THE NERVOUS SYSTEM --- LOCATION &

FUNCTION OF DIFFERERENT PARTS

SL.NO STRUCTURE LOCATION FUNCTION
1. Meninges On the CNS as connective Provides protection for the brain
tissue layers and spinal cord as it is regarded
as the protective membrane of
brain and spinal cord (outer dura
mater, middle arachnoid
membrane and inner pia mater)
2. Ganglia Along the nerve where cyton Aggregates of the nervous tissue
concentration is there responsible for transmission of
nerve impulse.
3. Myelin Sheath Myelinated Neuron  To increase the speed
(Protective covering of the of nerve impulse
neuron) conduction
 To insulate the axon
i.e. preventing mixing
of the impulses in the
adjacent fibre.
4. Nodes of Ranvier Present on the myelinated Conduction of nerve impulse
neurons in between the gaps from the myelinated fibres and
of the myelin sheath branching of the neurons takes
place from it.
5. Axon Part of a neuron which arises Acts as the efferent process
from the cell body or cyton. which receives the impulses from
Also present in the white the cyton and transmits to the
matter of the brain & spinal next neuron through synapse.
cord
6. Dendrons Part of a neuron that arises Acts as the afferent process
from the cell body or cyton which conducts impulses from
outside towards the cell body.
7. Cyton Present in the ganglia and also Receives the nerve impulses from
(Soma/Perikaryon/ in the gray matter of the brain the dendrites and transmits to the
Cell body) and spinal cord axon.
8. Acetylcholine Present within the vesicles of Acts as the neurotransmitter and
Pre- synaptic neuron responsible for synaptic
transmission by the involvement
of Calcium ions.
9. Synapse Junction between the two Allows the unidirectional flow of
neurons nerve impulse from axon terminal
(Pre- synaptic & Post- to the dendrites of next neuron.
synaptic) Also acts as the seat of fatigue in
the CNS.
10. Cerebrospinal Present within the sub Acts as the cushion and shock
fluid (CSF) arachnoid space of the brain absorber for the brain and spinal
and also present within the cord thereby protecting it from
ventricles of brain and central mechanical injury and internal
canal of spinal cord. damage.
11. Sensory neurons Throughout the body Conducts nerve impulses from
the receptors to CNS.
12. Motor neurons Throughout the body Conducts nerve impulses from
CNS to effector or target organs.
13. Brain (Encephalon Major part of the CNS which Acts as one of the most
- The delicate lies within the terminal of the controlled organ of our body.
organ) spinal cord and within the
skull.
14. Cerebrum Major part of the Acts as the seat of intelligence,
prosencephalon / Fore brain memory, thinking, planning and
reasoning. Also involved in the
sense of responsibility and acts as
the moral and civic sense and
involved in controlling all mental
activities
15. Frontal lobe Cerebrum Responsible for thinking,
reasoning, planning, memorizing,
parts of speech, movement,
emotions, problem solving and
intelligence. Acts as a seat of
intelligence.
16. Parietal lobe Cerebrum Responsible for perception of
different senses like temp,
pressure, touch etc. Also
associated with orientation,
recognition and perception of
stimuli
17. Temporal lobe Cerebrum Hearing (Auditory nerve from ear
connects to the temporal
lobe).Perception and recognition
of auditory stimuli
18. Occipital lobe Cerebrum Vision (Optic nerve from eye
connects to the occipital lobe).
Associated with the visual
processing
19. Corpus callosum Site where the two cerebral Transfer of information from one
hemispheres of cerebrum are cerebral hemisphere to other.
connected to each other.
20. Cerebellum Major part of the Responsible for the muscular
Rhombencephalon / Hind coordination of the body and
brain helps to maintain static
equilibrium.
21. Thalamus Base of the forebrain and Acts as the relay station as it
lateral to both the sides of the receives all afferent or sensory
third ventricle. fibres from all the parts of the
body and sends to the efferent or
motor fibres.
Also acts as the important centre
for emotions and reflex activities.
22. Hypothalamus Basal part of the forebrain and  Regulates body
forms floor of the third temperature and also
ventricle controls the emotional &
sexual behaviour and
secretory activities of the
pituitary gland
 Also acts as the highest
centre for ANS.Controls
the endocrine functions
of the body.
23. Olfactory lobes Forebrain / Prosencephalon Controls olfaction or smelling.
24. Optic lobes Dorsal side of theMidbrain / Controls vision
Mesencephalon
25. Corpora Midbrain / Mesencephalon Controls visual reflexes.
quadrigemina
26. Cruca Cerebri Midbrain / Mesencephalon Connects Prosencephalon with
Rhombencephalon.
27. Midbrain Uppermost portion of the Serves as the centre for mediating
(Mesencephalon) brain stem & connects visual, auditory and tactile
Prosencephalon with impulses
Rhombencephalon.
28. Pons Varolli Below the mid brain and just Connects the left and right
(Vermis fibres) above medulla oblongata. cerebellar hemispheres.
Also regulates respiration, heart
rate and blood pressure.
29. Purkyne Cells Gray matter of Cerebellum. Maintains Static equilibrium of
the body.
30. Medulla Caudal part of the brain stem Controls all the involuntary
oblongata lies just above the spinal cord. actions of the body such as
beating of heart and breathing
and cardiac activities.
Coughing, vomiting, sneezing etc
are controlled by medullary
centres.
31. Spinal cord Cylindrical part of the CNS Directly concerned with all reflex
presents within the vertebral actions and with Micturition.
canal and extends from
Foramen Magnum within the
cranium up to the second
lumbar vertebra.
32. Sclera Present as the first protective Protects and maintains shape of
layer of the eye which rounds the eyeball and also prevents the
the eyeball containing scattering of light.
collagen fibres.
33. Choroid (contains Present as second protective Proper nourishment, supplies
the pigment covering of the eye which oxygen and food to the eye and
Melanin) forms the inner lining of the prevents scattering of light.
opaque portion of the sclera.
(Vascular black layer)
34. Retina Innermost light sensitive Acts as the photosensitive layer
nervous third layer of the and is responsible for the
eyeball and present at the formation of an image of an
posterior side of the eyeball object.
35. Rod cells Retina For vision in dim light (scotopic
(contains vision)
Rhodopsin)
36. Cone cells Retina For vision in bright light
(contains (photopic vision) and also
Iodopsin) responsible for colour perception.
37. Eye muscles Six in number and are Holds eyeball in the orbit
attached to the sclera at one
end and orbit wall at the other
end (4 rectus muscles and 2
oblique muscles)
38. Conjunctiva Thin epithelial layer which Protects the corneal portion of the
lines the inside of the eyelids eyeball and prevents it from
and is continuous across the drying up. Viral infection causes
front of the eyeball. Conjunctivitis

39. Ciliary Muscles Thickened anterior part of the Helps in altering focal length of
(Ciliary body) choroid that rounds the the eye lens & holds the lens in
crystalline lens proper position.
40. Tear Glands Almond shaped exocrine  Keeps conjunctiva &
(Lachrymal gland located on the scleral cornea moist.
glands / Tarsal surface of the eyeball at the  Lubricates the surface of
glands/ base of the upper eyelid of the eyeball.
Meibomian each eye  Tears contain a
glands / Composition of Tears :- hydrolytic enzyme
Glands of Zeiss) (98.2% water and 1.8% Lysosyme which
solutes- both electrolytes as destroys the infective
well as non electrolytes). bacteria & harmful germs
Electrolytes includes NaCl, that enters the eye. It is
NaHCO3 while non- therefore bactericidal in
electrolytes includes glucose action.
& Urea  Also communicates
emotions.
41. Pupil Within the eye as a circular Allows the light rays to enter the
aperture within the ciliary eye.
body
42. Iris (Opaque & In the eye in between the Controls intensity of the light
pigmented disc of cornea and lens entering into the eye, thereby
tissues) alters the size of the pupil.
43. Yellow Spot (Area Particular area on the retina Area of the sharpest and distinct
of Best vision / which lies at the back of the vision. It is the site by which we
Fovea centalis / eye almost at the centre of the have to move our eye from word
Macula lutea) horizontal axis of the eyeball to word during reading.
and contains maximum
number of cone cells.
44. Blind Spot (Area Particular disc like area within Site at which the optic nerves
of no Vision) the eyeball located just below leaves the eyeball and blood
the yellow spot and has no vessels enters.
photo receptors (rods and
cones)
45. Cornea Sclera buldges out anteriorly and Helps in refracting light towards
becomes transparent in the front retina.
region that forms the outer
fibrous coat of the eyeball.
46. Lens / Crystalline Between aqueous humour and Serves as the good refractory
lens vitreous humour and forms the media of the eye and helps in the
elastic biconvex structure production of the image and also
which is held in position with separates the anterior and
the help of suspensory posterior chamber.
ligament.
47. Suspensory Radiates from the edge of the Holds the lens in proper position.
ligament lens and gets attached to the
ciliary body.
48. Aqueous Humour In between the cornea and It refracts light and produces
anterior surface of the lens. image on the retina and keeps the
lens moist thereby protecting it
from shock.
49. Vitreous Humour In between the posterior  Maintains the shape of
(largest part of the surface of the lens and inner eyeball.
eyeball) surface of the retina.  Refracts light rays.
 Maintains eyeball
pressure
(Intra Occular
Pressure)
50. Optic Nerve Arises from the blind spot in Visual impulse produced on the
the eye. retina will be conveyed to the
occipital lobe of the cerebrum of
brain by this nerve.
51. Ear Sense organ located at the Hearing and maintains dynamic
facial portion on either side of & static equilibrium of the body.
the head and behind the eyes.
52. Pinna External or outer Ear Collects sound waves from
different environments & directs
it to the external auditory canal.
53. Auditory Canal Funnel shaped zig – zag canal Receives the sound waves from
located in the external ear pinna & directs it to the
tympanum.
54. Ceruminous Above the external auditory Helps in the secretion of
glands / Wax canal Cerumen ( Ear Wax)
glands
55. Tympanum / Ear External ear ( beginning of Converts sound waves into
drum middle ear attached to three vibrations and directs it to the
ear ossicles) middle ear.
56. Ear ossicles Middle ear Conducts sound vibrations from
(Hammer, Anvil ear drum into the membrane of
& Stirrup; the oval window ( Fenestra
Biological name ovalis) of the internal ear.
are Malleus,
Incus & Stapes)
57. Stapes (smallest Middle ear Transmission of the sound
bone) vibrations from ear drums and
magnified the vibrations due to
the lever like action and
transmitted to the cochlea.
 58. Oval Window Upper oval window, situated Sound vibrations from the
( Fenestra ovalis) on the inner side of the middle tympanic membrane are picked
of the middle ear connecting up by the ear ossicles and from
middle ear with the scala there, transmitted to the
vestibule of cochlea. perilymph of the inner ear
through this window.

59. Round Window Lower round window situated The scala tympani end through
(Fenestra rotunda) on the inner side of the middle this membrane blindly. Its
ear connects scala tympani with the
middle ear.
60. Eustachain tube Middle ear Equalizes air pressure on both the
(Laryngopharynx) sides of the tympanum.
61. Semi circular Internal ear / Membranous Maintains dynamic equilibrium
Canal Labyrinth of the body.
62. Vestibular Internal ear / Membranous Maintains static equilibrium of
apparatus Labyrinth the body.
(Ampulla,
Utriculus &
Sacculus)
63. Cochlea Internal ear / Membranous Helps in hearing since it contains
Labyrinth in front of the audio – receptor region called
vestibular canals filled with Organ of Corti.
endolymph & perilymph and Converts sound vibrations to
makes 23/4 turns in humans & auditory impulses.
35 mm long. Incompletely
partitioned by upper Reissner’s
membrane & lower Basilar
membrane (Scala vestibule,
Scala media & Scala tympani)
64. Otolith ( Calcium Crista ampullaris ( Ampulla) Responsible for the dynamic
carbonate of the Vestibular apparatus, equilibrium of the body.
containing also oresent in the semi
crystals) circular canal
65. Vestibule Oval central portion of the Concerned with the Static
membranous labyrinth, Equilibrium.
consists of two sacs called
utricle & saccule
66. Organ of Corti Cochlea in scala media in ear
Audio receptive organ. Hearing
67. Utricle & Saccule Oval central portion of the
Contains receptors for static
membranous labyrinth
balance.
68. Auditory Nerve Arises from the scala media of
Transmits sound impulses to the
the cochlea of the internal ear.
temporal lobe of the cerebrum of
the brain
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Prepared by

Mr. Sumit Roy [Senior Biology Faculty] (9830431393/7044929409)

M.Sc (Zoology), Gold Medalist of Vidyasagar University, B.Ed

sumitroy888@gmail.com sumit@ssa.org.in