Which nerves are involved in the sensory functions of the human body?

Under normal circumstances, sensory functions of the human body involve several nerves, including the trigeminal nerve, facial nerve, glossopharyngeal nerve, vagus nerve, and spinal nerves. The specific functions are as follows:

1. Trigeminal Nerve: The trigeminal nerve mainly is responsible for sensory functions of the head and face, including touch, pain, and temperature sensations in areas such as the forehead, facial skin, eyes, nose, and oral mucosa. When the face comes into contact with an object, the trigeminal nerve transmits tactile information to the central nervous system, enabling people to perceive the texture and temperature of the object.

2. Facial Nerve: In addition to primarily controlling the movement of facial expression muscles, the facial nerve also is responsible for taste sensation in the anterior two-thirds of the tongue. It allows the body to perceive tastes such as sour, sweet, bitter, salty, and umami. When food enters the mouth, it dissolves in saliva, stimulating taste buds on the anterior two-thirds of the tongue. Sensory nerve fibers within the facial nerve then transmit taste information to the brain, allowing the taste of the food to be perceived.

3. Glossopharyngeal Nerve: The glossopharyngeal nerve is responsible for taste sensation in the posterior one-third of the tongue, sensation of the pharyngeal mucosa, and sensation in the carotid sinus and carotid body. It works in conjunction with the facial nerve to complete taste perception within the oral cavity. Additionally, it senses stimuli in the pharynx, and when there is foreign-body irritation in the pharynx, the glossopharyngeal nerve transmits sensory signals to the brain, triggering protective reflexes such as the swallowing reflex.

4. Vagus Nerve: The vagus nerve has a wide distribution, including the throat, trachea, esophagus, and thoracic and abdominal organs. It can sense various sensory information from these organs, such as sensations in the throat, feelings of fullness in the gastrointestinal tract, and sensations in the heart and lungs. When the stomach is filled, the vagus nerve transmits information about the stomach's expansion to the brain, creating a feeling of satiety.

5. Spinal Nerves: Spinal nerves originate from the spinal cord and are distributed throughout the trunk and limbs. Each pair of spinal nerves contains sensory nerve fibers and can be divided into different segments, including cervical nerves, thoracic nerves, lumbar nerves, and sacral nerves. These nerves are responsible for sensory functions of corresponding segments of skin, muscles, bones, and other tissues. They transmit various sensory information, including touch, pain, temperature sensation, and proprioception.

These nerves work together to form a complex and precise sensory nervous system that can detect various external stimuli and internal bodily changes.