This document discusses the five main categories of human sense organs: mechanoreceptors, chemoreceptors, electromagnetic receptors, thermoreceptors, and pain receptors. It focuses on three specific sense organs: taste buds, which are chemoreceptors that allow us to detect five basic tastes; the skin, which contains mechanoreceptors, thermoreceptors, and pain receptors that allow us to feel touch, temperature, and pain; and the eyes, which contain photoreceptors that allow us to see light and color. The document provides details on the types of sensory receptors found in each of these three sense organs and their functions in detection and perception.

1. HUMAN SENSE ORGANS
LIFE SCIENCES 2016

2. INTRODUCTION TO SENSE ORGANS
 Sensations and perceptions begin with sensory reception, detection of
stimuli by sensory receptors.
 Sensory receptors can detect stimuli outside and inside the body.
 Sensory receptors fall into five categories:
 Mechanoreceptors
 Chemoreceptors
 Electromagnetic receptors
 Thermoreceptors
 Pain receptors
• Campbell et.al, 2010 – CHAPTER 50

4. 1. CHEMICAL SENSES: TASTE
The receptors responsible for taste are called– CHEMORECEPTORS
 Gustation (taste) is dependent on the detection of chemicals called tastants.
 Taste receptors = TASTE BUDS
 Taste buds are located on tongue(mainly), hard palate, pharynx and epiglottis.
 The tongue very rough, due to numerous papillae.
 3 Types of papillae:
• - Fungiform- found on front and sides of tongue.
• - Foliate found on front 2/3 of tongue
• - Curcumvallate- found on the back of the tongue.

5. CHEMICAL SENSES: TASTE (CONTINUES)
 The taste buds are located on the papillae.
 Functions of taste buds:
 Chemical molecules in food, dissolve in the saliva.
 The molecules bind to the receptor proteins in the microvilli of the taste buds.
 This stimulates the taste cells to send an impulse through the sensory nerve fibers.
 Impulse move to the parietal lobe of cerebrum.
 Taste is interpreted
•
 5 primary taste perceptions: sweet, salty, bitter, sour and umami.

6. 2. SENSE ORGAN: SKIN
 Mechanoreceptors sense physical deformation caused by stimuli such as pressure, stretch,
motion, and sound
 The sense of touch in mammals relies on mechanoreceptors
 Thermoreceptors, which respond to heat or cold, help regulate body temperature by signalling
both surface and body core temperature.
 Pain receptors, or nociceptors, respond to excess heat, pressure, or chemicals released from
damaged or inflamed tissues.

8. SENSE ORGAN: SKIN (CONTINUES)
 The sensory cutaneous mechanoreceptors in the skin are:
 Ruffini's end organ (sustained pressure)
 Meissner's corpuscle (changes in texture, slow vibrations)
 Pacinian corpuscle (deep pressure, fast vibrations)
 Merkel's disc (sustained touch and pressure)
 Free nerve endings

11. 3. SENSE ORGAN: EYES
 Photoreceptors are sensory receptors that are sensitive to light.
 Animals and humans with 2 eyes facing forward have 3D or stereoscopic vision, visual fields overlap
and each eye is able to view and object from a different angle.
 Main parts of the eye found in 3 main layers
 Outer layer (Cornea, Sclera)
 Middle layer (Choroid, ciliary body, iris)
 Inner layer (Retina – rods, cones, fovea)
 Study, understand and know the structure and functions of the different structures of the human eye.
 The ability of the lens to change shape to enable the eye to focus on near and far objects.=
accommodation –

14. REFERENCE LIST:
 Campbell et.al, 2010 – CHAPTER 50
 Gotov .Kz (slideshare)
 Precious Concha (slideshare)
 Rizfarizan (slideshare)
 DrKiran Kumar (slideshare)