This is a usual problem with some people and is a problem that is similar to a muscular catch. The problem happens because of the muscles of the pharynx being pulled by the peristaltic action. In addition to this, the movement of the jaw muscles can also cause this problem. This means that you are probably opening your mouth too widely or that the muscles are causing a nerve to be depressed while they are in motion. Since there is a wide spectrum of causes that results in your condition, the problem could also be caused by an electrolyte imbalance in your body.
The region of the mouth that is affected in your case is called the palate or the roof of the mouth. This is an area that is comprised of some soft tissue called the torus palatinus and also of some bony structure above that. When we open our jaws in a yawning action (which is also when the mouth is opened at its widest) we sometimes experience a muscle spasm. This is caused by a muscle electrolyte imbalance. Our muscles are supplied with the impulse to move by electrical currents from the nerves. However, at the junction of the nerve and muscle and within the muscle, it is not the same type of electricity that controls movements. At the synaptic cleft of neurons, acetylcholine is released to trigger a release of sodium ions from sodium channel gateways. This also triggers the release of calcium ions within muscles that causes contraction of muscle. This system also requires an off switch that comes from the entry of potassium ions into the sodium-potassium channels. When there is an inadequate amount of potassium in the body, the off switch is not activated and we get a continuous muscle contraction or spasm – literally, a short circuit.
To relieve this situation, it is best to have some potassium chloride solution that is usually available with all chemists. This is one of the vilest tasting solutions that you will ever come across so mix some of this in some honey before consuming it. The other way to ensure a good intake of potassium in the body is to consume potassium-rich foods. Citrus fruits like oranges contain a high amount of potassium as do bananas. Mostly all foods will contain this essential element but just to be sure, stick to having a lot of fruit juices.