Hormones Revision Notes

Hormones are chemical substances produced by specialized glands in the body.

These glands release hormones directly into the bloodstream.

Each hormone is designed to affect specific organs or tissues called target organs.

• Produced by glands.
• Released into the blood.
• Target specific organs.

Once secreted, hormones travel through the bloodstream to reach their target organs.

The blood acts as a transport system distributing hormones throughout the body.

Only organs with specific receptors respond to a particular hormone.

• Travel via bloodstream.
• Reach target organs with matching receptors.
• Do not affect all organs, only specific targets.

Hormones modify or regulate the function of their target organs.

This regulation helps maintain internal balance and coordinate body activities such as growth, metabolism, and reproduction.

The effect depends on the hormone and the organ it targets.

• Change how target organs function.
• Help regulate body processes.
• Ensure coordinated responses.

The adrenal glands are located above the kidneys and produce adrenaline.

Adrenaline prepares the body for rapid action during stress, triggering the 'fight or flight' response.

• Located above kidneys.
• Produce adrenaline.
• Involved in stress response.

The pancreas produces insulin, a hormone that regulates blood glucose levels.

Insulin helps lower blood sugar by enabling cells to absorb glucose.

• Located near the stomach.
• Produce insulin.
• Regulate blood sugar levels.

The testes are male reproductive glands that produce testosterone.

Testosterone controls male secondary sexual characteristics such as facial hair and muscle growth.

• Male reproductive glands.
• Produce testosterone.
• Control male sexual development.

The ovaries are female reproductive glands that produce oestrogen.

Oestrogen regulates female reproductive development and the menstrual cycle.

• Female reproductive glands.
• Produce oestrogen.
• Control female sexual development and menstrual cycle.

Adrenaline is a hormone secreted by the adrenal glands during stressful or dangerous situations.

Its release triggers the body's 'fight or flight' response, preparing it for rapid action.

• Released by adrenal glands.
• Triggered by stress or danger.
• Prepares body for quick response.

Adrenaline increases the breathing rate to supply more oxygen to the muscles.

This helps meet the increased oxygen demand during stress or physical activity.

• Breathing rate increases.
• More oxygen enters the lungs.
• Supports muscle activity.

Adrenaline causes the heart to beat faster, increasing heart rate.

This pumps oxygenated blood more quickly to muscles and vital organs.

• Heart rate increases.
• Faster blood circulation.
• Improves oxygen delivery.

Adrenaline causes the pupils to dilate (increase in size).

Larger pupils allow more light into the eyes, improving vision in stressful situations.

• Pupils dilate.
• More light enters the eyes.
• Enhances vision.

The nervous system transmits signals as electrical impulses along neurons, allowing rapid communication to specific target cells.

The hormonal system releases chemical messengers called hormones into the bloodstream, which travel to target organs more slowly and affect multiple tissues.

• Nervous system uses electrical impulses via neurons.
• Hormonal system uses chemical signals (hormones) transported by blood.

Nervous responses are very fast because electrical impulses travel quickly along nerve cells, enabling immediate reactions such as reflexes.

Hormonal responses are slower since hormones must circulate through the blood to reach target cells, causing a delay before effects begin.

• Nervous system responses are rapid.
• Hormonal system responses are slower due to blood transport.

Nervous system effects are usually short-lived; once the electrical impulse stops, the response ends quickly.

Hormonal effects last longer because hormones remain in the bloodstream and continue to influence target organs after release.

• Nervous responses are brief.
• Hormonal responses are prolonged.

Glucagon is secreted by specialized cells in the pancreas when blood glucose levels fall too low.

It acts as a chemical messenger to regulate blood sugar balance.

• Produced by pancreas.
• Released when blood glucose is low.

Glucagon signals the liver to convert stored glycogen into glucose.

This glucose is then released into the bloodstream to raise blood sugar levels.

This process ensures a steady supply of glucose for energy, especially during fasting or between meals.

• Stimulates glycogen breakdown in liver.
• Raises blood glucose concentration.
• Works opposite to insulin to maintain balance.

Glucagon helps prevent hypoglycemia (low blood sugar) by increasing glucose availability.

It complements insulin, which lowers blood glucose, together maintaining homeostasis.

• Prevents low blood sugar.
• Balances insulin effects.

Adrenaline stimulates the liver to break down glycogen into glucose, increasing blood glucose levels.

This provides extra energy for muscles during stressful or emergency situations.

• Raises blood glucose by glycogen breakdown in liver.
• Supplies energy for rapid muscle activity.

Adrenaline increases heart rate, which boosts blood circulation.

Improved circulation delivers more oxygen and nutrients to tissues, supporting increased metabolic demands.

• Increases heart rate.
• Enhances blood flow and oxygen delivery.

By raising blood glucose and heart rate, adrenaline prepares the body for quick, intense physical activity.

These changes support the 'fight or flight' response to stress or danger.

• Prepares body for rapid action.
• Increases metabolic activity.