Slide 1: GENERAL PHYSIOLOGY Ms. Rust Room 2219, Adams Building, College of Medicine 806-4512 Lecture Topics: Introduction to the Endocrine System Hypothalamus Anterior and Posterior Pituitary
Slide 2: Homeostasis & Controls • Successful compensation – Homeostasis reestablished • Failure to compensate – Pathophysiology • Illness • Death Figure 1-5: Homeostasis
Slide 3: ENDOCRINE SYSTEM • Uses chemical signals for cell to cell communication • Coordinates the function of cells • Response to an endocrine signal occurs within minutes to hours
Slide 4: Chemical Regulating Systems: Overview • Pheromones: organism to organism communication • Hormones: cell to cell communication molecules – – – – Made in gland(s) or cells Transported by blood Distant target tissue receptors Activates physiological response
Slide 5: Paracrines and Autocrines • Local communication • Signal chemicals diffuse to target • Example: Cytokines – Autocrine–receptor on same cell – Paracrine–neighboring cells Figure 6-1c: Direct and local cell-to-cell communication
Slide 6: Long Distance Communication: Hormones • Signal Chemicals • Made in endocrine cells • Transported via blood • Receptors on target cells Figure 6-2a: Long distance cell-to-cell communication
Slide 7: Figure 6-2b, c: Long distance cell-to-cell communication
Slide 8: Signal Pathways • • • • • Signal molecule (ligand) Receptor Intracellular signal Target protein Response Figure 6-3: Signal pathways
Slide 9: • Membrane associated enzymes – External reactions – Internal reactions • Receptors bind specific ligand – Example: Hormones – Cell recognition molecules Figure 5-6: Cell membrane receptor
Slide 10: Membrane Receptor Classes • • • • Ligand- gated channel Receptor enzymes G-protein-coupled Integrin
Slide 11: Receptor locations • Cytosolic or Nuclear – Lipophilic ligand enters cell – Often activates gene – Slower response • Cell membrane – Lipophobic ligand can't enter cell – Outer surface receptor – Fast response Figure 6-4: Target cell receptors
Slide 12: HORMONE CLASSIFICATION • Protein and polypeptide • Amine • Steroid
Slide 13: PEPTIDE HORMONES • Consist of specific amino acids • Synthesized as large precursor proteins • Stored in membrane-enclosed compartments • Hydrophillic
Slide 14: Protein and Polypeptide Hormones: Synthesis and Release Figure 7-3: Peptide hormone synthesis, packaging, and release
Slide 15: Protein and Polypeptide Hormone Receptors • • • • • • Surface receptor Hormone binds Transduction Enzyme activation Open channels Second messenger systems • Synthesis Figure 7-5: Membrane receptors for peptide hormones
Slide 16: AMINE HORMONES • Derived from the amino acid tyrosine • Includes thyroid hormones and catecholamines • Stored until secreted
Slide 17: Amine Hormones Receptors – Surface – Intracellular • Small size, OH group • Benzine ring • Examples – Thyroxin – Epinephrine
Slide 18: STEROID HORMONES • Precursor: Cholesterol • Lipophillic • Immediately released from the cell following synthesis
Slide 19: Steroid Hormones • Cytoplasmic or nuclear receptors (mostly) • Activate DNA for protein synthesis • Slower acting, longer half-life • Examples: cortisol, estrogen & testosterone
Slide 20: Steroid Hormones: Action Figure 7-7: Steroid hormone action
Slide 21: Summary of the Endocrine System Figure 7-2-1: ANATOMY SUMMARY: Hormones
Slide 22: Feedback Loops Figure 6-26: Negative and positive feedback
Slide 23: HYPOTHALAMUS • Integrates functions that maintain chemical and temperature homeostasis • Functions with the limbic system • Controls the release of hormones from the anterior and posterior pituitary
Slide 24: Figure 11-3: Autonomic control centers in the brain
Slide 25: HYPOTHALAMUS Synthesizes & releases hypophysiotropic hormones: – – – – – – – Thyrotropin-releasing hormone (TRH) Corticotropin-releasing hormone (CRH) Gonadotropin-releasing hormone (GnRH) Growth hormone-releasing hormone (GHRH) Growth hormone-inhibiting hormone (GHIH) Prolactin-releasing factor (PRF) Prolactin-inhibitn hormone (PIH)
Slide 26: HYPOTHALAMUS • Synthesizes hypophysiotropic hormones in cell bodies of neurons located in the hypothalamus • Transports hormones down the axon and stored in the nerve endings • Secretion of hormones is in pulses
Slide 27: HYPOTHALAMUS: Secretion of Hypophysiotropic Hormones • Is influenced by emotions • Can be influenced by the metabolic state of the individual • Delivered to the anterior pituitary via the hypothalamic-hypophyseal portal system • Usually initiates a three-hormone sequence
Slide 28: Negative Feedback Controls: Long & Short Loop Reflexes Figure 7-14: Negative feedback loops in the hypothalamicanterior pituitary pathway
Slide 29: Negative Feedback Controls: Long & Short Loop Reflexes Figure 7-15: Control pathway for cortisol secretion
Slide 30: Endocrine Control: Three Levels of Integration Figure 7-13: Hormones of the hypothalamic-anterior pituitary pathway
Slide 31: ANTERIOR PITUITARY SECRETES TROPIC HORMONES IN PULSATILE FASHION
Slide 32: ANTERIOR PITUITARY ANTERIOR PITUITARY
Slide 33: ANTERIOR PITUITARY HORMONES Growth Hormone (GH, Somatotropin): primary hormone responsible for regulating body growth, and is important in metabolism Thyroid-stimulating Hormone (TSH): stimulates secretion of thyroid hormone & growth of thyroid gland Adrenocorticotropic Hormone (ACTH): stimulates cortisol secretion by the adrenal cortex & promotes growth of adrenal cortex
Slide 34: ANTERIOR PITUITARY Follicle-stimulating Hormone (FSH): Females: stimulates growth & development of ovarian follicles, promotes secretion of estrogen by ovaries. Males: required for sperm production Luteinizing Hormone (LH): Females: responsible for ovulation, formation of corpus luteum in the ovary, and regulation of ovarian secretion of female sex hormones. Males: stimulates cell in the testes to secrete testosterone Prolactin: Females: stimulates breast development and milk production. Males: involved in testicular function
Slide 35: ANTERIOR PITUITARY Synthesis of different anterior pituitary hormone is by different cell populations. Corticotropes Lactortropes Somatotropes Thyrotropes Gonadotropes ACTH Prolactin GH Thyrotropin FSH, LH
Slide 36: Endocrine Control: Three Levels of Integration • Hypothalamic stimulation–from CNS • Pituitary stimulation–from hypothalamic trophic Hs • Endocrine gland stimulation–from pituitary trophic Hs
Slide 37: Pathologies: Over or Under Production Figure 7-19: Negative feedback by exogenous cortisol
Slide 38: Pathologies: Due to Receptors Figure 7-20: Primary and secondary hypersecretion of cortisol
Slide 39: POSTERIOR PITUITARY Comprised of the endings of axons from cell bodies in the hypothalamus (supraoptic and paraventricular) Axons pass from the hypothalamus to the posterior pituitary via the hypothalamohypophysial tract Posterior pituitary hormones are synthesized in the cell bodies of neurons in the supraoptic and paraventricular nuclei
Slide 40: POSTERIOR PITUITARY Hormones synthesized in the hypothalamus are transported down the axons to the endings in the posterior pituitary Hormones are stored in vesicles in the posterior pituitary until release into the circulation Principal Hormones: Vasopressin & Oxytocin
Slide 41: Figure 7-12: Synthesis, storage, and release of posterior pituitary hormones
Slide 42: POSTERIOR PITUITARY Oxytocin: Synthesized as the precursor hormone: prepro-oxyphysin Action primarily on the breasts and uterus Increases contraction of smooth muscle of Vas Deferens
Slide 43: POSTERIOR PITUITARY Vasopressin Plasma osmolality is monitored by osmoreceptors in the hypothalamus Increases in plasma osmolality stimulates secretion of vasopressin Small changes above normal plasma osmotic pressure ( 285 mosm/kg) stimulate release of vasopressin
Slide 44: POSTERIOR PITUITARY Vasopressin secretion also stimulated by: 1. 2. Large decreases in blood volume Decreases in blood pressure
Slide 45: POSTERIOR PITUITARY Vasopression Action: Decreases water excretion by kidneys (V2 receptors) Constricts blood vessels (V1 receptors) Increases adrenocorticortropin Hormone (V1B receptors)
Slide 46: Summary of the Endocrine System Figure 7-2-3: ANATOMY SUMMARY: Hormones
Slide 47: Summary of the Endocrine System Figure 7-2-2: ANATOMY SUMMARY: Hormones