The Phrenic Nerves

Examples of The Phrenic Nerves in the following topics:

• Injuries to the Phrenic Nerves

  • The phrenic nerve provides motor innervation and receives sensory information from the diaphragm.
  • The phrenic nerve is a nerve that originates in the neck and passes down between the lung and the heart to reach the diaphragm.
  • The phrenic nerves contain motor, sensory, and sympathetic nerve fibers.
  • In the thorax, each phrenic nerve supplies the mediastinal pleura and pericardium.
  • The phrenic nerve and its relations with the vagus nerve.

• Neural Mechanisms (Cortex)

  • The phrenic nerves: The nerves that stimulate the activity of the diaphragm.
  • They are composed of two nerves, the right and left phrenic nerve, which pass through the right and left side of the heart respectively.
  • The posterior thoracic nerves: These nerves stimulate the intercostal muscles located around the pleura.
  • Damage to any of these three respiratory nerves can cause severe problems, such as diaphragm paralysis if the phrenic nerves are damaged.
  • Less severe damage can cause irritation to the phrenic or vagus nerves, which can result in hiccups.

• Cervical Plexus

  • The cervical plexus is the plexus of the ventral rami of the first four cervical spinal nerves.
  • Lesser occipital nerve - The lesser occipital nerve or small occipital nerve is a cutaneous spinal nerve arising between the second and third cervical vertebrae, along with the greater occipital nerve.
  • Great auricular nerve - The great auricular nerve originates from the cervical plexus, composed of branches of spinal nerves C2 and C3.
  • Supraclavicular nerves - The supraclavicular nerves (descending branches) arise from the third and fourth cervical nerves.
  • Phrenic (C3-C5 [primarily C4]) - The phrenic nerve is a nerve that originates in the neck and passes down between the lung and heart to reach the diaphragm.

• Function and Physiology of the Spinal Nerves

  • The peripheral nervous system includes 12 cranial nerves and 31 pairs of spinal nerves, which provide communication from the CNS to the rest of the body by nerve impulses that regulate the functions of the human body.
  • Spinal nerve C1 (suboccipital nerve): Provides motor innervation to muscles at the base of the skull.
  • These include the greater occipital nerve which provides sensation to the back of the head, the lesser occipital nerve which provides sensation to the area behind the ears, the greater auricular nerve, and the lesser auricular nerve.
  • The phrenic nerve arises from nerve roots C3, C4, and C5.
  • PNS nerves are involved in the erection of genital tissues via the pelvic splanchnic nerves 2–4.

• Neural Mechanisms (Respiratory Center)

  • The medulla and the pons are involved in the regulation of the ventilatory pattern of respiration.
  • Involuntary respiration is controlled by the respiratory centers of the upper brainstem (sometimes termed the lower brain, along with the cerebellum).
  • The medulla oblongata is the primary respiratory control center.
  • The pons is the other respiratory center and is located underneath the medulla.
  • Its signals limit the activity of the phrenic nerve and inhibits the signals of the apneustic center.

• Brief Overview of Cranial Nerves

  • Cranial nerves are the nerves that emerge directly from the brain (including the brainstem).
  • The Olfactory Nerve (I)-The olfactory nerve is instrumental for the sense of smell, it is one of the few nerves that are capable of regeneration.
  • The Optic Nerve (II)-The optic nerve carries visual information from the retina of the eye to the brain.
  • The Trochlear Nerve (IV)-The trochlear nerve is a motor nerve that innervates the superior obliuque muscle of the eye, which controls rotational movement.
  • The Abducens Nerve (VI)- The abducens nerve is a motor nerve that innervates the lateral rectus muscle of the eye, which controls lateral movement.

• Trochlear (IV) Nerve

  • The trochlear nerve (the fourth cranial nerve) is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye.
  • The trochlear nerve (the fourth cranial nerve) is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye.
  • The trochlear nerve is unique among the cranial nerves in several respects.
  • *Other than the optic nerve (cranial nerve II), it is the only cranial nerve that decussates (crosses to the other side) before innervating its target.
  • *It is the only cranial nerve that exits from the dorsal aspect of the brainstem.

• Accessory (XI) Nerve

  • The accessory nerve is designated the 11th of 12 cranial nerves and it controls the muscles of the shoulder and neck.
  • The accessory nerve is the 11th of 12 cranial nerves and it controls the sternocleidomastoid and trapezius muscles of the shoulder and neck.
  • Unlike the other 11 cranial nerves, the accessory nerve begins outside the skull.
  • Due to its unusual course, the accessory nerve is the only nerve that enters and exits the skull.
  • However, more modern characterizations of the nerve regard the cranial component as separate and part of the vagus nerve.

• Olfactory (I) Nerve

  • The olfactory nerve, or cranial nerve 1, is the first of 12 cranial nerves and is responsible for the sense of smell.
  • The olfactory nerve, or cranial nerve I, is the first of the 12 cranial nerves.
  • The olfactory nerve is the shortest of the 12 cranial nerves and only one of two cranial nerves (the other being the optic nerve) that do not join with the brainstem.
  • The specialized olfactory receptor neurons of the olfactory nerve are located in the olfactory mucosa of the upper parts of the nasal cavity.
  • The olfactory nerves consist of a collection of many sensory nerve fibers that extend from the olfactory epithelium to the olfactory bulb, passing through the many openings of the cribriform plate of the ethmoid bone.

• Oculomotor (III) Nerve

  • The oculomoter nerve (cranial nerve III) controls eye movement such as constriction of the pupil and open eyelids.
  • The oculomotor nerve is the third paired cranial nerve.
  • The occulomotor nerve is derived from the basal plate of the embryonic midbrain.
  • Sympathetic postganglionic fibers also join the nerve from the plexus on the internal carotid artery in the wall of the cavernous sinus and are distributed through the nerve, e.g., to the smooth muscle of levator palpebrae superioris.
  • Here the nerve is placed below the trochlear nerve and the frontal and lacrimal branches of the ophthalmic nerve, while the nasociliary nerve is placed between its two rami (the superior and inferior branch of oculomotor nerve).