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examBoard: Pearson Edexcel
examType: IGCSE
lessonTitle: Hormone Sources and Effects
Your body has two main control systems: the nervous system and the endocrine system. While the nervous system uses electrical impulses for rapid communication, the endocrine system uses chemical messengers called hormones for slower but longer-lasting effects. Let's explore how these hormones coordinate various body functions!
Key Definitions:
Nervous System:
Endocrine System:
Your body contains several endocrine glands that produce different hormones. Each gland has a specific location and role in maintaining homeostasis (balance) in the body.
Located at the base of the brain, often called the "master gland" as it controls many other glands. Produces growth hormone, prolactin and hormones that control other endocrine glands.
Found in the neck, produces thyroxine which controls metabolic rate (how quickly the body uses energy). Also produces calcitonin which helps regulate calcium levels.
Sit on top of the kidneys. Produce adrenaline for "fight or flight" responses and cortisol which helps manage stress and metabolism.
Located behind the stomach. Produces insulin and glucagon to control blood glucose levels. It's both an endocrine and exocrine gland (also produces digestive enzymes).
Male reproductive organs that produce testosterone, which controls male secondary sexual characteristics and sperm production.
Female reproductive organs that produce oestrogen and progesterone, which control female secondary sexual characteristics and the menstrual cycle.
One of the most important roles of hormones is maintaining normal blood glucose levels. Two pancreatic hormones work together to keep your blood sugar balanced:
Source: Beta cells in the pancreas
Trigger: Released when blood glucose is too high (after eating)
Effects:
Source: Alpha cells in the pancreas
Trigger: Released when blood glucose is too low (e.g., during fasting)
Effects:
Type 1 diabetes occurs when the pancreas cannot produce insulin. Without insulin, blood glucose levels remain dangerously high after eating. Before insulin was discovered in 1921, this condition was fatal. Today, people with Type 1 diabetes manage their condition by monitoring blood glucose levels and injecting insulin when needed. This highlights the critical role hormones play in maintaining homeostasis.
When you're scared or excited, your adrenal glands release adrenaline (also called epinephrine), preparing your body for emergency action.
Adrenaline prepares your body to either fight a threat or run away from it - the "fight or flight" response. Within seconds of release, adrenaline causes:
These changes happen rapidly and prepare you to respond to danger, whether that's running from a dog or giving an important presentation!
Hormones play a crucial role in reproduction and the development of secondary sexual characteristics during puberty.
Oestrogen:
Progesterone:
Testosterone:
The menstrual cycle is controlled by hormones from the pituitary gland and ovaries. A typical cycle lasts about 28 days and involves several phases:
Some hormones can affect your mood and behaviour! For example, low levels of serotonin are linked to depression, while oxytocin (sometimes called the "love hormone") is released during positive social interactions like hugging. This shows how hormones influence not just physical processes but also how we feel and behave.
Hormones are chemical messengers that coordinate complex processes throughout the body. They work more slowly than the nervous system but have longer-lasting effects. Each hormone has specific target organs and functions, from regulating metabolism and blood glucose to controlling reproduction and stress responses. Understanding how hormones work helps us appreciate how our bodies maintain balance and respond to changing conditions.
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