12th Zoology

Receptor Organs – Eye

Receptor Organs

The survival of animals depends on their ability to compute all the
information flowing from the environment and integrate them into meaningful
instructions to the effector organs. Information relating to the external and
internal environment can be gained only through the sensory receptor
organs.

These organs have specialized cells that can transform the stimuli
falling on them, whether it is chemical, radiant, electrical or mechanical, into
electrical signals and convey the same to the central nervous system. In the
CNS the integration and coordination of the data happens.

This ability of the sensory cells is known as transduction and the receptors are sometimes referred to as transducers. (Receptor Organs)

Eye – Receptor Organs

The visual system gives information about size, shape, color,
luminosity and movements of object in the external world. (a) Focusing Mechanism in the Human Eye Light rays entering the eye are redirected or refracted. Refraction occurs through three surface of the eye before the light reaches the retina.

The first of the refracting surfaces is the cornea, then the front surface of the
lens and finally the rear surface of the lens. Between the cornea and the lens is a colourless, watery fluid called aqueous humour. At the back of the eye between the lens and the retina is the vitreous humour made of a gelatinus mucoprotein.

The humours are transparent so that transmissions of light through the cavities of the eye to the retina is not normally impeded. Human eye has a lens apparatus whose convexity can be adjusted for focusing near and distant objects. This ability of the eyes to focus objects at varying distances is called ACCOMMODATION. (Receptor Organs)

The accommodation is achieved due to suspensory ligament, ciliary muscle and ciliary body. When a normal eye is looking at a distant object, the ciliary muscles is fully relaxed and parallel rays from the object come to focus on the retina.

Hence a clear image is seen. When the object is brought close to the eye the
refractive power of the eye is increased by the process of accommodation.
The increase in refractive power is the result of an increase in the curvature
of the anterior surface of the lens. This avoids the blurred image for a closer
object. (Receptor Organs)

Similar accommodation happens for viewing a distant object by stretching the suspensory ligament attached to the lens. This act alters the contour of the lens.

Related Topics in Zoology:

Bio Zoology All Important Topics


  1. Human Physiology Introduction

  2. Nutrition

  3. Carbohydrates Poly hydroxyaldehydes (or) ketones

  4. Proteins (Polypeptides)

  5. Lipids

  6. Vitamins – Functions Of Vitamins

  7. Deficiency of Vitamin

  8. Minerals – Water – Role of water

  9. Balanced diet

  10. Obesity

  11. Digestive System

  12. Dental Caries (Tooth decay)

  13. Root Canal Treatment

  14. Peptic ulcer

  15. Hernia and Types

  16. Appendicitis (Appendix)

  17. Gall Stones

  18. Hepatitis

  19. Fractures – Types of fractures

  20. Mechanism of fracture

  21. Dislocation of joints

  22. Arthiritis

  23. Rickets and Osteomalacia – Orthopedics

  24. Muscles

  25. Mechanism of muscle contraction

  26. Types of muscle contraction

  27. Myasthenia Gravis

  28. Respiration – Process of pulmonary respiration

  29. Mechanism of Breathing

  30. Regulation of Respiration

  31. Pneumonia Tuberculosis Symptoms Treatment

  32. Bronchitis – Acute bronchitis, Chronic Bronchitis Causes

  33. Circulatory System – Functioning of Human heart

  34. Cardiac Cycle

  35. Coronary blood vessel and its significance

  36. Myocardial infarction

  37. Angina pectoris

  38. Angiogram – Angioplasty

  39. Atherosclerosis

  40. Heart block Echo cardiography Heart Valves

  41. Rheumatic Heart Disease (RHD), ICCU – (Intensive Coronary Care Unit)

  42. Blood Pressure

  43. Heart transplantation

  44. Pulse rate

  45. Cardio Pulmonary Resuscitation (CPR)

  46. Blood – Composition of plasma – Blood cells

  47. Clotting of Blood or Haemostasis

  48. Thrombosis

  49. Nervous system Co-ordination systems

  50. The Brain – Fore Brain, Midbrain, Hindbrain

  51. Memory

  52. Sleep – Types of sleep

  53. Stroke – Brain haemorrhage

  54. Alzheimer – Meningitis (Brain fever)

  55. Conditioned reflex

  56. Electroencephalography EEG

  57. Right and Left brain concept

  58. Spinal cord functioning

  59. Chemical co-ordination – Functions of Endocrine glands

  60. Hypothalamus

  61. Pituitary gland – hormone

  62. Hormones of Neurohypophysis – vasopressin

  63. Thyroid gland

  64. Parathyroid Gland

  65. Pancreas

  66. Adrenal gland

  67. Gonads

  68. Receptor Organs – Eye

  69. Photochemistry of Retinal visual Pigments

  70. Errors of refraction

  71. Optometry – Retinopathy

  72. Cataract – Lens Replacement – Glaucoma – Nyctalopia

  73. Eye Infections and Eye Care

  74. Ear

  75. Mechanism of hearing

  76. Defects of the ear

  77. Hearing Aid – Noise pollution

  78. Skin and functions of skin

  79. Melanin functions

  80. Effects of solar radiation / UV radiation – Skin grafting

  81. Dermatitis

  82. Tongue – Mechanism of Stimulation

  83. Excretion Ureotelism Nephron

  84. Mechanism of urine formation

  85. Renal Failure, Dialysis, Kidney Machines

  86. Kidney stone – Kidney transplantation

  87. Diabetes mellitus

  88. Functioning of male reproductive system

  89. Functioning of female reproductive system

  90. Ovulation and fate of the ovum – Menstrual cycle

  91. Fertilization

  92. Birth control

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