest form = two-neuron reflex);
Cerebrovascular accident (CVA) = either part of blood supply being blocked (stroke) or bleeding more complex reflexes à several layers
into the brain and surrounding tissue à common cause of pathological change • Occurrence without higher levels of CNS
Brain flows in cerebrospinal fluid (CSF) = Division of reflexes
• provides mechanical protection and supplies certain aspects of nutrition
• generated by brain itself in lateral ventricles (= large chambers within brain) 1. Superficial = may be elicited by stimulation of the skin
• under some pressure to maintain flow in the system 2. Deep = e.g. knee jerk following the striking of the patella with a soft hammer
• circulates into midline 3rd and 4th ventricles; then out in spaces surrounding brain and 3. Special = more complex organization (e.g. constriction of pupil in bright light)
spinal cord; à then: absorbed into venous system
What functions remain if all other regions have been removed?
Hydrocephalus = “water in the brain”; caused by blocking of passages in ventricles where CSF
circulates 1. If section is above the 4th cervical segment à artificial respiration is required, but section
• good prognosis if diagnosed early below that is compatible with life
2. Spinal shock à progression from some reflex activity but little actual “behavior”
3. Locked-in syndrome =
stroke in brain stem effectively disconnects brain from the body;
loss of control over motor functions (exception: very limited movement – mostly eyes);
still full awareness
Divisions of the brain
The brain has evolved as a series of layers wrapped around a central core formed by the spinal
cord surmounted by the brain stem, and with each layer a “higher” level of functioning has
developed.
Using the ventricular system for diagnosis:
• Lumbar puncture =
needle is inserted in lumbar region of spine to withdraw CSF for inspection
• Ventriculography =
radio-opaque dye or bubble of air is introduced into system so that its outlines can be
traced by x-ray photography
The spinal cord
3 4
, Function
In decerebrate animals, the cranial nerves are intact, allowing full sensory information into the
system + intact final motor outflow;
cerebellum is still contributing to behavior, but otherwise the system is divorced from higher levels
of control
Midbrain’s specialized functions:
• Visual information is relayed to midbrain and some forms of visual reflex (e.g. blinking)
are organized here
• Auditory reflexes originate here
Certain aspects of autonomic function are organized in the brainstem à salivation, control of
blood pressure, respiration, etc. are influenced through ANS from this region (including parts of
vomiting).
Reticular formation = runs through brainstem;
Cells within this communicate with cells throughout the spinal cord, cerebellum, and higher
regions
• Ascending reticular activating system (ARAS) =
receives input from sensory pathways on upward journey + projects onto cerebral cortex
through a variety of intermediate centers;
result = generalized arousal of forebrain (important for wakefulness, consciousness,
The brainstem attention)
• Ensures brain is ready to receive information
1. Medulla oblongata
2. Pons Cranial nerves = enter at ARAS;
3. Midbrain consist of 12 pairs of nerves (sensory and motor) which almost entirely project to head and neck;
4. Cerebellum control of eye movements;
enter brain directly without passing through spinal cord
• Olfactory nerves (smell)
• Optic nerves (vision)
• Auditory nerves (hearing and equilibrium)
• Facial, glossopharyngeal, and vagus nerves (taste)
The cerebellum
5 6
, Coordinates muscular activity, both in postural and locomotor mechanisms (at subconscious • Fornix
level). • Amygdala
Most positions of the body are achieved by the antagonistic activity of opposed groups of • Septal region
muscles. • Cingulate gyrus
The cerebellum receives information from the skin and from muscles, tendons, joints, and the • Mammillary bodies
semicircular canals, as well as from visual and auditory systems;
in turn, it discharges out to the cerebral cortex and spinal cord, executing control over the timing Functions: Memory and learning, taming and some aspects of aggression, some primitive
of the execution of motor events. features of object recognition, sexual and exploratory behavior;
in animals: avoidance learning
The diencephalon – the subcortical forebrain
The limbic system rather undertakes the organization of these behaviors and the control
of their execution, while the hypothalamus is more concerned with their initiation in
response to the current level of motivation.
The telencephalon – the cerebral cortex
Thalamus = “main control center” governing sensation and movement;
(almost) all pathways travel to and from the thalamus as their final destination with an additional
The cerebral cortex forms the surface of the brain.
loop via the cerebral cortex (conscious awareness)
Folds in the cortex have made it possible to fit a larger cortex into an acceptable size for the
• Organization of reflexes
human head.
• Performance of more general underlying motor functions
• Gray matter = cell bodies
• Receives most sensory information (only localized in general awareness of touch,
• White matter = myelin covering the bundles of fibers forming tracts passing about the
temperature or pain)
brain
Damage may lead to resting tremor, chorea or rapid, jerky involuntary movements, and dystonia
Sulci = grooves on the surface of the cortex
or uncontrolled movement.
• Parkinson= associated with thalamic lesions
Gyri = bumps in between the grooves
Hypothalamus = contains pairs of nerve centers that influence eating and drinking, sleeping and
The lateral / Sylvian fissure/sulcus and the central / Rolandic fissure/sulcus act as landmarks that
waking, sexual behavior, organization for fight or flight, and response to reward and punishment
allow as to divide the brain into the four lobes:
• Frontal
Basal ganglia include the…
• Temporal
• Amygdala
• Parietal
• Globus pallidus
• Occipital
• Caudate
• Putamen
From the diencephalon up, we consider pairs of structures (two thalami, etc.) and the
and have functions largely associated with those described for the thalamus and hypothalamus.
telencephalon is formed of two cerebral hemispheres separated by the longitudinal fissure and a
large partition extending down from the meninges (= falx).
Limbic system = involves many parts of the basal ganglia, as well as parts of the telencephalon;
relatively ancient system concerned with many aspects of emotion and behavior
Two hemispheres are connected by…
• Hippocampus
• Anterior commissure
7 8
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