at a glance Introduction Terminologies used in the nervous system Division of nervous system Types of nerves- structure and functions Brain Cranial nerves Spinal cord Motor and sensory pathways of the spinal cord Autonomic nervous system

1. THE NERVOUS
SYSTEM
MRS.P.CHRISTENA,M.SC(N)
NURSING TUTOR,
DEPT OF OBG NSG

2. AT A GLANCE..
 Introduction
 Terminologies used in nervous system
 Division of nervous system
 Types of nerves- structure and functions
 Brain
 Cranial nerves
 Spinal cord
 Motor and sensory pathways of the spinal
cord
 Autonomic nervous system

3. INTRODUCTION
 Integrates and coordinates various activities of other organ
system in the body
 Controls
 muscle contraction,
 secretion of hormones from glands,
 rate and depth of the respiration,
 cardiac activities and
 GI activities
 Also in modulating and regulating a multitude of other
physiology

4. KEYS USED IN NERVOUS SYSTEM
 cerebr/o – cerebrum (brain)
 dur/o – dura mater (hard, tough)
 encephal/o – brain
 cephal/o – head
 myel/o – medulla (also marrow)
 myelin/o – myelin (Schwann cells)
 neur/o – nerve
 radic/o, radicul/o – nerve root
 psych/o – mind
 ment/o – mind
 gangli/o, ganglion – swelling, ganglion
(pl=ganglia)
 mening/i, mening/o – meninges
(membrane)
 esthesi/o – sensation
 phas/o – speech
 poli/o – gray matter
 phren/o – mind (also diaphragm)
 scler/o – hard

5. TERMINOLOGIES USED IN NERVOUS
SYSTEM
 Axons are long nerve processes which carry nerve impulses from the Soma to other
neurons, they vary in length but can become almost as long as half of the human
body.
 The soma (body) of the neuron contains the nucleus which acts as the cell's control
centre, these contain many small neurofibrils which project from the nucleus into the
dendrites.
 Dendrites are short, thick processes which branch out of the soma in a tree like manor.
They conduct nerve impulses to the soma

6. TERMINOLOGIES USED IN NERVOUS
SYSTEM
 A nerve is a bundle of fibres (axons and/or dendrites) outside the CNS.
 Neuroglia are cells of the nervous system that help protect and support it.
 Ganglia are groups of nerve cell bodies lying outside the CNS.
 A spinal tract is a bundle of fibres in the CNS that travel long distances up or down the
spinal cord. Ascending tracts carry impulses up the cord to the brain, while descending
tracts carry impulses down the cord from the brain. Tracts run along the spinal canal inside
the protective spinal column, conveying sensory and motor (movement ) information to
and from the brain. Spinal meninges are tough tubes of tissue which protect the cord.

7. Abbreviations and Acronyms
 BAER Brainstem Auditory Evoked Response
 CNS Central nervous system - the brain and spine
 CSF Cerebro spinal fluid
 EEG Electroencephalogram - brain scan
 LP Lumbar puncture
 NSE Neuron-Specific Enolase - a neural marker
 PNS Peripheral nervous system - nervous system outside the brain and spine.

8. DIVISION OF

9. STRUCTURE OF A NERVE
 A nerve consists of a cordlike structure with a
multiple of nerve fibres called as axon. This axon
has a layer called as connective tissue around it.
This connective tissue is called as endoneurium.
And this entire nerve is enclosed in this layer of
connective tissue called as the epineurium. Hence
these Nerves are responsible for all the activities
done by human beings in day to day life

10. TYPES OF NERVES

11. Sensory nervesSensory nerves
 These are the nerves that send messages to the brain or the spinal cord from the sense
organs.
 These are enclosed in the form of a bundle like structures or nerve fibers in the peripheral
nervous system.
 They carry information from the PNS to the CNS( Central nervous System).

12. Motor NervesMotor Nerves
 Motor nerves are those nerves those that carry the messages in the form of a response
from the brain or the spinal cord to other parts of the body such as the muscles and
glands.
 They are responsible in carrying the information from the CNS to the PNS.

13. Mixed NervesMixed Nerves
 These are the nerves that perform both the action of sensory nerves as well as motor
nerve.
 They transform electrical impulses from the central nervous system to the muscles of the
body.
 Generally the nerves transmit impulses at the rate of 120 meter per second.

14. The picture
describes about
how the sensory
and the motor
nerves function in
the human body.

15. BRAIN

17. CEREBRUM-largest part of brain

18. PARTS
 Two hemispheres
 Left hemisphere
 Right hemisphere
 Two hemispheres are Separated by
 Falx cerebri – a fold of dura mater in the midline
 Corpus callosum – a bridge of white matter below

19. LOBES
 a. Frontala. Frontal – voluntary motor control, learning,
planning, and speech
 b. Parietalb. Parietal – sensory, distance, size, shape, and
cognitive/intellectual processes
 c. Occipitalc. Occipital – vision and visual memory
 d. Temporald. Temporal – auditory, olfactory, speech,
judgment, reasoning, and willpower

20. FISSURES
IMPORTANT 4 FISSURES
•Central sulcus
•Parieto-occipital sulcus
•Callaso-marginal fissure
•Sylvian fissure

21. GREY MATTER
 Consist of nerve cells which constitute
the surface of hemispheres
 Also called as cerebral cortex
 Consists of number of folds or
convolutions
 These convolutions are separated by
fissures
WHITE MATTER
 Present in the interior of the
hemisphere
 Contains nerve fibres

22. FUNCTIONS
 Motor functions like
 Control of voluntary movements
 Sensory functions like
 Analysis of touch, temperature, pain, pressure, shape, etc
 Governing of conditional reflexes
 Control of intelligence, speech, memory, etc through higher centres of cerebrum

23. These functions are governed by,
Motor cortex
 Lies in front of central sulcus
 Controls voluntary movements of the body
 Controlling areas are arranged from
above downwards ( feet, lower limbs, hip,
trunk, arms and head in that order )
Sensory cortex
 Lies behind the central sulcus
 Deals with sensations like touch,
pressure, temperature, etc

24. SPECIALIZED
STRUCTURE OF
GREY MATTER
The pink
areas in Figure show
the grey matter of
the cerebral cortex
on the outer surface
of the cerebral
hemispheres. The
grey areas show
grey matter inside
the hemispheres and
in the front end of
the brain stem.

25. SPECIALIZED
STRUCTURE OF
GREY MATTER
• BASAL GANGLIABASAL GANGLIA
• CAUDATE NUCLEICAUDATE NUCLEI
• LENTIFORM NUCLEILENTIFORM NUCLEI
• AMYGDALOID NUCLEIAMYGDALOID NUCLEI
• CLAUSTRUMCLAUSTRUM
• INTERNAL CAPSULEINTERNAL CAPSULE
• THALAMUSTHALAMUS
• HYPOTHAMALUSHYPOTHAMALUS
CORPUS
STRIATUM

26. Cerebellum
 Cerebellum – below and posterior to the cerebrum
 1. The right and left hemispheres are connected by the central vermis
 2. Outer gray, inner white forms the arbor vitae
 3. Coordinates muscular movement, posture, balance, running, and walking
 4. Damage produces ataxia (a lack of coordination due to errors in speed, force, and
direction of movement)

27. Brainstem (damage = coma)
 1. Midbrain1. Midbrain – the upper part of the brainstem a. Controls postural reflexes and walking b.
Visual reflexes and auditory control, 3-4 cranial nerves
 2. Pons2. Pons – a two-way conduction pathway; mixed gray and white fibers a. Controls inspiration
b. Transverse fibers give it a bridge appearance c. Reflex mediation for 5-8 cranial nerves
 3. Medulla oblongata3. Medulla oblongata – the bulb (the lowest part before the foramen magnum); made of
white and gray fibers called the reticular formation a. 75% of nerve fibers cross here b.
Controls vital functions – respiration and circulation c. Pyramids – bulges of white tracts on the
ventral surface

28. The meninges
 The meninges are three layers of protective tissue called the
 dura mater,
 arachnoid mater, and
 pia mater that surround the neuraxis.
 The meninges of the brain and spinal cord are continuous, being linked
through the magnum foramen.

29. The meninges AND CSF- cerebro
spinal fluid

30. Dura Mater
 The dura mater is the most superior of the meningeal layers. Its name means "hard mother" in Latin
and it is tough and inflexible. This tissue forms several structures that separate the cranial cavity into
compartments and protect the brain from displacement.
 The falx cerebri separates the hemispheres of the cerebrum.
 The falx cerebelli separates the lobes of the cerebellum.
 The tentorium cerebelli separates the cerebrum from the cerebellum.
 The dura mater also forms several vein-like sinuses that carry blood (which has already given its supply
of oxygen and nutrients to the brain) back to the heart.
 The superior sagittal sinus runs across the top of the brain in an anterior-posterior direction.

31. Dura Mater
 Other sinuses include the straight sinus, the inferior sinus, and the transverse sinus.
 The epidural space is a potential space between the dura mater and the skull. If there is
hemorrhaging in the brain, blood may collect here. Adults are more likely than children to
bleed here as a result of closed head injury.
 The subdural space is another potential space. It is between the dura mater and the middle
layer of the meninges, the arachnoid mater. When bleeding occurs in the cranium, blood
may collect here and push down on the lower layers of the meninges. If bleeding continues,
brain damage will result from this pressure. Children are especially likely to have bleeding in
the subdural space in cases of head injury.

32. Arachnoid Mater
 The arachnoid or arachnoid mater is the middle layer of the meninges. In some areas, it
projects into the sinuses formed by the dura mater. These projections are the arachnoid
granulation/arachnoid villi. They transfer cerebrospinal fluid from the ventricles back into the
bloodstream.
 The subarachanoid space lies between the arachnoid and pia mater. It is filled with
cerebrospinal fluid. All blood vessels entering the brain, as well as cranial nerves pass
through this space. The term arachnoid refers to the spider web like appearance of the
blood vessels within the space.

33. Pia Mater
 The pia mater is the innermost layer of the meninges. Unlike the other
layers, this tissue adheres closely to the brain, running down into the sulci
and fissures of the cortex. It fuses with the ependyma, the membranous
lining of the ventricles to form structures called the choroid plexes which
produce cerebrospinal fluid.

34. Cerebrospinal Fluid
 Cerebrospinal fluid is a clear liquid produced within spaces in the brain called ventricles. Like
saliva it is a filtrate of blood. It is also found inside the subarachnoid space of the meninges which
surrounds both the brain and the spinal chord. In addition, a space inside the spinal chord called
the central canal also contains cerebrospinal fluid.
 It acts as a cushion for the neuraxis, also bringing nutrients to the brain and spinal cord and
removing waste from the system.

35. CRANIAL NERVES
 1. Olfactory – I: sensory, smell
 2. Optic – II: sensory, vision
 3. Oculomotor – III: motor, eye movement and pupil
 4. Trochlear – IV: motor, eye movement, peripheral vision
 5. Trigeminal – V: both, ophthalmic maxillary, mandibular (sensory); face and head (motor)
 6. Abducens – VI: motor, abducts eye
 7. Facial Nerve – VII: both, facial expression, taste, tongue movement
 8. Vestibulocochlear – VIII: sensory, hearing and balance
 9. Glossopharyngeal – IX: both, tongue, throat, swallowing
 10. Vagus – X: both, organ sense (thoracic and abdominal) inhibitor
 11. Accessory – XI: motor, spinal accessory, shoulder and head movement
 12. Hypoglossal – XII: motor, tongue and throat movement

40. CROSS SECTION OF SPINAL CORD

41. SPINAL CORD
 1. Deep grooves – anterior median fissure (deeper) and posterior median sulcus
 2. Two bundles of nerve fibers, called roots, project from each side of the cord a. Dorsal nerve root –
sensory afferent fibers b. Dorsal root ganglion – sensory cell bodies c. Ventral nerve root – motor
efferent fibers d. The nerve roots join together to form a single, mixed nerve called a spinal nerve
 3. “H” a. The gray matter of cell bodies of interneurons and motor neurons, divided into anterior,
posterior, and lateral horns
 b. White matter surrounds gray “H”; divided into anterior, posterior, and lateral columns (large bundles of
nerve axons divided into smaller bundles called tracts); ascending and descending, and lateral
organizational tracts
 c. Transcutaneous electrical nerve stimulation unit (TENS) – acts to close the gates of the ascending tracts;
therefore pain impulses are not allowed to get to the brain d. Lumbar puncture – a spinal tap between the
3rd and 4th lumbar vertebrae for CSF diagnostics

42. PATHWAYS OF THE SPINAL CORD

43. SENSORY PATHWAY
 Ascending Pathways
 Sensory information enters the spinal cord on the same side of the body as the stimulus. Ascending tracts
cross over the midline of the body to the contralateral side of the thalamus. The thalamus directs the
signal to the cerebral cortex for conscious perception. The pathway is direct with very few neurones
involved
 Spinocerebellar Tracts
 These tracts transmit information from proprioception receptors, including information from muscle
receptors, joint receptors and golgi tendon organs. Most sensory information enters the spinal cord on the
ipsilateral side to the stimulus but some do cross to the contralateral side of the body. Contralateral signals
pass back to the ipsilateral side of the body in the brain. Information is processed in the cerebellum and is
therefore processed unconsciously.
 Ascending Reticular Formation (Spinoreticular Tract)

44. Ascending Pathways
 1. Dorsal Columns
 Dorsal columns transmit information from touch and kinaesthesia; these are both classified as low
threshold information. There are two major dorsal columns; the gracile fasiculus situated medially which
conveys information from the hindlimbs and caudal trunk and the cuneate fasciculus which is situated
more laterally and conveys information from the forelimbs and cranial trunk.
 2. Spinothalamic Tracts
 Spinothalamic tracts transmit information from temperature and "pin prick" pain; these senses are
classified as fast, initial pain sensations. These tracts compare with the ascending reticular formation.
 3. Spinocervicothalamic Tracts
 The spinocervicothalamic tracts transmit information from touch and kinaesthesia, although these are
absent in man.

45. Spinocerebellar Tracts
 Dorsal Spinocerebellar Tract
 The dorsal spinocerebellar tract relays muscle spindle and golgi tendon organ information from the
hindlimbs to the cerebellum.
 Cuneo-cerebellar Tract
 The cuneo-cerebellar tract serves the same purpose for the forelimbs as the dorsal spinocerebellar tract
does for the hind limbs, but is much smaller.
 Ventral Spinocerebellar Tract
 The ventral spinocerebellar tract is similar to the dorsal spinocerebellar tract but it takes a less direct route
to the cerebellum. The forelimb equivalent is called the rostral spinocerebellar tract.

46. Ascending Reticular Formation
(Spinoreticular Tract)
 The ascending reticular formation is thought of as the true pain sensation as the pain lasts
longer.
 Sensory information enters the spinal cord on the ipsilateral side of the stimulus. Some signals
cross to the contralateral side of the body.
 The tract consists of several short neurones.
 Therefore the ascending reticular formation is bilateral and multineuronal, although this pain
pathway is thought to be more primitive than the spinothalmic tract.
 In humans, the ascending reticular formation is superceded by the spinothalamic tract. In
animals, the ascending reticular formation is the main pathway for pain to reach the cerebral
cortex.

47. MOTOR PATHWAYS
UPPER MOTOR NEURONE
Pyramidal cells of motor cortex of
brain to the anterior horn cells of
spinal cord
1. Impulses commence from the
pyramidal cells of motor cortex
2. The fibres pass through internal capsule
and pons and reach the medulla
oblongata
3. These fibres cross each other in the
medulla oblongata
4. Then they travel through the lateral
column of the spinal cord and
terminate in the anterior horn cells
LOWER MOTOR NEURONE
Anterior horn of the spinal cord to
peripheral nerve supplying the
muscle
1. The fibres from anterior horn cells reach
the anterior nerve root
2. The fibres of anterior nerve root unite
with the incoming fibres of posterior
nerve root and from the spinal nerve
3. The motor nerves emerging from the
spinal nerves supply the muscle

48. REFLEX ACTION
 Reflex action occurs independent of will and it is concerned with involuntary movements
 It is the defence mechanism manifesting as a quick and automatic motor response for a sensory stimulus
 Reflex arc: structures involved in reflex action
 Sensory organ
 Sensory nerve
 Spinal cord
 Motor nerve
 Importance
 Impulses are carried only to the spinal cord and not to the motor cortex, from spinal cord the conveyed to
the motor cortex. So the response is quick and immediate

49. Reflex action
Stimulus receptor reaches to sensory or afferent fibres
CNS
Response effector motor or efferent fibres

50. REFLEX ACTION

51. AUTONOMIC NERVOUS SYSTEM
 Visceral , vegetative or involuntary nervous system
 Widely distributed throughout the body
 Controls tissues which are not under control (e.g. Smooth muscles, heart and glands)
 consists of two division
 Sympathetic (thoraco-lumbar outflow )
 Para- Sympathetic (cranio-sacral outflow )

52. Sympathetic (thoraco-lumbar outflow )
 It arises from T1-L2 segments of spinal cord
 Axons of preganglionic sympathetic fibres leave spinal cord through ventral root
 Pass through white rami communicates to reach paravertebral ganglion chains
 Synaptic connections with cell bodies of post- ganglionic neurons

53. Para- Sympathetic (cranio-sacral outflow )
 Mostly concerned with vegetative functions e.g. Motility and secretion of gastrointestinal tract
 Essential for normal existence of the organism
 Preganglionic fibres
 From the midbrain, the fibres emerge through oculomotor nerve
 From medulla, they emerge through facial, glossophargeal and vagus nerve
 At the sacral portion of spinal cord, they arise from the anterior column of 2nd
, 3rd
, and 4th lumbar segments.
They then pass through anterior roots of the corresponding spinal nerve
 Postganglionic fibres
 They arise from the ganglia and then reach the structure which these nerve supply
 Chemical transmitter of parasympathetic system

54. Functions of Sympathetic nervous
system
 Promotes a fight-or-flight response, corresponds with arousal and energy generation, and inhibits digestion
 Diverts blood flow away from the gastro-intestinal (GI) tract and skin via vasoconstriction
 Blood flow to skeletal muscles and the lungs is enhanced (by as much as 1200% in the case of skeletal muscles)
 Dilates bronchioles of the lung through circulating epinephrine, which allows for greater alveolar oxygen exchange
 Increases heart rate and the contractility of cardiac cells (myocytes), thereby providing a mechanism for
enhanced blood flow to skeletal muscles
 Dilates pupils and relaxes the ciliary muscle to the lens, allowing more light to enter the eye and enhances far vision
 Provides vasodilation for the coronary vessels of the heart
 Constricts all the intestinal sphincters and the urinary sphincter , Inhibits peristalsis and Stimulates orgasm

55. Functions of Parasympathetic nervous
system
 The parasympathetic nervous system has been said to promote a "rest and digest" response, promotes calming
of the nerves return to regular function, and enhancing digestion.
 Dilating blood vessels leading to the GI tract, increasing the blood flow.
 Constricting the bronchiolar diameter when the need for oxygen has diminished
 Dedicated cardiac branches of the vagus and thoracic spinal accessory nerves impart parasympathetic
control of the heart (myocardium)
 Constriction of the pupil and contraction of the ciliary muscles, facilitating accommodation and allowing for
closer vision
 Stimulating salivary gland secretion, and accelerates peristalsis, mediating digestion of food and, indirectly,
the absorption of nutrients
 Sexual. Nerves of the peripheral nervous system are involved in the erection of genital tissues via the pelvic
splanchnic nerves 2–4. They are also responsible for stimulating sexual arousal.

56. Disorders of the Nervous System
 A. Shingles – herpes zoster viral infection; causes inflammatory vesicles along the peripheral nerves
 B. Neuralgia – a sudden, sharp severe stabbing pain along a nerve pathway
 C. Neuritis – inflammation of a nerve; causes pain, muscular atrophy, hypersensitivity, and paresthesia
 D. Tic douloureux – degeneration of the trigeminal nerves; causes repeated, involuntary muscle
twitching
 E. Bell’s palsy – unilateral facial paralysis, sudden onset, viral inflammation of the trigeminal nerve
 F. Poliomyelitis – (polio) is a highly infectious viral disease, which mainly affects young children. The
virus is transmitted through contaminated food and water, and multiplies in the intestine, from where it
can invade the nervous system; permanent paralysis or weakness

57. Disorders of the Nervous System
 G. Encephalitis – a viral inflammation of brain tissue; causes fever, lethargy, weakness, nuchal
rigidity and opisthotonos, coma, and death
 H. Meningitis – a bacterial or viral inflammation of the meninges; causes headache, fever, sore
throat, back and neck pain, and loss of mental alertness
 I. Meningiocele – a congenital hernia in which the meninges protrude through an opening in the
spinal cord
 J. Epilepsy – idiopathic recurring and excessive electrical discharge from neurons causing seizure
activity (grand mal, petit mal)
 K. Hydrocephalus – an increased accumulation of CSF within the ventricles; causes the cranium

58. Disorders of the Nervous System
 L. Parkinson’s disease – tremors, uncontrolled shaking; related to decreased amounts of dopamine
 M. Huntington’s chorea – a progressive dementia with bizarre involuntary movements; genetic
 N. Athetosis – slow, irregular, twisting, snakelike movements of the hands
 O. Hemiballism – jerking and twitching movements of one side of the body; caused by a tumor of the
thalamus
 P. Dysmetria – an inability to fix the range of movement in muscle activity
 Q. Cerebral palsy – a congenital brain disorder/damage causing damage to motor neurons; flaccid
or spastic paralysis

59. Disorders of the Nervous System
 R. Multiple sclerosis – autoimmunity destruction of oligodendrocytes leading to demyelination
with progressive muscular weakness
 S. Muscular dystrophy – a genetic defect in muscle metabolism; causes progressive atrophy
 T. Myasthenia gravis – a disease characterized by muscular weakness, possibly due to decreased
amounts of acetylcholine at the muscle effector sites
 U. Alzheimer’s disease – dementia-producing lesions in the cerebral cortex
 V. Anencephalic – infants born without a frontal cerebrum; congenital, possibly related to toxins,
may be related to a folic acid deficiency in the mother

60. BIBLIOGRAPHY
 https://nursessity.wordpress.com/2015/02/18/cranial-nerves-need-help-remembering/
 https://byjus.com/biology/nerves/
 http://www.csuchico.edu/~pmccaffrey//syllabi/CMSD%20320/362unit3.html