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These small muscles set deep in the posterior neck rotate the atlas (C1 vertebra) on the axis (C2) (the skull moves with the atlas).
They also extend the skull on the atlas. They are consider postural muscles rather than prime movers. |
Raymond Dart
This important sub-occipital group of muscles controlling the head is supplied by a single (sub-occipital) nerve from a single segment (first cervical) of the spinal chord. This single somite, or body segment, doubtless for a special reason, is the only segment of the entire series of post-cranial segments to have a nerve supply that is purely motor in character. The only one deprived of a segmental skin area proper to itself, the stimulation of which would have been too susceptible of reflex response.
Receptors affecting head-neck relationships:
Responses of a reflex sort, evoked by touch and leading to postural contraction of the sub-occipital musculature, can only be elicted in the muscle group by stimuli coming in from receptors of skin segments other than its own. The nearest tactual receptors are anteriorly the cranial trigeminal nerve (V) and posteriorly the second cervical nerve (C2). The root of V descends posteriorly (sensorily) to C4 (in the platypus as far as the firsst lumbar segment - L1). Receptors other than tactual are the visual nerves III, IV, and VI (oculomotor, trochlear, and abducens) which are linked to the trunk by the medial longitudinal bundle.
This important sub-occipital group of muscles controlling the head is supplied by a single (sub-occipital) nerve from a single segment (first cervical) of the spinal chord. This single somite, or body segment, doubtless for a special reason, is the only segment of the entire series of post-cranial segments to have a nerve supply that is purely motor in character. The only one deprived of a segmental skin area proper to itself, the stimulation of which would have been too susceptible of reflex response.
Receptors affecting head-neck relationships:
Responses of a reflex sort, evoked by touch and leading to postural contraction of the sub-occipital musculature, can only be elicted in the muscle group by stimuli coming in from receptors of skin segments other than its own. The nearest tactual receptors are anteriorly the cranial trigeminal nerve (V) and posteriorly the second cervical nerve (C2). The root of V descends posteriorly (sensorily) to C4 (in the platypus as far as the firsst lumbar segment - L1). Receptors other than tactual are the visual nerves III, IV, and VI (oculomotor, trochlear, and abducens) which are linked to the trunk by the medial longitudinal bundle.
