A Alraddadi, BPT, MSc, PhD

Assistant Professor of Human Anatomy

BMS-COM
King Saud bin Abdulaziz for Health Sciences

Introduction to Neuroanatomy

Dr. ABDULRAHMAN ALRADDAI

Office N: 1.CM.2.311
Email: raddadia@ksau-hs.edu.sa
Office Ext: 95280

1
 Lecture Objectives
Relevant weekly objectives
• Outline the anatomy of the nervous system.
• Explain the importance of spinal cord.
Lecture Objectives
By the end of the session the student will be able to:
• Describe neural cells; features that distinguish neurons (main parts) and
glia (astrocytes, oligodendrocytes, microglia).
• Describe the neural life support systems including: organisation of blood
supply, function of cerebrospinal fluid and blood brain barrier.
• Describe the aspects of basic organisation of central nervous system:
different functions (co-operation), sex differences, brain vs computer,
brain use, issues of laterality of projection.
• Describe the importance of spinal cord.
 Lecture Outline

1. Introduction to Nervous System

2. Nervous Tissue
3. Central Nervous System (CNS)
4. Cerebro-spinal Fluid & Vascular Supply to the
Brain
 1st
Introduction to Nervous System
 NERVOUS SYSTEM
• The nervous system, along with the
endocrine system, controls the
functions of the body within limits
that maintain health and helps to
maintain homeostasis
• It is responsible for all our
behaviors, memories, and
movements.
• The branch of medical science that
deals with the normal functioning
and disorders of the nervous
system is called neurology.
 Functions of the Nervous Systems
The nervous system functions can be classified into:
1. Sensory function:
– Sense changes in the internal and external environment through
sensory receptors
– Sensory (afferent) neurons serve this function
2. Integrative function:
– Analyze the sensory information, store some aspects, and make
decisions regarding appropriate behaviors
– Association or interneurons serve this function
3. Motor function:
– Respond to stimuli by initiating action
– Motor(efferent) neurons serve this function
 Major Divisions of Nervous System

Correlate & integrate of Conduct information

nervous information to and from the CNS

12 Pairs of Cranial
Nerves

31 Pairs of spinal
nerves and their
CNS PNS branches:

8 Cervical
12 Thoracic
5 Lumbar
5 Sacral
1 Coccygeal

Anatomically Divisions: CNS & PNS Functionally Divisions: Autonomic & Somatic
 Subdivisions of the PNS

I. Somatic (voluntary) nervous system (SNS):

– Sensory nerves from skin, bones & joints
– Motor nerves to skeletal (striated) muscle (including the diaphragm)
– Voluntary (NB reflexes)

II. Autonomic (involuntary) nervous systems:

– Sensory nerves from visceral organs to CNS
– Motor neurons to smooth & cardiac muscle and glands
• sympathetic division (speeds up heart rate)
• parasympathetic division (slow down heart rate)
– Involuntary (we don’t have to think about controlling our heart rate – it just
happens!)
 2nd
Nervous Tissue
 Nervous Tissue

• Relatively little intercellular space

• Cells rest on a continuous basal lamina
• Some cells have microvilli, cilia
• Strong tendency for cells to be bound to one another
• Clasping structures between connected cells called synapses
• Principle cells in the CNS: Neurons & Neuroglial Cells
 Neurons

• Functional unit of nervous system

“Great Communicators”
• Have capacity to produce action
potentials
• They receive information, chiefly
via synapses, integrate the
information, and then transmit
electrical impulses to another
neuron or effector cell
• Most are multipolar with many
dendrites and one axon

Cortical Neurons
 Neurons

Dendrites
• Cell body characterized by:
– Single nucleus +
prominent nucleolus
– Nissl bodies Cell Body
or Soma
Axon Hillock

(Chromatopilic
substance) Axon

– Cell processes: dendrites

and axons Nucleus and
Nucleolus
Neurons
Axon
• Conduct impulses away from cell
body
• Long, thin cylindrical process of
cell
• Arises at axon hillock
• Impulses arise from initial
segment (trigger zone)
• End in fine processes called axon
terminals
• Synaptic end bulbs contain
vesicles filled with
neurotransmitters
Neurons

Structural Classification of Neurons

Based on number of processes found

on cell body
I. Multipolar:
• Several dendrites & one axon
• Most common cell type
II. Bipolar neurons:
• One main dendrite & one axon
• Found in retina, inner ear &
olfactory
III. Pseudo-unipolar neurons:
• One process only(develops from a
bipolar
• Always sensory neurons
Neurons
Functional Classification of Neurons
a. Sensory (Afferent) Neurons:
Transport sensory information
from skin, muscles, joints, sense
organs and viscera to CNS
b. Motor (Efferent) Neurons:
Send motor nerve impulses to
muscles and glands
c. Interneurons (Association)
Neurons:
Connect sensory to motor
neurons
90% of neurons in the body
Examples of Different Types of Neurons
 Neuroglial Cells
• Glial cells (means ‘glue’ in Greek)
• Ten times more numerous in the
CNS than neurons.
• Smaller cells than neurons
• Cells can divided
4 Cell types in CNS:
1. Astrocytes
2. Oligodendrocytes
3. Microglia
4. Ependymal
2 cell types in PNS:
1. Schwann
2. Satellite cells
Neuroglial Cells
Astrocytes

• Star-shaped cells with many

processes
• 2 types:
Fibrous: long process; in
white matter
Protoplasmic: short
branched process, in gray
End foot
matter Cap
• Roles in support,
maintaining the blood-brain
barrier, environmental Astrocytes labelled immunohistochemically with
homeostasis antibodies against the intermediate filament protein
glial fibrillary acidic protein (GFAP)
• No connective tissue in the
CNS
Neuroglial Cells
Oligodendrocytes

• Most common glial cell type

• Produce myelin in the CNS
(NOT IN THE PNS)
• Have numerous branches
that extend to forms myelin
sheath around more than
one axons

Oligodendrocyte filled with fluorescent dye

Neuroglial Cells
Microglia

• Small cells found near blood

vessels
• Similar lineage to
macrophages (i.e.
hemopoietic origin)
• Phagocytic role; clear away
dead cells (Immune
monitoring and antigen
presentation) Microglia stained immunohistochemically for MHC
class II
Neuroglial Cells
Ependymal cells

Form epithelial-like membrane lining cerebral cavities and central canal

3 cell types:
a. Ependymocytes
– Cuboidal/columnar cells with cilia and microvilli
– Line ventricles and central canal
– Circulate and absorb CSF
b. Tancytes
– Long basal processes with end feet on capillaries
– Line the 3rd ventricle
– Monitor hormone levels in CSF
c. Choroidal epithelial cells
– Side and basis thrown into folds, tight junctions
– Cover surface of choroid plexuses
– Produce and secrete CSF
Neuroglial Cells
Ependymal cells

Ventricle Filled with CSF

Cilia

Ependymal cells

Ependymal cells line the central canal of the spinal

Ependymal cells line the ventricles in the CNS cord
Neuroglial Cells
Tancytes
Neuroglial Cells
Choroid Plexus

Pial Layer

Choroid epithelium with Blood vessel

tight junctions (Blood-CSF
Barrier)
Neuroglial Cells
Schwann Cell

• Cells encircling PNS axons

• Each cell produces part of the myelin sheath surrounding an axon in the PNS
• Myelin sheath:
– a multilayered of lipid and protein
– It electrically insulates the axon and increases the speed of nerve impulse
conduction
Schwann cell

Axons

Electron micrograph of a small peripheral nerve

Neuroglial Cells
Satellite Cells

• Flat cells surrounding neuronal cell bodies in peripheral ganglia

• Support neurons in the PNS ganglia

Sensory
neurons

Satellite
cells

Myelinated
Axons

Dorsal Root Ganglion

Neuroglial Cells

Blood-Brain Barrier (BBB)

• Protects cells from some toxins
and pathogens
• proteins & antibiotics can not pass
• Only small blood molecules like
oxygen, CO2 or ethanol, can
diffuse freely across capillaries
within the brain
• Structure:
- Astrocyte processes covering
capillaries
- continuous basement
membrane
- The astrocyte endfeet induce
the capillary endothelium to
form tight junctions
 3rd
Central Nervous System (CNS)
CNS
Regions of the Brain
a. Forebrain
1. Cerebrum
2. Diencephalon (Thalamus,
Hypothalamus)
b. Midbrain
c. Hindbrain
1. Cerebellum
T
2. Pons H
3. Medulla Oblongata

Brainstem:
Midbrain
Pons
Medulla
CNS
Brain Planes
Superior

Anterior
Posterior

Inferior
Lateral view of left side of brain

Horizontal Plane
 Coronal
Plane

Sagittal Plane
CNS
Gray & White Matter

Grey Matter White Matter

• From inside, the brain and spinal
cord divided into: Grey and white
matter
• Grey matter:
– Huge numbers of
unmyelinated neurons, cell

Anterior

Posterior
processes, synapses and
neuriglia (support cells)
– Forms outer layer of
cerebrum (cerebral cortex),
and Basal Ganglia nuclei deep
in brain
– Forms the internal centre (H- Gyrus (plural gyri)
shaped) of spinal cord
Sulcus (plural sulci)

Horizontal Slice Through The Brain and Cerebellum

CNS
Gray & White Matter

White Matter:
• Axons (most myelinated) of Gray matter White matter

neurons and their support cells Anterior

• Forms internal layer of cerebrum

and outer layer of spinal cord
• Cell bodies in the gray mater
• Axons form white matter tracts
In the brain: 3 types of tracts
(commissural, association, projection)
Posterior
In the spinal cord: 2 types of tracts:
sensory and motor tracts (ascending Horizontal section of the spinal cord
and descending)
Forebrain
Cerebrum

Longitudinal
• Cerebrum: largest portion of fissure
the brain
• 2 Cerebral hemispheres (Rt &
Precentral gyrus
Lf) by the longitudinal fissure Central sulcus
Precentral gyrus
• The cerebral cortex is folded
into ridges (gyrus) and grooves
(sulcus)
• Many gyri and sulci have
specific names and function

Brain (superior aspect). Right hemisphere with

arachnoid and pia mater
Forebrain
Cerebrum

Names of major, sulcus, gyri and regions

Forebrain
Lobes of the Cerebral Hemispheres

Central sulcus

Parieto-occipital sulcus

Preoccipital notch
Lateral sulcus
Forebrain
Lobes of the Cerebral Hemispheres

The insula lobe

It is normally hidden. To see it, cut away the temporal, frontal and
parietal opercula, shown in the box, that overhang the insula.

Short gyrus of insula Long gyrus of insula

Forebrain
Functional Areas of the Cerebral
Cortex
Forebrain

Somatotopic Organization of Cortex

(Homunculus)
Forebrain
Cerebral Dominance
Forebrain

Cerebral White Matter Tracts

1: Association Fibres
Within a hemisphere
Includes: short association fibres,
cingulum, superior longitudinal
fasciculus, inferior longitudinal
fasciculus
2: Commissural Fibres
Between hemispheres
Includes: corpus Callosum, anterior
commissure
3: Projection Fibres
Entering or leaving the cerebrum
Includes: internal capsule
Forebrain

Gray Matter Nuclei

(Basal Ganglia)

Modifies motor commands that

have originated from the cerebral
cortex
1. Caudate nucleus
Posture & limb movement
2. Putamen
Body movements
3. Globus pallidus
Muscle tone
4. Substantia Nigra
Eye movements
Forebrain
Diencephalon
At the center corn of the brain with
symmetrical right and left halves surrounding
the 3rd ventricles
4 major parts:
a. Thalamus
Major station for all the main sensory systems
(except the olfactory pathway)
b. Subthalamus
Involve in the control of muscle activity
c. Epithalamus
1. Habenular Nucleus:
Integration of olfactory, visceral, and somatic
afferent pathways
2. Pineal Gland:
Set the circadian rhythms of the body (awake-
sleep period)
d. Hypothalamus
Regulate body temperature, body fluids, drives
to eat and drink, sexual behavior, and emotion
Forebrain
The Limbic System

• “The emotional brain”

• Linking olfaction and memory
to basic emotional behaviors
• Main components:
1. Limbic lobe: includes the
hippocampus, the cingulate
gyrus, the insula and the dentate
gyrus
2. Amygdala: responsible for the perception of emotions such as anger, fear, and
sadness, as well as the controlling of aggression.
3. Olfactory bulbs: receives neural input about odours detected by cells in the nasal
cavity.
4. Mammillary bodies
5. Fornix
6. Hypothalamic Nuclei
 Midbrain
• Connects the forebrain to the
hindbrain
• Relay station between the cerebrum
and the spinal cord, and between the
cerebrum and cerebellum
• Cerebral aqueduct: connects 3rd and
4th ventricles
• Cerebellar peduncles: clusters of motor &
sensory white mater tracts between
cerebrum and cerbellum
• Substantia nigra: helps controls
subconscious muscle activity
• Red nucleus: rich blood supply & iron-
containing pigment
• Corpora Quadrigemina: Superior and
Inferior Colliculi
Reflex centers for eye movement, head
and neck movement (protection), pupil
size and eye tracking
Hindbrain
Pons

• 1 inch long; known as “bridge”

• Connects cerebrum to cerebellum
• Consists of multiple nuclei and
tracts
• Nuclei control both somatic
(voluntary) and visceral
(involuntary) motor responses
• Pneumotaxic & apneustic areas
help control breathing
• Middle cerebellar peduncles carry
sensory info to the cerebellum
• Cranial nerves 5 thru 7
Hindbrain
Cerebellum

• 2 hemispheres (connected by Vermis)

• 2 lobes (Anterior and Posterior Lobes)
• Has a superficial layer of gray matter
“cerebellar cortex”
• The deep layer consists of white matter
tracts and gray matter nuclei (the dentate
nucleus)
• 3 Cerebellar Peduncles:
– Superior to midbrain
– Middle to pons
– Inferior to medulla
• Evaluates and coordinates involuntary and
voluntary motor activities
• Regulates posture and balance
• Uses sensory data and stored memories
(muscle memory)
Hindbrain
Medulla Oblongata

• The most inferior part of the brain

stem
• Made up of white matter tracts
(ascending & descending) and
gray matter nuclei
• Information in & out of
cerebellum
• Gray matter nuclei:
- Regulate autonomic functions
- Reflex centers for regulating heartbeat
and blood pressure (cardiovascular
center), respiration (respiratory
center), vomiting, coughing, sneezing,
hiccupping, and swallowing
- Associated with 5 pairs of cranial
nerves (VIII, IX, X, XI, XII)
 Spinal Cord
• Length in adults = 16 to 18 inches
• 31 pairs of spinal nerves
• Provides innervation of trunk and limbs via
spinal nerves and peripheral branches
• Receives primary afferent fibres from
peripheral receptors in widespread somatic
and visceral structures
• Sends motor axons to skeletal muscle
• Houses preganglionic neurons of sympathetic
nervous system
• Houses some preganglionic neurons of
parasympathetic nervous system
 4th

Cerebro-spinal Fluid
Vascular Supply to the Brain
 Cerebro-spinal Fluid

• Clear liquid containing glucose,

proteins, & ions
• Volume ~120ml, 400-500ml/day
• Circulates around the brain &
spinal cord from the 4 ventricles to
the subarachnoid space
• Reabsorbed into the dural venous
sinuses by specialised structures:
“Arachnoid Granulations/Villi”
 Cerebro-spinal Fluid
• Secreted by specialised cells within
the ventricular system of the brain:
“Choroid Plexus (ependymal cells)”
• Functions:
– Mechanical Protection: floats
brain & softens impact with bony
walls
– Chemical Protection: optimal
ionic concentrations for action
potentials
– Circulation: nutrients and waste
products to and from
bloodstream
 Blood Supply to the Brain
Internal carotid artery + Vertebral artery
1. Internal carotid artery branches:
Anterior cerebral artery, middle cerebral artery,
posterior communication artery

2. Vertebral artery branches:

Posterior cerebral artery, superior cerebellar artery,
basilar artery, anterior inferior cerebellar artery,
posterior cerebellar artery, anterior spinal artery and
posterior spinal arteries

Circle of Willis:
Communication between 1 & 2 branches.

Include: anterior cerebral artery, anterior

communication artery, middle cerebral artery, posterior
communication artery and posterior cerebral artery
 Territories of the Major Cerebral
Arteries
Anterior cerebral artery
• Most of the anterior cranial fossa
• Laterally: most of the superior surface of
frontal and parietal lopes
• Medially: most of the medial side of the
frontal and parietal lopes
Middle cerebral artery
Lateral
• Most of the middle cranial fossa
• Laterally: most of the lateral side of the
frontal and parietal lopes and upper half of
the temporal lope
• Medially: only anterior 1/3 of the temporal
lope
Posterior cerebral artery
• Most of the posterior cranial fossa.
• Laterally: lower half of the temporal lope.
• Medially: the posterior 2/3 of the temporal
lope and the occipital lope
Medial
 Venous Drainage of the Brain
• The major venous drainage of the
brain is jugular vine
• Jugular vine receives blood from the
dura venous sinuses
• Major dura sinuses are: superior
sagittal sinus, straight sinus, and
occipital sinus drain blood to
confluence sinuses and then pass it to
transverse sinus then to sigmoid sinus
• Sigmoid sinus unites with inferior
petrosal sinus to form jugular vine
• Cavernous sinus at the core of the
brain is received blood from different
areas of the brain and is drained by
superior and inferior petrosal sinus
 Sex Differences in the Brain
Factor Males (M) Females F) Functional Effect
Brain Size M > F (10% larger) no functional effect

Cerebral Use LF hemisphere for use both hemispheres

Hemisphere verbal processing and RT for spatial and verbal
higher verbal ability in F
hemisphere for spatial processing
processing
Corpus Have greater intra- Have greater inter-
M = see individual issues
Callosum hemispheric connectivity hemispheric F = link everything together
connectivity
Lobes Have larger inferior parietal Have higher frontal & M = Higher mental mathematical abilities,
lobe temporal lobe volume understanding and manipulating spatial
perception of time and speed, and the ability
(Broaca’s and
to mentally rotate 3-d figures
Wetnicka’s areas) F = More attuned to words and sounds and are
normally better at learning languages
Gray & White M use more gray mater (7X) use more white matter W brain transfers data faster and attentive to
Matter (10X) multiple activities

F have larger hippocampus, deeper limbic system,

W are more emotional
dominant left ventromedial prefrontal cortex than M
Hippocampus,
Activate RT amygdala when activate left amygdala W feel more pain since the left amygdala more
Amyglada and associated with internal functions
experience pain when experience pain
Limbic System
have RT hippocampus have LF hippocampus W have more long term memory and recall
dominant dominant power
Brain Vs Computer
Thank You for Your Attention
 References
• Ricard S. Snell. Clinical Neuroanatomy for Medical
Students. 5th ed. 2001
• Kiernan, JA. Barr’s The Human Nervous System: An
Anatomical Viewpoint. 9th ed. 2009
• Keith L. Moore. Clinically Oriented Anatomy. 6th
ed.2010