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Coordination and Response - Hormones in humans

Grade 11A LevelBiology

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

🔑Concepts

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A hormone is a chemical substance produced by an endocrine gland and carried by the blood, which alters the activity of one or more specific target organs.

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Adrenaline is the 'fight or flight' hormone secreted by the adrenal glands. It increases heart rate and the concentration of blood glucose (C6H12O6C_6H_{12}O_6) to prepare the body for action.

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The pancreas regulates blood glucose levels by secreting two hormones: Insulin (to lower blood glucose) and Glucagon (to raise blood glucose).

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Insulin stimulates the liver to convert excess glucose (C6H12O6C_6H_{12}O_6) into stored glycogen.

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Glucagon stimulates the liver to break down stored glycogen back into glucose (C6H12O6C_6H_{12}O_6) when blood levels are low.

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The endocrine system transmits information via chemicals in the blood, which is generally slower than the nervous system's electrical impulses but produces longer-lasting effects.

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Negative feedback mechanisms ensure that if a level (such as blood glucose) deviates from the norm, the body acts to return it to the set pointset\ point.

📐Formulae

C6H12O6→InsulinGlycogen (stored in liver)C_6H_{12}O_6 \xrightarrow{\text{Insulin}} \text{Glycogen (stored in liver)}

Glycogen→GlucagonC6H12O6 (released to blood)\text{Glycogen} \xrightarrow{\text{Glucagon}} C_6H_{12}O_6 \text{ (released to blood)}

Aerobic Respiration: C6H12O6+6O2→6CO2+6H2O\text{Aerobic Respiration: } C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O

💡Examples

Problem 1:

Explain the role of adrenaline in preparing the body for vigorous exercise.

Solution:

Adrenaline is released from the adrenal glands. It causes an increase in heart rate and breathing rate. It also stimulates the liver to convert glycogen into C6H12O6C_6H_{12}O_6.

Explanation:

Increased heart and breathing rates deliver more O2O_2 and C6H12O6C_6H_{12}O_6 to the muscles, increasing the rate of aerobic respiration to provide energy for muscle contraction.

Problem 2:

Contrast the speed and duration of the nervous system and the endocrine system.

Solution:

Nervous system: Speed is very fast (electrical impulses); Duration is short-lived. Endocrine system: Speed is slower (blood transport); Duration is long-lasting.

Explanation:

Nervous signals travel via neurones at up to 100 m/s100\ m/s, while hormones must travel through the circulatory system and take time to be broken down by the liver.