Cranial Nerves
Presentation15 slidesB.Pharm, Pharm.D
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Notes on Cranial Nerves - Olfactory nerves, Optic nerves, Oculomotor nerves, Trochlear nerves, and so on.
- cranial nerves
- nervous system
- sensory nerves
- motor nerves
- neuroanatomy
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- Slide 1. CRANIAL NERVES Presented By Dr. AYESHA FATIMA PharmD Assistant Professor
- Slide 2. ❖ There are 12 pairs of cranial nerves originating from nuclei in the inferior surface of the brain, some sensory, some motor and some mixed. ❖ Their names suggest their distribution or function, which, in the main, is generally related to the head and neck. ❖ They are numbered using Roman numerals according to the order they connect to the brain, starting anteriorly. ❖ They are: Cranial Nerve Number Name Type I Olfactory Sensory II Optic Sensory III Oculomotor Motor IV Trochlear Motor V Trigeminal Mixed VI Abducens Motor VII Facial Mixed VIII Vestibulocochlear (Auditory) Sensory IX Glossopharyngeal Mixed X Vagus Mixed XI Accessory Motor XII Hypoglossal Motor
- Slide 3. I. Olfactory nerves (sensory) • These are the nerves of the sense of smell . • Their sensory receptors and nerve fibres originate in the upper part of the mucous membrane of the nasal cavity, pass upwards through the cribriform plate of the ethmoid bone and then pass to the olfactory bulb. • The nerves then proceed backwards as the olfactory tract, to the area for the perception of smell in the temporal lobe of the cerebrum.
- Slide 4. II. Optic nerves (sensory) • These are the nerves of the sense of sight . • Their fibres originate in the retinae of the eyes and they combine to form the optic nerves. • They are directed backwards and medially through the posterior part of the orbital cavity. • They then pass through the optic foramina of the sphenoid bone into the cranial cavity and join at the optic chiasma . • The nerves proceed backwards as the optic tracts to the lateral geniculate bodies of the thalamus. • Impulses pass from there to the visual areas in the occipital lobes of the cerebrum and to the cerebellum. • In the occipital lobe sight is perceived, and in the cerebellum the impulses from the eyes contribute to the maintenance of balance, posture and orientation of the head in space.
- Slide 5. III. Oculomotor nerves (motor) 🢝 These nerves arise from nuclei near the cerebral aqueduct. 🢝 They supply: 🢝 Four of the six extrinsic muscles, which move the eyeball, i.E. The superior , medial and inferior recti and the inferior oblique muscle 🢝 The intrinsic (intraocular) muscles: 🢝 Ciliary muscles , which alter the shape of the lens, changing its refractive power. 🢝 Circular muscles of the iris, which constrict the pupil 🢝 The levator palpebrae muscles , which raise the upper eyelids.
- Slide 6. IV. Trochlear nerves (motor) • These nerves arise from nuclei near the cerebral aqueduct. • They supply the superior oblique muscles of the eyes.
- Slide 7. V. Trigeminal nerves (mixed) 🢝 These nerves contain motor and sensory fibres and are among the largest of the cranial nerves. 🢝 They are the chief sensory nerves for the face and head (including the oral and nasal cavities and teeth), transmitting sensory impulses, e.g. for pain, temperature and touch. 🢝 The motor fibres stimulate the muscles for chewing (mastication). 🢝 there are three main branches of the trigeminal nerves. 🢝 The ophthalmic nerves are sensory only and supply the lacrimal glands, conjunctiva of the eyes, forehead, eyelids, anterior aspect of the scalp and mucous membrane of the nose. 🢝 The maxillary nerves are sensory only and supply the cheeks, upper gums, upper teeth and lower eyelids. 🢝 The mandibular nerves contain both sensory and motor fibres. These are the largest of the three divisions and they supply the teeth and gums of the lower jaw, pinnae of the ears, lower lip and tongue. 🢝 The motor fibres supply the muscles for chewing.
- Slide 8. VI. Abducens nerves (motor) 🢝 These nerves arise from nuclei lying under the floor of the fourth ventricle. 🢝 They supply the lateral rectus muscles of the eyeballs causing abduction. VII. Facial nerves (mixed) 🢝 These nerves are composed of both motor and sensory nerve fibres, arising from nuclei in the lower part of the pons. 🢝 The motor fibres supply the muscles of facial expression. 🢝 The sensory fibres convey impulses from the taste buds in the anterior two-thirds of the tongue to the taste perception area in the cerebral cortex.
- Slide 9. VIII. Vestibulocochlear (auditory) nerves (sensory) 🢝 These nerves are composed of two divisions, the vestibular nerves and cochlear nerves. 🢝 The vestibular nerves arise from the semicircular canals of the inner ear and convey impulses to the cerebellum. 🢝 They are associated with the maintenance of posture and balance. 🢝 The cochlear nerves originate in the spiral organ (of Corti) in the inner ear and convey impulses to the hearing areas in the cerebral cortex where sound is perceived.
- Slide 10. IX. Glossopharyngeal nerves (mixed) 🢝 The motor fibres arise from nuclei in the medulla oblongata and stimulate the muscles of the tongue and pharynx and the secretory cells of the parotid (salivary) glands. 🢝 The sensory fibres convey impulses to the cerebral cortex from the posterior third of the tongue, the tonsils and pharynx and from taste buds in the tongue and pharynx. 🢝 These nerves are essential for the swallowing and gag reflexes. 🢝 Some fibres conduct impulses from the carotid sinus, which plays an important role in the control of blood pressure
- Slide 11. X. Vagus nerves (mixed) 🢝 These nerves have the most extensive distribution of the cranial nerves; their name aptly means ‘wanderer’. 🢝 They pass downwards through the neck into the thorax and the abdomen. 🢝 These nerves form an important part of the parasympathetic nervous system. 🢝 The motor fibres arise from nuclei in the medulla and supply the smooth muscle and secretory glands of the pharynx, larynx, trachea, bronchi, heart, carotid body, oesophagus, stomach, intestines, exocrine pancreas, gall bladder, bile ducts, spleen, kidneys, ureter and blood vessels in the thoracic and abdominal cavities. 🢝 The sensory fibres convey impulses from the membranes lining the same structures to the brain .
- Slide 12. XI. Accessory nerves (motor) 🢝 These nerves arise from nuclei in the medulla oblongata and in the spinal cord. 🢝 The fibres supply the sternocleidomastoid and trapezius muscles . 🢝 Branches join the vagus nerves and supply the pharyngeal and laryngeal muscles in the neck. XII. Hypoglossal nerves (motor) 🢝 These nerves arise from nuclei in the medulla oblongata. 🢝 They supply the muscles of the tongue and muscles surrounding the hyoid bone and contribute to swallowing and speech.
