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Endocrine Web - The Endocrine System control with chemicals...

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The Endocrine System: control with chemicals Produces chemical signals (hormones) that integrate with nervous system to maintain homeostasis
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stimulus received stimulus converted to molecular signal Cells respond Sensory flow of Hormones Low on water , stomach full, or low blood sugar , for example… Response may be determined by multiple hormones Hormone travels through blood stream to target cells ( kidney , stomach, liver , for example) Retain water , release digestive enzymes, release glucose , etc.
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Hormones control many major processes Reproduction Growth and development Mobilization of body defenses Maintenance of much of homeostasis Regulation of metabolism
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Hormones can be classified chemically Most are 3 major types Amino acid– based (amines, peptides, and proteins) Steroids— made from cholesterol Prostaglandins— made from other lipids
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Mechanisms of Hormone Action Hormones affect only certain tissues = target cells or target organs Target cells have specific protein receptors Hormone-binding to receptors alters cellular activity
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Effects Caused by Hormones Change membrane permeability Synthesize proteins (enzymes) Activate or inactivate enzymes Stimulate mitosis Promote secretion Calcium homeostasis of blood 9–11 mg/100 ml Rising blood Ca 2+ levels Thyroid gland releases calcitonin Osteoclasts degrade bone matrix and release Ca 2+ into blood PTH Calcitonin Calcitonin stimulates calcium salt deposit in bone Parathyroid glands release parathyroid hormone (PTH) Thyroid gland Thyroid gland Parathyroid glands Falling blood Ca 2+ levels Imbalance Imbalance Why do they do all this again?
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… to help control these… Reproduction Growth and development Mobilization of body defenses Maintenance of much of homeostasis Regulation of metabolism
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Two basic chemical mechanisms (i.e. how hormones interact with molecules) Direct gene activation steroid hormones mainly, also thyroid hormone Second-messenger system
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Direct Gene Activation (Steroid Hormone Action) 1. Steroid diffuses through plasma membrane of target cells Nucleus Cytoplasm Steroid hormone Plasma membrane of target cell
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Figure 9.1a, step 2 Nucleus Cytoplasm Steroid hormone Plasma membrane of target cell 1. Lipid-like hormone diffuses through plasma membrane of target cells 2. Then it diffuses through nuclear membrane Direct Gene Activation (Steroid Hormone Action) Why? What’s in there? DNA!!
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Figure 9.1a, step 3 Nucleus Cytoplasm Steroid hormone Receptor protein Hormone-receptor complex Plasma membrane of target cell 1. Lipid-like hormone diffuses through plasma membrane of target cells 2. Diffuses through nuclear membrane 3. Binds to protein receptor in nucleus Direct Gene Activation (Steroid Hormone Action)
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Figure 9.1a, step 4 Nucleus Cytoplasm Steroid hormone Receptor protein Hormone-receptor complex DNA Plasma membrane of target cell Direct Gene Activation (Steroid Hormone Action) 1. Lipid-like hormone diffuses through plasma membrane of target cells 2. Diffuses through nuclear
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