09 Ex9.1 Ms Hormones

2/7/09

Question 1  The Figure below is a graph which shows how the concentration of blood sugar and the concentration of a certain hormone in the blood changed over a period of 5 hours.

HORMONES EX 9.1

Question 1a

Question 1 (b)  Name the hormone. Insulin;

i) 

What happened at the end of the first hour to cause the changes shown on a graph?

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There was an increase in blood glucose level at the end of the first hour due to intake of carbohydrates in a meal;

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ii) What type of sugar is ‘blood sugar’?

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Glucose;

iii) Why was the concentration of blood sugar slowly falling during the first hour?   The blood sugar (glucose) could be converted to glycogen for storage in the liver and muscles;   The tissue cells could also be oxidizing glucose to produce energy during tissue respiration;

Question 2 a) What is a hormone?  Hormones are chemical substances produced by the endocrine glands of plants or animals;  They are passed directly into the bloodstream and gets carried to the target organs to exert a profound effect;  Each hormone can alter the activity of one or more specific target organs and is then destroyed by the liver.

(b)  Explain why the two curves are similar in shape.   The secretion of insulin is triggered by an increase in blood sugar concentration. Therefore, the hormone curve follows the blood sugar curve closely;   More insulin is released when there is an a high blood sugar concentration;   The effect of insulin is to lower down the blood sugar concentration by increasing uptake of glucose into adipose and muscle cells and converting excess glucose to glycogen in the liver and muscle cells;   Once it is brought down, less insulin is secreted, and the insulin present in the blood stream is destroyed by the liver;

Question 2b  Nerves and hormones are both used to control processes within body. Using reflex action illustrated by your eyes and the regulation of blood sugar by insulin as examples to show how nervous and hormonal controls i) Resemble each other  Both require receptors to detect stimuli;  Both involve conduction of messages and are involuntary;  Both bring about response that is beneficial for the body (protection / homeostasis);

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2/7/09

Question 2b *For example:

Question 2bii)  Differ from one another

 When bright light (stimulus) reaches the eye, photoreceptors on retina (receptors) sense it, impulses are sent to the reflex centre of the brain via the sensory neurone of the optic nerve. Impulses are then sent to the iris muscles, causing a reduction in the size of the pupil (response); (need not describe the whole process of a reflex action here.)    After an intake of sugary food, there is an increase of blood glucose level (stimulus) after digestion & absorption, cells in the pancreas (receptor) sense an increase in the concentration of blood, messages are sent to the Islet of Langerhan to secrete insulin (response), to help us bring down the sugar content in the blood;

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