Summery of the human sensory organs

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)