BASIC

NEUROANATOMY
PREPARED BY: MANAL ADIL
FINAL YEAR STUDENT (2025)
The brain consists of three main structural divisions
The cerebrum (outer layer is the cerebral cortex)
The cerebellum,
• The brain stem at the base of the brain (which extends from the upper cervical
spinal cord to the diencephalon of the cerebrum)
 THE CEREBRUM:
The cerebrum is the major part of the brain, divided into left and right cerebral
hemispheres with folds and convolutions.
Gyri are the ridges on the brain’s surface; sulci (plural of sulcus) are the small
grooves between gyri; larger grooves are called fissures.
The cerebral hemispheres are covered in the cerebral cortex (gray matter) and
connected by the corpus callosum.
• The left hemisphere controls speech
and abstract thinking,
while the right hemisphere
controls spatial thinking.
The cerebrum is divided into four lobes: frontal, parietal, temporal, and occipital.
Frontal lobes (largest, behind the forehead) control language, motor function,
cognitive processes (e.g., self-awareness, mood, memory, attention, social/moral
reasoning).
Frontal lobe Clcontains Broca’s area, responsible for speech production.
Parietal lobes (center of the brain, between frontal and occipital lobes) interpret
sensory and memory functions.
Temporal lobes (near the skull base, also known as neocortex) process speech,
sensory information, memory, language, and emotions.
Temporal lobe contains the Wernicke area, responsible for understanding spoken
and written language.
• Occipital lobes (smallest, caudal part of the brain) are primarily responsible for
visual information interpretation
 THE CEREBELLUM:

The largest of the hindbrain is the cerebellum.

Upon reception of motor information from both the cerebral cortex and the
musculoskeletal structures of the body, the cerebellum coordinates these signals
to maintain the gait and posture of humans in motion.
Although the cerebellum itself does not initiate muscle contraction, it aids in the
refinement and accuracy of motor activity by controlling muscle tone.
In addition to its role in controlling balance and regulating motor movement, the
cerebellum also plays a role in the regulation of fear and other cognitive functions
such as attention, language, and the human response to pleasure.
 THE DIENCEPHALON:

The diencephalon is located above

the brainstem and between the
cerebral hemispheres.
It is relatively small in mass but
plays critical roles in brain and
body function.
• Contains a collection of complex
structures with varying functions.
• The following is a brief summary
of its contents.
 THALAMUS:
• The thalamus consist of two oval collections of nuclei that make up most of the mass of the diencephalon.
• The thalamus is often described as a relay station because almost all sensory information (with the
exception of smell) that proceeds to the cortex first stops in the thalamus before being sent on to its
destination.
• It is hypothesised that the thalamus serves a gating function in filtering information.
• The thalamus also plays an important role in regulating states of sleep and wakefulness
•

EPITHALAMUS:
• The epithalamus consists primarily of the pineal gland and the habenulae.
• The function of the epithalamus is to connect the limbic system to other parts of the brain.
• Some functions of its components include the secretion of melatonin and secretion of
hormones from the pituitary gland by the pineal gland circadian rhythms), and regulation of
motor pathways and emotions.
 HYPOTHALAMUS:

• The hypothalamus is a small, almond-sized region above the brainstem,

composed of various nuclei that regulate several vital functions.
• It receives input from limbic structures and has extensive output to the
autonomic nervous system (ANS).
• The hypothalamus is crucial for controlling pituitary endocrine function
and maintaining homeostasis, regulating hunger, thirst, temperature,
water and sodium balance.
• It also influences memory, emotional responses, and circadian rhythms
via retinal input to the suprachiasmatic nucleus.
• Additionally, it may affect sexual and emotional behavior, independent
of its endocrine role.
 SUBTHALAMUS :

A portion of the subthalamus is made up of tissue from the midbrain extending

into the diencephalon, hence parts of midbrain regions eg substantia nigra and
red nucleus are found in the diencephalon.
Also contains the subthalamic nucleus (densely interconnected with the basal
ganglia) and the zona incerta (many connections throughout the cortex and
spinal cord)
• Several collections of important fibers (e.g. somatosensory fibers) also pass
through the subthalamus.
 LIMBIC SYSTEM:
• The limbic system is not defined by strict anatomic boundaries but incorporates
several important structures.
• The limbic structures conventionally include the amygdala, the hippocampus,
the fornix, the mammillary bodies, the cingulate gyrus, and the
parahippocampal gyrus, which lie mainly on the medial side of the temporal
lobe. These structures form connections between the limbic system and the
hypothalamus, thalamus and cerebral cortex.
• The limbic system has been traditionally associated with our emotional
behaviour. The hippocampus is important in memory and learning, while the
limbic system itself is central in the control of emotional responses and provides
high-level processing of sensory information.
• The main outflow of the limbic system is to the prefrontal cortex and the
hypothalamus as well as to cortical areas.
• It appears to have a role in attaching behavioural significance and response to a
given stimulus. Damage to this area has profound effects on emotional
responses.
 BASAL GANGLIA:
• The basal ganglia are a group of nuclei
involved in movement control,
including the Neostratum (Caudate
and Putamen), Globus Pallidus,
Subthalamic Nucleus, and
Substantia Nigra.
• They are closely connected with the
thalamus, motor cortex, and
brainstem, playing a key role in
modulating movement.
• The Neostratum receives somatotopic
signals from the entire cortex and
sends them to the thalamus, which in
turn projects to various motor-related
areas, including the premotor cortex,
supplementary motor cortex, and
brainstem regions that control
locomotion and eye movements.
 THE BRAINSTEM:
The brain stem includes the medulla, B. LATERAL STRUCTURES
pons, and midbrain. 1. The nucleus ambiguus (CN IX, X, and XI)
It extends from the pyramidal 2. The vestibular nuclei (CN VIII)
decussation to the posterior 3. The inferior cerebellar peduncle, which contains the dorsal
commissure. spinocerebellar,
The brain stem receives its blood cuneocerebellar, and olivocerebellar tracts
supply from the vertebrobasilar 4. The lateral spinothalamic tract (spinal lemniscus)
system. 5. The spinal nucleus and tract of trigeminal nerves.
It contains cranial nerves (CN) III to XII
(except the spinal part of CN XI).
CROSS SECTION THROUGH THE
MEDULLA:
(Figure 10-3)
A. MEDIAL STRUCTURES
1. The hypoglossal nucleus of CN XII
2. The medial lemniscus, which
contains crossed fibers from the
gracile and cuneate
nuclei
3. The pyramid (corticospinal fibers)
CROSS SECTION THROUGH THE PONS:
LATERAL STRUCTURES:
(Figure 10-4)
1. Facial nucleus (CN VII)
The pons has a dorsal 2. Facial (intraaxial) nerve fibers
tegmentum and a ventral base. 3. Spinal nucleus and tract of
trigeminal nerve (CN V)
A. MEDIAL STRUCTURES:
1. Medial longitudinal fasciculus (MLF)
2. Abducent nucleus of CN VI (underlies
facial colliculus)
3. Genu (internal) of CN VII (underlies facial
nerve) (facial colliculus
. Abducent fibers of CN VI
5. Medial lemniscus
6. Corticospinal tract (in the base of the
pons)
 MIDBRAIN:
CROSS SECTION THROUGH THE ROSTRAL
MIDBRAIN:
(Figure 10-5)
The mid-brain has a dorsal tectum, an intermediate
tegmentum, and a base. The aqueduct lies
between the tectum and the tegmentum.
A. DORSAL STRUCTURES include the superior colliculi.
B. TEGMENTUM
1. Oculomotor nucleus (CN III)
2. Medial longitudinal fasciculus (MLF)
3. Red nucleus
4. Substantia nigra
5. Dentatothalamic tract (crossed)
6. Medial lemniscus
7. Lateral spinothalamic tract (in the spinal lemniscus)
C. CRUS CEREBRI (basis pedunculi cerebri, or cerebral
peduncle).
The corticospinal tract lies in the middle three-fifths of
 MENINGES:

MENINGES are three connective tissue membranes that surround the spinal cord and
brain.
A. The meninges consist of the pia mater, arachnoid mater, and dura mater.
1. The pia mater is a delicate, highly vascular layer of connective tissue. It closely
covers the surface of the brain and spinal cord.
2. The arachnoid mater is a delicate, nonvascular connective tissue membrane. It is
located between the dura mater and the pia mater.
3. The dura mater is the outer layer of meninges. It consists of dense connective
tissue that is divided into an outer periosteal (endosteal) layer and an inner meningeal
layer. The meningeal layer forms dural folds. Dural venous sinuses are located
between periosteal and meningeal layers of dura mater.
B. MENINGEAL SPACES
1. The subarachnoid space (Figure 4-1) lies between the pia mater and the
arachnoid. It terminates at the level of the second sacral vertebra. It contains the
cerebrospinal fluid (CSF).
2. Subdural space
a. In the cranium, the subdural space is traversed by “bridging” veins.
b. In the spinal cord, it is a clinically insignificant potential space.
3. Epidural space
a. The cranial epidural space is a potential space. It contains the meningeal
arteries and veins.
b. The spinal epidural space contains fatty areolar tissue, lymphatics, and
venous
plexuses. The epidural space may be injected with a local anesthetic to
produce a paravertebral (“saddle”) nerve block.
 Spinal Cord

GRAY AND WHITE RAMI COMMUNICANS:

A. Gray rami communicans contain unmyelinated postganglionic sympathetic fibers. They
are found at all levels of the spinal cord.
B. White rami communicans contain myelinated preganglionic sympathetic fibers. They
are found from T-1 to L-3 (the extent of the lateral horn and the intermediolateral cell
column).
TERMINATION OF THE CONUS MEDULLARIS:
occurs in the newborn at the level of the body of the third lumbar vertebra (L-3). In the adult, it
occurs at
the level of the lower border of the first lumbar vertebra (L-1). This is clinically relevant in
determining the appropriate position for performing lumbar puncture in children and
adults.
LOCATION OF THE MAJOR MOTOR AND SENSORY NUCLEI OF THE SPINAL
CORD:

A. The ciliospinal center of Budge, from C-8 to T-2, mediates the sympathetic innervation of the eye.
B. The intermediolateral nucleus (cell column) of the lateral horn, from C-8 to L-3, mediates the entire
sympathetic innervation of the body.
C. The nucleus dorsalis of Clark, from C-8 to L-3, gives rise to the dorsal spinocerebellar
tract.
D. The sacral parasympathetic nucleus, from S-2 to S-4
E. The nucleus of the accessory nerve, from C-1 to C-6
F. The phrenic nucleus, from C-3 to C-6
(FIGURE 6.2 GIVEN IN NEXT SLIDE)

THE CAUDA EQUINA:

Motor and sensory roots that are found in the subarachnoid

space below the conus medullaris form the cauda equina. They exit the vertebral canal
through the lumbar intervertebral and sacral foramina
THE MYOTATIC REFLEX
is a monosynaptic and ipsilateral muscle
stretch reflex (MSR). Like all reflexes,
the myotatic reflex has an afferent and
an efferent
limb. Interruption of either limb results
in areflexia.
A. The afferent limb includes a muscle
spindle (receptor) and a dorsal root
ganglion neuron and its 1a fiber.
B. The efferent limb includes a ventral
horn motor neuron that innervates
striated muscle (effector).
C. The five most commonly tested MSRs
are listed in ( Table given in next
slide. )
 FIVE MOST COMMONLY USED MUSCLE
STRETCH REFLEXES:

Muscle Stretch Reflex Cord Segment Muscle

Ankle jerk S-1 Gastrocnemius

Knee jerk L-2 - L-4 Quadriceps
Biceps jerk C5 - C6 Biceps
Forearm jerk C-5 - C6 Brachioradialis
Tricep jerk C7 – C8 Triceps
 TRACTS OF SPINAL CORD:
Ascending tracts (sensory):
1,dorsal columns (posterior funiculi):
• deep touch, proprioception, vibration
2,lateral spinothalamic tract:
• pain and temperature
• site of chordotomy to alleviate intractable pain
3.ventral spinothalamic tract:
• light touch
Descending tracts (motor) :
1.lateral corticospinal tract:
• main voluntary motor
• upper extremity motor pathways are more medial (central), which explains why a central
cord injury affects the upper extremities more than the lower extremities
2.ventral corticospinal tract:
• voluntary motor
 AUTONOMIC NERVOUS SYSTEM:
The autonomic nervous system (ANS) is a general visceral efferent
motor system that controls and regulates smooth muscle, cardiac muscle, and glands.
A. The ANS consists of two types of projection neurons:
1. Preganglionic neurons.
2. Postganglionic neurons. Sympathetic ganglia have interneurons.
B. AUTONOMIC OUTPUT is controlled by the hypothalamus.
C. The ANS has three divisions:
1. Sympathetic. Figure 7-1 shows the sympathetic innervation of the ANS.
2. Parasympathetic. Figure 7-2 shows the parasympathetic innervation of the ANS.
Table 7-1 compares the effects of sympathetic and parasympathetic activity on
organ systems.
3. Enteric. The enteric division includes the intramural ganglia of the gastrointestinal tract,
submucosal plexus, and myenteric plexus.
CRANIAL NERVES (CN) WITH PARASYMPATHETIC COMPONENTS :
It includes the following:

A. CN III (ciliary ganglion).

B. CN VII (pterygopalatine and submandibular ganglia).
C. CN IX (otic ganglion).
D. CN X [terminal (intramural) ganglia].

COMMUNICATING RAMI of the ANS:

It includes the following:

A. WHITE RAMI COMMUNICANTES, which are found between T-1 and L-2 and are
Myelinated
B. GRAY RAMI COMMUNICANTES, which are found at all spinal levels and are
unmyelinated.
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