Cranial Nerves Flashcards
INTRODUCTION TO CRANIAL NERVES III, IV &
VI
❖Cranial nerves III, IV, and VI are the ———, ———, and ——— nerves, respectively.
❖They are all predominantly (sensory/motor?) nerves that innervate the ——- muscles of the eye.
❖The nuclei of these three nerves are located in the ———.
INTRODUCTION TO CRANIAL NERVES III, IV &
VI
❖Cranial nerves III, IV, and VI are the oculomotor, trochlear, and abducens nerves, respectively.
❖They are all predominantly motor nerves that innervate the ocular muscles of the eye.
❖They control the movement of the eyeballs and the eyelids.
❖The nuclei of these three nerves are located in the brainstem.
❖The oculomotor nucleus is located in the ———, the trochlear nucleus is located in the ———, and the abducens nucleus is located in the ——.
❖The oculomotor nucleus is located in the midbrain, the trochlear nucleus is located in the midbrain, and the abducens nucleus is located in the pons.
❖The oculomotor nucleus is located in the ———, the trochlear nucleus is located in the ———, and the abducens nucleus is located in the ——.
❖The oculomotor nucleus is located in the midbrain, the trochlear nucleus is located in the midbrain, and the abducens nucleus is located in the pons.
THE OCULOMOTOR NERVE (CN III )
3rd cranial nerve
Entirely (motor/sensory?) in function
Is the largest of the extraocular motor nerves.
•ORIGIN: The oculomotor nerve originates from the ———- nucleus in the ——— at the level of the ———
THE OCULOMOTOR NERVE (CN III )
3rd cranial nerve
Entirely motor in function
Is the largest of the extraocular motor nerves.
plays a vital role in eye movement and pupil constriction.
•ORIGIN: The oculomotor nerve originates from the oculomotor nucleus in the midbrain at the level of the superior colliculus.
NUCLEI/ORIGIN
Two motor nuclei of origin, which are
NUCLEI/ORIGIN
Two motor nuclei of origin
1. The main oculomotor nucleus (somatic motor nucleus)
2. The accessory parasympathetic nucleus(visceral motor nucleus) Edinger-Westphal nucleus.
Oculomotor Nerve Nuclei
• The main oculomotor nucleus is situated in the ——- part of the gray matter that surrounds the cerebral aqueduct of the midbrain. It lies at the level of the ———-.
Oculomotor Nerve Nuclei
• The main oculomotor nucleus is situated in the anterior part of the gray matter that surrounds the cerebral aqueduct of the midbrain. It lies at the level of the superior colliculus.
Oculomotor Nerve Nuclei
The accessory parasympathetic nucleus (Edinger-Westpha l nucleus) is situated
( anterior/posterior?) to the main oculomotor nucleus
Oculomotor Nerve Nuclei
The accessory parasympathetic nucleus (Edinger-Westpha l nucleus) is situated
posterior to the main oculomotor nucleus
FUNCTIONAL COMPONENTS
This nerve has the following components , which are
FUNCTIONAL COMPONENTS
This nerve has the following components .
(a) General Somatic efferent (GSE) fibers.
(b) General visceral efferent (GVE) fibers or parasympathetic fibers .
(c) Proprioceptive impulses
FUNCTIONAL COMPONENTS
This nerve has the following components .
(a) General Somatic efferent (GSE) fibers arising in the oculomotor nucleus supply all ———- muscles of the eyeball for movements of the eyeball except the ——- and the ———.
(b) General visceral efferent (GVE) fibers or parasympathetic fibers (preganglionic) arising in the Edinger-Westphal nucleus and terminating in the ———- ganglion. Postganglionic fibers arising in this ganglion supply the ——— and the ———- muscles of the eye ) for constriction of pupil & accommodation.
(c) Proprioceptive impulses for the muscles of the eyeball.(those innervated by it)
FUNCTIONAL COMPONENTS
This nerve has the following components .
(a) General Somatic efferent (GSE) fibers arising in the oculomotor nucleus supply all extrinsic muscles of the eyeball for movements of the eyeball except the lateral rectus and the superior oblique.
(b) General visceral efferent (GVE) fibers or parasympathetic fibers (preganglionic) arising in the Edinger-Westphal nucleus and terminating in the ciliary ganglion. Postganglionic fibers arising in this ganglion supply the sphincter pupillae and the ciliary muscles of the eye ) for constriction of pupil & accommodation.
(c) Proprioceptive impulses for the muscles of the eyeball.(those innervated by it)
The oculomotor nerve emerges on the ———- surface of the brainstem between the pons and the midbrain and passes forwards in the ———— fossa (subarachnoid space) where it is covered by ——- mater.
It passes forward between the ——— and the ———- arteries.
.
The oculomotor nerve emerges on the anterior surface of the brainstem between the pons and the midbrain and passes forwards in the interpeduncular fossa (subarachnoid space) where it is covered by pia mater.
It passes forward between the posterior cerebral and the superior cerebellar arteries.
.
Oculomotor nerve
It then continues into the ——— cranial fossa in the lateral wall of the ——— sinus. Leaving the cavernous sinus, cranial nerve III passes through the ———— fissure, a bony opening located in the posterior part of the orbit. It enters the ——, which is the eye socket.
Here, it divides into ——— and ——— rami (behind the orbital fissure). These divisions then transverse the superior orbital fissure within the common ——-to enter the orbit.
It then continues into the middle cranial fossa in the lateral wall of the cavernous sinus. Leaving the cavernous sinus, cranial nerve III passes through the superior orbital fissure, a bony opening located in the posterior part of the orbit. It enters the orbit, which is the eye socket.
Here, it divides into superior and inferior rami (behind the orbital fissure). These divisions then transverse the superior orbital fissure within the common tendinous ring to enter the orbit.
Innervation
Within the orbit, cranial nerve III branches into several smaller nerve branches that innervate the following muscles:
Innervation
Within the orbit, cranial nerve III branches into several smaller nerve branches that innervate the following muscles:
Superior Rectus: Innervates the superior rectus muscle, which elevates the eye and contributes to vertical eye movements.
Medial Rectus: Innervates the medial rectus muscle, responsible for adduction (movement towards the nose) of the eye.
Inferior Rectus: Innervates the inferior rectus muscle, which depresses the eye and assists in downward eye movements.
DISTRIBUTIONS of oculomotor nerve
Supplies nerve impulses to 4 of the extraocular muscles of the eye
(except the ——— and the ———)
•Six pairs of striated muscles produce the eye movements which are:
DISTRIBUTIONS
Supplies nerve impulses to 4 of the extraocular muscles of the eye
(except the superior oblique and the lateral rectus)
•Six pairs of striated muscles produce the eye movements
– Medial rectus – Lateral rectus – Superior rectus – Inferior rectus
– Superior oblique – Inferior oblique
Parasympathetic Function of oculomotor nerve
• Supplies the ———— for Constriction of the pupil, reducing the amount of light entering the eye and
• ——— muscles – Contracts, causes the lens to become more spherical, and thus more adapted to short range vision
Parasympathetic Function
• Supplies the sphincter pupillae for Constriction of the pupil, reducing the amount of light entering the eye and
• Ciliary muscles – Contracts, causes the lens to become more spherical, and thus more adapted to short range vision
Parasympathetic Function of oculomotor nerve
• Supplies the ———— for Constriction of the pupil, reducing the amount of light entering the eye and
• ——— muscles – Contracts, causes the lens to become more spherical, and thus more adapted to short range vision
Parasympathetic Function
• Supplies the sphincter pupillae for Constriction of the pupil, reducing the amount of light entering the eye and
• Ciliary muscles – Contracts, causes the lens to become more spherical, and thus more adapted to short range vision
