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The spinal cord has...
- spinal nerves
- -theses are segmental
- -they cover a specific region of skin and/or muscle
- -and are always mixed (sensory+motor)
Why does the brain need cranial nerves?
in side the skull, the presence of head-only muscle groups (e.g for eye movement), head only sensations (e.g vision, hearing) and head only autonomic functions (e.g salivation) along with all the other stuff means that the head needs cranial nerves
What are the twelve cranial nerves?
- I. Olfactory
- II. Optic
- III. Oculomotor
- IV. Trochlear
- V. Trigeminal
- VI. Abducens
- VII. Facial
- VIII. Vestibulocochlear
- IX. Glossopharyngeal
- X. Vagus
- XI. Accessory (Spinal Accessory)
- XII. Hypoglossal
- "Oh, Oh, Oh, To Touch And Feel Very Green Vegetables, AH"
- to remember which are sensory, motor or both
- Some Say Marry Money, But My Brother Says Big Brains Matter More.
Cranial Nerve I: Olfactory
carries olfactory (i.e. smell) information from the olfactory epithelium inside the nasal sinuses, to the brain.
Cranial nerve II: Optic
carries optic (ie. sight, visual) information from the retina lining the inside of the eye to the brain
Cranial nerve III: Oculomotor
- innervates four of the six muscles: medial rctus, superior rectus, inferior rectus, and inferior oblique muscle.
- It also innervates the iris muscle which controls the size of he pupil.
- see p.575
Cranial nerve IV: Trochlear
- innervates the superior oblique muscle, which passes through the trochlea.
- see p. 575
Cranial nerve VI: Abducens
- So named because it abducts the eye (carries it away from the midline), so it innervates the lateral rectus.
- see p. 575
Cranial nerve V: Trigeminal
- a mixed nerve (sensory+motor) but is primarily sensory for the face
- This nerve has three divisions:
- -ophthalmic or V1 ("eye") for the eye and forehead
- -Maxillary or V2, for the cheek and upper jaw (Maxilla)
- -Mandibular or V3, for the lower jaw (mandible)
- The trigeminal is the larges cranial nerve
- see p.576
Cranial nerve VII: Facial
- a mixed nerve (sensory+motor) but is primarily motor for the muscles of facial expression.
- it innervates the lacrimal glands which produces tears and submandibular and sublinqual glands which produce saliva
- its sensory function is to carry taste information from the anterior 2/3 of the tongue. This info joins the other taste fibers to form a nerve called the chorda tympani
Cranial nerve VIII: Vestibulocochlear
- Hearing and Balance
- See p. 578
Cranial nerve IX: Glossopharyngeal
- Parotid gland, soft palate, some taste
- innervates the posterior 1/3 of he tongue
- also innervates the parotid gland- the largest of the salivary glands
- carries info from the carotid body, a sensory organ on the carotid artery which senses blood pressure.
Cranial nerve X: Vagus
- "The Wanderer"
- Innervates many organs in the thorax and abdomen
Cranial nerve XI: (Spinal) Accessory Nerve
- pure motor
- innervating two muscles: the trapezius along the back of the neck and shoulders, and the sternocleidomastoid, which connects the sternum(sterno), clavicle (cleido) and mastoid process of the temporal bone.
Cranial nerve XII: Hypoglossal Nerve
- purely motor and does only one thing.
- it sticks out the tongue