Chapter 10 The Endocrine System

10-1: Homeostasis Chemical messages help maintain homeostasis in the body –Coordinated by nervous & endocrine systems hormones target cellsEndocrine system uses hormones to act on specific target cells –Can affect multiple tissues & organs

10-1 Checkpoint 1.How is homeostasis maintained in the body?

10-2: The Endocrine System endocrine cellsEndocrine system includes endocrine cells & tissues that release secretions HormonesHormones—chemical messengers released in one tissue & transported to reach other tissues

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Structure of Hormones Peptide hormonesPeptide hormones—chains of amino acids (largest class) steroid hormonesLipid-based hormones include steroid hormones (testosterone, estrogen) Mechanisms of Hormone Action Mechanisms of Hormone Action target cellsHormones alter cells by changing proteins in target cells –Receptors –Receptors bind hormones to cells

Receptors on or inside plasma membrane allow hormones into the cell Steroid hormones bind to receptors in the cytoplasm or nucleus Secretion/Distribution of Hormones Hormones enter bloodstream through capillaries –Circulate freely in blood or attached to proteins

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Control of Hormone Activity Hormone secretion controlled by negative feedback mechanisms May be controlled by: –Humoral stimuli –Humoral stimuli (blood levels) –Hormonal stimuli –Hormonal stimuli (other hormone levels) –Neural stimuli –Neural stimuli (neurotransmitter) Hypothalamus provides most hormonal control

10-2 Checkpoint 1.Define hormone. 2.What does a hormone need in order to enter a cell? 3.What are the three types of stimuli that control hormone secretion?

10-3: The Pituitary Gland Pituitary gland is attached to the base of the brain –Has anterior & posterior lobes Anterior Lobe of Pituitary Gland Stimulated by hypothalamus Capillaries surround & provide hormones entry into bloodstream

Anterior Lobe Hormones Thyroid-stimulating hormone (TSH)Thyroid-stimulating hormone (TSH) –Triggers release of thyroid hormones Adrenocorticotropic hormone (ACTH)Adrenocorticotropic hormone (ACTH) –Stimulates release of hormones by adrenal gland Follicle-stimulating hormone (FSH)Follicle-stimulating hormone (FSH) –Females: promotes egg development –Males: supports sperm production

Luteinizing hormone (LH)Luteinizing hormone (LH) ovulation –Females: induces ovulation, promotes secretion of estrogen/progesterone androgens testosterone –Males: stimulates production of androgens (testosterone) Prolaction (PRL)Prolaction (PRL) –Stimulates mammary glands & milk production Growth hormone (GH)Growth hormone (GH) –Stimulates cell growth gonadotropins gonadsFSH & LH are gonadotropins—regulate gonads

Posterior Lobe Hormones Antidiuretic hormone (ADH)Antidiuretic hormone (ADH) –Decreases urine formation –Secretion of ADH less urine –Secretion of ADH = prevents dehydration; body forms less urine –Inhibition of ADH more urine –Inhibition of ADH = promotes dehydration; body forms more urine Oxytocin (OXT)Oxytocin (OXT) –Females: stimulates contractions of uterus –Males: stimulate smooth muscles in sperm duct

10-3 Checkpoint 1.If a person were dehydrated, how would the amount of ADH released change? 2.What does a gonadotropin do? 3.What effect would elevated circulating levels of cortisol, a hormone from the adrenal gland, have on the pituitary secretion of ACTH?

10-4: The Thyroid Gland thyroid cartilageThyroid gland lies in front of the trachea, below the thyroid cartilage Thyroid Follicles & Thyroid Hormones Thyroid folliclesThyroid follicles—spheres surround fluid containing hormones –Stimulated to release hormones by TSH

Thyroxine (T 4 ) & triiodothyronine (T 3 )Thyroxine (T 4 ) & triiodothyronine (T 3 ) –Regulate cellular metabolism, tissue growth & metabolism –Calorigenic effect –Calorigenic effect—increased cell energy use –Hypothyroidism (low metabolism) & hyperthyroidism (high metabolism) Calcitonin (CT)Calcitonin (CT) –Regulates calcium concentrations –Released when blood calcium levels are high; inhibits osteoclasts

10-4 Checkpoint 1.Identify the hormones of the thyroid gland. 2.What signs and symptoms would you expect to see in someone whose thyroid gland is overactive? 3.How does calcitonin aid the body in decreasing high blood calcium levels?

10-5: The Parathyroid Glands Parathyroid glands embed in the posterior surface of the thyroid gland Parathyroid hormone (PTH)Parathyroid hormone (PTH) –Regulates calcium concentrations –Released when blood calcium levels are low; stimulates osteoclasts & inhibits osteoblasts

10-5 Checkpoint 1.Identify the hormone secreted by the parathyroid glands. 2.Removal of the parathyroid glands would result in decreased blood concentrations of what important mineral?

10-6: The Adrenal Glands Each adrenal gland sits on top of a kidney adrenal cortex adrenal medulla –Contains outer adrenal cortex & inner adrenal medulla Adrenal Cortex corticosteroidsProduces over 2 dozen corticosteroids— steroid hormones –Divided into three subgroups

Mineralocorticoids: aldosteroneMineralocorticoids: aldosterone –Conserves sodium, eliminates potassium, regulates blood pressure Glucocorticoids: cortisol, corticosterone, cortisoneGlucocorticoids: cortisol, corticosterone, cortisone anti- inflammatory –Affect glucose metabolism, have anti- inflammatory effects AndrogensAndrogens –Sex hormones; produced in small quantities

Adrenal Medulla Inner portion of adrenal gland Epinephrine (E) & norepinephrine (NE)Epinephrine (E) & norepinephrine (NE) –Break down glucose to provide ATP –Increase heart rate & contraction force

10-6 Checkpoint 1.Identify the two regions of the adrenal gland, and list the hormones secreted by each. 2.What effect would elevated cortisol levels have on blood glucose levels?

10-7: The Pineal Gland Pineal gland lies within brain MelatoninMelatonin circadian rhythms –Maintains circadian rhythms (day-night patterns) seasonal affective disorder (SAD) –Increased melatonin secretion occurs in darkness; may be linked to seasonal affective disorder (SAD)

10-7 Checkpoint 1.Increased amounts of light would inhibit the production of which hormone by which structure? 2.How does melatonin differ from melanin?

10-8: The Pancreas Pancreas lies between stomach & small intestine Pancreatic islets Islets of LangerhansPancreatic islets (Islets of Langerhans) contain 2 types of cells –Alpha cells glucagon –Alpha cells produce glucagon –Beta cells insulin –Beta cells produce insulin

Regulation of blood glucose levels 1.Blood glucose levels rise insulin 2.Beta cells release insulin—stimulates glucose transport into cells; forms energy reserves 3.Blood glucose levels fall glucagon 4.Alpha cells release glucagon—energy reserves in liver release glucose into blood Diabetes mellitusDiabetes mellitus characterized by high blood glucose levels –Type 1: insulin dependent –Type 2: non-insulin dependent

10-8 Checkpoint 1.Identify two important types of cells in the pancreatic islets and the hormones produced by each. 2.Which pancreatic hormone causes cells to convert glucose into energy reserves? 3.What effect would increased levels of glucagon have on the amount of glycogen stored in the liver?

10-9: Other Endocrine Organs Kidneys CalcitrolCalcitrol –Stimulates absorption of calcium Erythropoietin (EPO)Erythropoietin (EPO) –Stimulates red blood cell production Renin & angiotensin IIRenin & angiotensin II –Restricts salt & water loss

The Thymus ThymosinsThymosins –Develop immune defenses The Gonads testosteroneTestes produce testosterone –Produces sperm, determines secondary sex characteristics estrogen progesteroneOvaries produce estrogen & progesterone –Support egg maturation & uterine lining growth, determines secondary sex characteristics

10-9 Checkpoint 1.Identify two hormones secreted by the kidneys and describe their functions. 2.How does testosterone’s action differ from estrogen and progesterone’s actions?

10-10: Hormone Responses Hormones responsible for growth –GH, thyroid hormones, insulin, PTH & calcitrol, reproductive hormones Hormones & Stress StressStress—any condition that threatens homeostasis –Can be physical, emotional, environmental, or metabolic (starvation)

General adaptation syndrome (GAS)General adaptation syndrome (GAS) –Alarm phase –Alarm phase—immediate response to stressor –Resistance phase –Resistance phase—shift glucose metabolism to brain tissues –Exhaustion phase –Exhaustion phase—exhaustion of energy reserves; can be fatal Oversecretion or undersecretion of hormones can lead to behavioral changes

10-10 Checkpoint 1.The lack of which hormones would inhibit skeletal formation and development? 2.Explain the steps of the general adaptation syndrome.