2. Dr. Ashfaqur Rahman
MBBS, M.Phil (Anatomy)
Associate Professor and Head, Anatomy
Monno Medical College

3. INTRODUCTION
NEUROANATOMY: THE STUDY OF THE NERVOUS
SYSTEM.
2 body systems control all the functions of
the body-
1. Nervous system- which works very rapidly
2. Endocrine system- which works more or less slowly.
Nervous system is also called ‘master system of the
body’.

4. Functions of the nervous system:
1. Reception of sensory stimuli
2. Integration of sensory information
3. Coordination and control of motor activities
4. Assimilation and storage of experiences
5. Programming of basic instincts
Memory
Sensory stimuli Correlation Effectors

5. Classification of nervous system
Anatomically:
Functionally/physiologically:
Central nervous system (CNS)-Brain and
1. Somatic nervous system (SNS)
spinal cord
2. Autonomic nervous system (ANS)
Functions:
1. Integration, processing and
coordination of sensory data
2. Giving appropriate motor commands
3. The seat for higher functions
Peripheral nervous system (PNS)-
peripheral nerves and associated ganglia
Functions:
1. Provides sensory information to CNS
2. Carries motor commands of CNS to
the effectors

6. CELLULAR ORGANIZATION
The tissue forming the nervous system is called
nervous tissue, which is one of the 4 basic tissues of
the body. Essentially nervous tissue is a cellular type of
tissue, composed of 2 types of cells without ICM.
Composition:
1. Neurons/nerve cells-Excitable, non-dividing cell
2. Neuroglia/glial cells-Non-excitable, dividable cell
Neuroglia are 10 times more in number than neurons. Blood
vessels are also found within nervous tissue which provide
nutrition to the neurons and neuroglia.

7. Types of the nervous tissue:
White matter- The nervous tissue which appears white. It
Grey matter- The nervous tissue which appears Grey. It is is
white due to presence of myelin and less blood supply. It has
grey due to rich blood supply and absence of myelin. It has
less
rich blood supply because it does not cell bodies of the of
contains contain cell bodies
the neuron.
neuron.
Composition:
1. Cell bodies of neurons
Distal myelinated portion of axons
2. Dendrites and proximal/initial (non-myelinated) portion of
Supporting cells-neuroglia (fibrous
axons, sometimes whole axons (also non-myelinated)
astrocyte, intrafascicular oligodendrocyte, microglia)
3. Supporting cells-neuroglia (Protoplasmic
Blood vessels (few) (supplying the neuroglia present in
astrocyte, perineuronal oligodendrocyte, microglia)
the white matter)
Organization of(abundant) white matter-
4. Blood vessels
grey and
1. Primitive organization-inner grey matter, outer white
matter- e.g. Brain stem and spinal cord.
2. Modified organization-outer grey matter, inner white
matter- e.g. Cerebrum and cerebellum.

8. Neuron-Structural & functional unit of nervous system
Neuron doctrine: by Ramon y Cajal- 6 tenets in 1 sentence
Neuron is the anatomical, genetic, functional, polarized, pathologic and regenerative unit of nervous system.
2 parts of neuron-
1. Cell body/soma/perikaryon
2. Process/neurite
2 types of neurite-
1. Axon
2. Dendrite
Axon (& dendrite) is called nerve fiber.
Collection of neuron (cell body) inside CNS is called NUCLEUS.
Collection of neuron (cell body) outside CNS is called GANGLION.
Collection of nerve fiber inside CNS (specially within spinal cord) is
called TRACT.
Collection of nerve fiber outside CNS is called NERVE (PERIPHERAL
NERVE).

9. Classification of neurons:
According to polarity (number of neurites)/morphological
classification:
• Bipolar neurons- Functionally sensory neurons. E.g.
Multipolar neurons- Functionally motor neurons. E.g.
• Unipolar (pseudounipolar) neurons- Functionally sensory
neurons. hornNeuronsspinal cord, pyramidal cells of
Anterior E.g. cells of of olfactory cells, neurons cranial
Bipolar neurons of retina,DRG, neurons of sensoryof
ganglia, neuronsPurkinje cells and cochlear (spiral)
cerebral cortex, of ganglion) of cerebellar
vestibular (Scarpa’s mesencephalic nucleus of trigeminal
nerve. interneurons, neurons of autonomic ganglia.
cortex,
ganglion.
Most of the neurons of CNS are multipolar type.

10. Classification of neurons:
According to function:
Sensory/receptor neurons- E.g. Neurons of
Motor/effector neurons- E.g. Anterior horn cells of
Interneurons/internuncial/intercalated/central/assoc
spinalneurons of sensory cranial ganglia, neurons of cells
DRG, cord, pyramidal cells of cerebral cortex, Purkinje
iational/connectorneurons of autonomic ganglia.this type.
neurons. >99.9% neurons are of
mesencephalic nucleus of trigeminal nerve, bipolar neurons
of cerebellar cortex,
E.g. Column cells of spinal cord.
• retina, olfactory cells, neurons of vestibular
of UMN (Scarpa’s
• LMN
ganglion) and cochlear (spiral) ganglion.
• Preganglionic
• Post ganglionic
• Primary
• Secondary
• Tertiary

11. Classification of neurons:
According to length of neurites (axons)/according to size of neuron:
Golgi type I neurons- (microneurons)- E.g. Granule cells and
II neurons E.g. Anterior horn cells of spinal
stellate cells of cells of cerebral interneurons. They of
cord, pyramidalcerebellar cortex,cortex, Purkinje cellsact as
associational/interneurons.
cerebellar cortex. They act as relay neurons.

12. Classification of neurons:
Other types: neurons (cell bodies):
Locations of
Development of neurons:
1. Amacrine neurons of CNS
1. Within gray matter
1. CNS neurons- from neural tube
2. Microneuronsmatter of CNS as nuclei
2. Within white (7µM)
3. Paraneurons (apolar neurons) from neural crest and
2. Neurons of peripheral ganglia-
3. Within peripheral ganglia
ectodermal placodes
4. Within olfactory epithelium, retina

13. Structure of a neuron:
Cell body
• Nissle body
(substance/granules)/tigroid
or chromodial substance
• Neurofibrils
• Centrosome
• Axon hillock
Dendrites
• Dendritic spine/gemmules
Axon
• Parts
• Preaxon/initial segment
• Axon proper
• Axon terminale (terminal part)
• Telodendria
• Terminal boutons/synaptic
knob
• Axolemma
• Axoplasm
Endoneurium
Perineurium
Epineurium

14. Difference between axon and dendrite
Neurolemma/neurolemma sheath/sheath of Schwann
Schimidt-Lantermann incisura/fissure and segment

15. Nerve fibers
According to functions: are called nerve fibers.
Axons (and dendrites) of neurons
1. Motor (efferent) nerve fibers
Classification:
2. Sensory (afferent) nerve fibers
According to presence of myelin sheath:
1. Myelinated nerve fibers
2. Unmyelinated nerve fibers- unmyelinated peripheral
nerves are known as fibers of Remak
Periphery

16. Nerve fibers
Combined classification:
Fiber Sub CV Diameter Function Myelin
type type m/s m
A  70-120 12-20 Motor (extra-fugal fibers of skeletal +
muscle)
 40-70 5-12 Sensory (touch, pressure, vibration) +
 10-50 3-6 Motor (intra-fugal fibers of skeletal +
muscle)
 6-30 2-5 Sensory (temperature, pain-sharp & +
localized)
B 3-15 <3 Motor (preganglionic autonomic fiber) +
C 0.5-2.0 0.4-1.2 Motor (postganglionic autonomic fiber) _
Sensory (temperature, pain-diffuse &
deep)

17. Receptors (SENSORY)
Biological transducers responsible for reception of any
sensory stimulation and conversion of this stimulation into
nerve impulse to be carried by nerve fibers are called
receptors.
Receptors are sensory nerve endings specialized for
reception of stimuli and transforming them in the form of
nerve impulses (ref. Vishram Singh).

18. Classification:
• According to location-
 Exteroceptors (cutaneous receptors)-from superficial
structures like skin, superficial fascia
 Interoceptors-from viscera and blood vessels
 Proprioceptors-from muscle and joint
• Functional classification-
 Mechanoreceptors
 Thermoreceptors
 Nociceptors
 Chemoreceptors
 Electromagnatic receptors
• Anatomical classification-

19. Uncapsulated Free nerve ending Epidermis, cornea, gut, dermis, fascia, Pain, temperature,
receptors tendon, ligaments, touch (crude),
joint capsules, bone, periosteum, pressure
perichondrium, dental pulp, tympanic
membrane, muscle
Tactile discs of Thick (hairless) skin-epidermis Touch and pressure
Merkel/Merkel’s disc
Hair follicle Thin (hairy) skin-dermis Touch
receptor/Peritrichial
plexus
Encapsulated Meissner’s tactile Dermis of thick (hairless) skin, Touch (2 point TD)
receptors corpuscle external genitalia, nipple
Pacinian corpuscle Dermis, S/C tissue, joint capsules, Vibration and
ligaments, peritoneum, pleura, pressure
external genitalia, nipple
Ruffini’s corpuscle Dermis of thin (hairy) skin Stretch
End bulbs of Golgi- Genital skin
Mazzoni
End bulbs of Krause Mucocutaneous junctions, conjunctiva Temperature (cold)
Neuromuscular spindles Skeletal muscle Stretch-muscle
length
Golgi tendon organ Tendons Compression-muscle
length

20. Cutaneous receptors Joint receptors
Sensory modalities Type of receptors Free nerve endings
Ruffini’s corpuscles
Pain, touch and Free nerve endings
temperature Pacinian corpuscles
Merkel’s discs Golgi tendon organ
Peritrichial plexus
Pressure and vibration Meissner’s corpuscles
Pacinian corpuscles
Deep pressure Ruffini’s corpuscles

21. Neuroglia/Glial cells
• But the basic difference is tissue of nervous
They represent connectivethat neuroglia are
• Neuroglia (except cellular supporting element of
The non-excitable,microglia), like
capable of division by times more numerous than
system. They are 5-10 mitosis whereas neurons
neurons, develop from
NS is called neuroglia. neuroectoderm.
are not.
neurons.

22. Classification:
A. Neuroglia of CNS (central neuroglia):
Macroglia Microglia
Astrocyte Oligodendrocyte/ Ependymal cell
oligodendroglia
Resting microglia Gitter cell
Perineuronal Intrafascicular
/satellite
Fibrous Protoplasmic Ependymocyte Tanycyte Choroidal
Epithelial cell

24. B. Neuroglia of PNS (peripheral neuroglia):
(some authors regard supporting cells of PNS are not
neuroglia. They regard supporting cells of CNS as
neuroglia)-
• Schwann cell/neurolemmal cell/neurolemmocyte
• Capsular cell/satellite cell/perineuronal cell/ganglionic
gliocyte/amphicyte
• Others: Pituicyte, Bergman glial cell, Muller cell

25. • Perivascular feet, forms BBB
Astrocyte
Astrocyte
• Cell body and process contain intermediate
Outer glial limiting membrane, forms pia-glial
• Most numerous glial cell
membrane
filament, named GFAP (gliofibrils)
• Star shaped (stellate) body with numerous
• Source of development- Neuroectoderm (neural
Inner glial limiting membrane, forms ependyma-
radiating process
glial membrane
tube)
• Fibrous astrocyte- found in
white matter, each process is
long, slender, smooth, not much
branched. Number of filament
numerous.
• Protoplasmic astrocyte- found in
gray matter, each process is
shorter, thicker, more branched.
Number of filament fewer.

26. Functions of astrocytes
• Phagocytosis insulator by covering synapse
• Structural support-for nerve cell bodies and fibers
Form electrical
Absorb neurotransmitters and limit actions
Act asBBB
• Replacementfor + from migration of young nerve
gliosishelpof neurotransmitter cells
• Act asbarrier K spreadECF nutrition of nerve
• Formup trophicand for in for neurons
Store a excess
Take glycogen substances
Secrete scaffolding
cell during IUL

27. Blood brain barrier
The composite barrier that exist between blood in the
Composition:
Functions:
1. Nonfenestratedbrain brain circulating harmful
capillary endothelium and tight junctions
vessel and neurons of from is called blood brain
1. Protection of
between them.
barrier.
substances of blood.
2. Continuous basement membrane of capillary
2. Selective transport of substances from blood by
endothelium.
3. specialized foot processsystem. bodies) of astrocytes.
Perivascular transport (and cell

28. Blood brain barrier
The barrier is absent in:
Median eminence of hypothalamus
Posterior pituitary
Pineal body
Area postrema
OVLT
Intercolumnar tubercle
Subfornical organ
Choroid plexus

29. Oligodendrocyte (oligodendroglia)
Functions of oligodendrocyte
• Small cell body with few delicate process (hence
• Intrafascicular/perifascicular oligodendrocyte- Formation
oligodendro)
• and maintenance of myelin sheath (medullary sheath)
No intermediate and other filaments
• around nerve fibers in CNS
Location:
• Perineuronal satellite oligodendrocyte- Surround nerve
1. gray matter around nerve cell bodies as satellite cell
cell bodiesmatter in rows biochemical environment of
2. white and influence along myelinated nerve fiber
• neuron. of development- Neuroectoderm (neural tube)
Source

30. Microglia
• Smallest of all neuroglia
Functions of microglia
• They are part of MPS
• Normally body with wavy branching process
Small cell they are inactive- resting microglia that give off
• numerous spine-like projections condition- Gitter cell-
Enlarge and proliferate in disease
• Possessphagocytosis, act as scavenger cells of CNS, act as
help in amoeboid movement when activated.
• Location: gray and white matter
APC
• Source of development- macrophage (mesenchyme).
They migrate to CNS during fetal life.

31. Ependymal cell
• Source of development- Neuroectoderm (neural
tube).
• Have no basal lamina.
1. Ependymocyte- cuboidal or low columnar shaped
cell, with cilia and microvilli, line ventricles of
brain and central canal of spinal cord.
2. Tanycyte- line floor of the 3rd ventricle overlying
median eminence of hypothalamus, possess long
basal processes.
3. Choroidal epithelial cell- cover surfaces of choroid
plexus. Form blood-CSF barrier.

32. Functions of ependymal cell
1. Ependymocyte- Help in circulation of CSF by ciliary
beat. Absorb CSF by microvilli.
2. Tanycyte- Transport chemical substances from CSF
to hypophyseal portal system and play a part in
control of hormone production by anterior
pituitary.
3. Choroidal epithelial cell- Production and secretion
CSF from choroid plexus.

33. Blood CSF barrier
Composition:
The composite barrier that exist between blood in
1. Fenestrated capillary endothelium.
choroid capillary and CSF within ventricles of brain is
Functions: basement membrane of capillary
2. Continuous
called blood CSFbrain fromis a weaker barrier than
1. Protection of barrier. It circulating harmful
endothelium.
blood brain barrier.
3. substances of blood.
Pale cell layer.
4. Continuous basement of substances from blood by
2. Selective transport membrane of choroidal epithelial
cell.
specialized transport system
5. Choroidal epithelial cell and tight junctions (performing
actual barrier function) between them.

34. A
E
M
A
A
O
A

35. Schwann Cells (Neurolemmocytes)
Derived from the neural crest.
Found only in the PNS
Responsible for myelination in
PNS
One Schwann cell forms myelin
around a segment of one
axon, in contrast to the ability of
oligodendrocytes to branch and
sheath parts of more than one
axon.

36. Satellite Cells of Ganglia/Ganglionic Gliocytes
Derived from the neural
crest.
Form a covering layer
over the large neuronal
cell bodies in PNS ganglia.
The satellite cells exert a
trophic or supportive
role, but the molecular
basis of their support is
poorly understood.

37. Synapse
Classification of synapse- between two or more
Specialized areas of contacts
1.neurons. Now-a days neuromuscular junctions are
Chemical synapse
2.also called synapse
Electrical synapse.

38. Chemical synapse
•Synapse where transmission of impulse occurs
Structure cleft (neuropil area)
Synaptic of chemical
20nm
through chemical substances called
synapse-
•neurotransmitters.
Synaptic delay (0.5msec)
• Presynaptic neuron
• Enzymes
• Presynaptic
• Neurotransmitters- knob
(synaptic/terminal)
excitatory/inhibitory feet)
(bouton terminale/end
•
• Receptors- (transmitter)
Presynaptic
excitatory/inhibitory
vesicle (synaptosome)
•
• Parts of a receptor protein-
Presynaptic
• binding presynaptic
membrane,component
• ionophore component
density, release site, voltage
gated Ca ++ channel
• 2 types-
• Postsynaptic
1. ion channel- cation
membrane, postsynaptic
channel/anion channel
density (synaptic or activator
2. 2nd messenger
• subsynaptic web)
EPSP/IPSP

39. Types-
According to
Structurally and
synapsing
functionally-
structures-
1. Asymmetrical/type
1. Axodendritic- 80-
1/excitatory synapse
95%
2. Symmetrical/type
2. Axosomatic- 5-20%
3. 2/inhibitory synapse
Axoaxonic
4. Dendrodendritic
5. Somatodendritic
6. Somatosomatic

40. Neurotransmitters/Neuromediators
Chemical substances secreted by presynaptic neuron at synaptic cleft of chemical
synapse which transmit nerve impulse to the post synaptic neuron.
Classification-
• Principal
1. Small molecule, rapidly acting transmitters
 Class I
 Acetylcholine- Both excitatory and
inhibitory
neurotransmitters
 Class II: The Amines  Acetylcholine (nicotinic)
 Norepinephrine- Both excitatory and
inhibitory  Glutamate
 Epinephrine- Both excitatory and
inhibitory  GABA
 Dopamine- Both excitatory and
inhibitory • Neuromodulators
 Histamine
 Serotonin- Inhibitory  Acetylcholine
 Class III: Amino acids
(muscarinic)
 GABA- Inhibitory
 Glycine- Inhibitory  Serotonin
 Glutamate- Excitatory
 Aspartate- Excitatory  Histamine


Class IV
NO
 Adenosine
2. Large molecule, slowly acting transmitters  Neuropeptides
(Neuropeptides)

41. Structure:
Ganglion in shape
• Ovoid
Collection of (cell bodies of) neuron outside CNS is
• Contain collection of cell bodies of neurons-
called ganglion. or bipolar in case of sensory
(pseudo)unipolar
ganglion, multipolar in case of motor ganglion.
• Each cell body is covered by a layer of capsular/satellite
cells.
• Each ganglion is covered by a connective tissue
capsule.
Structure of autonomic ganglion
Connective tissue capsule
Cell bodies of post ganglionic neurons
Interneurons – SIF cells
Satellite/capsular cells
Nerve fibers-Pre- and postganglionic fibers
and fibers traversing the ganglion without synapse

42. Classification
Motor ganglion (Autonomic ganglion)
Sensory ganglion (Somatic ganglion)
Parasympathetic ganglion
•Motor ganglion (Autonomic ganglion)
• Cranial ganglion (cranial parasympathetic
Collateral ganglia
• ganglia)
Sympathetic ganglion of C5
Trigeminal ganglion
• ••Lateral (paravertebral) ganglia- Ganglionated
Geniculate ganglion of C7
Ciliary ganglion
••sympatheticand spiral ganglion of C8
Vestibular trunk ganglion
Pterygopalatine
• ••Subsidiary and inferior ganglion of C9
Superior ganglia ganglion
Submandibular
•• Superior and inferior ganglion of C10
Otic ganglion
Collateral (prevertebral) ganglia
•• Spinal Superior mesenteric or within wall of
• ganglion
Terminal ganglia- close to ganglion
• Inferior mesenteric
• viscera root ganglion ganglion
Dorsal
• Aorticorenal ganglion (renal)
Ganglia of cardiac plexus
• Superiorof pulmonaryganglion
Ganglia hypogastric plexus
• •Terminal ganglia- Adrenal medulla
Ganglia of myenteric plexus
• Ganglia of submucosal plexus
• Inferior hypogastric ganglion

43. Myelination
CNS-By Oligodendrocyte
Of spinal cord-at 4th month of IUL, sensory fibers first
Of brain-at 6th month of IUL, motor fibers first
PNS-By Schwann cell

46. Structure of a myelinated nerve fiber
Of CNS-
Axon
Myelin sheath
Of PNS-
Axon
Myelin sheath
Neurilemma
Basement membrane
Endoneurium