18 - Motor Pathways II Flashcards
1
Q
Brainstem Pathway LMN are…
A
- Cranial Nerve Nuclei
- Ipsilateral to exit from CNS
- So, LMN signs are ipsilateral to damage
2
Q
Corticobulbar UMNs controls which nuclei, and which does it not?
A
- Only fucks with SVE, GSE;
- Controls all SVE + 12
- Does not control any GSE except for 12
- Controls:
- Trigeminal motor nucleus (jaw)
- Facial nucleus (facial expression)
- Nucleus ambiguus (larynx, pharynx, and palate)
- Hypoglossal nucleus
- Accessory nucleus
- DOES NOT CONTROL EYES
- Oculomotor nucleus
- Trochlear nucleus
- Abducens nucleus
3
Q
CN Nuclei with unilateral corticobulbar inputs
A
- Facial nucleus (7)
- Neurons that innervate the lower quadrant of the face only receive unilateral, contralateral input
- Hypoglossal nucleus (12)
- Neurons that innervate tongue only receive unilateral, contralateral input
4
Q
Unilateral corticobulbar lesion effect
A
- Generally do not produce clinical symptoms because most CN nuclei are bilaterally supplied by CBS
- WIll show CN 7 (opposite lower quadrant of face) and CN 12 (opposite half of tongue) paresis
5
Q
Eye movement control UMNs
A
- NOT FROM M1
- Corticopontine fibers from fronal eye field and parietal eye field
- Activate CPGs controlled by superior colliculus
6
Q
Corticobulbar fibers exit where for which cranial nerves?
A
- PONS: 5, 7
- MEDULLA: 9, 10, 12
- FORAMEN MAGNUM (to SC): 11
7
Q
GSE CN Nuclei innervation
A
Paramedian branches
8
Q
CN 12 Function, Innervation, Location, Lesion
A
- GSE nucleus in medulla
- Innervated by ASA paramedians
- Nerve comes out in pre-olivary sulcus
- Functions:
- Extrinsic tongue muscles:
- Geniglossus: protrusion
- Styloglossus: retraction
- Hypoglossus: depression
- Intrinsic tongue muscles control shape
- Extrinsic tongue muscles:
- Lesions:
- Nucleus or nerve = tongue points to side of lesion due to intact genioglossus
- Supranuclear = tongue points to opposite side of lesion
- BE CAREFUL: you can’t tell just from the tongue which side/level is lesioned!
9
Q
Abducens Nucleus Function
A
- Innervates lateral rectus, muscle that abducts the eye on each side
10
Q
Trochlear Nerve Function
A
- Innervates superior oblique of eye CONTRALATERAL to nucleus
- L nerve from R nucleus makes L eye tilt inward and downward
11
Q
Oculomotor Nerve Function
A
- Innervates every other movement besides abduction and inward/downward tilt
12
Q
Eye Muscles, CNs, Directions
A
- To look straight up: superior rectus (to move the eye up), and inferior oblique to counteract torsion
- To look straight down, inferior rectus moves the eye down, superior oblique counteracts torsion
- If eye is abducted (AWAY from nose), you’re fully in line with the rectus, so you don’t use the obliques to counteract anything
- You may also use superior or inferior rectus to look up or down, but still no obliques because there’s no torsional movement introduced
- If eye is looking to midline (converging), you do not use rectus at all; just superior oblique and inferior oblique to control
- You only use the superior oblique when you’re looking down at near objects (trochlear nerve!)
13
Q
Conjugate Gaze vs Intorsion/Extorsion
A
- Elevation of gaze: eyes look upward
- Depression of gaze: eyes look downward
- Horizonal conjugate gaze: both eyes look L or R
- One eye adducts (CN 3), one eye abducts (CN 6)
- Extortion: R eye movement when head tilts L
- Intortion: R eye movement when head tilts R
14
Q
CN VI Palsy
A
- Lesion to actual nerve of CN 6
- Palsy of ipsilateral lateral rectus muscle
- Eye on affected side drifts medially during forward gaze
- Eye on affected side fails to abduct past midline on horiztonal conjugate gaze to the affected side
15
Q
Trochlear Nerve Muscle
A
- Superior oblique
- Critical for binocular vision
- When eye is abducted, SO depresses the eye
- When eye is adducted, SO intorts the eye
