The Endocrine System 3 (2023) PDF

WEEK 16 MPharm Programme Normal Systems The Endocrine System 3 Dr G Boachie-Ansah [email protected] Dale 113 ext. 2617 MPharm PHA112 The Endocrine System WEEK 16 The Adrenocortical Hormones Mineralocorticoids (aldosterone) essential for life maintain Na+ & K+ balance an...

WEEK 16 MPharm Programme Normal Systems The Endocrine System 3 Dr G Boachie-Ansah [email protected] Dale 113 ext. 2617 MPharm PHA112 The Endocrine System WEEK 16 The Adrenocortical Hormones Mineralocorticoids (aldosterone) essential for life maintain Na+ & K+ balance and ECF volume principal site of action is the distal & collecting tubules of the kidney promote Na+ retention & K+ excretion   fluid retention & expansion of ECF volume actions mediated via intracellular receptors secretion regulated by angiotensin II (RAAS), elevated serum K+ levels & ACTH (minor) Slide 58 of 85 MPharm PHA112 The Endocrine System WEEK 16 Control of Aldosterone Release Slide 59 of 85 MPharm PHA112 The Endocrine System WEEK 16 The Adrenocortical Hormones Glucocorticoids (cortisol) involved in the regulation of carbohydrate, protein & fat metabolism  gluconeogenesis and  cellular glucose uptake and utilisation   blood glucose levels  protein synthesis and  protein catabolism in muscle   mobilisation of free amino acids  lipolysis   mobilisation & oxidation of free fatty acids play a key role in adaptation to stress exert anti-inflammatory & immunosuppressive effects Slide 60 of 85 MPharm PHA112 The Endocrine System WEEK 16 Cortisol – Control of Release & Actions Slide 61 of 85 MPharm PHA112 The Endocrine System WEEK 16 Slide 62 of 85 The HPA Feedback System MPharm PHA112 The Endocrine System WEEK 16 The Anti-inflammatory & Immunosuppressive Actions of Cortisol Slide 63 of 85 MPharm PHA112 The Endocrine System WEEK 16 The Adrenocortical Hormones Sex hormones (‘androgenic’ DHEA) supplement sex hormones secreted by gonads exert minor effects on reproductive function physiologically significant in females Growth of pubic & axillary hair Enhancement of pubertal growth spurt Development & maintenance of female sex drive promote protein anabolism & growth Slide 64 of 85 MPharm PHA112 The Endocrine System WEEK The Adrenal Medulla 16 A modified sympathetic postganglionic neuron Innervated by preganglionic sympathetic axons Secretes Adrenaline & Noradrenaline (& dopamine) Main functions Reinforce “fight-or-flight” responses Maintenance of arterial blood pressure  heart rate, cardiac output & respiratory rate  glycogenolysis   glucose mobilisation  lipolysis   mobilisation of free fatty acids Slide 65 of 85 MPharm PHA112 The Endocrine System WEEK The Endocrine Pancreas 16 Consists of clusters or ‘islands’ of secretory cells, called islets of Langerhans Comprise 3 types of secretory cells  (alpha) cells Secrete glucagon  (beta) cells Secrete insulin D (delta) cells Secrete somatostatin Secretions regulated by changes in blood glucose concentration Slide 66 of 85 MPharm PHA112 The Endocrine System WEEK 16 The Pancreas & Secretory Cells Slide 67 of 85 MPharm PHA112 The Endocrine System Pancreas Hormones WEEK 16 Insulin Important anabolic hormone – regulates fuel metabolism Promotes cellular uptake & storage of glucose, fatty acids & amino acids   blood levels Enhances their conversion into glycogen, triglycerides & proteins  glycogenesis,  glycogenolysis & gluconeogenesis  triglyceride synthesis and  lipolysis  protein synthesis and  protein degradation Effects mediated via insulin receptors (TK-linked) Slide 68 of 85 MPharm PHA112 The Endocrine System WEEK 16 Slide 69 of 85 Main Actions of Insulin MPharm PHA112 The Endocrine System WEEK 16 Insulin – Control of Release & Actions Slide 70 of 85 MPharm PHA112 The Endocrine System WEEK Pancreas Hormones 16 Glucagon Generally opposes actions of insulin Mobilizes energy-rich molecules from storage sites into blood stream   blood levels  glycogenesis,  glycogenolysis & gluconeogenesis   hepatic glucose production & release  lipolysis & ketogenesis,  triglyceride synthesis  protein synthesis and  protein degradation Secreted in response to a direct effect of a fall in blood glucose concentration Slide 71 of 85 MPharm PHA112 The Endocrine System WEEK 16 Complementary Interactions of Glucagon and insulin Slide 72 of 85 MPharm PHA112 The Endocrine System WEEK 16 Hormones Involved in Calcium Homeostasis Parathyroid hormone (PTH) Secreted by parathyroid glands (4 rice grain-sized glands located on dorsal surface of thyroid glands) Single most important regulator of blood Ca++ levels ([Ca++]) Raises plasma Ca++ levels via 3 mechanisms:  bone resorption   release of Ca++ into blood  renal reabsorption of Ca++   blood [Ca++]  renal activation of vitamin D   intestinal absorption of Ca++   blood [Ca++] Secretion regulated by blood Ca++ levels Slide 73 of 85 MPharm PHA112 The Endocrine System WEEK 16 Regulation of Plasma [Ca++] by PTH Slide 74 of 85 MPharm PHA112 The Endocrine System Hormones Involved in Calcium Homeostasis WEEK 16 Vitamin D (cholecalciferol) Synthesized by the skin & activated in the liver & kidneys Supplemented by dietary intake Second most important regulator of blood [Ca++] Controls plasma Ca++ levels via 3 mechanisms:  intestinal absorption of Ca++   blood [Ca++]  bone resorption   release of Ca++ into blood  PTH synthesis Slide 75 of 85 MPharm PHA112 The Endocrine System WEEK 16 Activation & Actions of Vitamin D Slide 76 of 85 MPharm PHA112 The Endocrine System WEEK 16 Actions & Interactions of PTH & Vit D Slide 77 of 85 MPharm PHA112 The Endocrine System WEEK 16 Hormones Involved in Calcium Homeostasis Calcitonin Secreted by parafollicular or C cells of thyroid gland Exerts opposite effects to PTH Lowers plasma Ca++ levels via 2 mechanisms:  bone resorption   release of Ca++ into blood  renal reabsorption of Ca++   blood [Ca++] Minor physiological regulator of blood [Ca++] Secretion regulated by blood Ca++ levels Slide 78 of 85 MPharm PHA112 The Endocrine System WEEK 16 Control of PTH & calcitonin secretion Slide 79 of 85 MPharm PHA112 The Endocrine System WEEK The Gonads 16 The gonads are the sex organs, comprising the Testes – the male sex organ Ovaries – the female sex organ The primary functions of the testes include Production of sperm (spermatogenesis) Secretion of male sex hormones (androgens) – testosterone The primary functions of the ovaries include Production of ova or egg cells (oogenesis ) Secretion of female sex hormones – oestrogens & progestins/progestogens (progesterone) Slide 80 of 85 MPharm PHA112 The Endocrine System WEEK 16 The Male Sex Hormones (Androgens) Testosterone Secreted by Leydig cells of the testes Converted into dihydrotestosterone (DHT) in target tissues Production increases rapidly at puberty Key functions: Promotes development of the male reproductive organs Promotes development & maintenance of male secondary sexual characteristics – facial hair, deeper voice, etc Increases & maintains sexual drive & desire Increases bone thickness & periosteal bone formation Increases basal metabolic rate & muscle mass Promotes RBC formation & protects against anaemia Slide 81 of 85 MPharm PHA112 The Endocrine System WEEK 16 Regulation of Testosterone Production Slide 82 of 85 MPharm PHA112 The Endocrine System WEEK The Female Sex Hormones 16 Oestrogens (Oestradiol) Secreted by granulosa cells of the ovarian follicle Production increases rapidly at puberty Key functions: Promotes maturation & maintenance of the reproductive organs in their mature functional state Promotes development & maintenance of female secondary sexual characteristics – breasts, pubic hair, fat distribution Plays critical roles, along with progesterone, in the normal female reproductive cycle (menstruation, pregnancy & childbirth) Reduces bone resorption & increases bone density Mediates important cardio- and vaso-protective effects Slide 83 of 85 MPharm PHA112 The Endocrine System The Female Sex Hormones WEEK 16 Progestins/Progestogens (Progesterone) Secreted by granulosa & theca cells of the ovarian follicle Production increases markedly during the luteal phase Called the “hormone of pregnancy” Key functions: Plays critical roles, along with oestradiol, in the normal female reproductive cycle Helps mediate sexual response in the brain Prepares the uterus for implantation Renders cervical canal impenetrable to sperm after implantation Inhibits uterine contractions during gestation Inhibits Na+-retaining activity of aldosterone   natriuresis   fluid retention Slide 84 of 85 MPharm PHA112 The Endocrine System WEEK 16 Mean Sex Hormone Levels in Plasma in Males and Females Slide 85 of 85 MPharm PHA112 The Endocrine System