TASTE, SMELL AND SKIN SENSATION

TASTE, SMELL AND SKIN SENSATION

• The perceptions of taste (rasa), smell (gandha), and touch (sparsha) are vital sensory experiences governed by respective indriyas (sense organs) and their supportive structures.

• According to Ayurveda, these sensations arise due to the contact (samprayoga) of the indriya, indriyartha (sense object), manas, and atma.

• In modern physiology, these sensations are regulated by specialized receptors, neural pathways, and brain centers.

TASTE (RASA) SENSATION

AYURVEDIC PERSPECTIVE

• Taste (rasa) is perceived by rasanendriya located in the jihva (tongue).

• It is influenced by ap mahabhuta (water element), which is predominant in rasa.

• There are six types of rasa: madhura, amla, lavana, katu, tikta, and kashaya.

PHYSIOLOGICAL BASIS (MODERN SCIENCE)

• Taste is mediated by taste buds located mainly on the tongue.

• Taste buds contain gustatory receptor cells connected to cranial nerves VII (facial), IX (glossopharyngeal), and X (vagus).

• Sembulingam describes the five primary tastes as sweet, salty, sour, bitter, and umami.

• The signal is transmitted to the gustatory cortex via thalamus.

RECEPTORS INVOLVED

• Chemoreceptors respond to dissolved substances in saliva.

• Each taste bud contains 50-100 receptor cells.

SIGNAL PATHWAY

• Taste receptor → Gustatory nerve → Solitary nucleus (medulla) → Thalamus → Gustatory cortex (insula and frontal operculum).

SMELL (GANDHA) SENSATION

AYURVEDIC PERSPECTIVE

• Smell (gandha) is perceived by ghranendriya, which is located in the nasika (nose).

• It is associated with prithvi mahabhuta, which is dominant in gandha.

PHYSIOLOGICAL BASIS (MODERN SCIENCE)

• Smell is mediated by the olfactory epithelium in the upper nasal cavity.

• Olfactory receptor neurons detect volatile odorant molecules.

• Sembulingam explains that cranial nerve I (olfactory nerve) carries impulses directly to the olfactory cortex without thalamic relay.
  
  

RECEPTORS INVOLVED

• Olfactory receptors are bipolar neurons with cilia (olfactory hairs).

• These receptors regenerate every 30-60 days.
  
  

SIGNAL PATHWAY

• Odorant binds to receptor → Olfactory bulb → Olfactory tract → Primary olfactory cortex (temporal lobe) and limbic system (emotions and memory).

SKIN SENSATION (SPARSHA)

AYURVEDIC PERSPECTIVE

• Touch (sparsha) is perceived by twak indriya, with vayu and akasha mahabhuta being predominant.

• It is present throughout the body but especially sensitive in the skin.

• Sparshanendriya is said to be sarvavyapi (ubiquitous).

  
  

PHYSIOLOGICAL BASIS (MODERN SCIENCE)

• Skin sensations include touch, pressure, vibration, pain, and temperature.

• Sembulingam classifies them into general sensations mediated by mechanoreceptors, thermoreceptors, and nociceptors.

  
  

TYPES OF SKIN RECEPTORS

• Meissner’s corpuscles – fine touch

• Merkel discs – steady pressure

• Pacinian corpuscles – vibration

• Ruffini endings – skin stretch

• Free nerve endings – pain and temperature

  
  

SIGNAL PATHWAY

• Skin receptor → Sensory neuron → Spinal cord (dorsal root) → Thalamus → Somatosensory cortex (postcentral gyrus).

COMPARATIVE OVERVIEW OF SENSORY PATHWAYS