V, VI, VII, VIII Cranial nerves detail.pptx

V, VI, VII, VIII Cranial nerves detail

1. FUNCTIONAL COMPONENTS OF CRANIAL NERVES

2. INTRODUCTIOn Refers to the types of nerve fibres each Cranial Nerve carries along with their specific roles and the areas/ organs they supply. Cranial nerves can be: Sensory in function  carrying only sensory nerve fibres. Motor in function  carrying only motor nerve fibres. Mixed in function  carrying both types of nerve fibres. Nerve fibres of cranial nerves can be categorized as follows: By signal direction Afferent/ Motor: carries signals from periphery to central nervous system. Efferent/ Sensory: carries signals from central nervous system to periphery.

3. By the structure it’s supplying Somatic: supplies to special sense organ derived from ectoderm & voluntary muscles derived from somites Visceral: supplies to special sense organ derived from endoderm, voluntary muscles derived from branchial arches & involuntary muscles By function or sensation General: nerves recognizing general sensations (like touch, pain, pressure, etc.) or carrying signals for parasympathetic/ motor functions to these sensations which can be also be done by the spinal nerves. Special: nerves recognizing sensations (like taste, smell, hearing & vision) or carrying signals for motor functions pertaining to these sensations which is only done by the cranial nerves.

4. DEVELOPMENT A groove, Sulcus limitans divides the neural tube into two parts: Alar Lamina Basal Lamina Each of the seven types of nerve fibres arise from seven specific nuclei present in only one of these two lamina. Alar lamina: contains all nuclei giving rise to afferent fibres called as Sensory column Basal lamina: contains all nuclei giving rise to efferent fibres called as Motor column

5. Types of Nerve Fibre Supply Cranial nerves with the fibre GSA General somatic senses & proprioceptive senses from muscles & joints V, VII, IX, X GVA General senses from viscera IX, X SSA Special senses (eye & ear) I, II, VIII SVA Special senses (nose and tongue) VII, IX GSE Skeletal muscles of somatic origin III, IV, VI, XII GVE Smooth muscles, cardiac muscles & glands III, VII, IX, X SVE Skeletal muscles of branchial origin V, VII, IX, X, XI

6. CN Functional Components Distribution & Function I SSA Olfaction II SSA Vision III GSE GVE Motor to inferior oblique, medial, inferior & superior rectus Parasympathetic to sphincter pupillae, ciliary muscles for pupillary constriction & accommodation IV GSE Motor to superior oblique

7. CN Functional Components Distribution & Function V Trigeminal division: Ophthalmic: GSA Maxillary: GSA Mandibular: GSA Sensation from forehead, scalp, eyelids, nose and eye, including conjunctiva Sensation from lower eyelid, nasal cavity and paranasal sinuses, upper lip and palate Sensation from lower face and scalp, tongue and floor of mouth, proprioception from muscles of mastication & temporomandibular joint VI GSE Motor to lateral rectus

8. CN Functional Components Distribution & Function VII GSA SVA GVE SVE Sensation from external acoustic meatus and skin behind pinna. Proprioception from facial muscles Taste from anterior two-thirds of tongue P arasympathetic to lacrimal gland and mucous membrane of nasal and oral cavities & submandibular and sublingual glands Motor to muscles of facial expression, stapedius, posterior belly of digastric and stylohyoid VIII Vestibular region: SSA Cochlear region: SSA Sensations of equilibrium and motion Hearing

9. CN Functional Components Distribution & Function IX GSA GVA SVA GVE SVE General sensation from posterior one-third of tongue, oropharynx and middle ear Sensory from carotid body & carotid sinus Taste from posterior one-third of tongue Parasympathetic to parotid salivary gland Motor to stylopharyngeus

10. CN Functional Components Distribution & Function X GSA GVA GVE SVE General sensation from pharynx, larynx, trachea, oesophagus, part of auricle and external auditory meatus Sensory from thoracic and abdominal viscera, aortic arch & aortic bodies Parasympathetic to glands and smooth muscle in the pharynx, larynx; thoracic and abdominal viscera Motor to pharyngeal, external laryngeal and oesophageal striated muscles

11. CN Functional Components Distribution & Function XI Cranial root: SVE Spinal root: SVE Motor to muscles of soft palate and intrinsic muscles of larynx Motor to sternocleidomastoid and trapezius XII GSE Motor to all intrinsic and extrinsic muscles of the tongue, except palatoglossus

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