3. Subdivision of the nervous system
Anatomical subdivision:
1. Central nervous system(CNS)
brain and spinal cord
Integration, processing and coordination of
sensory data and motor commands
Higher functions
2. Peripheral nervous system (PNS)
a. Cerebrospinal nervous system
12 pairs of cranial nerves
31 pairs of spinal nerves
b. Autonomic nervous system
7. Neuron
“Excitable” cells
Structural & functional unit
of the nervous system.
100 billion
Properties : excitability &
conductivity
Highly differentiated cell &
lost their power of division
EXCEPT olfactory
10. Classification of Neuron
1. According to numbers of
processes:
Unipolar neuron :
mesencephalic nucleus
Pseudounipolar neurons :
sensory & spinal ganglia
Bipolar neuron :
vestibulocochlear ganglia,
bipolar neuron of retina
Multipolar neuron : neurons in
cerebrum & cerebellum
11. 2. According to relative length of axons &
dendrites
• Golgi type I neuron : long axon
• Golgi type II neuron : short axon or
no axon
12. 3. Functional Classification
1. Sensory (Afferent)
1. Somatic
2. Visceral
2. Motor (Efferent)
A. .
1) Somatic
2) Visceral
B. .
1. Upper motor
2. Lower motor
C. .
1. Preganglionic
2. Postganglionic
3) Interneurons
13. 4. According to shape of the cell body
• Pyramidal cell
• Pyriform cell
14. Interesting facts
LONGEST NEURON :
sensory neurons of S1 (1st sacral spinal nerve )
NEURON WITH MANY NEUTRITES BUT NO AXON
Amacrine Neurones Of Retina
NEURON WITH NO PROCESS
Para Neurons Of Adrenal Medulla
15. Neuron Organization
Divergence - One neuron synapses with several,
effectively "spreading the word".
Convergence - Several neurons synapse with a
single neuron, concentrating the input.
Serial processing - step-wise, sequential
Parallel processing - simultaneous processing of
different information
16. Neuroglia (Glue)
Structural & functional
support to the neuron.
5-10 times more than
neuron
All the neuroglia
develop from
neuroectoderm except
microglia (mesoderm)
17. Classification of neuroglia
Neuroglia in CNS
1. Astrocytes
2. Oligodendrocyte
3. Ependymal cells
4. Microglia
Neuroglia in PNS
1. Schwann cell or Neurolemmocytes
2. Satellite cells
Macroglia
18. Astrocytes: largest & most numerous
• Blood –brain barrier (BBB)
• Structural framework & repairs
• Regulation of ions, and nutrients,
to maintain metabolic
environment for the neuron
• Protoplasmic astrocyte
• Fibrous astrocyte
19. Blood Brain Barrier
Barrier
Endothelium of Capillary
Basement Membrane
Foot process of Astrocyte
Areas in brain don’t have
BBB
portion of hypothalamus
pineal gland
Pituitary
Area Postrema
choroid plexus
29. Functions of neuroglia
Structural & functional support to the neuron.
Blood- brain barrier.
Phagocytosis
Formation of myelin sheath.
Produce CSF.
30. Some Terminology
Collections of cell bodies –
ganglion in PNS
nucleus in CNS
Pseudoganglion
Bundles of axons –
tracts in CNS
nerves in PNS
“White matter” = myelinated axons, both nerves and tracts
“Gray matter” = non-myelinated material, dendrites, synapses
and cell bodies as well as nonmyelinated axons
31. Ganglion
Collections of nerve cell bodies
outside the CNS is called ganglion
1.cerebrospinal ganglia
2. autonomic ganglia
• sympathetic ganglia lie away from viscera they
supply
• Parasympathetic ganglia lie near the viscera
they supply
34. Subdivisions of Brain
1. Brain Stem
a. Midbrain
b. Pons
c. Medulla oblongata
2. Cerebellum
3. Diencephalon
Thalamus and
Hypothalamus
4. Cerebral Hemispheres
35. • Resides inside vertebral canal
• Extends to L1
• 31 segments, each associated
with a pair of dorsal root
ganglia
• Two enlargements
• Cervical and Lumbar
• Conus medullaris
• Cauda Equina
• Filum Terminale
Spinal cord:
37. Organization of Spinal Cord
Gray matter - interior horns
posterior - somatic and visceral sensory nuclei
anterior (and lateral) gray horns – somatic and visceral motor control
gray commissures - axons carrying information from side to side
White matter - tracts or columns
posterior white column -
anterior white column
lateral white column
anterior white commissure
functions
ascending tracts - sensory toward brain
descending tracts - motor from brain
39. Lumbar Puncture
(= Spinal Tap)
For clinical examination of CSF or
administration of radiopaque dyes,
drugs and anesthetics
However: mostly “epidurals” for
anesthetics
L3
S1
40. Reflexes
Fast, preprogrammed, inborn,
automatic responses
Occur in the CNS at the spinal
cord or brainstem levels
(cranial nerves)
May be either monosynaptic or
polysynaptic
All require
a. stimulus at receptor
b. sensory information relay
c. processing at CNS level
d. activation of motor
response
e. response of peripheral
effector
46. Blood & Nerve Supply
Vasa nervorum
Vessels of Nerve
Nervi nervorum
Nerve of Nerve
47. Classification of peripheral nerves
Cranial nerves :
Spinal nerves:
Splanchnic nerve
Sensory nerves
Motor nerves
Mixed nerves
48. Cranial nerves
12 cranial nerves
2 attach to forebrain (Tel- &
Diencephalon)
10 attach to brainstem
(Mes-, Met- and Myelencephalon)
“0” pair cranial nerve
“nervi terminalis”
Motor :3,4,6,11,12
Sensory : 1,2,8
Mixed : 5,7,9,10
49. 1. Olfactory
2. Optic
3. Occulomotor
4. Trochlear
5. Trigeminal
6. Abducent
7. Facial
8. Vestibulocochlear
9. Glossopharyngeal
10.Vagus
11.Accesary
12.Hypoglossal
Oh, Once One
Takes The
Anatomy Final,
Very Good
Vacations
Appear
Heavenly
50. Olfactory Nerve (= CN or N I)
C: Sensory
O: Olfactory Epithelium in nasal cavity
D: Olfactory bulbs (by way of cribriform plate of
ethmoid)
Only CN directly attached to Cerebrum
51. Optic Nerve (N II)
C: Sensory
O: Retina
D: by way of optic
foramen of
sphenoid to
Diencephalon
(optic chiasma)
and to occipital
lobe
52. Oculomotor (N III)
C: Motor
O: Mesencephalon
D: Somatic motor to
superior, inferior,
medial recti and
inferior oblique;
visceral motor to
intrinsic eye muscles
by way of superior
orbital fissure
SO4, LR6, Rest are by 3
53. Trochlear (N IV)
C: Motor
O: Mesencephalon
D: superior oblique muscle
by way of superior
orbital fissure
54. Trigeminal (CN V)
C: Mixed
three major branches
1. Ophthalmic (sensory)
2. Maxillary (sensory)
3. Mandibular (mixed)
O: face / nuclei of pons
D: sensory nuclei in pons /
muscles of mastication
56. Facial (CN VII)
C: Mixed
O: sensory from taste receptors
of anterior 2/3 of tongue /
motor from pons
D: Sensory to sensory nuclei of
pons / motor muscles of facial
expression, visceral motor to
tear gland.
Bell’s Palsy
58. Glossopharyngeal (CN IX)
C: mixed
O: sensory from posterior
1/3 of tongue / motor from
medulla oblongata
D: medulla / muscles for
swallowing, parotid gland
Stylopharyngeus
59. Vagus (CN X)
C: Mixed
O: Sensation from pharyngeal area and outer
ear / motor from medulla
D: Sensory to medulla / visceral (autonomic)
motor to thoracic and abdominal cavities
and their organs. Major motor pathway for
ANS
Most important Cranial Nerve!
61. Accessory (CN XI) Spinal Accessory
C: Motor
O: Motor nuclei of medulla and
spinal cord
D: Swallowing, trapezius &
sternocleidomastoid muscles
Hypoglossal (N XII)
C: Motor
O: Motor nuclei of medulla
D: Tongue musculature
64. Organization of Spinal Nerves:
1. Root – inside vertebral canal
a. dorsal sensory root with a ganglion
b. ventral motor root
2. Mixed spinal nerve
3. Rami
a. dorsal - mixed to skin and muscles of back
b. ventral - mixed “spinal nerve” to ventrolateral body surfaces
and limbs
c. white ramus communicans motor ANS
d. gray ramus communicans motor ANS
68. Principal Plexuses
A blend, or network, of nerve
fibers from several spinal
roots.
• Cervical plexus
• Brachial plexus
• Lumbar plexus
• Sacral plexus
74. Nerves of the Lower limb
• Sciatic N.
•Thickest and Longest
•Branches to Tibial and
Fibular Nerves
• Femoral N.
•Front of Thigh
• Obturator Nerve
•Medial side of thigh
75. Synapse
Site of communication
between two nerve cells or
nerve cell and effector cell
Presynaptic and
postsynaptic neurons
neuro-effector junctions,
e.g., Motor End Plate
Electrical vs.
chemical synapses
77. Chemical Synapse vs. Electrical Synapse
Space between two cells
Signal transduction via a
neurotransmitter, usually
ACh
Most common
Direct physical contact between cells =
gap junctions
Direct signal transduction
Rare, but occurs in CNS and HEART
78. Chem.
Synapse
Structure
1. Axon terminal of presynaptic cell, with vesicles of
neurotransmitter(NT)
2. Synaptic cleft
3. Dendrite or cell body of postsynaptic cell
4. Unidirectional
80. Conduction of action potential
The “signal,” or Action
Potential is carried along
the Neurilemma Sheath
Faster if axon is
myelinated
83. Overview of ANS
Pathway for Visceral Motor Output
The somatic NS uses one effector nerve but the
ANS output always involves two neurons
between spinal cord (CNS) and effector.
84. Overview of ANS
ANS has two divisions with both structural
AND functional differences:
1. Parasympathetic – Rest and Repose
1. Craniosacral output
2. Digestion, “housekeeping”
3. Postganglionic axons release Ach
(Cholinergic)
2. Sympathetic- Fight or Flight
1. Thoracolumbar output
2. Heart Rate, Respiration
3. Vasoconstriction
4. Postganglionic axons release NE
(Adrenergic)
85. •Craniosacral division
Preganglionic neurons (cell bodies)
located in brain stem & sacral segments
of spinal cord.
Cranial Nerves III, VII, IX, X
Pupils (III), Lacrimal and Salivary Glands
(VII), Viscera (X)
Sacral segments S2-4
Bladder, Genitals
1. Parasympathetic
Division
87. Constriction of Pupils (opposite
sympathetic)
Secretion of Digestive Glands
Secretion of Digestive Hormones
Insulin, etc.
Visceral Smooth Muscles
Defecation and Urination
Constriction of Respiratory System
Decrease Heart Rate
Sexual Arousal
Parasympathetic
Division
Some functions:
88. 2. Sympathetic
Division
Thoracolumbar division
Preganglionic neurons (cell bodies) located
between T1 & L2 of spinal cord
Ganglionic neurons (cell bodies) in ganglia
near vertebral column, AKA “Chain
Ganglia.”
Paravertebral ganglia = sympathetic chain
ganglia
Prevertebral ganglia = collateral ganglia
Special case: adrenal medulla is a modified
ganglion
92. Special Case:
Adrenal Medulla
Fig. 17-6
“Modified sympathetic ganglion”
Terminus for neuron #1, stimulates
specialized 2nd order neurons with
very short axons in adrenal medulla
to release NT into blood stream (=
hormones)
Epinephrine (adrenaline) ~ 80% and
norepinephrine (noradrenaline)
Endocrine effects are longer lasting
than nervous system effects
93. Dual Innervation
Each organ receives
innervation from
sympathetic and
parasympathetic fibers
Fibers of both divisions meet
& commingle at plexuses
(fig 17-9) to innervate
organs close to those
centers
Names of plexuses derived
from locations or organs
involved
95. Sympathetic
Thoraco-lumbar [ T1 – L2]
Preganglionic fibre – Short
Postganglionic Fibre - Long
Nerve ending - Adrenergic
Fight or Flight
Works for Today
Sphincter - Closed
Nerve of emergency
Parasympathetic
Cranio-sacral
[III, VII, IX, X, S2,S3, S4]
Long
Short
Cholinergic
Rest & Digest
Works for tomorrow
Relax
Nerve of tranquility