The vagus nerve is the 10th cranial nerve that is also denoted as CN X. It is composed of sensory, motor and parasympathetic nerves. It has approximately 80% afferent fibres and 20% efferent fibres. It is one of the longest and most complex nerves of cranial nerves. The vagus nerve runs through the brain to the face and from the thorax to the abdomen.
The vagus nerves affect the respiratory, gastrointestinal and cardiovascular systems. It divides and spreads to different parts, such as the Inferior cervical cardiac branch, Pharyngeal nerve, Hering–Breuer reflex in alveoli etc.
Functionally, the vagus nerve sends motor impulses to different parts, such that it controls the rate of heartbeat, constriction of bronchi, peristalsis stimulation, sweating, speech and gastrointestinal secretions.
Damage to the vagus nerve can lead to hyperphagia (increases hunger), decreased antral contractions, inpaired pyloric relaxation and defective gastroduodenal coordination.
The phrenic is a mixed nerve that originates from the C3 to C5 spinal nerves in the neck. It originates as the left and right nerves from the neck travel through the chest between the heart and lungs up to the diaphragm. The phrenic nerves are composed of sensory, motor and sympathetic neurons.
The major function of the phrenic nerves is to control the contraction of the diaphragm and help in the breathing process. The phrenic nerves supply motor neurons to the diaphragm, mediastinal pleura and pericardium. The nerve induces the activation of the diaphragm contraction, thus expanding the lungs. This draws air into them.
Injury to the phrenic nerve can cause diaphragmatic paralysis, and irritation to the nerve causes a reflex of hiccups.
Vagus vs Phrenic Nerves
|Vagus Nerves||Phrenic Nerves|
|The vagus nerve is a mixed nerve that is also the tenth cranial nerve.||The phrenic nerve is a mixed nerve that arises from the C3-C5 spinal nerves in the neck.|
Type of Nerve
|Cranial Nerve||Spinal Nerve|
|It is composed of sensory, motor and parasympathetic fibres.||It is composed of sensory, motor and sympathetic fibres.|
|The vagus nerve runs from the brain to the face and from the thorax to the abdomen.||It originates from the neck to travel through the chest between the heart and lungs up to the diaphragm.|
|The vagus nerve controls the heartbeat, peristaltic movements, and gastrointestinal secretions.||The phrenic nerves innervate the diaphragm with motor impulses to allow respiration.|
Damage to the Nerve
|Damage to the vagus nerve can cause:
||Damage to the phrenic nerve can cause:
Visit BYJU’S Biology for more interesting topics
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Frequently Asked Questions on Difference between Vagus and Phrenic Nerves
Is the phrenic nerve autonomic or somatic?
The phrenic nerve is a mixed somatic nerve.
What’s the longest nerve in the human body?
The sciatic nerve is the longest nerve in the human body.