Peripheral Nervous System

1. Peripheral Nervous System
Prof. Mukul Sharma
Medi-Caps University, Indore

2. Introduction
Nervous system coordinates Voluntary and Involuntary movements of
human body and transmits signals between different body parts.
• Functions- Detect changes inside and outside of body.
• Maintains homeostasis.
• Regulate various activities of the body by rapidly using nerve impluses.
The branch of medical science that deals with structure, Functions and
diseases of nervous system is called Neurology.
Nervous system
• 1. Central nervous system 2. Peripheral Nervous system
Brain and Spinal cord Somatic SNS and Autonomic ANS
(Thoughts, Emotions, Memories) (SNS-Voluntary- sensory and motor neuron)
Prof. Mukul Sharma

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Fig 1: Components of Nervous System

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Neurons: Structural and Functional unit of Nervous tissue.
Fig: Myelinated and Non-myelinated
neurons
Sensory neuron- Convey information from smells, taste, limbs etc. to the CNS.
Motor neuron- Impulse from the CNS to skeletal muscles.

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Table: Cranial Nerves (12 pairs)
Originate from nuclei in
the inferior surface of
brain, some sensory,
some motor and mixed.

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Fig: Types of Neurons and Neural Junctions

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Hypoglossal (XII)
Motor
Accessory XI (Motor)
Fig: Connection between
Cranial nerves with Brain
•12 pairs of cranial nerves
•31 spinal nerve pairs,
•basis of the peripheral
nervous system.

8. Spinal nerves
• The second set of peripheral nerves are spinal nerves.
• There are 31 pairs: (C8,T12,L5,S5,Co1)
• Their numbering relates to the vertebral column exit level;
cervical spinal nerves are numbered according to the vertebra
located below, while all the rest according to the vertebra
situated above.
Prof. Mukul Sharma

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Fig: Spinal Nerves

10. Autonomic Nervous System
• The autonomic nervous system controls specific body processes, such as
circulation of blood, digestion, breathing, urination, heartbeat, etc. The
autonomic nervous system is named so, because it works autonomously,
i.e., without a person’s conscious effort.
• The primary function of the autonomic nervous system is homeostasis.
Apart from maintaining the body’s internal environment, it is also involved
in controlling and maintaining the following life processes:
• Digestion
• Metabolism
• Urination
• Defecation
Prof. Mukul Sharma

11. ANS
• Blood pressure
• Sexual response
• Body temperature
• Heartbeat
• Breathing rate
• Fluid balance
• There are two types of autonomic nervous system:
• Sympathetic autonomic nervous system
• Parasympathetic autonomic nervous system
Prof. Mukul Sharma

12. Autonomic Nervous System: (Involuntary)
• The ANS is responsible for providing sensory and motor innervation
to smooth muscles, blood vessels, glands, and internal organs. As such, it
provides a coordinated regulation of visceral and glandular functions,
playing a role in maintaining homeostasis.
• Symphathetic
• Parasymphetic
• Enteric
• Pre-ganglionic: The portion of the nerve before the ganglion is referred to
as pre-ganglionic and carries the impulse towards the cluster of cell bodies.
• Postganglionic: The portion located from the ganglion onwards is
called postganglionic and carries the impulse away from the cell bodies.
Prof. Mukul Sharma

13. Symphathetic and Parasymphathetic
• The sympathetic division prepares the body for dealing with
periods of increased physical activity through actions such as
regulating blood vessels (often, but not always, vasoconstriction),
dilating pupils, increasing heart rate and blood pressure, and
decreasing peristalsis.
• The parasympathetic division helps the body to conserve energy, it
has ‘rest and digest’, feeding, and breeding functions. This is carried
out by actions that slow the cardiovascular system, stimulates
gland secretion and increases peristalsis. It also involved in sexual
arousal and lacrimation (crying).
Prof. Mukul Sharma

14. Sympathetic Nervous System
• The preganglionic fibers of the sympathetic nerves leave the spinal cord
through the T1 to L2 anterior roots, entering the corresponding spinal
nerve.
• The fibers then travel through the white rami communicantes to
paravertebral ganglia of the sympathetic trunks, located on either side of
the vertebral column.
• Some fibers synapse here, while others travel through it without synapsing,
exiting the sympathetic trunks as the splanchnic nerves (greater, lesser,
least, lumbar, sacral).
• These splanchnic nerves synapse closer to their target organs
in prevertebral ganglia called celiac, aorticorenal, and mesenteric (superior
and inferior).
Prof. Mukul Sharma

15. Symphathetic Nervous System
• The postganglionic fibers then project onto their target structures
either directly, or by returning through the grey ramus
communicantes and following the path of spinal nerves throughout
the body.
• Target organs include blood vessels, sweat glands, arrector pili, the
iris, and internal organs.
• Example : Target organ is the adrenal gland. Sympathetic nervous
system activity stimulates the release of epinephrine/adrenaline via
the sympathetic-adrenal medullary system.
Prof. Mukul Sharma

16. Parasympathetic Nervous System
• The parasympathetic nervous system is divided into cranial and
sacral outflows.
• The preganglionic fibers of the cranial outflow exit the
brainstem within the oculomotor, facial, glossopharyngeal, and
vagus cranial nerves.
• They synapse in the ciliary, otic, submandibular,
and enteric ganglia.
• The postganglionic fibers ultimately innervate salivary glands
of the head, iris and ciliary muscles of the eye.
Prof. Mukul Sharma

17. Parasympathetic Nervous System
• The preganglionic fibers of the sacral outflow are much more
restricted, only exiting the spinal cord through the anterior
roots of the S2-S4 spinal nerves.
• They travel with the pelvic splanchnic nerves, ultimately
innervating the pelvic viscera (descending colon, sigmoid
colon, rectum, bladder, penis/clitoris).
Prof. Mukul Sharma

18. Prof. Mukul Sharma
Difference Between Parasymphathetic and Sympathetic

19. The Enteric Nervous System (ENS)
• lies within the walls of the gastrointestinal tract and consists of
the myenteric (Auerbach) and submucosal (Meissner)
plexuses.
• They work together to control peristalsis within the digestive
system.
• This system is often described as the second brain because it
acts independently while only being influenced by impulses
from the ANS.
Prof. Mukul Sharma

20. Highlights and important notes
Locations of Neurons
1. Multipolar neuron- Several dendrites and one axon.
• Eg: present in Brain, Spinal cord
2. Bipolar Neuron- One dendrite and one axon
Eg: Retoma pf eye, Inner ear, olfactory area of brain
3. Unipolar neuron- axon and dendrite fuse into a single process that
divides into two branches a short distance from the cell body.
• Sensory neuron that begin in the embryo as bipolar neurons.
Prof. Mukul Sharma

21. Neuroglia (Glia)
• Neuroglia: Half the volume of CNS. They are smaller than neurons. They
donot generate action potential and they can multiply and divide in the
mature nervous system
• support, nourish and protect neurons and maintain homeostasis in
intestinal fluid that bathes neurons.
• Types:
• Astrocytes (Star shaped with many process), Maintain environment for
generation of nerve impulse, provide nutrients to neurons, help in blood
brain barrier.
• Oligodendriocytes: small than astrocytes with fewer process, round and
oval body. Form supporting network around CNS network, produce myline
shealth.
Prof. Mukul Sharma

22. Neuroglia
• Microglia: small cells with few process, derived from
macrophages and monocytes. Protect CNS cells from diseases.
• Ependymal cells: cuboidal and colluminar cells arranged in
single layer.
Forms Cerebruspinal fluid, present in brain and spinal cord.
• Schwann cells: flattended cells that encircle PNS axon.
Participation in regeneration of PNS axon.
• Satellite cells: flattended cells arranged around the cell bodies
of neurons in ganglia.
Prof. Mukul Sharma

23. Structure and Functions of Special
Sensory organs

24. Special Sensory Organs
• TONGUE
• EYE
• NOSE
• EAR
Prof. Mukul Sharma

25. Tongue
• The tongue is a muscular organ in the mouth. The tongue is covered with
moist, pink tissue called mucosa. Tiny bumps called papillae give the
tongue its rough texture. Thousands of taste buds cover the surfaces of the
papillae. Taste buds are collections of nerve-like cells that connect to
nerves running into the brain.
• The tongue is anchored to the mouth by webs of tough tissue and mucosa.
The tether holding down the front of the tongue is called the frenum. In
the back of the mouth, the tongue is anchored into the hyoid bone. The
tongue is vital for chewing and swallowing food, as well as for speech.
• The four common tastes are sweet, sour, bitter, and salty.
• Tongue is vital for chewing and swallowing food, as well as for speech.
Prof. Mukul Sharma

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Structure of Tongue

27. Tongue disorders
• Thrush (candidiasis): Candida albicans (a yeast) grows over the
surface of the mouth and tongue. Thrush can occur in almost
anyone, but it occurs more often in people taking steroids or with
suppressed immune systems, the very young, and the elderly.
• Oral cancer: A growth or ulcer appears on the tongue and grows
steadily. Oral cancer is more common in people who smoke and/or
drink alcohol heavily.
• Macroglossia (big tongue): These include inflammatory, traumatic,
cancerous, and metabolic causes. Thyroid disease, lymphangiomas,
and congenital abnormalities are among some of the causes of an
enlarged tongue.
Prof. Mukul Sharma

28. Tongue disorders
• Geographic tongue: Ridges and colored spots migrate over the
surface of the tongue, periodically changing its appearance.
Geographic tongue is a harmless condition.
• Burning mouth/burning tongue syndrome: a relatively common
problem. The tongue feels burned or scalded, or strange tastes or
sensations develop. Apparently harmless, burning mouth syndrome
may be caused by a mild nerve problem.
• Atrophic glossitis (bald tongue): The tongue loses its bumpy
texture, becoming smooth. Sometimes this is due to anemia or a B
vitamin deficiency.
Prof. Mukul Sharma

29. Tongue disorders
• Canker sores (aphthous ulcers): Small, painful ulcers appear periodically on the
tongue or mouth. A relatively common condition, the cause of canker sores is
unknown; they are unrelated to the cold sores caused by herpes viruses. Canker
sores are not contagious.
• Oral leukoplakia: White patches appear on the tongue that can’t be scraped off.
Leukoplakia may be benign, or it can progress to oral cancer.
• Hairy tongue: Papillae can overgrow the surface of the tongue, giving it a white
or black appearance. Scraping off the papillae corrects this harmless condition.
• Herpes stomatitis: The herpes virus can uncommonly cause cold sores on the
tongue. Herpes virus cold sores are usually on the lip.
• Lichen planus: A harmless condition that can affect the skin or the mouth. The
cause is unknown; however, it is believed to be caused by the immune system
attacking the skin and lining of the mouth.
Prof. Mukul Sharma

30. Sensory Organ- EYE

31. EYE

32. Prof. Mukul Sharma

33. EYE Anatomy
• Each eye constantly adjusts the amount of light it lets in, focuses on objects near and far,
and produces continuous images that are instantly transmitted to the brain.
• The orbit is the bony cavity that contains the eyeball, muscles, nerves, and blood vessels, as
well as the structures that produce and drain tears. Each orbit is a pear-shaped structure
that is formed by several bones.
• The outer covering of the eyeball consists of a relatively tough, white layer called
the sclera (or white of the eye).
• Near the front of the eye, in the area protected by the eyelids, the sclera is covered by a
thin, transparent membrane (conjunctiva), which runs to the edge of the cornea. The
conjunctiva also covers the moist back surface of the eyelids and eyeballs.
•
Prof. Mukul Sharma

34. • Light enters the eye through the cornea, the clear, curved layer in front of
the iris and pupil. The cornea serves as a protective covering for the front
of the eye and also helps focus light on the retina at the back of the eye.
• After passing through the cornea, light travels through the pupil (the black
dot in the middle of the eye).
• The iris—the circular, colored area of the eye that surrounds the pupil—
controls the amount of light that enters the eye. The iris allows more light
into the eye (enlarging or dilating the pupil) when the environment is dark
and allows less light into the eye (shrinking or constricting the pupil) when
the environment is bright.
• Thus, the pupil dilates and constricts like the aperture of a camera lens as
the amount of light in the immediate surroundings changes.
Prof. Mukul Sharma

35. EYE Anatomy
• The size of the pupil is controlled by the action of the pupillary sphincter muscle
and dilator muscle.
• Behind the iris sits the lens. By changing its shape, the lens focuses light onto the
retina. Through the action of small muscles (called the ciliary muscles), the lens
becomes thicker to focus on nearby objects and thinner to focus on distant
objects.
• The retina contains the cells that sense light (photoreceptors) and the blood
vessels that nourish them. The most sensitive part of the retina is a small area
called the macula, which has millions of tightly packed photoreceptors (the type
called cones). The high density of cones in the macula makes the visual image
detailed, just as a high-resolution digital camera has more megapixels.
•
Prof. Mukul Sharma

36. EYE Anatomy
• Each photoreceptor is linked to a nerve fiber. The nerve fibers from the photoreceptors are
bundled together to form the optic nerve. The optic disk, the first part of the optic nerve, is
at the back of the eye.
• The photoreceptors in the retina convert the image into electrical signals, which are carried
to the brain by the optic nerve. There are two main types of photoreceptors: cones and
rods.
• Cones are responsible for sharp, detailed central vision and color vision and are clustered
mainly in the macula.
• Rods are responsible for night and peripheral (side) vision. Rods are more numerous than
cones and much more sensitive to light, but they do not register color or contribute to
detailed central vision as the cones do. Rods are grouped mainly in the peripheral areas of
the retina.
•
Prof. Mukul Sharma

37. Eye Anatomy
• The eyeball is divided into two sections, each of which is filled with fluid.
The pressure generated by these fluids fills out the eyeball and helps
maintain its shape.
• The front section (anterior segment) extends from the inside of the cornea
to the front surface of the lens. It is filled with a fluid called the aqueous
humor, which nourishes the internal structures.
• The anterior segment is divided into two chambers. The front (anterior)
chamber extends from the cornea to the iris. The back (posterior) chamber
extends from the iris to the lens.
• Normally, the aqueous humor is produced in the posterior chamber, flows
slowly through the pupil into the anterior chamber, and then drains out of
the eyeball through outflow channels located where the iris meets the
cornea.
Prof. Mukul Sharma

38. Eye Anatomy
• The back section (posterior segment) extends from the back
surface of the lens to the retina. It contains a jellylike fluid
called the vitreous humor.
• Facts:
6 Millions Cones and 120 Millions Rods present in each eye.
Prof. Mukul Sharma

39. Disorders of Eye
Cataracts
• Cataracts are a degenerative form of eye disease in which the lens
gradually becomes opaque and vision mists over.
Colour blindness:
• Colour blindness is not actually blindness in the true sense but rather is a
colour vision deficiency—people who are affected by it simply do not
agree with most other people about colour matching.
Strabismus:
• Crossed eyes (or strabismus) occur when a person's eyes are not able to
align on the same point at the same time, and appear to be misaligned or
pointed in different directions.
Prof. Mukul Sharma

40. Disorder of Eye
Glaucoma:
• Glaucoma occurs when a build-up of fluid in the eye creates pressure,
damaging the optic nerve.
• Ratinal Detechment :
• When the retina detaches, light sensitive membrane in the back of the eye
becomes separated from the nerve tissue and blood supply underneath it.
• Conjuctivitis
• Pink eye (conjunctivitis) is an inflammation or infection of the transparent
membrane (conjunctiva) that lines your eyelid and covers the white part of
your eyeball. When small blood vessels in the conjunctiva become
inflamed, they're more visible and seems in red/pink in color.
Prof. Mukul Sharma

41. Disorder of Eye
Anemia:
• At the macula, hemorrhages, edema, or hard exudates can cause
impairment of vision. Alternatively, vision loss may occur due to
disc edema or optic neuropathy.
• Cotton wool spots: Retinal nerve fiber layer infarction due to
retinal hypoxia in anemia causes these superficial fluffy white
lesions.
Cataract:
• cataract is a dense, cloudy area that forms in the lens of the eye.
This diseases that are linked with the development
of cataracts include glaucoma and diabetes.
Prof. Mukul Sharma

42. Sensory organ- Ear

43. Prof. Mukul Sharma

44. Anatomy of Ear
The ear is the organ of hearing and balance. The parts of the ear
include:
External or outer ear, consisting of:
– Pinna or auricle. This is the outside part of the ear.
– External auditory canal or tube. This is the tube that connects the outer
ear to the inside or middle ear.
• Tympanic membrane (eardrum). The tympanic membrane divides
the external ear from the middle ear.
Prof. Mukul Sharma

45. Anatomy of Ear
Middle ear (tympanic cavity)
• Ossicles. Three small bones that are connected and transmit the sound
waves to the inner ear. The bones are called:
• Malleus
• Incus
• Stapes
– Eustachian tube. A canal that links the middle ear with the back of the nose. The
eustachian tube helps to equalize the pressure in the middle ear. Equalized
pressure is needed for the proper transfer of sound waves. The eustachian tube
is lined with mucous, just like the inside of the nose and throat.
Inner ear , consisting of:
– Cochlea. This contains the nerves for hearing.
– Vestibule. This contains receptors for balance.
– Semicircular canals. This contains receptors for balance.
Prof. Mukul Sharma

46. Mechanism of Ear
• Hearing starts with the outer ear. When a sound is made outside the outer
ear, the sound waves, or vibrations, travel down the external auditory canal
and strike the eardrum (tympanic membrane). The eardrum vibrates.
• The vibrations are then passed to 3 tiny bones in the middle ear called the
ossicles. The ossicles amplify the sound. They send the sound waves to the
inner ear and into the fluid-filled hearing organ (cochlea).
• Once the sound waves reach the inner ear, they are converted into
electrical impulses. The auditory nerve sends these impulses to the brain.
The brain then translates these electrical impulses as sound.
Functions of Ear: Hearing and body balance.
Prof. Mukul Sharma

47. Ear disorders
• A variety of conditions may affect your hearing or balance:
• Ear infections are the most common illness in infants and young children.
• Tinnitus, a roaring in your ears, can be the result of loud noises, medicines
or a variety of other causes.
• Meniere's disease may be the result of fluid problems in your inner ear; its
symptoms include tinnitus and dizziness.
• Ear barotrauma is an injury to your ear because of changes in barometric
(air) or water pressure.
• Ear blockage: Due to excess wax production or any obstacles in passage.
• Deafness: Loss of hearing.
Prof. Mukul Sharma

48. Prof. Mukul Sharma
Structure of Nose

49. Nose
• The nasal cavity extends from the external opening, the nostrils, to
the pharynx (the upper section of the throat), where it joins the
remainder of the respiratory system.
• It is separated down the middle by the nasal septum, a piece of
cartilage which shapes and separates the nostrils.
• Each nostril can be further divided into roof, floor, and walls.
• The nasal cavity can be divided into the vestibule, respiratory and
olfactory sections.
•
Prof. Mukul Sharma

50. Anatomy of Nose
• Nasal vestibule
The nasal vestibule is the dilated area at the nostril opening.
• Respiratory section
The respiratory section of the nasal cavity refers to the passages through
which air travels into the respiratory system. The respiratory section of
each nostril contains four conchae (protrusions or bumps) which are also
referred to as turbinate bones or lobes and are covered by the nasal
mucosa. Underlying these conchae are meatuses (passages to interior
body structures). The meatuses of the nasal cavity connect to the
paranasal sinuses.
• Olfactory region
The olfactory receptors (receptors for smell sensations) are found in this
section of the nasal cavity. Bowman’s glands are also found in this section
of the nasal cavity.
Prof. Mukul Sharma

51. Nose Common Disorder
Sinusitis: sinus infections, congestion, and airway blockage.
• Symptoms : Pain in your face, upper teeth or in your ear, and
drainage that is obstructed or abnormal, or nasal congestion.
Symptoms of congestion include feelings of pressure in your
head, headaches, and dizziness. Airway blockage of the nose is
not being able to breathe properly through the nose.
• Reasons : Allergies, to viral or bacterial infections produced
septum.
Prof. Mukul Sharma

52. References
• Waugh Anne, Grant Allison, Ross & Wilson: Anatomy and
physiology in health & illness 2006, edition 10th, Elsevier
publication.
• Tortora GJ, Derrickson B, Principles of anatomy & physiology
2007, edition 11th, John wiley & sons. Inc.
• Ingawale K D., Mandlik K. S., Human Anatomy and Physiology,
Fourth edition, 2018, Nirali pakashan.
Prof. Mukul Sharma