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Faculty of Applied Medical Sciences

Department of Rehabilitation science

Neuroscinces
Introduction to Neuroscience & Neuroanatomy

Introduction to Brain Anatomy

• The human central nervous system (CNS) consists of the brain and spinal cord.
• The human brain weighs about 400 g at birth, and this weight triples during the first 3 years of life, primarily
due to the addition of myelin and the growth of neuronal processes.
• The adult brain weighs approximately 1,400 g and is thus a relatively small structure, constituting about 2% of
body weight.
• The brain is concerned with functions as diverse as thought, language, learning and memory, imagination,
creativity, attention, consciousness, emotional experience, and sleep.
• The spinal cord is in some ways a simpler part of the CNS in that it has a uniform organization throughout its
course.
• Receptors of many kinds outside of the CNS act as transducers that change physical and chemical stimuli in our
environment into nerve impulses that are sent to the spinal cord.
• The spinal cord carries all of the motor information that supplies our voluntary muscles and, thus, participates
directly in control of body movement.
• It plays a direct role in regulating visceral functions, and it serves as a conduit for the longitudinal flow of
information to and from the brain.

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Nervous System Divisions

ØThe nervous system is divided into two primary components.
1. The central nervous system (CNS)
is comprised of the brain and the spinal cord.
2. The peripheral nervous systemis(PNS)
comprised of the cranial and spinal nerves.
• When information flow is described in the nervous system, it can either be afferent communication, meaning it is
moving from the periphery to the brain, or efferent communication, meaning it is moving from the brain to the
periphery.

Anatomical Teminology

Ø Anatomical Directions:
• Anterior: In front of; toward the face
• Posterior: Behind; toward the back
• Superior: Above; toward the head
• Inferior: Below; toward the feet
• Medial: Toward the middle
• Lateral: Toward the edge
• Dorsal: Toward the top of the brain or the back of the spinal cord
• Ventral: Toward the bottom of the brain or the front of the spinal
cord
• Rostral: Toward the front of the brain or the top of the spinal cord
• Caudal: Toward the back of the brain or the bottom of the spinal
cord

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Dorsal
Superior

Forebrain
Rostral Caudal
Anterior Posterior

Ventral
Superior Rostiral
Inferior
Midbrain
Pons
Medulla
Anterior Ventral Dorsal Posterior Spinal Cord

Caudal Inferior

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Anatomical Planes

Axial view is horizontal. Sagittal view is side-on. Coronal view is front-on.

Anatomical Terminology
Cerebral Hemisphere

Rostral Caudal

Ventral Dorsal

The anterior aspect of the cerebral hemisphere is The top of the cerebral hemisphere is dorsal and
rostral and the posterior aspect is caudal. the bottom is ventral.

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Anatomical Terminology
Brainstem

Ventral
Dorsal

The anterior aspect of the brainstem is ventral and the The top of the brainstem is rostral and the posterior
aspect is dorsal. bottom is caudal.

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Gross Anatomy of the CNS

• Surface Anatomy:
• Brain:

Telencephalon is composed of the massive

Forebrain cerebrum, which is divided into two cerebral
hemispheres.
cerebrum
basal ganglia

Brain 3D
thalamus
Diencephalon hypothalamus
subthalamus

Gross Anatomy of the CNS

• Cerebellum

Midbrain
• Brainstem Medulla
Pons

Brainstem 3D
Cerebellum 3D

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External Brain Anatomy

• The brain is comprised of the cerebrum, cerebellum, and brainstem.
• The cerebrum is the most prominent region of the brain, it is
divided into left and right hemispheres.

• The surfaces of the cerebral hemispheres are marked by

rounded elevations called gyri (singular: gyrus) and grooves
called sulci (singular: sulcus).
• The cerebral hemispheres in humans have many folds to
increase the surface area of the brain.
• The ridges are called gyri and the grooves are called sulci.
• Large sulci are often called fissures.
• Gyrus = ridge
• Sulcus = groove between ridges
• Fissure = deep sulcus (‘fissure of Sylvius’)

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Cerebrum: Cerebral Hemispheres

• The cerebral cortex processes sensory, motor, and memory information and is the site for reasoning, language,
nonverbal communication, intelligence, and personality.
• The longitudinal fissure divides the two cerebral hemispheres.
• Each cerebral hemisphere is subdivided into six lobes:
• Frontal
• Parietal
• Temporal
• Occipital
• Limbic
• Insular
• The first four lobes are named for the overlying bones of the skull.
• The limbic lobe is on the medial aspect of the cerebral hemisphere.
• The insula is a section of the hemisphere buried within the lateral sulcus, and revealed by separating the temporal and
frontal lobes.

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Cerebrum:
Cerebral Hemispheres
• The boundary betweenfrontal
the lobe
and theparietal lobe
, marked by the
central sulcus
.
• The boundary betweenparietal
the lobe
and theoccipital lobe
, clearly marked only on the medial
hemisphere by the
parieto-occipital sulcus
.
• The division of the
temporal lobe
and thefrontal lobe
, marked by the
lateral sulcus.
• The limbic lobe, on the medial surface of the hemisphere, bounded by the cingulate sulcus and by the margin
of theparahippocampal
gyrus.

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Cerebral Hemispheres: White and gray matter

Ø White matter is composed of axons, projections of nerve cells that usually convey information away from the cell body, and myelin,
an insulating layer of cells that wraps around the axons.
• Areas with a large proportion of myelin appear white because of the high fat content of myelin.
• A bundle of myelinated axons that travel together in the central nervous system is called a tract, lemniscus, fasciculus, column,
peduncle, or capsule.
Ø Gray matter is the areas of the central nervous system that appear gray contain primarily neuron cell bodies.
• In the central nervous system, groups of cell bodies are most frequently called nuclei, although gray matter on the surface of the
brain is called cortex.
The axons in white matter convey information among parts of the nervous system. Information is integrated in gray matter.

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Cerebrum: Internal Anatomy

• Thecorpus callosum
is a huge commissure that connects most areas of the cerebral cortex.
• Within the white matter of the hemispheres are additional areas of gray matter; the
basal
mostganglia
prominent
. is the
• Basal ganglia nuclei
in the cerebral hemispheres include the caudate, the putamen, and the globus pallidus
• Theputamen
and theglobus pallidus
together are calledlenticular
the nucleus
.
• Thecaudate
and theputamen
together are calledcorpus
the striatum
.
• Two additional nuclei,
subthalamic
the nuclei
(in the diencephalon) and
substantia
the nigra
(in the midbrain), are part of the
basal ganglia neural circuit.
• limbic system, located in the diencephalon and the cerebral hemispheres, its parts of the hypothalamus,
l thalamus, and cerebra
cortex.

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Diencephalon
The diencephalon consists of several sets of paired structures on
either side of the third ventricle.
1. The largest structure is the thalamus, consisting of two
“eggshaped” nuclear masses.
• The thalamus is a critical processing station for all sensory
information (except olfactory) on its way to the cortex and
plays key roles in processing motor information, in
integrating higher order cognitive and emotional information,
and in regulating cortical activity.
• The thalamus can be considered the “gatekeeper” to the
cortex.
2. The hypothalamus is structurally part of the diencephalon but
functionally part of the limbic system.
• It plays key roles in coordinating and integrating endocrine,
auto- nomic, and homeostatic functions.
3. The subthalamus is part of the basal ganglia and plays an
important role in modulating and integrating voluntary
movement and muscle tone.

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Brainstem

• The brainstem is located in the posterior cranial fossa.

• It merges with the spinal cord caudally at the level of the foramen magnum
and with the diencephalon rostrally.
• Three distinct areas can be identified in the brainstem:
1. the medulla oblongata (or medulla) caudally,
2. the pons
3. the midbrain rostrally

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Brainstem

Medulla • The medulla is

continuous with the spinal cord.
Pons
• Superior to the medulla is the pons.
• The junction of the medulla and the pons is marked by
a transverse line.
Midbrain
• The superior section of the brainstem is the midbrain.

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Cerebellum

• The cerebellum consists of two large cerebellar

hemispheres and a midline vermis.
• Vermis means “worm,” a fitting description for the
appearance of the cerebellar midline.
• Internally, the cerebellar hemispheres are composed of the
cerebellar cortex on the surface, underlying white matter,
and centrally located deep nuclei.
• The cerebellum is connected to the posterior brainstem by
large bundles of fibers called peduncles.
• The superior, middle, and inferior peduncles join the
midbrain, pons, and medulla with the cerebellum.
• The function of the cerebellum is to coordinate
movements.

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Cranial Nerves

• Twelve pairs of cranial nerves emerge from the surface of the brain.
• Each cranial nerve is designated by a name and by a Roman
numeral.
• Numbering is assigned according to the site of attachment to the
brain, from anterior to posterior.
• Most cranial nerves innervate structures in the head, face, and neck.

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Spinal cord
• Within the vertebral column, the spinal cord extends from the
foramen magnum to the level of the first lumbar vertebra.
• The spinal cord has 31 segments, and a pair of spinal nerves
arises from each segment.
• Each spinal nerve is connected to the cord by a dorsal root
and a ventral root.
• An enlargement of the dorsal root, the dorsal root ganglion,
contains the cell bodies of sensory neurons.
• Cell bodies of neurons forming the ventral root are located
within the spinal cord.
• The spinal nerve exits the vertebral column via openings
between vertebrae, then divides into dorsal and ventral rami
that communicate with the periphery.
• The rami conduct signals between the spinal cord and the
sympathetic ganglia.

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Spinal Region

• Cross-sections of the spinal cord reveal centrally located gray matter forming a
shape similar to the letter “H” sur- rounded by white matter.
• Each side of the gray matter is subdivided into ventral, lateral, and dorsal horns.
• These horns contain cell bodies of motor neurons, interneurons, and the endings of
sensory neurons. The gray matter commissure connects the lateral areas of gray
matter.
Ø The white matter is divided into three areas (funiculi):
1. Anterior column
2. Lateral column
3. Dorsal column
Ø The spinal cord has two main functions:
1. To convey information between neurons innervating peripheral structures
and the brain
2. To process information
• The cord conveys somatosensory information to the brain and conveys signals
from the brain to neurons that directly control movement.

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Peripheral Nervous System

• Within a peripheral nerve are afferent and efferent
axons.
• Afferent axons carry information from peripheral
receptors toward the central nervous system.
• Efferent axons carry information away from the central
nervous system.
• Peripheral components of the somatic nervous system
include axons, sensory nerve endings, and glial cells.
• These components enable peripheral nerves to convey
information from sensory receptors into the central
nervous system, and to transmit signals from the central
nervous system to skeletal and smooth muscle and
glands.

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