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Control and Coordination - Chemical coordination: animal hormones

Grade 10CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Hormones are chemical messengers secreted by endocrine glands (ductless glands) directly into the bloodstream to reach specific target organs.

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The Pituitary Gland, located at the base of the brain, is known as the 'Master Gland' as it regulates other glands and secretes Growth Hormone (GH). Deficiency leads to Dwarfism, and excess leads to Gigantism.

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The Thyroid Gland requires Iodine (II) for the synthesis of Thyroxine. Thyroxine regulates the metabolism of carbohydrates, proteins, and fats. Deficiency causes Goitre.

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The Pancreas acts as both an exocrine and endocrine gland. It secretes Insulin, which helps in lowering blood glucose levels by converting glucose into glycogen. Deficiency leads to Diabetes Mellitus.

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Adrenal Glands secrete Adrenaline (often referred to as the 'Fight or Flight' hormone) during emergency situations, increasing heart rate and blood pressure to provide more oxygen to muscles.

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The Feedback Mechanism ensures that hormones are secreted in precise quantities and at the right time. For example, high blood sugar levels trigger the pancreas to produce more Insulin, which then lowers the sugar levels, eventually slowing down the Insulin production.

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Testes in males secrete Testosterone and Ovaries in females secrete Oestrogen and Progesterone, which are responsible for secondary sexual characteristics and reproductive health.

📐Formulae

Iodine+Thyroglobulin→Thyroxine (T4)\text{Iodine} + \text{Thyroglobulin} \rightarrow \text{Thyroxine } (T_4) status

High Blood Glucose→StimulatesPancreas→ReleasesInsulin\text{High Blood Glucose} \xrightarrow{\text{Stimulates}} \text{Pancreas} \xrightarrow{\text{Releases}} \text{Insulin}

Glucose⇌GlucagonInsulinGlycogen\text{Glucose} \xrightleftharpoons[\text{Glucagon}]{\text{Insulin}} \text{Glycogen}

Adrenaline secretion∝Heart Rate↑+Breathing Rate↑\text{Adrenaline secretion} \propto \text{Heart Rate} \uparrow + \text{Breathing Rate} \uparrow

💡Examples

Problem 1:

A person has a very short stature (dwarfism). Which hormone is deficient and which gland is responsible for this condition?

Solution:

The deficient hormone is the Growth Hormone (GHGH) and the gland responsible is the Pituitary Gland.

Explanation:

The Pituitary gland secretes Growth Hormone which regulates growth and development of the body. If there is a deficiency of this hormone during childhood, it results in Dwarfism.

Problem 2:

Why is it advised to use iodised salt in our diet?

Solution:

Iodised salt provides Iodine (II), which is essential for the Thyroid gland to produce Thyroxine hormone.

Explanation:

Thyroxine regulates carbohydrate, protein, and fat metabolism. Without sufficient II, the thyroid gland cannot function properly, leading to its enlargement, a condition known as Goitre.

Problem 3:

Explain the feedback mechanism that occurs when blood sugar levels rise.

Solution:

Blood Sugar Level↑→Detected by Pancreas Cells→Insulin Secreted→Blood Sugar Level↓\text{Blood Sugar Level} \uparrow \rightarrow \text{Detected by Pancreas Cells} \rightarrow \text{Insulin Secreted} \rightarrow \text{Blood Sugar Level} \downarrow

Explanation:

When glucose levels in the blood rise, the β\beta-cells of the pancreas detect this and secrete Insulin. Insulin facilitates the uptake of glucose by cells and conversion to glycogen in the liver, bringing the blood sugar level back to normal. As the level falls, insulin secretion is reduced.