Presentation on theme: "The Endocrine System Chp. 6 Primary endocrine organs: main function is to secrete hormone(s) Secondary endocrine organs: secrete hormones as a secondary."— Presentation transcript:
The Endocrine System Chp. 6 Primary endocrine organs: main function is to secrete hormone(s) Secondary endocrine organs: secrete hormones as a secondary function
Primary endocrine organs Hypothalamus and pituitary gland secrete hormones and regulate other endocrine organs. They are the main regulatory organs of the endocrine system.
Hypothalamus Located below the thalamus and above the pituitary gland (=epiphysis) Regulates the pituitary gland secretions through two different mechanisms
Hypothalamus - neurohypophysis 1- Neurons, receiving information from receptors, fire APs which travel down to the post pituitary gland and stimulate the release of stored neurohormones – Oxytocin (OT) and anti-diuretic hormone (ADH)
Hormones of the posterior pituitary RegulationHormoneTarget organActionPathology ReflexOxytocin- Uterus (smooth muscle) - breast tubules (smooth muscles) -labor and delivery - milk-let down -- Reflex (osmoreceptor)ADH (vasopressin) - DCT in kidney tubules - promote H2O reabsorption - not enough: diabetes insipidus - too much: ↑ BP?
Hypothalamus – adenohypophysis 2- Upon stimulation, secretory cells located in the hypothalamus secrete “releasing” hormones which travel down a capillary bed toward the anterior pituitary gland (adenopituitary). Each type of releasing hormones will stimulate the secretion and release of a pituitary hormone. Hormones which control the secretion of other hormones are tropic hormones (found in hypothalamus and pituitary gland
Figure 6.5 Hormones of the hypothalamus and anterior pituitary gland
Figure 6.8 Anterior pituitary RegulationHormoneTarget organActionPathology GHRH and GHIHGrowth hormone (GH)Many cells (bones..) Stimulate cell growth and cell division - not enough: children pituitary dwarfism too much: gigantism (children) – acromegaly (adult) PRH - PIHProlactin (PL)Breast secretory cells - milk secretion -- TRHThyroid stimulating hormone (TSH) Thyroid gland- promote thyroid gland secretion (T3 and T4) - not enough: hypothyroidism (cretinism in children) - too much: hyperthyroidism CRHAdrenocorticotropic hormone (ACTH) Adrenal cortex (3 layers) - stimulates secretion of adrenal cortex - not enough: Addison's disease - too much: Cushing syndrome GnRHGonadotropin - Follicle stimulating hormone (FSH) - Luteinizing hormone (LH) Stimulate gamete maturation Stimulate gonadal gland secretion and gamete formation - infertility
Figure 23-17 Same Individual with Acromegaly (evolution over 20 years)
Figure 6.8a The thyroid gland - Chp 21 p 623-625 Located in the neck, just below the larynx Secrete 2 types of hormone: - thyroid hormones stimulate cell metabolism, triiodothyronine (T3) and thyroxine (T4) – iodine is needed to synthesize these hormones - calcitonin decrease blood calcium
Thyroid hormones T3 and T4 secreted by the follicular cells Stored as colloid Parafollicular cells (C cells) secrete calcitonin (Chp 19)
Thyroid Hormones T3 and T4 Target organs: all cells Role: Increase cell metabolism, oxygen consumption Permissive role for some other hormones (growth hormone)
Goiter Both hypo and hyperthyroidism can have goiter as a symptom Goiter is a swelling of the neck due to hypertrophy of the thyroid gland How can one explain that?
Goiter in hypothyroidism Most often due to a lack of dietary iodine The thyroid hormone is unable to synthesize a functional thyroid hormone (T3 and T4) The person express symptoms of hypothyroidism The nonfunctional T3/T4 cannot promote a negative feedback on TRH and TSH the hypotalamus and pituitary gland increase their secretions the thyroid gland is stimulated to secrete more T3 and T4 … In children, the lack of functional T3/T4 result in cretinism, a form a mental retardation
Goiter in hyperthyroidism The cells secreting TRH or TSH on the hypothalamus and pituitary gland (respectively) have become abnormal and no longer are sensitive to the negative feedback they continue to secrete TRH or TSH continuous stimulation of the thyroid gland with excess thyroid hormones being formed symptoms of hyperthyroidism
Parathyroid glands Four nodules located in the back of the thyroid gland Secreted parathyroid hormone or parathormone or PTH Action of PTH opposes action of calcitonin Both hormones play a role in calcium metabolism
Roles of calcium Most calcium ions are stored in the bones Calcium is an important cofactor for enzymatic activity, plays a role in blood coagulation and action potentials. Calcitonin and PTH participate in calcium regulation Vitamin D helps PTH activity
Calcium regulation: Calcitonin promotes blood calcium decrease, by: -1. calcium deposition on bone -2. calcium dumping by the kidney PTH promotes blood calcium increase by: -1. bone resorption -2. calcium reabsorption by kidney -3. increase calcium absorption by intestine
Calcium Metabolism: Figure 23-20: Calcium balance in the body
The pancreas Located in the left upper abdominal cavity Exocrine and endocrine glands The endocrine function is due to the cells of the islets of the Langerhans -- α cells glucagon -- β insulin -- δ somatostatin
Glucose regulation Glucose level controlled by insulin and glucagon Insulin promotes a decrease in blood glucose Glucagon promotes an increase in blood glucose
Diabetes mellitus Type I: autoimmune disease beta cells of the islets of Langerhans are destroyed by antibodies Type II: The cells become insulin-resistant glucose does not enter the cells as readily http://faculty.weber.edu/nokazaki/Human_Physio logy/Class%20notes/diabetes.htmhttp://faculty.weber.edu/nokazaki/Human_Physio logy/Class%20notes/diabetes.htm