Medical Neuroscience: Cn Iii, Iv, Vi

Front 1

Which cranial nerves have the nuclei for ocular motion?

Back 1

CN III, IV, VI

Front 2

What 2 nuclei are associated with CN III?

Back 2

-Oculomotor Nucleus
-Edinger-Westphal Nucleus
(both are near the midline and in the midbrain)

Front 3

What nucleus is associated with CN IV?

Back 3

The trochlear nucleus, which is located near the midline in the midbrain

Front 4

What nucelus is associated with CN VI?

Back 4

The abducens nucleus, which is located near the midline in the caudal pons

Front 5

Where is the oculomotor nucleus located?

Back 5

midbrain at the level of the superior collculus

Front 6

What do the two pathways of cranial nerve II do?

Back 6

-one controls the size of the pupil
-one controls lens accommodation and convergence

Front 7

What is the consensual light reflex?

Back 7

-response in opposite eye when light is shone in the other

Front 8

What pathway is associated with controlling the size of the pupil?

Back 8

-occurs in bilateral neuronal pathway involving the pretectal area and the iris (pupillae muscle)

Front 9

What is the direct pupillary light reflex?

Back 9

The response of the iris directly stimulated by the light

Front 10

What are the first and second order neurons in the pupillary pathway for pupil constriction?

Back 10

-first order neuron: bipolar neuron
-second order neuron: ganglion neuron (which forms the optic nerve)

Front 11

Lay out the pathway of the axons in the pupillary pathway for iris constriction.

Back 11

-bipolar neuron
-ganglion neurons
-synapse in the pretectal area
-neurons then project bilaterally to the Edinger-Westphal nucleus
-neurons then project to the ciliary ganglion which projects to the pupillae muscle

Front 12

Where is the pretectal area located?

Back 12

rostral end of the superior colliculus in the midbrain

Front 13

What is the effect of the bilateral projection of the puliarry pathway for iris constriciton?

Back 13

The pupillae muscles of both eyes constrict even if light is only shown into one eye.
(because neurons from the pretectal area project to Edinger-Westphal nucleus on both sides)

Front 14

Is the cortex involved in pupillary constriction?

Back 14

No, the information travels to the midbrain

Front 15

What are the pre and post ganglionic parasympathetics to the pupillary constrictor muscles?

Back 15

-Preganglionic: parasympathetics from teh E-W nucleus
-Postganglionic: Ciliary ganglion

Front 16

How is pupillary dilation accomplished?

Back 16

-pupillary dilator muscle sends info to the carotid plexus
-Travels to the superior cervical ganglion then to the inferior cervical ganglion
-Through the white rami communicantes of T1 nerve root
-Up spinal cord to the autonomic regulatory nuclei of the hypothalamus

Front 17

Outline the pathway for lens accomodation and convergence.

Back 17

-Visual info reaches the visual cortex
-neurons from the visual cortex project to the pretectal area
-The pretectal area projects axons to the oculomotor nucleus in the E-W Nucleus
-Oculomotor nucleus causes contraction of the medial recti muscles (causes convergence)
-E-W Nucleus projects to the ciliary ganglion which causes contraction of teh ciliary muscles to adjust the tension on the lens

Front 18

Which cranial nerves have parasympathetic fibers?

Back 18

CN 3, 7, 9, 10

Front 19

What cranial nerves are needed for the pupillary pathway for lens accomodation and convergence to work?

Back 19

CN 2 and 3

Front 20

What happens for accomodation to occur?

Back 20

-At rest, lens is thin
-Upon contraction of the ciliary muscles, tension is relieved from zonule fibers, and the lens thickens

Front 21

What cranial nerves are associated with eye movements?

Back 21

CN 4 and 6

Front 22

Where is the trochlear nucleus located?

Back 22

midbrain at the level of the inferior colliculus

Front 23

Where is the abducens nucleus located?

Back 23

In the pons

Front 24

What does PPRN stand for?

Back 24

parapntine reticular nucleus

Front 25

Where is the PPRN located?

Back 25

in the brain stem

Front 26

What is the function of the PPRN?

Back 26

-center for organizing input from CN 3 and 6
-there is one located on the left for moving eyes to the left and one on the right for moving eyes to the right

Front 27

Which side is the input to the PPRN from?

Back 27

-The PPRN recieves input from CN VI on the ipsilateral side, via the abducens nucleus
-And input from CN 3 on contralateral side, via oculomotor nucleus and abducens nucleus

Front 28

What muscle does CN 6 carry information from?

Back 28

Lateral Rectus

Front 29

What muscle does CN 3 carry information from?

Back 29

Medial Rectus

Front 30

What are MLF?

Back 30

Interneurons which carry input from CN 3 after the oculomotor nucleus to the abducens nucleus