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The tensor veli palatini muscle contributes to tension of the soft palate and opening of the auditory tube. Its tendon changes direction around a bony pulley region. Its trigeminal motor supply distinguishes it from several neighboring muscles of the palate and pharynx.

The thorax is the trunk region between neck and abdomen. Its rib cage and associated muscles surround the lungs and mediastinum, while the respiratory diaphragm forms the lower partition. Movement of its boundaries contributes directly to breathing.

T. O'Kelly is the first author of a 1993 study testing the role of nitric oxide in relaxation of the human internal anal sphincter. Isolated muscle strips were mounted in organ baths for measurement of tension at fixed length. Electrical stimulation evoked nerve-dependent relaxation, allowing the investigators to test which chemical pathway connected stimulation to the mechanical response.^[ref]

Several interventions converged on the same explanation. A compound releasing nitric oxide relaxed the strips; inhibitors of nitric oxide synthase suppressed electrically evoked relaxation; adding the appropriate form of arginine reversed that inhibition. The opposite enantiomer did not have the same effect. A substance that scavenges nitric oxide also abolished the response. This combination of mimicry, inhibition, rescue and specificity controls supported a role for nitric oxide in neural relaxation of smooth muscle. It provided stronger causal evidence than observing a correlation between chemical abundance and relaxation alone.^[ref]

The triceps brachii is the principal elbow-extensor muscle group of the posterior arm. Its heads join a tendon inserting at the ulna, while the long head also crosses the shoulder. Different joint positions can therefore affect the mechanical contribution of its components.

The trigeminal nerve is a cranial nerve providing major sensory pathways from the face and motor pathways to muscles of mastication. Its three main divisions distribute different territories. Sensation and jaw movement can therefore be affected differently by a lesion.

The trochlea of superior oblique is a pulley-like structure in the anterosuperomedial orbit. It redirects the tendon of the superior oblique muscle. The redirection explains why the muscle’s effective pull differs from a straight line between its belly and the eyeball.

Ulf Dimberg investigated responses to emotional faces using facial electromyography. Measuring activity in selected facial muscles can reveal small reactions that are difficult to judge by ordinary observation. His brief-presentation work examined reactions under conditions intended to limit awareness of the expression, distinguishing the muscle measurement from a participant’s report of what was seen. A congruent facial response does not by itself identify the complete emotional experience. ^[ref]

Primary publication: doi.org/10.1111/1467-9280.00221

Publication text or primary record: pubmed.ncbi.nlm.nih.gov/11228851/

Psychological Science 11, 86–89; backward-masked targets and facial muscle recordings.

Historical anatomical model of perineal muscle and fascia; it should not be read as a universally uniform muscular sheet between two identical fascial layers.

The urogenital triangle is the anterior subdivision of the perineum. It contains the external urogenital openings and associated muscles and membranes. Its name identifies a topographic region; it is not synonymous with the older, anatomically misleading concept of a uniform urogenital diaphragm.

A uterine contraction is shortening and force generation by the myometrium. Patterns vary across reproductive states, including coordinated activity during childbirth. Local muscle activity, global coordination and the resulting pressure are distinct measurements of the same organ's mechanical behavior.

Venous return is blood flow returning toward the heart. Over a stable interval it balances cardiac output, but transient storage changes can occur. Venous pressures, compliance, surrounding muscle activity and breathing contribute to the return pathway.

A ventral root is a bundle of outgoing motor axons leaving the anterior side of the spinal cord. It contains somatic motor fibres and, at appropriate spinal levels, autonomic efferent fibres. It joins a sensory dorsal root to form a mixed spinal nerve.^[ref]

For example, an action potential destined for a limb muscle can leave the spinal cord through a ventral root, then continue through a mixed spinal nerve and an anterior spinal nerve ramus. The directional separation near the spinal cord does not mean every later branch is motor-only. A ventral root is also distinct from the anterior branch formed after the roots unite.

A voltage clamp uses electrical feedback to hold a preparation's membrane potential near a commanded value while measuring the electric current required to maintain it. Holding voltage separates changes in electrical conductance from changes in electrical driving force. Imperfect voltage control and finite recording bandwidth limit the inference. The muscle experiment under ionotropic receptor used separate intracellular electrodes for voltage control and a sealed patch pipette for recording local electric current.^[ref]