The inner ear assumes dual functionalities of auditory perception and equilibrium maintenance. The vestibule is the organ responsible for balance. This organ contains mechanoreceptors, specifically hair cells, endowed with stereocilia, which aid in deciphering information regarding the position and motion of our heads. Two intrinsic components, the utricle and saccule, help perceive head position, while the semicircular canals track head movement. Neurological messages initiated in the...

Vomiting is a complex physiological response to expel harmful or irritating substances from the body. It's a defensive mechanism triggered by stimuli like poisons, microbial toxins, cytotoxic drugs, and mechanical abdominal distension. The process is centrally coordinated by the vomiting (or emetic) center located in the medulla of the brainstem. This area, rich in muscarinic M1, histamine H1, neurokinin 1 (NK1), and serotonin 5-HT3 receptors, coordinates the act of vomiting through...

Serotonin, a crucial neurotransmitter synthesized by enterochromaffin cells, plays a cardinal role in regulating gastrointestinal (GI) motility. With over 90% of the body's total serotonin in the GI tract, its influence on digestive processes is profound. Serotonin is swiftly released upon various stimuli, such as food boluses or certain drugs, triggering intrinsic sensory neurons in the myenteric plexus and extrinsic vagal and spinal sensory neurons. This leads to the activation of the...

The vestibular system is a set of inner ear structures that provide a sense of balance and spatial orientation. This system is comprised of structures within the labyrinth of the inner ear, including the cochlea and two otolith organs—the utricle and saccule. The labyrinth also contains three semicircular canals—superior, posterior, and horizontal—that are oriented on different planes.

Sensory impulses related to touch, pressure, vibration, and proprioception from various body parts, such as the limbs, trunk, neck, and posterior head, travel to the cerebral cortex through the posterior column-medial lemniscus pathway. The pathway’s name derives from the two white-matter tracts that convey the impulses: the spinal cord's posterior column and the brainstem's medial lemniscus. First-order sensory neurons extend their axons into the spinal cord, forming the...

5-HT3 receptor antagonists, such as dolasetron, granisetron (Kytril), ondansetron (Zofran), and palonosetron (Axoli), are crucial in managing chemotherapy-induced nausea and vomiting (CINV) and postoperative nausea. These drugs selectively block 5-HT3 receptors in the visceral vagal and spinal afferent nerves, chemoreceptor trigger zone, and the vomiting center. They have a rapid onset of action and can be given as a single dose before chemotherapy. Ondansetron and granisetron, in particular,...