2. SOME TO KNOW…..
• The activities of nervous system are linked
with every aspects of our lives, that is physical,
psychological, and intellectual.
• NS is most complex system of the body.
• NS is the chief controlling and coordinating
system of the body.It adjusts the body to the
surroundings and regulates all the body
activities both voluntary and involuntary.
3. CONT…
• THERE ARE ABOUT 200 BILLION
NEURONS IN AN ULT BRAIN.
• Adult brain in air is 1500gm.
4. Importance of nervous system…
1. It is first appearing control system of the
body.
2. It controls the rapid and fast activities of the
body.
3. It has regulatory effect upon endocrine
system.
4. It helps in adjustment of the body with the
external environment.
5. Structural Organization of the nervous
system…..
A. Central Nervous System (CNS)
a. brain
1.fore brain
-cerebrum
-diencephalons
2.midbrain
3.hindbrain
-medulla oblongata
-pons
-cerebellum
b. spinal cord
6. Cont..
B. Peripheral nervous system(PNS)
a. somatic:
1.cranial nerves (12 pairs)
2.spinal nerves (31 pairs)
b. autonomic:
1.sympathetic nerves
2.parasympathetic nerves
7. Nervous system
Peripheral nervous systemCentral nervous system
Motor nerves Sensory nerves
Sympathetic nervous
system
Parasympathetic nervous
system
Somatic Nervous system Autonomic Nervous System
13. • The brain is protected by the thick bones of the
skull, suspended in cerebrospinal fluid, and
isolated from the bloodstream by the blood–
brain barrier.
15. Neuron
• The nerve cell with its process is called a
neuroun.
• It is structural and functional unit of nervous
system.
• It is responsible for reception, conduction,
integration, and transmission of nerve impulse.
16. Anatomy of a Neuron
Each neuron contains:
- Cell body with
nucleus
- Dendrites : fibers that
receive messages from
other neurons
- Axons : fibers that
send messages to other
neurons
17. • Neurons do NOT touch;
there is a gap between
them called a synapse
• Messages are sent
across the synapses by
special chemicals called
neurotransmitters
• Myelin sheath
• Schwann cell
• Node of ranvier
18. Classification of neuron:-
According to no. of processes.
1. Unipolar
2.Bipolar.
3.pseudo-unipolar
4.multipolar
According to function
1. motor/ efferent neurons.
2.sensory/afferent neurons.
3.internucial neurons.
19. Cont….
According to position:
1. upper motor neuron:- the neurons in the
cerebral cortex and brainstem,the axon of which
forms the descending tract.
2. lower motor neuron:- the spinal and cranial
motor neurons that leave the CNS and innervates
the muscles.
According to myelination:-
1.myelinated
2.non mylinated.
20. NOTE:-
• Nerve fibers is the name given to an axon or
dendrites of nerve cells.
• Gray matter:-it is composed of nerve cells.
• White matter:- it is composed of nerve fibers.
White color is due to myelin sheath.
• Nerve tract:- tracts may be defined as a bundle
of nerve fibers one or group of motor or
sensory impulse.
22. Cont…
• Each of the two hemispheres is divided into
four separated lobes:
• the frontal :-control of specialized motor
control, learning, planning, and speech;
• parietal :-control of somatic sensory functions
• occipital:-control of vision; and
• temporal lobes:-control of hearing and some
speech.
23.
24. Cont…
• The cerebellum coordinates skeletal muscles to
produce smooth, graceful motions. The
cerebellum receives information from our
eyes, ears, muscles, and joints about the
position in which our body is currently. It also
receives output from the cerebral cortex about
where these parts should be.
25.
26.
27. Neuroglia/Glial cells…
• These are the non-excitable supporting cells/
connective tissues present in the nervous system.
• Structurally the neuroglia can be classified into:-
1.macroglia:
-astrocytes:-act as BBB
-oligodendrocytes:-form myelin sheath
2.microglia: phygocytosis.
3.Ependymal cells:- formn and regulation of
CSF
30. Nervous system
Peripheral nervous systemCentral nervous system
Motor nerves Sensory nerves
Sympathetic nervous
system
Parasympathetic nervous
system
Somatic Nervous system Autonomic Nervous System
31. Bones of the Skull…
• Skull consists of the 28 bones -
brain case is composed of 14 bones
A. paired
1.parietal
2.temporal
3.malleus
4.incus
5. stapes
B.Unpaired
1.frontal
2.occipital
3.sphenoid
4.ethmoid
32. The facial skeleton is composed of 14
bones..
A. Paired
1.Maxilla
2.zygomatic
3.nasal
4.lacrimal
5.palatine
6.inferior nasal concha
B. Unpaired
1.mandible
2.vomer
33.
34.
35.
36.
37. Arterial Supply of cerebral cortex..
• Middle cerebral artery is main artery on
superolateral surface.
• Anterior cerebral artery is chief artery on
medial surface.
• Posterior cerebral artery is principal on inferior
surface.
42. Spinal cord…
• Spinal cord is the long cylindrical lowest part of
CNS.
• It gives raise to 31 pairs of spinal nerves.
cervical-8, thoracic-12, lumber-5, sacral-5,
coccygeal-1.
• 33 vertebrae-C-7,T-12,L-5,S-5,CO-4.
• It extend from the foramen magnum to disc of L1-
L2
• The distal end terminates as conus medullaris.
43. Cont..
• The spinal cord has cervical enlargement (c4-
t2) for supply of upper limb muscles.
• And lumber enlargement (l2 to s3) for supply of
muscle of lower limb.
• Posterior columns of gray matter:-
stimulated by sensory impulses from
periphery of the body.
• Anterior columns of gray matter :-
composed of cell body of the lower motor
neurones.
44. Cont..
• In T1-L1 and S2-S5 segment has lateral horn
for supply of the viscera.
FUNCTION OF SPINAL CORD
The two major function is to
-transmit impulses to or from brain.
-to house spinal reflexes.
45.
46.
47.
48.
49. Tracts of spinal cord
Nerve tract:- tract may be defined as a bundle
of nerve fibres one or a group of motor or
sensory impulses to and from the brain.
TYPES:-
1. ascending tracts or sensory tracts.
2.descending tracts or motor tracts.
59. Circulation of CSF…
• Cerebrospinal fluid is a clear, colorless, body
fluid that occupies the subarachnoid space and the
ventricular system around and inside the brain and
spinal cord.
• It is formed mainly in the choroid plexus of
lateral ventrical and lesser amount by choroid
plexus of 3rd and 4th ventricals.
• It runs from lateral ventricle through foramen
of monro 3rd ventricle through cerebral
aquedect 4th ventricle foramen of luschka
and magendia subarachnoid space around brain
and spinal cord.
60. Blood brain barrier
• The selective barrier between the blood and
the brain tissue is known as “blood brain
barrier”
• Structture forming the BBB
-the endothelial cell in the wall of the capillary
-the continous basement membrane.
-the foot processes of astrocytes.
61.
62. Function of BBB..
• It permits a selective passag of blood content
to nervous tissue.
• Gases and water pass readily through the
barrier,but glucose and electrolytes pass more
slowely.
• Toxic and harmful substances are prevented
from reaching the brain .
63. Reflex arc and reflex
• Reflex arc:-
complete pathway of reflex action is
called reflex arc.
• Reflex:-
it is the involuntary response due to
any sensory stimulus.
67. Reflex arc and reflex
Reflex arc:-
complete pathway of reflex action is called reflex arc.
IT consists of the following parts:-
1.afferent limb
-receptor
-afferent nerve
2.center
3.synapse
4.efferent limb
-efferent nerve
-efferent organ
68. Classification
1. Monosynaptic reflex arc:-
it has two neurons or only one synapse.
E.g-strech reflex.
2.Disynaptic reflex arc:-
it has three neurones or two synapse.
E.g- extension reflex
3.Polysynaptic reflex arc:-
here more then two synapse are present.
E.g:- withdrawal reflex
69. • Reflex:-
it is the involuntary response due to any sensory
stimulus.
Types of reflex
1.superficial reflex:- these are elicited by stimulating
the appropriate receptors of skin or mucus
membrane.
E.g corneal reflex.
2.deep reflex:- these are stretch reflexes, which are
produce by tapping over tendons.
E.g- knee jerk, ankle jerk.
70. 3.Visceral reflex:-
these are reflexes where at least a part of the
reflex arc is formed by autonomic nerve.
E.g:- Pupillary reflex, vomiting reflex.
According to the no. of synapses in the reflex arc.
1.monosynaptic reflexes:- e,g –strech reflexes.
2.polysynaptic reflexes:- e.g- withdrawal reflex.
71.
72. Synapse :-
• Synapse is the junction between two neurons
where one neuron end and other neuron begins
. It is functional continuity between two
neurons.
• Components of synapse:-
1.Presynaptic membrane or element
2.Synaptic cleft
3.Postsynaptic element or membrane.
73. Functions of synapses:-
1. Transmission of nerve impulse from one
neurons to other or to the effector cells.
2. Formation of reflex arc.
3. Integration of nerve impulse.
4. Acts as a connection spot in a neural chain
5. Modulation of neural activity.
74. Mechanism of impulse:-
A. Presynaptic event
arrival of the impulse at the presynaptic nerve
terminal
depolarization of the nerve terminal by the action
potential
entry of ca++ through voltase-gated ca++
channels
ca++ causes fusion of synaptic vesicle with
presynaptic membran
release of neurotransmeter at synaptic cleft
diffusion of neurotransmeter across the cleft
75. B. Postsynaptic event:-
banding of NM with the receptor on the
postsynaptic membrane
activation of receptor which changes in ion
conductance
depolarization (Na+ influx) of postsynaptic
membrane
impulse is produced.
77. There are 12 pair of cranial nerves originating
from nuclei in the inferior surface of the brain,
Some are
sensory nerves (1,2,8)
motor nerves
mixed nerves(5,7,9,10)
78. Name of cranial nerves
I. Olfactory : sensory
II. Optic : sensory
III. Oculomotor : motor
IV. Trochlear : motor
V. Trigeminal :mixed
VI. Abducent : motor
VII.Facial : mixed
VIII.Vestibulocochler : sensory
IX. Glossopharyngeal : mixed
X. Vagus :mixed
XI. Accessory :motor
XII.Hypoglossal :motor
79. NOTE
Out of these ,the 1 and 2 nerve
are attached to the forebrain;
the 3 and 4 to the midbrain; the
5,6,7,and 8 to the pons and the
9,10,11 and 12 to medulla.
80.
81. FUNCTIONS OF CN….
Olfactory : sensory- responsible for sense of
smell.
Optic : sensory- sense of sight
Oculomotor : motor
- four extraocular muscles.
-ciliary muscles of the iris
Trochlear nerves : motor- superior oblique
muscle of eyes.
82. Trigeminal nerves(mixed)
This nerve contain sensory and motor fibres.
-the chife sensory nerve for the face and head
-motor fibers stimulstes the muscles of
mastications.
It has three main branch
1.Ophthalmic nerves(s)
2.maxillary nerves(s)
3.mandibular nerves(mix)
83. Abducent nerves (motor)
They supply the lateral rectus muscles of the
eyeballs
7. Facial nerves (mixed)
-The motor fibers supply to the muscle of
facial expression.
-the sonsory fibers convey impulses from
the teste buds in the anterior two-third of
the tongue
84. 8.Vestibulocochlear nerves(sensory)
Two distinct sets of fibers,
-Vestibular nerve:-arise from the semi circular
canals of the inner ear and convey impulses to
the cerebellum.
- The Cochlear nerves originate in the organ of
corti in the inner ear and convey impulses to
to the hearing area in the cerebral cortex where
sound is perceived.
85. 9.Glossopharyngeal nerves(mixed)
-the motor fibers stimulates the muscles of the
tongue and pharynx and the secretory cells of
parotid gland
-the sensory fibers convey impulse to the
cereberal cortex from the posterior third of the
tongue, the tonsils and pharynx and from teste
buds in the tongue and pharynx.
86. 10. Vagus nerves (mixed)
The motorfibers supply the smooth muscles and
secretory gland of the pharynx ,larynx, trachea,
heart, oesophagus, stomach, intestines,
pancreas, gall bladder, bile ducts, spleen,
kidneys, ureter, and blood vessels in thoracic
and abdominal cavities.
The sensory fibers convey impulses from the
lining membranes of the same structures to the
brain.
87. 11. Accessory nerves(motor)
• These nerves supply to the
sternocleidomastoid and trapezius muscles.
12. Hypoglossal nerves (motor)
they supply the muscles of the tongue and
muscles surrounding the hyoid bone and
contribute to swallowing and speech.
89. Sympathetic nervous system
-Thoracolumber out flow….
-Neurons convey impulses from their origin in
the hypothalamus, reticular formation and
medulla oblongata to the effector organe and
tissues.
It has 1.the preganglionic neurone.
2.the postganglionic neurone.
90.
91. Preganglionic neuron
This has it cell body in lateral colomn of gray matter
in spinal cord (t1 to l2-l3)
The nerve fiber of this cell leaves the cord by the
anterior root and terminates in one of the ganglia.
Acetylcholine is the neurotransmitter.
POSTGANGLIONIC NEURONE.:-
this has the cell body in a ganglion and terminates
in the organ or tissue supplied.
NORADRENALIN is the neurotransmiter.
92. Adrenergic and Cholinergic Synaptic
Transmission
• ACh is NT for all preganglionic
Sympathetic fibers
Parasympathetic fibers
• Transmission at these synapses is termed
cholinergic
• All preganglionic fibers terminate in
autonomic ganglia
93. Adrenergic and Cholinergic Synaptic
Transmission
• ACh is NT released by -
Most postganglionic
parasympathetic fibers
Some postganglionic sympathetic
fibers
• Postganglionic autonomic fibers
innervate the target tissue
94.
95. Sympathetic Effects
• Fight, Fright or flight response
• Release of Neurotransmitters (NT)-
Norepinephrine (NT) from postganglionic
fibers (noradrenaline)
Epinephrine (NT) from adrenal
medulla(adrenaline)
96. Sympathetic Effects
• Mass activation prepares for intense activity
Heart rate (HR) increases
Bronchioles dilate
Blood [glucose] increases
• GI-motility decreases
• Contraction of sphincters
• Relaxation of
Detrusor muscle
Ciliary muscle
• Mydriasis
97. PARASYMPATHETIC
OUTFLOW
• -craniosacral outflow..
CN 3,7,9,10 and sacral segments 2,3,4.
Pregangionic neurone:-has its cell bodies either in
the brain or the spinal chord.
ACETYLCHOLINE is the NT
Postgangionic neurone:-has its cell body either in a
ganglion or in the wall of the organ supplied.
ACETYLECHOLINE is the NT.
98.
99.
100. Parasympathetic Effects
• Normally not activated as a whole
Stimulation of separate parasympathetic nerves.
• Release ACh as NT
• Relaxing effects-
Decreases HR.
Dilates visceral blood vessels.
Increases digestive activity.
101. Cont…
• Bronchonstriction
• GI motility increases
• Relaxation of sphincters
• Contraction of
Detrusor muscle
Ciliary muscle
• Miosis
104. note
Adrenergic NT act via alfa and beta receptor
B1 – heart, JE cells of kidney
B2 – bronchi, blood vessels ,uterus, liver,
B3- adipose tissue
105.
106.
107. Nerve impulse
Nerve impulse is “all or none” it either goes or not
there is no halfway.
• A neuron needs a threshold stimulus, the
minimum level of stimulus needed to trigger the
Na-K pump to go and the impluse to travel.
• A neuron cannot immediately fire again , it need
time for Na and K to there place and everything to
return to normal ,this time taken is called the
Refractory period.
108. A wave of depolarization moves down the axon of
a neuron.
A. Gated Na channels opens, allowing Na ion to
enter and make the inside of the cell positively
charged and the outside negatively charged.
B. As the impulse passes, gated Na channels close,
stoping the influx of Na ions. Gated K channels
open , letting K out of the cell. This is called as
repolarization of cell.
C. As the gated K channels closes , the Na+/K+
Pump restores the ion distribution.
109.
110. Peripheral NS Vs Central NS---
• Sensory and motor
neurons.
• Interneurons : brain and
spine
• Covered with three
membranes , the
meningies
• Brain has gray matter on
outside and white matter
in center
• Spine has just opposite.
