CRANIAL NERVE: COMPONENT, ORIGIN, AND INSERTION, FUNCTION AND EXAMINATION: PART 1(1st and 2nd nerve that is olfactory and optic nerve)
Hey, guys hope you are doing well, today I am going to tell you about one of the nerves called Cranial nerve.
Cranial nerve is the nerves that emerge from the brain. There are 12 pairs of cranial nerves. 10 out of 12 cranial nerves emerges from the brainstem.
Olfactory and optic nerve emerge from cerebrum or forebrain.
Each cranial nerve is paired and present both sides.
The numbering of cranial nerve from 1 to 12 pair is based on the order in which they emerge from the brain, from front to back(brainstem).
12 pairs of cranial nerves are following-
I. Olfactory nerve
II. Optic nerve
III. Oculomotor nerve
IV. Trochlear nerve
V. Trigeminal nerve
VI. Abducens nerve
VII. Facial nerve
VIII. Vestibulocochlear nerve
IX. Glossopharyngeal nerve
X. Vagus nerve
XI. Spinal accessory nerve
XII. Hypoglossal nerve
Olfactory nerve-1st nerve
• COMPONENT: olfactory nerve is a Sensory nerve.
• FUNCTION: Smell is the main function of the olfactory nerve
• ORIGIN: it originates from cerebrum( Olfactory receptor nerve cells)
• OPENING TO THE SKULL: Opening is in cribriform plate of ethmoid.
• EXAMINATION-For examination of olfactory nerve you need to examine for its function that is the smell.
• Test both perception and identification using aromatic non -irritant material example-soap, clove, coffee
• One nostril is closed while the patient sniff with another nostril along with that eyes should be closed so that material which is used by examiner can be identified by a person visually.
OPTIC NERVE: -2nd nerve
• COMPONENT: Optic nerve is a Sensory nerve.
• FUNCTION: Vision
• ORIGIN: Back of the eyeball
• OPENING TO THE SKULL: Optic canal
• EXAMINATION-for optic nerve examination
• 1.visual equity is checked -in this
• Severe deficit- a.can patient see light and movement both are checked?
• b.can patient count fingers?
• Mild deficit -record reading acuity with wall and hand chart. chart used are following-
• Jaeger type card for near vision labeled according to size.
• Snellen’s wall chart- in this patient need to sit at the 6m distance from the wall chart.
• Visual field -for visual field checking there is gross testing is done called as confrontation, in this comparison the patient field of vision by advancing a moving finger or, more accurately, a red 5mm pin from the extreme periphery towards the fixation point. This maps out cone vision.
• A 2mm pin will define central field defects which may only manifest as loss of color perception.
• Patient fixes on a central point. a point of light is moved centrally from the extreme periphery. The position at which the patient observes target is marked on a chart. Repeat testing for multiple directions .patient should sit in front and equal in height to the examiner.
• Pupil examination – when doing pupil examination following can be checked
• A.size- small/large
• Reaction to light – both pupils constrict when the light is shone in either eye.
• Reaction to accommodation and convergence- pupil constriction occurs when the gaze is transferred to near point object.
this was the description of only two nerves. As it is only part 1. Description of other nerves is given in the next parts.