Course 18.3Lesson 1 of 3
The wall of the heart makes ANF, which lowers the blood pressure. The kidney makes erythropoietin, which raises the number of red cells. The stomach and the small intestine make gastrin, secretin, CCK and GIP, which control the digestive juices. Many tissues also make growth factors.
Try the code and the simulations beside the lesson.
You have met the glands whose only work is to make hormones. But organs with other main work make hormones too. The heart pumps blood, the kidney filters it and the gut digests food. Each of them also sends a chemical message.
This lesson is not in the NEET syllabus text for this chapter. NCERT teaches it, and the text of A-Level and IB biology covers the same hormones. The hormones of the heart and the kidney meet the excretion unit of NEET, and the gut hormones meet the digestion unit of the textbooks.
The wall of the atrium of the heart makes a peptide hormone, the atrial natriuretic factor (ANF). The word natriuretic comes from the Latin name for sodium and means "making sodium pass in the urine".
When the blood pressure rises, the atrial wall stretches and releases ANF. ANF makes the blood vessels dilate, which means that they become wider. The resistance to the flow of blood falls, so the blood pressure falls.
ANF works against the hormones that raise the pressure. When the pressure falls, the juxtaglomerular cells of the kidney release renin. Renin starts a chain that makes angiotensin II, which narrows the blood vessels and makes the adrenal cortex release aldosterone. You study this system in the chapter on excretion. ANF is the opposite signal.
The juxtaglomerular cells of the kidney, according to NCERT, produce a peptide hormone, erythropoietin. Many other textbooks name other cells of the kidney cortex as the source. NEET follows NCERT.
Erythropoietin stimulates erythropoiesis, the making of red blood cells in the red bone marrow. The kidney releases more of it when the oxygen supply is low. This is why a person who lives high in the mountains has more red cells. And it is why a person with a long standing kidney disease can be anaemic. The kidney makes too little of the hormone.
Endocrine cells in the stomach and the small intestine make four major peptide hormones.
Standard physiology books add what starts each one. Protein food in the stomach releases gastrin. Acid food entering the duodenum releases secretin. Fat in the duodenum releases CCK. Glucose and fat in the duodenum release GIP.
Several tissues that are not endocrine glands make hormones called growth factors. They are essential for the normal growth of tissues, and for their repair and regeneration after an injury.
You should find that each stimulus gives one hormone, one target and one effect. Say them aloud as a chain: food, hormone, target, juice.
The program looks up the hormone for one stimulus.
Try each one on your own first. If you are stuck, open a hint. Then check with Show the answer.
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