Endocrine System Chapter 16 Human Anatomy & Physiology 8/e, Marieb & Hoehn. (Pearson 2010)

Today’s class Endocrine glands and hormones Mechanisms of hormone action Hypothalamus and pituitary gland Adrenal gland Thyroid and parathyroid glands Pancreas

Nervous and endocrine systems Two systems of internal communication and regulation act individually or together Nervous system high-speed electrical signals via neurons Endocrine system endocrine glands secrete hormones slower, longer-acting responses

Endocrine glands Ductless Secrete hormones into bloodstream hormones affect target with receptor some prehormones and prohormones fig 16.1

Types of chemical signals pheromones endocrine paracrine Human Reproductive Biology, 3/e. by S. Mader. McGraw Hill publishers. 2005. fig 5A

Hormones trigger cell signalling Three stages: reception signal transduction response

Structural categories of hormones Polypeptides and proteins Amino acid derivatives (amines) Steroids (Eicosanoids)

Examples (autocrine regulator) Struture determines if they find the receptor in/ out cell (autocrine regulator) (Anatomy and Physiology, 8/e, Seeley, Stephens and Tate, 2008, McGraw Hill, fig 17.3)

General hormone effects Interactions Synergistic (effect of 2 combine better than one) Permissive Antagonistic Concentration half-life (how long in the blood stream) Target cell specificity receptor type, number and affinity upregulation, desensitization/downregulation Affinity: how well the receptors will bind with the hormones. -Can change the number of receptors

testosterone synthesized but no functional receptor Importance of receptors e.g. complete androgen insensitivity syndrome (AIS) XY individual testes present no ovaries or uterus testosterone synthesized but no functional receptor Human Reproductive Biology, 3/e. by S. Mader. McGraw Hill publishers. 2005. fig 3.14

Mechanisms of hormone action Peptide/protein/amines: receptors in Plasma membrane (cuz the molecules are too big) different mechanisms, between from getting point A to B e.g. cAMP – second message. 1st message in hormone DAG/IP3 (phospholipase C) – cut the phosphol tyrosine kinase Activate “premade” proteins Lipids: intracellular receptors reach target via carrier proteins in plasma why the need for carrier? Need a carrier cuz there hydrphobic and direct to the right tissue nuclear hormone receptors as transcription factors They create protein with transcription, translation, termination.

Recall cAMP as second messenger Signal transduction fig 16.2

Phospholipase C system PIP2 IP3 + DAG phospholipase C Human Physiology, 10e, by Fox, McGraw Hill publishers, 2008, fig 11.9

Insulin and its tyrosine kinase receptor Phosphorylates no second messenger required Human Physiology, 10e, by Fox, McGraw Hill publishers, 2008, fig 11.11

Lipid-soluble hormones Last longer compare to premade protein fig 16.3

Control of hormone release Endocrine gland stimuli Humoral Neural Hormonal Nervous system modulation

Control of hormone release Chemical control hormonal release -Low calcium stimulates PTH (stimulates osteoclast) fig 16.4

Hypothalamus and pituitary Control much of endocrine system Integrate nervous and endocrine systems receives nerve signals from body initiates appropriate responses Neurosecretory cells Posterior pituitary – not true (keeper and releaser of hyperthalmus) stores and releases hormones made by hypothalamus Anterior pituitary Hypthalmus when to make/ nt make the hormones true endocrine gland makes 6 trophic hormones

Hypothalamus and posterior pituitary Oxytocin releasing milk What are functions of oxytocin and ADH? fig 16.5a

Hypothalamus and anterior pituitary Dual capillary bed – rare Anterior makes and release under the direction o the hypothalmus fig 16.5b

Targets of anterior pituitary hormones Prolactin – make the milk Human Physiology, 10e, by Fox, McGraw Hill publishers, 2008, fig 11.15

Hypothalamus and anterior pituitary Hypothalamic-releasing hormones stimulate anterior pituitary gonadotropin-releasing hormone (GnRH) prolactin-releasing hormone (PRH) growth hormone-releasing hormone (GHRH) corticotropin-releasing hormone (CRH) thyrotropin-releasing hormone (TRH)

Hypothalamus-pituitary-target axis Hypothalamus  anterior pituitary  target GnRH  FSH, LH  gonads  sex hormones PRH  prolactin  mammary glands GHRH  growth hormone  various CRH  ACTH  adrenal cortex  corticosteroids (stress response) TRH  TSH  thyroid  metabolism hormones Axis: Feedback loops – homeostasis

Feedback examples hypothalmus-pituitary-thyroid hypothalmus-pituitary-gonad axis hypothalmus-pituitary-thyroid axis Human Physiology, 10e, by Fox, McGraw Hill publishers, 2008, figs 11.17, 11.18

Thyroid gland Located just inferior to larynx Follicles follicular cells thyroxine colloid fluid Parafollicular cells calcitonin metabolism fig 16.8

Thyroid hormones T3 and T4 (thyroxine) Calcitonin elevate basal metabolic rate stimulate protein synthesis, increase respiration, etc Calcitonin lowers blood calcium concentrations inhibits dissolution of calcium phosphate in bone stimulates excretion of calcium in urine

Synthesis of thyroid hormone Need iodine>> transport to cell> send both iodine thoridglobin >> to co fig 16.9

Diseases of thyroid: hypothroidism Hypothyroidism:  thyroid function slower than normal metabolism myxedama (fluid/mucoprotein accumulation in subcutaneous tissue) Causes Gland defect (e.g. by Hashimoto’s thyroiditis) Too little TRH and/or TSH for trophic effects Endemic goiter: by iodine deficiency Hyperthyroidism:  thyroid function more rapid than normal metabolism e.g. by Grave’s disease (autoimmune) autoantibodies are TSH receptor agonists fig 16.10

Parathyroid glands 4 glands embedded in lateral lobes of thyroid gland Secrete parathyroid hormone (PTH) control of blood Ca2+ levels fig 16.11

Recall fig 16.12

Adrenal gland Outer cortex Medulla no neural innervation steroid hormones corticosteroids (corticoids) aldosterone effects will be covered in more detail with urinary system Medulla preganglionic sympathetic neurons catecholamines epinephrine (mainly) norepinephrine

Adrenal gland Each zone make different hormones fig 16.13

Cushing’s syndrome: excess glucocorticoid Excess carocoid fig 16.15

Stress and adrenal gland Medulla make corticoamines fig 16.16

Aldosterone release from adrenal cortex * Aldosterone targets kidneys fig 16.4

Pancreas Exocrine and endocrine Islets alpha cells: glucagon in response to  blood glucose stimulates liver: glycogen  glucose, fat hydrolysis beta cells: insulin in response to blood glucose promotes entry of glucose into tissue glucose  glycogen, fat feeding versus fasting?

Pancreas and blood glucose homeostasis Human Physiology, 10e, by Fox, McGraw Hill publishers, 2008, fig 11.31 fig 16.18

Other hormones Pineal gland: melatonin Gonads (testes and ovaries): sex hormones will be covered with reproductive system Other organs (non-endocrine glands) secrete hormones heart, GI tract, kidneys, skin, adipose tissue, skeleton, thymus

Up next December office hours Exam (cumulative) Monday, December 6: 10-12, 2-4 Monday, December 13, 2-5 Exam (cumulative) Tuesday, December 14, 9-11