Introduction to Endocrine System MCQ - Practice Questions with Answers

• We have seen that the neural system provides point-to-point rapid coordination among organs. 
• Neural coordination is fast but short-lived. 
• As the nerve fibres do not innervate all cells of the body and the cellular functions need to be continuously regulated; a special kind of coordination and integration has to be provided. 
• This function is carried out by hormones. 
• The neural system and the endocrine system jointly coordinate and regulate physiological functions in the body.
• The main difference between two systems are as follows :

Endocrine Glands:

• Endocrine glands lack ducts and are hence, called ductless glands. 
• Their secretions are called hormones.
• The classical definition of the hormone is a chemical produced by endocrine glands and released into the blood and transported to a distantly located target organ.
• Hormones are non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts.

Human Endocrine System:

• The endocrine glands and hormone-producing diffused tissues/cells located in different parts of our body constitute the endocrine system.
• Pituitary, pineal, thyroid, adrenal, pancreas, parathyroid, thymus and gonads (testis in males and ovaries in females) are the organised endocrine bodies in our body.
• In addition to these, some other organs, e.g., gastrointestinal tract, liver, kidney, the heart also produce hormones.
  

Discovery of Hormones:

• English physiologist William M. Bayliss and Ernest H. Starling discovered the first hormone secretin in 1903. It is present in the intestinal mucosa.
• The term hormone was introduced by Starling in 1905.

Properties of Hormones:

• They are synthesized and secreted by endocrine cells 
• Hormones are non-nutrient chemicals. 
• They act as intercellular messengers and are produced in trace amounts.
• Hormones are transported by the bloodstream from the endocrine cells to serve as ‘chemical messengers’ which act on target cells or organs.
• Hormones do not provide energy or building materials but they do have effects on growth differentiation and metabolic activities of their target cells.
• They have low molecular weight.
• Hormones are effective in low concentration.
• Excess or deficiency leads to disorders.
• They may accelerate or inhibit a specific physiological process.
• Hormones are often used up in their regulatory activities.

Mode of Action:

• Two or more hormones can interact to affect the response of cells in a variety of ways.
• The three most common types of interaction are as follows:
• The permissive effect, in which the presence of one hormone enables another hormone to act.
• The synergistic effect, in which two hormones with similar effects produce an amplified response.
• The antagonistic effect, in which two hormones have opposing effects.