PSYCH 454 Lecture Notes - Lecture 23: Orbicularis Oculi Muscle, Facial Motor Nucleus, Zygomaticus Major Muscle
24 May 2018
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Lecture 23: Emotion part 2
Pathways from Motor Cortex innervating facial Muscles → skeletal muscle, Somatic NS (not
autonomic)
●Smile: activate orbicularis oculi muscle (skin
around eye muscle) and zygomaticus (lifting of
mouth and cheek)
●Frown in anger: activate corrugator (skin
around eye, eyebrow)
●Grimace in disgust: active levator (controls top
of mouth near nose)
●Muscle groups are controlled by motor cortex;
ex: smile muscles
○Motor cortex → brain stem (pons), specifically the facial nucleus → project to
facial muscle
○Orbicularis oculi: motor neurons in cortex → brain stem, facial nucleus →
projects bilaterally (ipsi and contra, both)
■Will project to BOTH side, some ipsi and some contra
■Causes smiling gesture
○Zygomaticus → contralateral innervation
●Muscles controlling upper and muscles controlling lower have
distinct projections from motor cortex and difference in path
○Lower face: contralateral from motor cortex; ex:
zygomaticus
○Upper face: bilaterally (ipsi and contra); ex: orbicularis
Sensory Trigeminal pathway from face to somatosensory cortex
●Action of smiling lead to our own perception of the action themselves (ex: lift corners of
mouth, and change eyes to smile → will feel sensory information that you feel when
smiling)
●We perceive our facial expressions
○Touch and proprioceptive signals carried along trigeminal path to the cortex (lect
17)
○Mechanoreceptor in mouth (sensory afferent projects up) → brainstem →
thalamus (VPM) → sensory cortex
○Can send info from muscles back to cortex to illicit happiness
●Different facial expressions feel different due to use of different muscles
○Smiles feel different than frowns → elicit different responses and emotions;
different afferent info being sent to somatosensory cortex
Document Summary
Pathways from motor cortex innervating facial muscles skeletal muscle, somatic ns (not autonomic) Smile: activate orbicularis oculi muscle (skin around eye muscle) and zygomaticus (lifting of mouth and cheek) Frown in anger: activate corrugator (skin around eye, eyebrow) Grimace in disgust: active levator (controls top of mouth near nose) Muscle groups are controlled by motor cortex; ex: smile muscles. Motor cortex brain stem (pons), specifically the facial nucleus project to facial muscle. Orbicularis oculi : motor neurons in cortex brain stem, facial nucleus projects bilaterally (ipsi and contra, both) Will project to both side, some ipsi and some contra. Muscles controlling upper and muscles controlling lower have distinct projections from motor cortex and difference in path. Lower face: contralateral from motor cortex; ex: Upper face: bilaterally (ipsi and contra); ex: orbicularis zygomaticus. Sensory trigeminal pathway from face to somatosensory cortex.
