What controls the bowel peristalsis is the brainstem. If you feel constantly stressed, the brainstem commands the sympathetic nerves to become dominant and therefore it makes the parasympathetic nerves become somewhat dormant.
Meanwhile, the vagus nerve, one of the cranial nerves that regulates the functions of the internal organs such as digestion and heart rhythm, belongs to the parasympathetic nervous system. Therefore, we can say that nervousness such as from anxiety, despair, guilt feelings, anger, etc. causes the vagus nerve to be inactive, thus bringing lower immunity, indigestion, slow bowel movement, constipation, irregular pulse, etc.
While it is still a theory, muscle stiffness also affects the vagus nerves. For instance, tight neck muscles may press adjacent vagus nerves and affects the functions of the internal organs. Tight muscles can also disturb neurotransmission of the enteric nervous system that regulates the digestive organs with or without the vagus nerve.
It has been empirically reported that sudden bowel movement occurs when certain muscles are massaged and their tightness is released. This would be one of the manifestations based on the above theory that suggests that releasing muscle stiffness could innervate the vagus nerves or the enteric nervous system, as all the nervous systems are connected through ganglia.
While it is not clinically proven, tight muscles such as those of your thighs, hamstrings, neck, shoulders, etc., after long desk work may cause a sensation of sourness on your tongue, especially when waking from sleep. It sounds crazy but it could be associated with the facial nerve, one of the cranial nerves that conveys sensory input from the tongue.
Muscle tightness often affects the functions of the adjacent nerves. When the neurotransmission is disturbed by muscle stiffness the sensory input could be different from what is supposed to be.
In this case, stiffness of the muscles of the legs, lumbar or shoulders may affect the neck muscles and then press the facial nerves. These pressed facial nerves transmit the taste of sourness to your brain as if it were being sensed on your tongue. This is the hypothetical scenario behind this phenomenon. However, it has been empirically observed that relieving the tightness of the muscles stops the sour sensation.
In other words, when you wake up in the morning and have sourness on your tongue, it could be an indication that you have severe stiffness in some muscles that are affecting your neck.
While there may not as yet be enough clinical evidence, it may be suspected that stiffness of the neck muscles associates with the pain of the tooth.
The majority of the scenarios could be attribute to the molar teeth perhaps previously treated. The major muscles that pull the tooth root (the interior surface of the mandible) would be the mylohyoid. The associated muscles would include the digastric, the omohyoid, the stylohyoid, and the sternohyoid that connect to the hyoid bone.
If it applies to you, the muscles that are affecting those neck muscles need to be released.
Have you experienced food such as apples or peanuts getting stuck in your throat? If the food remains there, proliferously multiplying germs create inflammation and cold-like symptoms.
Swallowing disorder may be associated with tight neck muscles such as the digastric, the omohyoid, the sternohyoid, the thyrohyoid, etc.
Meanwhile, if your speech is slurred with no ailment in your brain, it could be caused by stiffness of your neck. The specific muscles, called the digastric muscles, are responsible for movement of the tongue.
Furthermore, ones who suffer from sudden coughing with no ailments of the lungs or the bronchi, could blame stiffness of the digastric muscles that triggers sensitiveness of the parotid gland.
Incidentally, this is our own theory as the modern medicine does not seem to ground such symptoms on muscle stiffness.
It can be seen that the digastric muscles contract when your neck is tilted backward and expand when your neck is tilted forward. It means that persons with slouched posture or text neck syndrome (prolonged text messaging with neck tilted forward) tend to have such symptoms.
To solve it, muscles that are pulling the neck need to be released.