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Name: Class: Date: #23 Notes – Endocrine System Homeostasis = maintaining a stable (constant) internal environment maintained by the endocrine system and the nervous system, both working together What does the endocrine system do? It produces chemical signalers (a.k.a. hormones) that go to another place by traveling through the bloodstream. How do the nervous system and the endocrine system interact? Part of nervous system only neuron - a nerve cell; has three parts: cell body, axon, dendrites Part of both systems hypothalamus - receives messages from brain and internal organs - stimulates ---------------------------------> (tells it what to do) Part of endocrine system only Pituitary gland - main organ of the endocrine system - located at the base of the hypothalamus - controls other glands In general, how does the endocrine system work? produces a that travels via to reach a A gland ------------------> hormone ---------------------> bloodstream -----------------> target cell and attaches to a found on either --------------------> receptor (a.k.a. binding site) ----------------------> cell membrane or nucleus. Example of endocrine control: Hypothalamus monitors blood sugar levels too low? tells pituitary gland to make hGH (human growth hormone) normal or too high? tells pituitary gland to stop making hGH hGH binds to receptor on target cells (liver cells) liver releases more glucose *This is also an example of negative feedback – the amount of one substance decreases the amount of another substance Negative feedback: Example 1: hGH (see above) Example 2 (generic): Gland A produces Hormone X. When the body has enough of Hormone X, Gland A gets a message to stop producing Hormone X results in stable levels of chemicals/molecules in our body (stabilization); a.k.a. equilibrium; a.k.a. homeostasis Example 3: blood water levels o if blood water levels are low, the hypothalamus tells the pituitary gland to release antidiuretic hormone (ADH) o ADH binds to receptors on kidney cells so that water is reabsorbed and you urinate less (less water in urine) o If you drink water to replenish blood water levels, the hypothalamus tells the pituitary gland to stop releasing (secreting) ADH, so you go to the bathroom more often (more water in urine) Example 4: regulation of blood glucose levels – Your explanation below can be a summary, bullet points, diagram, etc. Read Problem-Solving Lab 35.3 on page 932 of your text. 1. Examine the graph and explain how exercise affects the concentrations of insulin and glucagons in the blood. The more you exercise, glucagon increases and insulin decreases. 2. Relate the changes shown on the graph to what is occurring in muscle cells as well as to blood glucose levels. As muscle cells take in glucose (cellular respiration), more glucagon is produced (by the pancreas), which tells the liver to release more glucose. (Because you don’t want to store glucose, so the amount of insulin should decrease.) 3. Design a flowchart that shows the steps involved in maintaining homeostasis of blood glucose during exercise. Begin your flowchart with muscle cells. Types of Hormones: Steroid hormone Peptide hormone Is composed of Lipids Amino acids Can it enter the cell? Yes No Why/Why not? Because the cell membrane is made out of the same material, the hormone is soluble in it. (like dissolves in like) Cell membrane is impermeable to the amino acid. Too big? Action Binds to a hormone receptor inside the cell to form a hormone-receptor complex Binds to a hormone receptor on the _cell membrane of the _target cell_ Travels to the _nucleus_ to stimulate mRNA synthesis (a.k.a. ___transcription_) Opens _ion__ channels in the target cell’s _(cell) membrane_ Activates an enzyme inside the cell Ions can _go in__ or ___go out of_ the cell Enzyme acts as a stimulus for other molecules in the cell (How? By lowering activation energy – the energy needed to start a reaction (rxn) Immediate result Then _protein synthesis occurs – the protein made is what the cell specifically needs (based on the mRNA template made earlier) Label the figure below with the principal human endocrine glands. Glands: Name of gland Location Name of hormones secreted Type Hormones affect/result in Regulate Steroid Inc glucose Increase blood pressure Stress levels Peptide Inc blood pressure Inc heart rate Inc respiration rate Inc efficiency of muscles Inc blood sugar levels (adrenaline rush) Fight-or-flight response Thyroxine Peptide Rate at w/c the body uses energy Determines food intake requirements Growth, development, metabolism Calcitonin Peptide Inc Ca excretion in kidneys Inc Ca absorption of bone Growth, development, metabolism - Ca levels in the blood Peptide Inc Ca, P, Mg absorbed by the intestines Releases Ca, P from bones Inc Ca, Mg removed from urine (kidneys) Growth, development, metabolism - also regulates minerals (CA, P, Mg) Glucocorticoids and Aldosterone Adrenal glands (why plural?) Superior to kidneys Epinephrine (a.k.a. adrenaline) and Norepinephrine Thyroid gland Parathyroid glands Ovary or Testes neck Neck (attached to thyroid glands) Ovary or Testes Parathyroid hormone Estrogen Progesterone Testosterone Menstrual cycle, pregnancy Steroid puberty Sperm cell production