How a part of central nervous system brain is attached to the other part of body?
Introduction
We know that brain is a part central nervous system it control whole the body through their network of neuron they arise from brain and attached to specific area there they perform their function.
What is cranial nerve?
A neuron which arise from central nervous system especially from brain and attached to the body part is called cranial nerve. There are twelve pairs of cranial nerve which attached to body part by arising from brain. All of these are sensory, motor or mixed nerves. For more about nervous systemhttps://healthduhs.blogspot.com/2026/05/what-is-nervous-system-and-how-it-is.html
Their origin is from different areas 2pairs arise from four brain, 2pairs from midbrain and 8pairs from hindbrain( 4pairs from pons and 4pairs from medulla oblongata ).
Below the detail of cranial nerves are discussed.
Olfactory nerve ( I )
This is a first cranial nerve which is
Sensory in function and send a signal to the brain about smell.
There are special receptor that are present in the mucousal epithelium of upper part of nose they are responsible for detecting the odor of any fluid.
When the odor molecule inter the nose and they mixed with the fluid of nose and the mixed odor will be detected by the olfactory receptor and they send a signal to the brain through olfactory nerve.
On the surface of cerebroform plate there is a oval shaped setructure called olfactory bulb. This bulb receive signal first and organize those signal before going to functional area.
After organization of these signals by olfactory bulb these signal will be send to the temporal area of the brain through olfactory tract.
After reaching the olfactory cortex or temporal area they start to rememorization through hippocampus ( where all memory is present from the beginng of birth) and after recognization next it send send to amygdala which gives pleasure about smell and hypothalamus is involved which is responsible for involuntary responses.
Optic nerve ( II )
It is the second cranial nerve that arise from the diencephalon and which is responsible for vision. It is also sensory in function.
First rods which is more sensitive in dimlight and second cones which is more sensitive in bright light both convert light into electrical signal.
After conversion of electrical signal it sends to bipolar which is just a relay centre and send this signal to ganglion cells at the axon side of ganglion cell they form a disk after optic disk optic nerve start here.
Actually optic nerve ia made up of thousand of nerve fibers( that are axon of ganglion cells) and retina has two parts one is nasal surface that is near to nose and another is temporal serface which is near to ear and temporal bone.
Inside the optic nerve all those fibers goes straight toward its side e.g from righ eye to right side of the brain and from left eye to left side of the brain these fibers are called
Temporal retinal fibers.
And the second type of nerve fibers in which left eye fibers goes toward right side of brain and right eyes fibers goes toward left side of brain
Nasal retinal fibers.
All those fibers where they cross each other are called optic chiasm.
After optic chiasm they start to form an optic tract.
After optic tract the impulse goes to lateral ganiculate body (LGB) which is a relay centre of optic nerve.
What is optic tract?
After optic chiasm the nasal retinal fiber and temporal fiber of opposite eye and form one tract that is called optic tract.e.g
Nerve fiber of Right eye ( each eye contain temporal and retinal cornea fiber) after optic chiasm the right nasal fiber goes toward the left side where it combine with the left temporal retinal fiber which goes straight make one tract.
Secondly the left eye which also contains both temporal and nasal cornea fiber. Nasal cornea fiber of left eye after optic chiasm goes toward right side and combine with right temporal retinal fiber and form another optic tract. The temporal retinal fiber of left eye goes on the same way.
After optic tract signal goes to lateral geniculate area which receive signal and just a relay centre. There are two lateral geniculate area which receive signal present in the thalamus on the both side of the brain.
The second last part which is called optic radiation that receive signals from lateral geniculate area and transfer it to visual cortex.
Visual cortex is the last function area where visual information collect and make a response.
It is located at the back of brain in occipital lobe.
Occulomotor ( III )
It is the third cranial nerve that arise from mid brain and is important for the movement of eye in the upward, downward, medially and slightly inward rotation. It control these movements by controlling superior rectus, inferior rectus, medial rectus,inferior oblique and also open eye lids.
It also help in the contraction of pupil which is a parasympathetics function.
Trochlear nerve ( IV )
It is the four cranial nerve. Which originate from the dorsal back of the midbrain
It control only one muscle of human eye that is superior oblique muscle which help rotating eye inward, moving eye outward slightly and when looking inward it move the eye downward.
Trigeminal nerve ( V )
It is a 5th cranial nerve which is mixed in nature ( mean both sensory ot motor function ).
It carries sensation from these areas
* Forehead
* Eyes
* Cheeks
* Nose
* Upper jaw
* Lower jaw
* Teeth
It also control three muscles
*Masseter
*Temporalis
* Pterygoid muscle
These muscles help us in
* Chewing food
* Movement of jaw
* Bite of food
It has three branches
1. Opthalmic
Region of forehead and eye
2. Maxillary
Region Upper jaw
3.Mandibular
Region of Lower jaw chewing muscle
Abducen nerve ( VI )
It is the 6th cranial nerve which is motor in function and originate from pons of the brain stem.
It is responsible for the abduction of eye or movement of eye away from nose.
Facial nerve ( VII )
It is the 7th cranial nerve which is mixed in function and origanate from the pons of brain stem.
It control facial expression like smiling and frowning.
It is responsible for test almost 75% which give us the test of every thing.
It also control the secretion of lacrimal and slivary gland.
Vestibulocochlear nerve ( VIII )
It is the 8th cranial nerve which is originate from the pon of brain stem.
It is responsible for both hearing and balance of human body.
It's vestibular part is responsible for human equlibrium and cochlear part is responsible for hearing both are attached to the inner human ear.
Glossopharyngeal nerve ( IX )
It is the 9th cranial nerve that is mixed in function.
It carries sensation from the back of the tongue, phyrnx, middle ear and tonsil.
It also play a role in the felling of test of 30%.
* It also help in swallowing
* Stimulate parotid salivary gland which is help in the production of sliva
Vagus nerve ( X )
It is the 10 cranial nerve that is mixed in function.
It control muscle of phyrnx and lyrnx and help in speaking and swallowing.
* It carries sansation from pharynx, larynx, abdominal organ and thorasic organ.
* It reduce breathing rate, decrease heart beat and increase the rate of digestion that is important that is its main function in parasympathetic activities.
Accessory nerve ( X )
It is the 11th cranial nerve that is motor in function and originate from medulla oblongata.
It is responsible for the movement of head and shoulder.
Hypoglossal nerve ( XII )
It is the 12th cranial nerve which is motor in function and originate from medulla oblongata.
It supplies all interinsic and most extrensic muscle to the tongue.
It is responsible for speaking, swallowing and chewing or moving food inside the mouth. We can say it is responsible for the movement of tongue.
WHO -World Health Organisation
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