Question

Injury to vagus nerve in humans is not likely to affect (a) tongue movements (b) gastrointestinal movements f (c) pancreatic seqetion (d) cardiac movements.

Short answer

Tongue movements are not primarily controlled by the vagus nerve and would not be likely affected by its injury.

Step-by-step solution

Identify the Function of the Vagus Nerve

Determine what areas the vagus nerve affects. The vagus nerve, which is the tenth cranial nerve, primarily impacts the control of muscles in the pharynx, larynx, and palate, and it also sends sensory information from the throat, external ear, and meninges. It regulates the smooth muscles of the trachea, bronchi, and digestive tract, as well as controlling the heart's rate of contraction.

Match Functions to Options

Connect the functions of the vagus nerve to the given options. The vagus nerve does not primarily innervate the tongue muscles for movement; these are primarily controlled by the hypoglossal nerve (cranial nerve XII). The vagus nerve does affect gastrointestinal movements, pancreatic secretions, and cardiac movements.

Determine the Unaffected Function by Vagus Nerve Injury

Identify which option would be least affected by an injury to the vagus nerve. Considering the roles of the vagus nerve, injury to it would least likely affect tongue movements.

Key concepts

Cranial Nerves

The human body is equipped with twelve cranial nerves, each with specific functions that connect the brain to different parts of the head, neck, and torso. Among these, the vagus nerve, also known as cranial nerve X, is one of the most extensive, extending well beyond the head and neck to innervate various organs. Unlike some other cranial nerves which may have a singular or limited role, the vagus nerve has extensive parasympathetic functions influencing heart rate, gastrointestinal motility, sweating, and several muscle movements in the mouth.

Role of the Vagus Nerve in Cranial Nerve System

As for its relevance in our discussion, the vagus nerve doesn't contribute to the movement of the tongue. This task is primarily managed by the hypoglossal nerve (cranial nerve XII), responsible for the motor supply to the muscles of the tongue.

Neurological Anatomy

Neurological anatomy involves the structural framework of the nervous system, including how nerves are organized and interconnect to control various functions. The vagus nerve’s anatomy is quite complex; it emerges from the brainstem and travels down to the colon. Understanding its path is crucial when determining the effects of potential nerve injuries.

Pathway and Innervation

The vagus nerve, after originating in the medulla oblongata, gives rise to various branches that innervate many thoracic and abdominal viscera. This expansive reach explains why its impairment can lead to a number of seemingly unrelated symptoms, from voice changes (due to laryngeal innervation) to altered heart function.

Parasympathetic Nervous System

The parasympathetic nervous system (PNS) is one of the two divisions of the autonomic nervous system and is often referred to as the 'rest and digest' system. It conserves energy as it slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles in the gastrointestinal tract. The vagus nerve is a critical component of the PNS as it innervates the heart, lungs, and digestive tract.

Vagus Nerve and Rest and Digest Responses

As a part of the PNS, the vagus nerve helps lower heart rate and promotes gastrointestinal activity, including the movements and secretions necessary for digestion. This is why damage to the vagus nerve can lead to problems with heart rhythm, loss of digestive movement, or insufficient production of digestive juices.

Biological Responses to Nerve Injury

Injuries to nerves, like the vagus nerve, can have significant biological consequences due to the interruption of the signals they carry. This can lead to muscle paralysis, loss of sensation, or dysfunctions in the organs they innervate.

Repercussions of Vagus Nerve Damage

Specific to vagus nerve injury, one might experience voice changes due to impaired control of the larynx, difficulty swallowing, abnormal heart rate, and problems with the body's digestive processes. This highlights the importance of the neurological health and its maintenance for holistic wellbeing. In any scenario where a nerve injury occurs, it's essential to understand the original function to predict and manage the outcomes effectively.