voice

Precentral Gyrus of Motor Cortex

Controls voluntary vocalizations.

Midbrain:

Periaqueductal Grey Matter (PGM):

1. Production of emotional and involuntary sounds.

2. Generate specific respiratory and laryngeal motor patterns fundamental to speech and singing.

3. Muscular activity corresponding to the production of voiced and voiceless sounds are represented here.

Midbrain:

Nucleus Retroambigualis (NRA):

A column of neurons generated from PGM.

1. Generating respiratory pressure and laryngeal adduction.

2. Helps in vocalizations and vegetative maneuvers like cough.

Pyramidal tracts:

• Originates in the sensorimotor areas of the cerebral cortex down through the brainstem to the spinal cord.
• It includes corticobulbar tracts and corticospinal tracts.
• The frontobulbar portions of the pyramidal tracts connect with cranial nerves IX-XII, controls articulation, phonation, and respiration.

Extrapyramidal tracts:

• Part of the motor system network causing involuntary actions.
• It centers on the modulation and regulation (indirect control) of anterior (ventral) horn cells.
• They are chiefly found in the reticular formation of the pons and medulla, and target lower motor neurons in the spinal cord that are involved in reflexes, locomotion, complex movements, and postural control.

Cerebellum

It controls motor movements on motor system. It regulates force, speed, range, timing and direction. It also regulates muscle tone required for required for posture and changing position.

Vagus Nerve.

• It is the longest nerve of the autonomic nervous system in the human body.
• The vagus nerve extends through the jugular foramen, then passes into the carotid sheath between the internal carotid artery and the internal jugular vein down to the neck, chest, and abdomen, where it contributes to the innervation of the viscera, reaching all the way to the colon.
• Glossopharyngeal – accessorius.

Division of Vagus Nerve:

• The right vagus nerve gives rise to the right recurrent laryngeal nerve, which hooks around the right subclavian artery and ascends into the neck between the trachea and esophagus.
• The left vagus nerve enters the thorax between left common carotid artery and left subclavian artery and descends on the aortic arch. It gives rise to the left recurrent laryngeal nerve, which hooks around the aortic arch to the left of the ligamentum arteriosum and ascends between the trachea and esophagus.

Branches Of Vagus Nerve:

• Pharyngeal nerve
• Superior laryngeal nerve
• Recurrent laryngeal nerve
• Superior cervical cardiac branches of vagus nerve
• Inferior cervical cardiac branch
• Thoracic cardiac branches
• Branches to the pulmonary plexus
• Branches to the esophageal plexus
• Anterior vagal trunk
• Posterior vagal trunk
• Hering-Breuer reflex in alveoli[3]

Superior laryngeal nerve:

• It originates from the vagus at the Ganglion nodosum (inferior ganglion) and sub-divides into the internal and external superior laryngeal nerves.

• Internal branches of superior laryngeal nerve consists both sensory and parasympathetic secretomotor fibers (To secret a substance), which supply glands within the tissue above the level of the vocal folds.

• Branch of SLN divides in to three branches supplying Valleculae Epiglottis and Pyriform sinuses.

• The density of the nerve endings providing sensory innervations appears to be greatest at the laryngeal Inlet as part of the protective mechanism for respiratory system.

• Epiglottis consists of greatest laryngeal surface hence got greatest laryngeal innervation.

• Vocal folds have lower density fibers. Anterior portion of vocal folds have lower density of touch receptors than posterior portion.

• The external branch of the SLN provide motor supply to the cricothyroid muscle.

Recurrent laryngeal nerve

• It provide the motor supply to the intrinsic muscles except cricothyroid muscle which is innervated by the external branch of SLN.

• The RLN contain both the adductor and abductor fibers.

• Right and Left RLNs significantly regard to their origins.

• The right RLN arises from the main trunk of the vagus in-front of the sub-clavian artery.

• The left RLN arises from the vagus arch of the aorta round, which it winds before ascending the larynx.

• Left RLN is more liable to injury due to its extensive course than right RLN. Left RLN is especially vulnerable to pressure from aortic aneurysm and intra-thoracic masses.

• The left VF is affected twice as frequently as right by laryngeal paralysis.

• Both RLNs ascend the groove between the trachea and esophagus from both sides from a variable distance in different individuals. Then they divide into anterior and posterior branches before entering the larynx behind the cricothyroid.

• The RLN provides the sensory supply to the glottis and sub-glottis.

Pharyngeal nerve.

• It descends between internal and external carotid arteries, its fibers subsequently joins the glossopharyngeal and external laryngeal nerves, together which branches from the sympathetic trunk to form the pharyngeal plexus.

Other nerves.

• Cranial nerves V (trigeminal), VII (facial) and XII (hypoglossal) and cervical spinal nerves c-1 and c-3 provide motor supply for the extrinsic laryngeal muscles.