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# Lecture 25: The Endocrine System ## The Endocrine System ### What is it? * Regulates body functions * Using hormones * Endocrine glands secrete hormones into bloodstream ### Hormones * Chemical messengers * Travel through the body via blood * Affect distant cells/tissues ### Compared to the...

# Lecture 25: The Endocrine System ## The Endocrine System ### What is it? * Regulates body functions * Using hormones * Endocrine glands secrete hormones into bloodstream ### Hormones * Chemical messengers * Travel through the body via blood * Affect distant cells/tissues ### Compared to the Nervous System | Feature | Endocrine System | Nervous System | | --------------- | ---------------------------- | ----------------------------------- | | Signal Type | Chemical (hormones) | Electrical & Chemical (neurotransmitters) | | Transmission | Bloodstream | Nerve cells | | Speed | Slower | Faster | | Duration | Longer-lasting | Shorter | | Target | Cells with specific receptors | Specific cells | ## Major Endocrine Glands ### Hypothalamus * Brain region * Controls pituitary gland * Regulates: * Body temperature * Hunger * Thirst * Sleep * Circadian rhythms * Emotional responses ### Pituitary Gland * "Master gland" * Controlled by hypothalamus * Secretes many hormones * Growth * Blood pressure * Reproduction ### Pineal Gland * Produces melatonin * Regulates sleep ### Thyroid Gland * Metabolism * Growth * Development ### Parathyroid Glands * Calcium levels in blood ### Thymus * Immune function ### Adrenal Glands * Stress response * Metabolism * Blood pressure * Kidney function ### Pancreas * Regulates blood sugar ### Ovaries * Female * Estrogen * Progesterone ### Testes * Male * Testosterone ## Hormone Action ### Receptors * Hormones bind to receptors on/in target cells * Each receptor is specific to a hormone ### Mechanisms * Altering gene expression * Activating/inactivating enzymes * Changing membrane permeability ## Regulation ### Feedback Loops * Negative feedback: reverses a change * Positive feedback: amplifies a change ### Example: Blood Sugar 1. **High blood sugar**: Pancreas releases insulin 2. **Insulin**: Tells body to store glucose, blood sugar drops 3. **Low blood sugar**: Pancreas releases glucagon 4. **Glucagon**: Tells body to release glucose, blood sugar rises ### Disorders * Diabetes (Type 1 & 2) * Thyroid disorders * Growth disorders * Adrenal disorders ## Diagram The image shows a diagram illustrating the endocrine system and the locations of the major glands in the human body. The glands include the pituitary, pineal, thyroid, parathyroid, thymus, adrenal, pancreas, ovaries (in females), and testes (in males). The hypothalamus is also labeled in the brain. Arrows indicate the general direction of hormone secretion and the hormones' effects on various organs and systems in the body.