12th Zoology

Circulatory System – Functioning of Human heart

The Circulatory System

All cells of our body require constant nutrition and waste removal
since they are metabolically active. Most of the body cells are located at
some distance from the nutrient sources such as the digestive tract and sites
of waste disposal such as kidneys. The cardiovascular system which
consists of the heart, blood vessels and blood, connects the various tissues
of the body. While the heart pumps the blood through the blood vessels, the
blood delivers nutrients and collect waste products.

Functioning of Human heart (Circulatory System)

Heart is a pumping organ. It receives blood from different parts of
the body through the veins that open through inferior and superior vena
cavae and pulmonary veins. While the right atrium receives deoxygenated
blood, the left atrium receives the oxygenated blood from the lungs. When
the wall of the atria contract the right and left atria pump the blood into the
right and left ventricles respectively. A pulmonary trunk arising from the
right ventricle takes away the blood to the lungs for oxygenation. The left
ventricle gives rise to an aorta, from which oxygneated blood is supplied to
the coronary arteries and the systemic circulation of the body. The blood flow between the right atrium and the right ventricle is
regulated by the tricuspid valve. The bicuspid or mitral valve regulates
the flow on the left chambers of the heart. In the pulmonary trunk and the
aorta, back flow of blood is prevented by a set of semilunar valves.

Origin and conduction of heart beat (Circulatory System)

During pumping action of heart, the heart muscles cause rhythmic
contraction and relaxation of the heart chambers in a specific sequence. The
rhythmic, sequential functioning of the cardiac chamber is maintained by
sino-atrial node (SA node), atrio-ventricular node (AV node), bundle of His
and Purkinje fibres.

The SA node situated in the upper, lateral wall of the right atrium is a
small, flattened strip of muscle fibre that is 1.5cm x 3mm in size. The fibres of
the SA node are closely associated with the muscles of auricles. SA node is
capable of generating action potential that can travel throughout the auricles.
The velocity of conduction is 0.3m/sec. The excitation from the SA node
stimulates the AV node. The AV node in turn conducts the stimulus to bundle
of His and Purkinje fibres. These myocardial fibres are found all over the
wall of the ventricles. In the conduction of stimulus through the AV node and
the fibrous system there is a delay in transmission.

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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