Endocrine System Chapter 18

Introduction The endocrine system consists of cells, tissues, & organs that secrete hormones into the blood Hormone – an organic substance secreted by a cell that has an effect on the metabolic activity of another cell or tissue Target cells – cells that are affected by the hormone Have specific receptors for the hormones Types of hormones Steroid Amino acid derivative Peptide

Human Anatomy, 3rd edition How Hormones Work Activation of 2nd messengers Hormone (first messenger) binds to receptor on cell membrane Receptor/hormone complex activates another substance in the cell (2nd messenger) Triggers cell’s response Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition How Hormones Work Activation of genes Hormone crosses cell membrane Hormone binds to a receptor Cytoplasm Nucleus Receptor/hormone complex binds to DNA Alters gene activity Human Anatomy, 3rd edition Prentice Hall, © 2001

The Hypothalamus & Endocrine Regulation Sympathetic neurons Adrenal medulla Releases hormones Antidiuretic hormone (ADH) Oxytocin Secretes regulatory hormones Anterior pituitary gland Releasing factors Inhibiting factors Human Anatomy, 3rd edition Prentice Hall, © 2001

Overview of the Endocrine System Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition The Pituitary Gland aka hypophysis Located in sella turcica Infundibulm connects to hypothalamus Master gland of the endocrine system 2 parts Posterior pituitary = neurohypophysis Anterior pituitary = adenohypophysis Human Anatomy, 3rd edition Prentice Hall, © 2001

Hypophyseal Portal System Median eminence Neurons secrete regulatory factors 2 capillary beds #1 in hypothalamus RFs diffuse in #2 in anterior pituitary RFs diffuse out Portal veins connect the capillary beds Human Anatomy, 3rd edition Prentice Hall, © 2001

Posterior Pituitary Neurohypophysis is nervous tissue Cell bodies in the hypothalamus make hormones Axons run down the infundibulum Carry hormones to axon terminals Axon terminals in the posterior pituitary store hormones

Posterior Pituitary Produces 2 Hormones Antidiuretic hormone (ADH) Target – kidneys Effect – reabsorption of water Oxytocin Targets – reproductive organs Effects – contractions of smooth muscles (labor contractions, milk ejection; ductus deferens, prostate gland – ejaculations)

Anterior Pituitary Hormones Gonadotropins stimulate growth & development of gonads Follicle stimulating hormone (FSH) stimulates gametes Targets – follicle cells (females), testes (males) Effects – follicle development & estrogen secretion (females), sperm maturation (males) Luteinizing hormone (LH) Targets – follicle cells (females), interstitial cells of testes (males) Effects – ovulation, formation of corpus luteum, secretion of progesterone (females), testosterone secretion (males)

Anterior Pituitary Hormones Thyroid stimulating hormone (TSH) Target – thyroid gland Effect – triggers the release of thyroid hormones Adrenocorticotropic hormone (ACTH) Target – adrenal cortex Effect – cells that produce glucocorticoids (steroid hormones)

Anterior Pituitary Hormones Prolactin Target - breast Effect - stimulates milk production Growth hormone Target – all cells Effect - stimulates growth in general and the skeletal system in particular Melanocyte stimulating hormone (MSH) Target - melanocytes Effect – increases melanin production and distribution

Human Anatomy, 3rd edition Pituitary Hormones FG19_05.JPG Title: Pituitary Hormones and Their Targets Notes: This schematic diagram shows the hypothalamic control of the pituitary gland, the pituitary hormones produced, and the responses of representative target tissues. Keywords: pituitary hormones, targets, adrenal medulla, adrenal cortex, thyroid, peripheral tissues, mammary glands, testes, ovaries, melanocytes, kidneys, anterior pituitary, posterior pituitary, ACTH, TSH, GH, PRL, FSH, LH, MSH, ADH, hypothalamus, oxytocin Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition The Thyroid Gland Location – inferior to thyroid cartilage Thyroid follicles make thyroid hormones Tyrosine + iodine T4 (thyroxine) or (T3) (triiodothyronine) Target cells – most cells Effect of thyroid hormones increase energy utilization, oxygen consumption, growth, development Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition The Thyroid Gland C cells Produce calcitonin (CT) Targets – bone, kidneys Effect – lowers blood calcium levels Human Anatomy, 3rd edition Prentice Hall, © 2001

Control of Thyroid Hormones FG19_08.JPG Title: The Regulation of Thyroid Secretion Notes: This negative feedback loop is responsible for the homeostatic control of thyroid hormone release. Keywords: thyroid activity, regulation, homeostasis, anterior pituitary, TSH, thyroid gland, T3, T4, body temperature Human Anatomy, 3rd edition Prentice Hall, © 2001

The Parathyroid Glands Location – posterior surfaces of thyroid gland Principal cell Chief cells produce parathyroid hormone (PTH) Target cells – bone, kidneys, intestines Effect Increases blood calcium levels Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition The Thymus Gland Location – posterior to the sternum Produces thymosins Enhance lymphycyte production Development Childhood – large Puberty – largest Adulthood – decreases in size Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition The Adrenal Glands Location – on top of the kidney Structure Capsule Cortex Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition The Adrenal Medulla Secretes epinephrine & norepinephrine Target – most cells Effect - stimulates heart beat & tissue metabolism, increases alertness, prepares body to deal with emergencies Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition The Adrenal Cortex Zona glomerulosa secretes mineralocorticoids, mostly aldosterone Target – kidneys Effect – increases blood sodium, decreases blood potassium Zona fasciculata – secretes glucocorticoids (cortisol, corticosterone) Target – most cells Effect – conserve blood glucose, anti-inflammatory effects Zona reticulares – secretes androgens Effects are uncertain Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition The Pancreas Location – between the spleen and the duodenum Functions – both exocrine and endocrine Endocrine cells are in the Islets of Langerhans Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Islets of Langerhans Alpha cells secrete glucagon Targets – liver, adipose tissues Effect - increase blood sugar levels Beta cells secrete insulin Targets - most cells Effect - decrease blood sugar levels Diabetes mellitis Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition The Pineal Gland Location = epithalamus Pinealocytes secrete melatonin Derived from seratonin Light inhibits production Regulates circadian rythms Target – hypothalamus Effects – Inhibits FSH & LH secretion Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition The Testes Divided into internal compartments containing seminiferous tubules Spermatogenesis Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Seminiferous Tubules Interstitial cells secrete androgens; testosterone is the most important Target – most cells Effects – maturation of sperm; protein synthesis in skeletal muscle; male secondary sex characteristics & behaviors Some interstitial cells secrete inhibin Target – anterior pituitary Effect – inhibits the secretion of FSH Human Anatomy, 3rd edition Prentice Hall, © 2001

The Ovaries – Follicle Cells Estrogen Targets – most cells Effects – follicle maturation; female secondary sex characteristics and behaviors Inhibin Target – anterior pituitary Effect – inhibits secretion of FSH Human Anatomy, 3rd edition Prentice Hall, © 2001

The Ovaries – Corpus Luteum Progesterone Targets – uterus, mammary glands Effects – prepare uterus for implantation, mammary glands for secretion Relaxin Targets – pubic symphysis, uterus, mammary glands Effects – loosens pubic symphysis, relaxes cervical muscles, stimulates mammary gland development http://www.healthsquare.com/fgwh/wh1ch17.htm Human Anatomy, 3rd edition Prentice Hall, © 2001

Hormonal Regulation of the Female Reproductive System FG27_18.JPG Title: The Hormonal Regulation of Female Reproductive Function Notes: A diagrammatic view of the hormonal regulation of female reproductive function. Keywords: hormones, female reproductive functions, hypothalamus, pituitary, estrogens, progestins, GnRH, LH, FSH Human Anatomy, 3rd edition Prentice Hall, © 2001