Download A Beginner`s Guide to Neuroanatomy

A Beginner's Guide to
Neuroanatomy
Alexander Gonski AM, BSc,
FRCS(Ed.), FRACS
Illustrated by
Julian Meagher MBBS
Editor: Peter Arnold BSc, MBBCh, BA
Introduction
The teaching of Anatomy in general, and of
neuroanatomy in particular, has declined during the last
fifty years.
Students are expected to search out relevant anatomical
explanations when confronted in their clinical years with
pathology affecting the nervous system. This could be
time-consuming, particularly in the earlier stages of their
studies, as some knowledge of neuroanatomy is
essential, if only to limit the search to an area likely to be
relevant.
This beginner's guide builds on a prior basic knowledge
of the gross anatomy of the nervous system. To assist in
remembering the descriptive anatomical names, the
Latin is translated into English and added in parentheses
when each term in introduced.
Alexander Gonski
Neurosurgeon
Sydney, July 2006
Copyright © Alexander Gonski, Sydney, 2006
Provided that Alexander Gonski is acknowledged as the author, this publication,
or parts of it, may be reproduced and transmitted without his permission.
Graphic Design: Amber Gastin
Contents
The brain ................................................................................7
The spinal cord......................................................................8
The cerebellum ....................................................................10
The cerebellar peduncles ..................................................11
The motor system: pyramidal pathways ........................12
The motor system: extra-pyramidal pathways ..............12
The lower motor neurones ................................................14
The sensory system ............................................................14
The thalamus ......................................................................16
The basal ganglia ................................................................18
The special senses ..............................................................20
The autonomic nervous system........................................23
1. The brain
The structure of the cerebrum (brain) and the configurations of
its component parts are easily found in standard books, but the
associations between different areas (the fibres connecting one
part of the brain with the other parts) need to be understood.
Cortical representation of motor
homunculus in the pre-central gyrus
Shoulder
Hand
Fingers
Thumb
Leg
Cortical representation of sensory
homunculus in the post-central gyrus
Trunk
Foot
Arm
Wrist
Genitalia
Face
Lips
Vocalisation
Tongue
Swallowing
Hand
Teeth
Pharynx
The main association fibres
The corpus callosum (thick-skinned body) is the major bundle of
association fibres connecting the two cerebral hemispheres. It
consists inferiorly of a rostrum (head) attached to the lamina
terminalis (terminal plate), a genu (knee), a body and it then
expands posteriorly into the splenium (bandage). The anterior
fibres, the forceps minor (small tongs), project into the frontal
lobes, whilst posteriorly the fibres of the splenium spread out
into the occipital lobes as the forceps major (large tongs).
The frontal, temporal and occipital cerebral lobes on each side
are connected by a superior longitudinal fasciculus (little
bundle), whilst the temporal and occipital lobes of each side are
connected by an inferior longitudinal fasciculus. Short
association, arcuate (bow-like) fibres connect neighbouring
cerebral areas, whilst intermediate-sized uncinate (hook-like)
fibres associate the frontal and temporal lobes.
Other connections between the left and right sides of the
cerebrum are made by the anterior commissure (joining seam),
joining the two olfactory bulbs, and by the posterior
commissure, a part of the rhinencephalon (nose brain), which
processes smell sensation.
Cortical representation
(After Penfield)
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It would be worthwhile looking at pictures of the motor and
sensory homunculi (imaginary caricatures of the human body
superimposed on the surface of the cerebrum), noting that the
lower limb representation is to be found on the medial
(internal) aspect of each hemisphere. Note how hugely the
hand and face are represented on the lateral aspects of the
cortex (bark).
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2. The spinal cord
This is a compact packaging of white bundles of fibres around
a roughly H-shaped core of grey masses of cells. You need to
familiarize yourself with the transverse sections of the cord (at
cervical, thoracic, lumbar and sacral levels) as well as with the
anatomy of simple spinal reflexes. The bundles are called
funiculi (little umbilical cords), within which lie the fibre tracts,
the fasciculi.
The size of each funiculus depends on the number of fibres it
contains; thus, in the posterior columns distally, there is only a
fasciculus gracilis (slender), which, running cranially, enlarges
into a further fasciculus, the fasciculus cuneatus (wedge-shaped).
This enlargement is due to the inclusion of the extensive
sensory fibres from the arm. By contrast, motor bundles are
bigger proximally and diminish progressively in size distally. If
fasciculi are bruised in a spinal cord injury, they have the
potential, like peripheral nerves, to recover. However, if the
axons within the fasciculi are severed, they cannot regenerate.
Cross Section of Lower Cervical Cord
Fasciculus cuneatus and fasciculus gracilis
(touch and vibration)
Fibres run upwards in the dorsal columns
Lateral
corticospinal
tract
(motor)
The spinal cord reflex (for instance, the knee-jerk) originates
with a stimulus moving along a sensory nerve, entering the
body of that nerve cell in the dorsal root ganglion and
continuing into the spinal cord. This stimulates neuronal cells
in the posterior horn to trigger, through a single synapse, motor
cells to emit a stimulus which will activate the relevant
muscles. The spinal cord reflex may involve just two or three
neurones, but usually many more are involved.
The stimulus can also cross over to the anterior horn cells on the
opposite side. Normally these cells are under the control of the
cortico-spinal and extrapyramidal efferents, so that a simple,
fluid, smooth contraction is produced by a suitable sensory
stimulus. Without this controlling input from the cortex, the
reflex is exaggerated and repetitive (spastic). These
extrapyramidal connections are extensive. They can be
followed down from the cerebral cortex to the basal ganglia
(p. 18) and the thalamus (inner chamber or bedroom, p.16): there
are cortico-thalamic projection fibres to the globus pallidus (pale
globe), the caudate (tail-like) nuclueus, the corpus striatum
(striped body) and the substantia nigra (black substance).
From the basal ganglia, efferent fibres—a host of descriptively
named fibres—associate various nuclear masses, then connect
to the anterior horn cells, affecting tone and repetitive
movements and fulfilling other facilitatory functions, including
inhibition of movement.
Spinal Cord Reflex Arc
Post.
Dorsal root ganglion
Sensory axon
Ant.
Spinothalamic tract
(pain and temperature sensation)
Fibres cross at segmental levels
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Motor
axon
Ant.
Reflex arc under control of
corticospinal and extrapyramidal
efferents at this point
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3. The cerebellum
The primary function of the cerebellum (little brain) is the
synergy (co-ordination) of repetitive movement. Such
movement requires proprioceptive information (messages
about internal sensations, such as movements of muscles and
joints) from the entire body, in order for exteroceptive, indirect
influences to be correlated and then forwarded to both the
cognitive and motor areas of the brain.
For this complex correlation to be effective, communication is
needed between the cerebellum, the cord and the rest of the
body (via the brainstem and spinal cord), as well as from cells
of the spinal cord themselves. This communication is the
function of the three cerebellar peduncles (little feet).
Ventral aspect of the Cerebellum
Middle cerebellar
peduncle
Superior cerebellar
peduncle
4. The cerebellar peduncles
The middle peduncles are the most prominent of the three,
consisting of fibres uniting the cerebrum and the cerebellum.
They originate from the pyramidal cells of the frontal and
temporal cerebral lobes and end in the nuclei ponti (nuclei of the
bridge). From here, most of the connecting axons cross the
midline and aggregate to form the middle cerebellar peduncle
entering the cerebellum and the cerebellar cortex; from here,
efferent fibres pass to the deep cerebellar nuclei.
The superior cerebellar peduncles originate from fibres arising in
the dentate (tooth-like) nucleus of the cerebellum and run
mainly to the red nucleus of the mesencephalon (midbrain).
Some fibres can be identified again in the reticular (net-like)
formation, where they cross over to the other side, in the
superior cerebellar decussation (crossing over). From the red
nucleus, fibres descend down the rubro(red)-spinal tract to the
spinal cord. The fibres within the reticular formation re-form
and proceed distally as the reticulo-spinal tract.
The inferior cerebellar peduncles are composed of ascending fibres
from the spinal cord, fibres from the medulla, fibres from the
olivary (olive-shaped) nucleus, and fibres from the arcuate
reticular nuclei, together with the vestibulo-cerebellar
fasciculus passing into the cerebellum.
The peduncles form the junction of the cerebrum, cerebellum
and brain stem. Fibres cross twice or more often as they
progress through the peduncles.
Inferior cerebellar peduncle
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5. The motor system: pyramidal
pathways
We do not know how the wish to move a muscle initiates the
movement. What we do know is that the earliest motor signal
begins in large cells in the cerebral cortex. These cells are found
mostly in the prefrontal motor cortex, but they do exist
elsewhere in the cerebral cortex.
facilitating and overall, by regulating, the stimulated anterior
horn cells. Major cell areas such as the basal ganglia and the
reticular formation are described later.
Pyramidal Tract
Motor cortex
They induce a flow down their axons which course through the
white matter (fibres) to the internal capsule—a boomerangshaped area bounded anteriorly by the caudate nucleus,
posteriorly on its medial aspect by the thalamus and posterolaterally by the lentiform (lens-shaped) nucleus.
Internal
capsule
This bundle of fibres, recognisable as the cortico-spinal (or
pyramidal) tract, passes through the midbrain (in the pes
pedunculi - foot of the little feet) into the pons (bridge) and then
into the medulla (marrow). Here the tracts cross over to the
opposite side in the pyramidal decussation (previously called
the pyramids). They then pass into the postero-lateral
compartment of the spinal cord until, in turn, they reach the
level of the relevant muscle, where the axons synapse with
another cell or, more probably, with a group of cells, known as
the anterior horn cells, in the grey matter of the cord.
Corticobulbar and
Corticospinal tracts
Midbrain
VII
nerve
The synapse is not a discrete, one-to-one stimulation, as the
anterior horn cells are also bombarded by impulses from other
cortico-spinal units and from cells of the extra-pyramidal
system.
X, XI, XII
nerves
6. The motor system:
extra-pyramidal pathways
All fibres originating in the cerebral or cerebellar tissues and
coursing down to synapse with the anterior horn cells, other
than the pyramidal (ie cortico-spinal) tracts, are called extrapyramidal. Their origins are varied, some from the cerebral
cortex and others from the cerebellum or its nuclei.
Their names, such as vestibulo-spinal or more complex names,
such as cerebello-ponto-spinal, generally indicate their origins
and destinations. These pathways modify the effects of the
pyramidal pathways on the anterior horn cell by inhibiting,
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Pons
Medulla
Lateral
corticospinal
tract
Muscle
Lower motor
neurone
Pyramidal decussation
(80% of fibres cross the
midline)
Anterior corticospinal tract
(fibres decussate at segmental
levels)
(After Collander)
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7. The lower motor neurones
spino-thalamic tract; the other does not yet cross, but
continues cranially in the dorsal funiculus (the
fasciculus gracilis and lateral to it, in the fasciculus
cuneatus).
The bodies of these cells lie in the anterior part of the spinal
cord, grey in colour because of the abundance of cells with
comparatively few fibres. We noted above how these cells are
stimulated or affected by synapsing with the upper motor
neurone system and the extrapyramidal system.
The fibres which crossed over into the spino-thalamic
tract lie in the antero-lateral aspect of the spinal cord,
and course cranially through the medulla, pons and
midbrain (where they are also called the medial
fasciculus), into the thalamus, where they synapse onto
neurones. These are the second sensory neurones.
The axons of these cells then leave the cord, some joining with
others of the posterior nerve root to constitute the spinal cord
reflex, whilst the majority exit as the motor (anterior) nerve
root. They then join with the sensory fibres to form the
peripheral nerve or plexus coursing on to the appropriate
muscle endings at the motor nerve end-plate.
The next and last relay of crossed fibres now pass
through the internal capsule to the sensory area of the
cortex.
The uncrossed fibres in the gracilis and cuneatus
fasciculi synapse onto cells in the gracilis and cuneatus
nuclei at the uppermost part of the spinal cord. These
cells are the second sensory neurones in the previously
uncrossed pathway.
8. The sensory system
This is more complicated than the motor pathways. It is the
way sensations are transmitted to the sensorium, that part of
the cerebral cortex in which sensation is represented.
Whereas the motor pathways are a ‘two-neurone’ system, with
the upper motor neurone connecting the cortex to the anterior
horn cell and the lower motor neurone connecting the anterior
horn cell to the motor end-plate, sensation is a three-neurone
system.
Sensation from the skin, joints, muscles and organs, and the
special senses are discussed. The following points are general.
Different sensations are perceived and transmitted differently:
touch, pain, temperature (hot and cold) and vibration.
Sensations from the joints travel with sensations from the skin,
but joint and vibration modes course up primarily in the dorsal
columns.
i.
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Touch is perceived by tactile receptors (Meissner's
corpuscles) which transmit impulses along the nerve
fibres of the peripheral nerves to the cell bodies of
those nerves clustered in the dorsal root ganglia
(singular: ganglion), adjacent to, but outside, the
spinal cord. This is the first sensory neurone. Its
branches enter the dorsal funiculus of the spinal cord.
Here, fibres carrying touch sensation divide into two
groups. One group crosses the midline to enter the
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From these synapses, new axons cross over to the other
side in the sensory decussation of the medulla and enter
the medial lemniscus (ribbon; plural: lemnisci) where
they join up with the spino-thalamic tract which is
already in this lemniscus, and all end together in the
thalamus. They then course together into the cerebral
cortex adjacent to other sensory fibres.
ii.
Pain Sensation follows the same route map outlined
iii.
Temperature sensation (both hot & cold)
iv.
above for touch, into the spino-thalamic tract. Unlike the
Meissner's corpuscles sensitive to touch, there are no
known nerve endings subserving pain as such. Pain
stimuli, to be appreciated, must be directed to the
simple nerve endings themselves. Pain tracts follow the
peripheral nerves to the lateral root ganglia, then course
via the crossed spino-thalamic tract to the thalamus and
finally, via the posterior part of the internal capsule, to
the sensory cortex.
takes the same route as pain. Once again, there are no
specialised nerve endings for temperature.
Vibration sensation accompanies the fibres of
touch, via the dorsal gracilis and cuneatus columns, to
the thalamus and so onto the sensorium.
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9. The thalamus
The thalamus is the rostral portion of the brainstem; the
diencephalon, (between brain); it relays and integrates with the
pathways from and to the cerebrum and from and to the lower
motor centres. It is divided anatomically into the thalamus
proper, the hypothalamus, the subthalamus and the
epithalamus.
There is one thalamic complex on each side, united minimally
across the midline by the massa intermedia (intermediate mass).
Each is a well-defined mass of grey matter (nuclei) on either
side of the third ventricle, is bounded laterally by the internal
capsule, and is adjacent anteriorly to the caudate nucleus.
The thalamus functions mainly as an interchange of impulses
from other centres, including:
here because of their complexity, and because of uncertainty as
to their function.
It should be recalled that this is the ‘flight or fight’ centre and
that autonomous responses originate here; for example,
thermo-regulatory, glucose metabolism, fat metabolism factors,
and a sleep challenge. This is a fundamental part of the limbic
system, terminating via the fornix (vault) in the mammillary
bodies.
The subthalamus is functionally related to the basal
ganglia.
The epithalamus is situated posteriorly to the thalamus
and includes the pineal body, whose function has not yet been
clearly defined.
auditory impulses from the inferior colliculus (little hill)
nucleus via the inferior quadrigeminal (quadruplets) brachium
(arm) onto the auditory cortex in the temporal lobe;
visual impulses from the lateral geniculate (knee-like) body of
the superior quadrigeminal brachium to the visual cortex in the
calcarine (like a cock's spur) area of the occipital lobe;
visceral impulses from the bladder and bowel, and their
correlation with the higher centres of emotion and cultural
inhibition;
arousal impulses from the reticular formation to the cerebral
cortex;
pain sensation, perceived in the thalamus and transmitted to
the cortex;
balance (cerebellar information) from the dentate nucleus
crosses to the red nucleus and thence, via the rubro-spinal and
rubro-reticular tracts, to the brain stem and reticular formation;
and
cortical information, which passes through the thalamus
to the caudate nucleus and globus pallidus and back to the
cortex.
The hypothalamus, ie. the optic chiasma, tuber cinereum (ashy
swelling) and mammillary (breast-like) bodies including the
infundibulum (funnel), has many separate nuclei not discussed
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10. The basal ganglia
Basal ganglia is the name given to the mass of grey matter deep
in the insula (island). Note that the thalamus is not included in
the basal ganglia. The region is made up of clusters of neuronal
cells with fibres passing through them and also integrating
with them.
In the coronal section of the brain, starting from the cortical
grey matter and working medially, one sees deep to the insula:
•
the ‘extreme’ capsule of fibres;
•
the external capsule of fibres;
•
•
•
•
Coronal Section of brain
showing basal ganglia
the claustrum (barrier)—a thin layer of cells;
the lentiform nucleus continuous with the head of the
caudate nucleus anteriorly;
the internal capsule, described previously, largely
composed of the cortico-spinal tract (motor) and also the
spino-thalamic tract (sensory); and
Corpus callosum
Internal capsule
External capsule
the caudate nucleus, its head anteriorly, body and tail
‘wrapping’ the above structures, its tail inferiorly, ending
in the amygdaloid (almond-shaped) nucleus.
NB: More posterior to the head of the caudate nucleus and
medial to the internal capsule is the thalamus, previously
described.
The body of the caudate nucleus surrounds the thalamus on its
course around the basal ganglia.
Claustrum
Insula
Caudate nucleas
(tail)
which can be readily subdivided into a lateral putamen
(something which falls off when pruning) and a more medial
globus pallidus.
The intricate functions of the basal ganglia are beyond the
scope of this summary. Basically, they are involved with
repetitive movements, co-ordinating and modulating function.
They are under the control of the cerebral cortex, and are
concerned with the initiation and cessation of functions which
depend on awareness, and which occur independently of
conscious volition.
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Extreme capsule
Thalamus
The lentiform nucleus is a large lens-shaped area of cells,
Corpus striatum is an old name for an entity comprising
the caudate nucleus, plus the putamen, plus the structures of
the internal capsule .
Caudate nucleus
(head)
Putamen
Globus pallidus
}
Lentiform nucleus
(After Samson)
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11. The special senses
11a. Smell
Suitable stimulation of the olfactory mucosa is transmitted to
the olfactory nerves which pass through the cribriform (sievelike) plate of the skull, entering the olfactory bulb. From each
bulb, a tract passes distally, dividing into three (the trigone,
triangle). The two main divisions, the lateral and the medial,
end in the olfactory cortex, known as the cuneus, and in the
deeper hippocampus (sea-horse). The few remaining central
fibres enter the anterior perforate substance, anterior to the
optic chiasma (crossing).
The hippocampus originates as a gyrus (circle) on the medial
aspect of the brain; it continues as the fimbria (fringes) and then
curves around anteriorly to form the fornix, crus (cross) and
body of the hippocampus. The left and right fornices are joined
by the hippocampal commissure, finally becoming columns of
fornix and ending in the mammillary bodies, which protrude
on the base of the brain.
From these mammillary bodies, tracts relay impulses to the
thalamus, caudate nucleus, tegmentum (covering) and globus
pallidus, whilst further fibres descend to connect with anterior
horn cells (this is important in extrapyramidal dysfunction, and
therefore, in the treatment of Parkinsonism).
11b. The visual system
These anatomical pathways are more direct. Stimuli traverse
the optic lens onto the retina (note the blind spot, where the
retina is deficient due to the exit there of the fibres which
constitute the optic nerve). The stimuli are then separated as
the two optic nerves join to form the chiasma. The portion of
the optic nerve conveying fibres from the medial half of the
retina crosses to the opposite side via the chiasma, whilst the
portion of the fibres from the lateral half of the retina do not
cross, but join with the crossed fibres from the opposite side, to
form the optic tract on each side. This ends by synapsing with
cells of the lateral geniculate body, then forms a well defined
geniculo-calcarine tract which terminates in the calcarine visual
cortex on the medio-posterior portion of the occipital lobe.
each side (the superior quadrigeminal bodies) comprise some
of the fibres from the optic tract and some from the cortex,
synapsing with fibres from the cord and brainstem. These are
responsible for those eye movements, such as following a
moving object, which utilise exteroceptive stimuli. They are not
involved with pupillary reactions, which depend on
sympathetic and parasympathetic influences. Note that the
parasympathetic input, constricting the pupil, arrives via
pretectal nuclei to the oculomotor nerve, the ciliary ganglion
and onto the iris. The sympathetic input, dilating the pupil,
occurs via the superior sympathetic ganglion onto the internal
carotid artery, the ophthalmic artery and so to the iris.
Optic pathway viewed from above
Nasal/medial
fibres cross
sides at the
optic chiasma
Optic chiasma
Nasal
retina
Light from
lateral images
(lat. visual
fields)
Temporal
retina
Optic nerve
Optic tract
Geniculo-calcarine
tract
Lateral
geniculate
body of the
thalamus
The corpora quadrigemina are four small colliculi (singular:
colliculus) which are rounded prominences making up the
tectum (roof) of the mid brain. The two rostral colliculi, one on
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11c. The trigeminal system
This comprises four nuclei, three of which are sensory.
Sensation from the face and dura enters branches of the
trigeminal system, together with the ophthalmic, maxillary and
mandibular nerves, each traversing the skull through its named
foramen, then coming together to form the semilunar (halfmoon-shaped) ganglion, entering the brainstem into three
separate nuclei, the distal one being a nucleus of the spinal
tract, and two proximal nuclei which are mesencephalic.
Communication is then mainly to the thalamus and on to the
sensory cortex.
The motor nucleus, which is likely to comprise three separate
sub-entities, innervates the muscles of mastication. The motor
nerve lies clearly separate from the semilunar ganglion and
exits the skull via the foramen ovale.
11d. The acoustic system
The eighth nerve consists of a cochlear (hearing) and a
vestibular (balance) portion. Stimuli enter the cochlear nuclei
via the spiral organ of Corti. Fibres from these nuclei form a
conspicuous bundle (the trapezoid body). They then form the
lateral lemniscus extending to the inferior colliculus on each
side (part of the quadrigeminal body), and then pass on to the
cortex.
The vestibular portion is derived from the three semicircular
canals. The sacculus (little sac) and utriculus (small bag) detect
head movements, sending information along the vestibular
nerve, which has its nerve bodies in the vestibular ganglion,
then to the medulla and on to the pons. Some branches pass
onto the cerebellum, others to the motor nuclei of the eye (the
cells of cranial nerves III, IV and VI) and some run distally, as
the vestibulo-spinal tracts, to the anterior horn cells of the
spinal cord.
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12. The autonomic nervous
system
This effector system is only occasionally influenced
voluntarily. It supplies smooth muscle, glands and blood
vessels. Although conscious perceptions can alter bowel
motility, raise hairs, speed up the heart rate or increase
sweating, the system mostly functions in a regular, routine,
involuntary way.
There are no special autonomic sensory routes; these are served
by the peripheral sensory system. Cerebral origins of the
autonomic system are observed in many cranial areas at most
levels: frontal and temporal cortical, insular (in the midbrain)
and specifically, hypothalamic. These connections are difficult
to observe and to identify.
The system is divided into the sympathetic and the
parasympathetic (names which do not help our understanding
of their course or function). Both are two-neurone systems. The
secondary neurones of the sympathetic system lie in the
sympathetic ganglia, whilst those of the parasympathetic are
in distal ganglia, intimately related to the target organs.
The sympathetic system is anatomically evident, consisting of
two substantial chains lying antero-lateral to the vertebral
bodies, one on each side. There are about 23 interconnected
ganglia on each side, joined by a long chain of nervous tissue.
Each chain starts at the T1 level and extends distally to the
sacral region. Above the level of T1 are inferior (stellate, starlike), the middle and the superior cervical ganglia, with the
inferior joined to the T1 ganglion. The middle cervical
ganglion supplies the heart, lungs and stomach. The superior
supplies the pupils, secretory glands of the head and the heart.
Fibres run from their cranial origins down the medulla into the
lateral fasciculus of the spinal cord. Entry from the cord to the
sympathetic chain is via the white fibres. Synapses occur in the
ganglia of the chains, but not necessarily at specific cord levels;
the fibres may course up and down, and then synapse; the next
relay of neurones exit via the grey fibres into the sympathetic
chains, then form the greater and lesser splanchnic (viscus)
nerves, the coeliac ganglion, and the mesenteric ganglion.
Together, these innervate the gall bladder, upper intestine,
kidneys, adrenal glands, and, via the hypogastric plexus, the
large intestine.
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The distal large intestine is innervated by fibres from the S2, S3
and S4 segments.
The parasympathetic system originates cranially and is
represented in various cortical areas. Impulses flow via
cortico-hypothalamic fibres to exit via cranial nerves III, VII, IX
and particularly X, targeting the spheno-palatine and coeliac
ganglia, where they synapse. The vagus (wanderer) nerve is the
most prominent carrier distally, synapsing in the visceral
ganglia for the respective viscera. Vagal stimuli do not go
further than the proximal colon.
More distally, information exits via the parasympathetic sacral
outflow of the spinal cord at S2, S3 and S4. This outflow forms
the pelvic plexus (plural: plexi) and the hypogastric ganglia
and terminates in the distal colon, bladder and genitals.
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INDEX
(main reference in bold type)
acoustic system, 22
amygdaloid nucleus, 18
anterior commissure, 7
anterior horn cells, 9, 12, 13, 14, 22
anterior perforate substance, 20
arcuate fibres, 7
arcuate reticular nuclei, 11
arousal impulses, 16
auditory cortex, 16
auditory impulses, 16
autonomic nervous system, 23
balance, 16
basal ganglia, 9, 18
bladder impulse, 16
blind spot, 20
bowel impulses, 16
calcarine area, 16
calcarine visual cortex, 20
caudate nuclueus, 9, 12, 16, 20, 18
cerebellar peduncles, 10, 11
cerebello-ponto-spinal, 12
cerebellum, 11, 12, 22, 10
cerebral cortex, 12
ciliary ganglion, 21
claustrum, 18
co-ordination, 18
cochlear nuclei, 22
coeliac ganglion, 23, 24
corpora quadrigemina, 20
corpus callosum, 7
corpus striatum, 9, 18
cortex, 7
cortico-hypothalamic fibres, 24
cortico-spinal (pyramidal) tract, 12, 18
cortico-spinal efferents, 9
cortico-thalamic fibres, 9
cribriform plate, 20
crus of hippocampus, 20
cuneus, 20
dentate nucleus, 11, 16
diencephalon, 16
dorsal funiculus, 8, 14, 15
dorsal root ganglia, 14
dura sensation, 22
eighth cranial nerve, 22
epithalamus, 16, 17
external capsule, 18
exteroceptive influences, 10
extra-pyramidal pathways, 12
extrapyramidal efferents, 9
extrapyramidal system, 12
extreme capsule, 18
face sensation, 22
facial nerve, 24
fasciculi in spinal cord, 8
fasciculus cuneatus, 8, 9, 15
fasciculus gracilis, 8, 14, 15
fat metabolism, 17
fimbria of hippocampus, 20
flight or fight centre, 17
foramen ovale, 22
forceps major, 7
forceps minor, 7
fornix, 17
fornix of hippocampus, 20
fourth cranial nerve, 22
frontal lobes of cerebrum, 7
funiculi in spinal cord, 8
geniculo-calcarine tract, 20
genu of corpus callosum, 7
globus pallidus, 9, 16, 18
glucose metabolism, 17
greater splanchnic nerve, 23
hippocampal commissure, 20
hippocampus, 20
homunculi, 7
hypogastric ganglia, 24
hypogastric plexus, 23
hypothalamus, 16
inferior cervical ganglion, 23
inferior colliculus, 16, 22
inferior longitudinal fasciculus, 7
inferior quadrigeminal brachium, 16
infundibulum, 16
insula, 18
internal capsule, 12, 15, 16, 18
internal carotid artery, 21
iris, 21
lamina terminalis, 7
lateral fasciculus, 23
lateral geniculate body, 16, 20
lateral lemniscus, 22
lateral root ganglia, 15
lentiform nucleus, 12, 18
lesser splanchnic nerve, 23
limbic system, 16
lower motor neurones, 14
mammillary bodies, 16, 17, 20
mandibular nerve, 22
massa intermedia, 16
maxillary nerve, 22
medial fasciculus,, 15
medial lemniscus, 15
medulla, 11, 12, 15, 22, 23
Meissner's corpuscles, 14
mesencephalon, 11
mesenteric ganglion, 23
midbrain, 12
middle cervical ganglion, 23
modulation, 18
motor end-plate, 14
muscles of mastication, 22
ninth cranial nerve, 24
nuclei ponti, 11
occipital lobes of cerebrum, 7, 16, 20
oculomotor nerve, 21
olfactory bulbs, 7, 20
olfactory mucosa, 20
olivary nucleus, 11
ophthalmic artery, 21
ophthalmic nerve, 22
optic chiasma, 16, 20
optic lens, 20
optic nerve, 20
optic tract, 20
pain sensation, 15, 16
parasympathetic sacral outflow, 24
Parkinsonism, 20
pelvic plexus, 24
pes pedunculi, 12
pineal body, 16
pons, 12, 15, 22
posterior commissure, 7
posterior root ganglion, 9
prasympathetic system, 23
pretectal nuclei, 21
proprioceptive information, 10
pupillary reactions, 21
putamen, 18
pyramidal cells, 11
pyramidal decussation (pyramids), 12
red nucleus, 11, 16
repetitive movements, 18
reticular formation, 11, 16
reticulo-spinal tract, 11
retina, 20
rhinencephalon, 7
rostral colliculi, 20
rostrum, 7
rubro-reticular tract, 16
rubro-spinal tract, 11, 16
sacculus, 22
second cranial nerve, 20
semicircular canals, 22
semilunar ganglion, 22
sensorium, 14
sensory decussation, 15
seventh cranial nerve, 24
sixth cranial nerve, 22
sleep challenge, 16
smell, 20
spastic reflex, 9
spheno-palatine ganglion, 24
spinal cord, 8
spinal reflex, 14, 9
spino-thalamic tract, 15, 18, 14
spiral organ of Corti, 22
splenium, 7
stellate ganglion, 23
substantia nigra, 9
subthalamus, 17
subthalamus, 16, 17
superior cerebellar decussation, 11
superior cervical ganglion, 23
superior longitudinal fasciculus, 7
superior quadrigeminal bodies, 21
superior quadrigeminal brachium, 16
superior sympathetic ganglion, 21
sympathetic chain, 23
sympathetic ganglia, 23
sympathetic system, 23
tectum, 20
tegmentum, 20
temperature sensation, 15
temporal lobes of cerebrum, 7, 16
tenth cranial nerve, 17, 24
thalamus, 9, 12, 15, 17, 18, 20, 16
thermo-regulation, 17
third cranial nerve, 21, 22, 24
third ventricle, 16
touch, 14
trapezoid body, 22
trigeminal motor nucleus, 22
trigeminal system, 22
trigone, 20
tuber cinereum, 16
uncinate fibres, 7
upper motor neurone, 14
utriculus, 22
vagus nerve, 17, 24
vestibular ganglion, 22
vestibular nerve, 22
vestibulo-cerebellar fasciculus, 11
vestibulo-spinal tract, 12, 22
vibration sensation, 15
visceral impulses, 16
visual impulses, 16