1. NEUROANATOMY - I
BY
ADESEJI WASIU A.
ALABI ADEOLA
ADIGUN OLANIYI
DEPARTMENT OF ANATOMY,
UNIVERSITY OF ILORIN.
2. Divisions of the Nervous System
2 main subdivisions:
Central Nervous System
◦ the brain & spinal cord
Peripheral Nervous System -
◦ groups of neurons called ganglia and peripheral nerves
◦ provides pathways to & from the central nervous system
for electrochemical signals (impulses)
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3. The Peripheral Nervous System
Composed of 2 divisions:
Somatic
◦ Provides sensory information (voluntary)
◦ Transmits impulses to and from skeletal muscles -
usually conscious actions
Autonomic
◦ motor system for viscera (smooth muscles & glands-
involuntary)
◦ Autonomic is further divided into 2 subdivisions
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5. The Autonomic Nervous System
2 subdivisions of Autonomic:
Sympathetic
◦ participates in body’s response to stress; fight or flight
Parasympathetic
◦ returns body to resting state & conserves resources
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6. Orientation of the PNS
Dorsal roots carry sensory info to the spinal
cord
Ventral roots carry outgoing motor axons
Peripheral nerves formed from dorsal &
ventral roots
Symmetry of PNS
◦ Arranged on 2 axis:
◦ longitudinal: rostral to caudal ( head to tail)
◦ dorsal to ventral (back to front)
Segmented:
◦ 31 pairs of spinal nerves
◦ 12 pairs of cranial nerves
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7. Neurons
The basic and functional unit of the nervous system.
Consist of a cell body (perikaryon) and processes arising
from it.
The processes arising from the cell body of a neuron are
called neurites.
Several short branching processes called Dendrites
One longer process called an Axon
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9. Synapse
Synapses are sites of junction
between neurons.
Types
axosomatic synapse
axoaxonal synapse
dendro-axonic or dendro-dendritic
somato-dendritic
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10. Supporting cells of nervous system
Non conducting cells of the nervous
systems.
Collectively referred to as Neuroglia
Astrocyte
Microglia
Schwann cells
Oligodentrocytes
They provide mechanical support to neurons
Serve as insulators and prevent neuronal impulses
from spreading in unwanted directions.
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11. The Central Nervous System
Consists of following Regions:
◦Spinal Cord
◦Brain
◦ Cerebrum
◦ Cerebellum
◦ Diencephalon: the caudal (posterior) part of the forebrain, containing the
epithalamus, thalamus, hypothalamus, and ventral thalamus
and the third ventricle.
◦ Brain Stem
◦ Midbrain
◦ Medulla
◦Pons
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12. Protection of the Brain & CNS
The skull & spinal column
The Meninges
◦ 3 layers of tissue protecting brain
◦ Dura mater
◦ outer tough layer
◦ Subdural space – normally small
◦ Arachnoid membrane
◦ next to dura mater
◦ Subarachnoid space - spongy layer filled with cerebrospinal fluid and blood
vessels
◦ Pia mater
◦ membrane that covers the brain
Cerebrospinal fluid (CSF) - cushions brain; circulates around the
brain & spinal cord
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13. The Spinal Cord- gross anatomy and internal structure
The spinal cord is roughly cylindrical in shape.
It begins superiorly at the foramen magnum
in the skull.
It terminates inferiorly in the adult at the level
of the lower border of the L1.
In the young child, it usually ends at the upper
border of L3.
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14. Spinal Cord (cont’d)
ENLARGEMENTS
Cervical & lumbar enlargements
In the cervical region, it gives origin to the brachial plexus
In the lower thoracic and lumbar regions, it gives origin to
the lumbosacral plexus
CONUS MEDULLARIS:
Inferiorly, the spinal cord tapers off into the conus medullaris.
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15. FILUM TERMINALE:
From the apex of conus medullaris
Prolongation of the pia mater, descends to be attached to the posterior surface
of coccyx.
FISSURE & SULCI
In the midline anteriorly, the anterior median fissure.
On the posterior surface, a shallow furrow, the posterior median sulcus.
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16. SPINAL NERVES
Along the entire length of the spinal cord are attached 31 pairs of spinal nerves
Cervical …… 8
Thoracic …… 12
Lumbar …… 5
Sacral …… 5
Coccygeal …..1
Each connects to the spinal cord by 2 roots – dorsal and ventral.
Each root forms from a series of rootlets that attach along the whole
length of the spinal cord segment.
Ventral roots are motor while dorsal roots are sensory.
The 2 roots join to form a spinal nerve prior to exiting the vertebral column.
Almost immediately after emerging from its intervertebral foramen, a spinal nerve will divide
into a dorsal ramus, a ventral ramus, and a meningeal branch that re-enters and innervates the
meninges and associated blood vessels.
Each ramus is mixed.
Joined to the base of the ventral rami of spinal nerves in the thoracic region are the rami communicantes. These are sympathetic fibers.
Dorsal rami supply the posterior body trunk whereas the thicker ventral rami supply the rest of the body trunk and the limbs.
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17. Plexuses
Except for T2 to T12, all ventral rami branch extensively and join one another lateral to the
vertebral column forming complicated nerve plexuses.
Within a plexus, fibers from different rami criss cross each other and become redistributed.
Internal Structure:
The spinal cord is composed of an inner core of gray matter, which is surrounded by an outer
covering of white matter.
GRAY MATTER
On cross section; the gray matter is seen as an H-shaped pillar with anterior and posterior gray
columns, or horns, united by a thin gray commissure containing the small central canal.
A small lateral gray column or horn is present in the thoracic and upper lumbar segments of the
cord.
The amount of gray matter present at any given level of the spinal cord is related to the amount
of muscle innervated at that level.
Thus, its size is greatest within the cervical and lumbosacral enlargements of the cord.
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18. Grey and White Matter of Spinal Cord
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WHITE MATTER
• The white matter, may be divided into anterior,
lateral, and posterior white columns or funiculi.
• The anterior column on each side lies
between the midline and the anterior nerve
roots;
• The lateral column lies between the anterior
and the posterior nerve roots;
• The posterior column lies between the
posterior nerve roots and the midline.
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Amyotrophic Lateral Sclerosis, ALS (or
Lou Gehrig’s Disease
• Upper and lower motor
neuron disease
– with gradual degeneration of
motor neurons
– Progressive weakening of
skeletal muscles occurs
• atrophy and fasciculation (fine
twitching) occur
• May involve genetic factor
– Mutation of SOD1 gene (on
xsome 21) reported
– FALS runs in family
• Symptoms starts around 40-
60 years (more in men)
• Patient may die from
respiratory failure
– due to paralysis of diaphragm
27. The Brain
Remaining 6 areas of the CNS are part of the brain
The control center of the body
◦ Regulates body activity; enables you to think
Surface is gray matter - 6 x 106 cell bodies / cc
Under gray matter is white matter - formed of myelinated
axons.
Surface of the brain (neocortex) is convoluted
◦ Increases surface area
◦ ridges = gyri
◦ grooves = sulci
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29. The Cerebral Hemispheres
Largest region of brain; 7/8 by weight - Includes:
◦ Cerebral cortex – outer surface of gray matter
◦ underlying white matter
◦ 3 nuclei (clusters of related neurons):
◦ the basal ganglia
◦ the hippocampal formation
◦ the amygdala
◦ these are masses of gray matter at the base of the
cerebrum that serve the motor cortex
◦ paired cavities = lateral ventricles
◦ Divided into 2 ‘half spheres’ = hemisheres
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30. The Cerebral Cortex
The convoluted outer surface
◦ grooves = sulci
◦ elevated regions = gyri
Composed of gray matter
2-5 mm thick
Contains ~ 12 billion neurons
Most of the cerebral cortex is concerned with processing
sensory information or motor commands
2 bands of tissue – one sensory, one motor
Divided into primary, secondary, & tertiary
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31. The Forebrain
Telencephalon
◦ Olfactory bulb
◦ Cerebral cortex
◦ Basal telencephalon (basal ganglia)
◦ Corpus callosum
◦ commissure between cerebral hemispheres
◦ Internal capsule
◦ connections with brain stem
◦ Lateral ventricles
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32. Lobes of the Cerebrum
2 sides called hemispheres
Joined by a bridge = Corpus Callosum
Separated by a deep fissure front to back
Like 2 mirror images (but not quite)
Divided into 4 lobes
◦ 1. Frontal
◦ 2. Parietal
◦ 3. Temporal
◦ 4. Occipital
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33. Lobes of the Cerebrum
Parietal Lobe
Temporal Lobe
Frontal Lobe
Limbic Lobe
Occipital Lobe
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45. White matter of Cerebral hemisphere
The surface of the cerebral hemisphere is covered by a thin layer of grey
matter called the cerebral cortex.
The greater part of the cerebral hemisphere deep to the cortex is occupied by
white matter within which are embedded certain important masses of grey
matter.
These fibres may be:
Association fibres that interconnect different regions of the cerebral cortex.
Projection fibres that connect the cerebral cortex with other masses of grey
matter; and vice versa.
Commissural fibres that interconnect identical areas in the two hemispheres.
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46. Internal capsule
The internal capsule may be divided into the following parts.
The anterior limb lies between the caudate nucleus medially, and the anterior part of
the lentiform nucleus laterally.
The posterior limb lies between the thalamus medially, and the posterior part of the
lentiform nucleus on the lateral side.
In transverse sections through the cerebral hemisphere the anterior and posterior
limbs of the internal capsule are seen to meet at an angle open outwards. This angle
is called the genu (genu = bend).
Some fibres of the internal capsule lie behind the posterior end of the lentiform
nucleus. They constitute its retrolentiform part.
Some other fibres pass below the lentiform nucleus (and not medial to it). These
fibres constitute the sublentiform part of the internal capsule
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48. The Primary Sensory & Motor Cortex
Primary Motor Cortex:
◦ controls voluntary movements of limbs & trunk
◦ contains neurons that project directly to spinal cord to activate
somatic motor neurons
Primary Sensory Areas
◦ receive information from peripheral receptors with only a few
synaptic relays interposed
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49. Brodmann Areas
Cytoarchitectural areas of neocortex
Regions with similar cell structure
Numbered
◦ each represents a functionally distinct area
Examples:
◦ Area 17 is the primary visual cortex
◦ at the caudal pole of the occipital lobe
◦ Area 4 is the primary motor cortex
◦ primary auditory cortex on left side of temporal lobe
near language center
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50. Secondary & Tertiary Areas
Surrounding primary areas are higher order (secondary & tertiary)
sensory & motor areas
◦ Process & integrate info coming from the primary sensory areas.
Higher order motor areas send complex info required for motor actions to
primary motor areas
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51. Association Areas
Three other large regions of cortex surround the primary, secondary &
tertiary areas Called association areas
In primates, association areas are majority of cortex
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54. Integration of Brain Functions
Interactions of all areas sensory, motor & motivational systems is
essential for behavior.
Example: throw a ball - info about motion of ball, impact of ball,
position of arms, legs, hands, etc. - sensory, motor, motivational systems
Anatomical organization of each major functional system (sensory,
motor, motivational) follows 4 principles
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55. Principles of Anatomical Organization
Each system contains relay centers
◦ These don’t just transmit info; also modify it
◦ Most important relay center is the thalamus
◦ almost all sensory info to cerebral cortex processed by
thalamus
Each system is composed of several distinct pathways
◦ Example: touch & pain
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56. Principles of Anatomical Organization (Cont.)
Each pathway is topographically organized
◦ neural map - clustered functions
Most pathways cross the body’s midline
◦ Thus each hemisphere controls the actions/sensations of the
opposite side.
◦ Left side dominates language; right side -spatial perception,
musical ability
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57. Diencephalon
Thalamus & hypothalamus taken together
Important structures found in the cerebrum
Between the midbrain & cerebral hemispheres
◦ Thalamus
◦ Hypothalamus
◦ Third ventricle
Retina and optic nerves
◦ develop from optic vesicle that pouches off from
diencephalon during development
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58. The Thalamus & Hypothalamus
Thalamus
◦ relay center - processes & distributes almost all sensory &
motor info going to the cerebral cortex
◦ links nervous & endocrine system
◦ emotional control
Hypothalamus
◦ under the thalamus
◦ regulates autonomic nervous system
◦ connects to thalamus, midbrain & some cortical areas
◦ Controls body temperature, thirst, hunger, emotional
behavior
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59. Cerebellum
The cerebellum consists of a part lying near the midline called the vermis, and
of two lateral hemispheres.
two surfaces, superior and inferior
Dorsal to the pons & medulla
Mostly white matter covered with a thin layer of gray matter
Pleated surface; divided into several lobes
Receives sensory input from the spinal cord, motor info from the cerebral
cortex & input about balance from receptors in the inner ear
Therefore, can coordinate planning & timing of voluntary muscle movement &
maintain balance
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62. The Medulla Oblongata & Pons
Medulla Oblongata
◦ Bottom (rostral) region of the brainstem
◦ Regulates blood pressure and respiration; controls
breathing, swallowing, digestion, heart & blood
vessels.
Pons
◦ Above medulla
◦ links cerebellum to cerebrum; relays info from
cerebral hemispheres to cerebellum
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63. The Midbrain
Mesencephalon
◦ Tectum (roof)
◦ superior colliculus + inferior colliculus
◦ Tegmentum (floor)
◦ Cerebral aqueduct
Controls responses to sight (e.g. eye movements)
Relay station of auditory & visual signals
Motor control of some skeletal muscles
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64. The Brainstem
Anatomically, from the bottom up:
◦ Medulla Oblongata
◦ Pons
◦ Midbrain
Taken together = brainstem
◦ Contains all the nerves that connect the spinal cord with the
cerebrum
◦ Receives sensory info from head, face, & neck
◦ Motor neurons control muscles of head & neck
◦ 12 pairs of cranial nerves carry input & output
◦ Also involved in hearing, taste & balance
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65. The Limbic System
A functional & evolutionary division, rather than anatomical
Group of structures in center of the brain above the
brainstem:
◦ hypothalamus
◦ pituitary
◦ hippocampus
◦ important role in memory
◦ hippocampal gyrus
◦ amygdala
◦ coordinates actions of the autonomic & endocrine systems
◦ involved in emotions
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66. Functions of the Limbic System
Sometimes called the “mammalian brain because most
highly developed in mammals
One of the oldest areas of brain from an evolutionary
standpoint
Maintains homeostasis: e.g. helps maintain
temperature, blood pressure, heart rate, blood sugar
Also involved in emotional reactions needed for survival
4 F’s: fleeing, fighting, feeding.
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69. Ipsilateral/Contralateral
The cerebral hemispheres are involved with inputs and outputs
from the contralateral side of the body
◦ Damage to neocortex causes problems on the opposite side
◦ In patients with epilepsy, surgeons occasionally cut corpus
callosum to relieve seizures. Flash different pictures in each
eye, patients could describe what they saw with right eye,
but not left, but could pick out object - example: Heart =
ART.
The cerebellum is involved with the control of movement on
the ipsilateral side of the body.
◦ Damage to the cerebellum causes motor deficits on the
same side.
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70. Injury Mechanisms
The brain is a complex and delicate organ, and one
that is vulnerable to injury from a variety of different
traumas. These include:
Frontal Lobe Injury
Occipital Lobe Injury
Temporal Lobe Injury
Side Impact Injury
Coup/Contre-coup Injury
Diffuse Axonal Injury
Epidural Hematoma
Subdural Hematoma
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71. Frontal Lobe Injury
The frontal lobe of the brain can be injured
from direct impact on the front of the head.
During impact, the brain tissue is
accelerated forward into the bony skull. This
can cause bruising of the brain tissue and
tearing of blood vessels.
Frontal lobe injuries can cause changes in
personality, as well as many different kinds
of disturbances in cognition and memory.
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72. Occipital Lobe Injury
Occipital lobe injuries occur from
blows to the back of the head.
This can cause bruising of the brain
tissue and tearing of blood vessels.
These injuries can result in vision
problems or even blindness.
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73. Temporal Lobe Injury
The temporal lobe of the brain is
vulnerable to injury from impacts of
the front of the head.
The temporal lobe lies upon the bony
ridges of the inside of the skull, and
rapid acceleration can cause the
brain tissue to smash into the bone,
causing tissue damage or bleeding.
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74. Side Impact Injury
Injuries to the right or left side of the brain can
occur from injuries to the side of the head.
Injuries to this part of the brain can result in
language or speech difficulties, and sensory
or motor problems.
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75. Coup/Contre-coup Injury
A French phrase that describes bruises
that occur at two sites in the brain.
When the head is struck, the impact
causes the brain to bump the opposite
side of the skull. Damage occurs at the
area of impact and on the opposite side of
the brain.
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76. Diffuse Axonal Injury
Brain injury does not require a direct head
impact. During rapid acceleration of the head,
some parts of the brain can move separately
from other parts. This type of motion creates
shear forces that can destroy axons
necessary for brain functioning.
These shear forces can stretch the nerve
bundles of the brain.
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77. Diffuse Axonal Injury
The brain is a complex network
of interconnections. Critical
nerve tracts can be sheared and
stressed during an acceleration-
type of injury.
Diffuse axonal injury is a very
serious injury, as it directly impacts
the major pathways of the brain.
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78. Epidural Hematoma
An epidural hematoma is a blood clot
that forms between the skull and the
top lining of the brain (dura).
This blood clot can cause fast changes
in the pressure inside the brain.
When the brain tissue is compressed, it
can quickly result in compromised
blood flow and neuron damage.
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79. Subdural Hematoma
A subdural hematoma is a blood clot that
forms between the dura and the brain
tissue.
The clot may cause increased pressure and
may need to be removed surgically.
When the brain tissue is compressed, it can
quickly result in compromised blood flow
and tissue damage.
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