Warm Up – Monday 5/1 Describe the function of each hormone. State the name of the gland that secretes each hormone. Skip “HCG” for now (Epinephrine)
Pancreas Adrenal glands Testes Pituitary gland Ovaries Embryo Placenta
Hormones & the Endocrine System
What is the function of the endocrine system? Maintains the internal environment in the body (the optimum biochemical environment) Influences metabolic activities Integrates and regulates growth and development. Controls, maintains and initiates sexual reproduction, including gametogenesis, fetal growth and development and nourishment of the newborn
How are neurotransmitters different from hormones?
Neurotransmitters vs. Hormones Neurotransmitters belong to the nervous system, whereas hormones belong to the endocrine system. Transmission of neurotransmitters is across the synaptic cleft, whereas that of hormones is by blood. Hormones are produced by endocrine glands while neurotransmitters are produced by neurons. Target cells of neurotransmitters can be specific neurons or other cells, whereas that of hormones can be some distance from endocrine gland. Action of neurotransmitters is extremely fast, which could be up to few milliseconds. In contrast, effect of hormones could be last for a long period which could be in the range of few seconds to few days.
What “parts” are associated? Key endocrine glands: Pineal gland Pituitary gland Thyroid gland Thymus Adrenal gland Pancreas Ovary (female) Testes (male) Endocrine glands from: http://en.wikipedia.org/wiki/Endocrine_gland
How does leptin contribute to the control of fat? Secreted by adipose cells (fat storage cells) Increases as the amount of adipose tissue (fat) increases Hormone attaches to areas of the hypothalamus, which is the part of the brain that controls appetite. Binding of leptin to receptors cause long term appetite inhibition Research has found that most cases of obesity in humans are not due to insufficient leptin secretion, but rather than target cells are resistant to leptin.
How does melatonin work to control circadian rhythms?
How does melatonin work to control circadian rhythms? Secreted by the pineal gland, controlled by areas of the hypothalamus and affected by exposure to light Secretion increases in the evening and drops to a low level at dawn as it is removed from the blood by the liver High levels causes drowsiness, thereby promoting sleep Melatonin receptors found in kidneys – suggesting decreased urination during the night as adaptation
Central Dogma of the Endocrine System A stimulus is received and processed. Hormones are secreted by glands, directly into the blood. They are carried to the target tissues/target site (the place of intended action). The action of the hormone changes the condition of the tissue.
Homeostasis is Regulated by Negative and Positive Feedback Systems Positive Feedback: causes a self-amplifying cycle where decreases lead to further decreases, and increases lead to further increases. Example: release of oxytocin from the hypothalamus during labor causes further release of the hormone, and stimulates more contractions. Negative Feedback: recognizes a change in the body, and activates mechanisms to reverse that change. Examples: regulation of blood glucose, and thermoregulation
Examples of Positive Feedback Loop (change causes MORE of that change) Blood clotting Child birth
The Hypothalamus: The Body’s Thermostat Thyroxin: hormone that regulates metabolism ; increased secretion of thyroxin results in higher rates of metabolism (heat production)
Hormones Involved in the Control of Blood Sugar Glucagon: Produced/secreted by alpha (α)cells of pancreas when glucose levels are LOW Stimulates conversion of glycogen (stored in the liver) into glucose Insulin: Produced/secreted by beta (β) cells of pancreas when glucose levels are HIGH Stimulates conversion of glucose to glycogen (i.e. reduces amount of glucose in blood)