Visceral motor response

This occurs as a result of changes in the autonomic nervous system (ANS), which is distributed throughout the central and peripheral nervous systems. The ANS can alter heart rate, respiratory rate, blood flow, piloerection, sweat gland activity and gastrointestinal motility. These responses occur via changes in smooth muscle, cardiac muscle and various glands throughout the body.

The ANS has two sub-divisions (sympathetic and parasympathetic) which produce the opposite affects on the body. This antagonistic action is essential in maintaining homeostasis (a stable internal environement) and is integrally linked with opposing emotional states.

Sympathetic nervous system

This initiates changes in the heart and lungs, smooth muscle of blood vessels, hair follicles, sweat glands and abdominal organs in preparation for some kind of challenge/threat. The efferent output comes from the spinal cord, the paravertebral ganglia of the sympathetic trunk (Levels T₁ – L_2/3), to various ganglia/nuclei and onto effector glands/organs.

Parasympathetic nervous system (including the enteric division)

This modifies the action of similar organs to the sympathetic division but its action is directed towards conserving and restoring energy. The efferent output comes from nuclei in the brain stem (cranial nerves III, VII, IX and X) and from the spinal cord grey matter (levels S_2/3/4) to various ganglia close to the organs that they innervate and onto the effector glands/organs.

Posture

Alterations in posture associated with emotional behaviour occur in part via the vestibular system (S2.10) and the reticular formation (S2.10).

Facial expression

This is achieved by a highly coordinated output from the motor specific facial nerve (VII cranial nerve) (S2.10), which innervates all 20 of the muscles involved in facial expression (e.g. occiptal frontalis, orbicularis oris, buccinator, orbicularis oculi and platysma).

Posture and distal movement

Voluntary changes in posture and fine control of distal movement also occur via voluntary control of the descending tracts (S2.14) to alpha motor neurons at all levels of the spinal cord.