Reticular Formation & Movement

Question 1

What are some functions of the reticular formation?

Answer 1

Input from all sensory modalities, motor (postural adjustments, pattern generator, etc.), forebrain modulation (sleep, cortical arousal), visceral fxn, pain modulation

Question 2

What is the function of reticular formation in midbrain and rostral pons?

Answer 2

Modulate forebrain

Question 3

What is the function of the RF in caudal pons and medulla?

Answer 3

Modulate motor/visceral function

Question 4

Where is the RF?

Answer 4

Poorly differentiated, in the tegmentum of brainstem

Question 5

What are the 5 descending motor tracts to cord?

Answer 5

CST, rubrospinal tract (red nuc), pontine reticulospinal, medullary reticulospinal, lateral vestibulospinal

Question 6

What are the 5 brainstem motor areas?

Answer 6

Red nuc (rostral midbrain), mesencephalic motor area (PPtN, caudal mid, rost pons), pontine motor area (caudal pons, MPRF), medullary motor area (rost med), vestibular complex (rost med)

Question 7

What does the red nucleus do?

Answer 7

Flexes elbows

Question 8

What does the PPtN/mes motor area do? Where does it project? What other functions is it involved with?

Answer 8

Posture, basic motor programs like walking; NOT to cord, modulates pontine and medullary motor areas; ACh and glut neurons linked to cortical arousal, REM sleep

Question 9

What does the pontine motor area do?

Answer 9

Desc pontine reticulospinal motor fibers, extensors, also overlaps area linked to REM sleep, called MPRF (medial pons RF)

Question 10

What does the medullary motor area do?

Answer 10

Med retic tract for posture, basic motor programs like walking

Question 11

What does the vestibular complex/lateral vestibulospinal tract do?

Answer 11

Extends elbow/knee, plantar flexion of ankle - “fights gravity”

Question 12

What is constraint-induced movement therapy?

Answer 12

Force person with spastic paralysis upper limb to use it, improves fxn perhaps due to rubrospinal latent function

Question 13

What modulates the MRF and PRF?

Answer 13

Mesencephalic motor area/PPtN, MRF by cortex also

Question 14

What modulates the vestibular complex?

Answer 14

Vestibular and spinal cerebellum

Question 15

What modulates the red nucleus?

Answer 15

Pontocerebellum, and cortex (inhibits)

Question 16

What is decerebrate rigidity? Decorticate rigidity?

Answer 16

Decerebrate: extensor rigidity/posturing
Decorticate: flexor rigidity/posturing

Question 17

What does midbrain damage inferior to the red nucleus cause?

Answer 17

Extensor rigidity because of unopposed lateral vestibulospinal tract

Question 18

What does damage superior to red nucleus cause?

Answer 18

Disinhibited elbow flexion because red nuc not inhibited by cortex, knee extension (lat vestibulospinal)

Question 19

Does flexor or extensor rigidity indicate a better outcome for coma?

Answer 19

Flexor because no brainstem involvement

Question 20

What are other brainstem signs in coma?

Answer 20

Mid: lose CN 3 (fixed dilated pupil, no consensual light reflex)
Pons: lose 5/7 (no jaw-jerk or corneal reflex)
Med: lose 9/10 (no gag, tracheal cough, lose breathing)

Question 21

What are RF viscerosensory functions?

Answer 21

Solitary nuc: cardiovascular, resp, GI, liver, gustation

Question 22

What are cardiovascular control areas of RF?

Answer 22

Medullary pressor area (glutamate, adrenergic, maintains symp tone, tonically active), depressor area (GABA, noradrenergic), baroreceptor response

Question 23

Where is the medullary pressor area? How does it control sympathetic tone?

Answer 23

Rostral anterolateral medulla, overlaps ALQ; projects to ACh pregang symp in IML column, which fires postgang NE neurons to heart/vessels

Question 24

Where is the medullary depressor area? How does it control sympathetic tone?

Answer 24

Caudal anterolateral medulla, overlaps ALQ; inhibits pressor area with GABA, inhibiting firing of IML column

Question 25

Describe the baroreceptor reflex pathway.

Answer 25

CN 9/10 viscerosensory input aortic/carotid stretch receptors -> sol nuc -> GABA in depressor -> inhibits pressor. Sol nuc ALSO -> DMNX and ambig to increase PSNS

Question 26

What are the respiratory cell groups in the medulla?

Answer 26

Posterior/dorsal area and anterior/ventral groups

Question 27

Where is the post resp area? Where does it receive input from, and what is it for?

Answer 27

Distinct part of solitary nucleus; input from pulmonary stretch receptors (CN X), pace maker system for breathing

Question 28

Where are the anterior respiratory cell groups? What do they do?

Answer 28

Anterolateral caudal medulla near depressor group over ALQ; inspiration group (to phrenic) and expiration group (to thoracic/lumbar LMN)