ANATOMY AND PHYSIOLOGY | Science of the human body



Chapter 11 Endocrine System

| Endocrine System: |

|The endocrine system is made up of the cells, tissues, and organs that secrete hormones into body fluids such as the blood stream. What is its function? |

|To control certain physiological activities and help maintain homeostasis |

|What is the difference between an endocrine gland and an exocrine gland? Endocrine glands secrete hormones which circulate in the blood, while exocrine |

|glands secrete substances into ducts leading to a body surface |

| hormone: |

|What types of chemicals can hormones be? Steroids, amines, peptides, proteins, or glycoproteins |

|What is the tissue called that hormones affect? Target tissues |

| hormonal mechanisms: |

| |

|___Steroid_____ hormones are lipid-soluble and can pass through cell membranes. |

|Their receptors are located in the target cell's __nucleus___. |

|The hormone-receptor complex binds with the _DNA__ and activates specific __genes___ that, in |

|turn, direct the synthesis of specific ___proteins__. |

| |

|__non-steroid__ hormones combine with receptors in target cell __membranes__; the receptors have a |

|___binding_____ site and a/an __activity_______ site. |

|The hormone-receptor complex (as first messenger) triggers a cascade of biological activity. What happens after the |

|complex forms? Generally activates a G-protein, which then activates an enzyme on the inner surface of the cell membrane.. This produces a second |

|messenger inside the cell that then activates prteins to induce changes within the cell |

| |

|What is the name of the second messenger? The most common second messenger is cAMP |

| |

|Prostaglandins are locally-produced lipids that affect the organ in which they are produced with a variety of effects. |

|What are some of these effects? Relax or contract smooth muscle, stimulate secretion, influence blood pressure |

|hormone control: |

|There are several ways in which hormone release is very closely regulated. All of these mechanisms use negative |

|feedback. |

| |

|Release of __tropic_ hormones from the hypothalamus controls secretions of the _anterior pituitary_. |

|The __nervous____ system influences certain endocrine glands directly with impulses. |

|Other glands respond directly to changes in the __internal_____ fluid composition. |

| |

|Negative Feedback Systems – Explain in general how negative feedback works. |

|When the concentration of a regulated substance reaches a certain level, the gland is inhibited from secreting more hormone. How would this function |

|in the above three situations? |

| Pituitary Gland: |

|The pituitary gland is attached to the base of the brain and has a front lobe called the __anterior pituitary__ |

|and a rear lobe called the ___posterior pituitary___. |

| |

| |

|The brain controls the activity of the pituitary gland in two ways. |

|Releasing hormones from the _hypothalamus____ control the secretions of the anterior pituitary and are |

|carried in the bloodstream by ___hypophyseal portal____ veins. |

|The posterior pituitary releases hormones into the bloodstream in response to nerve impulses from the |

|___hypothalamus___. |

| Anterior pituitary: |

|The anterior pituitary consists mostly of __epithelial __ tissue arranged around blood vessels and |

|enclosed in a capsule of collagenous ___connective__tissue. |

| |

|How many hormones does it secrete? Six |

|What function do most of them have in common? Several stimulate other endocrine glands |

| growth hormone GH: |

|What is the function of GH? Stimulates body cells to grow and reproduce |

|What factors influence growth besides GH? Nutritional status |

| |

|What hormones from the hypothalamus control the levels of GH? GH-Releasing Hormone and GH_Release-Inhibiting Hormone |

| |

|What disorders may result from a lack of or too much GH? Too little: pituitary dwarfism. Too much: giantism |

| prolactin PRL: |

|What is the function of PRL? Promotes milk production in lactating women |

| |

|What is its target tissue? The breasts |

| |

|What hypothalamic hormones affect it? PR- Releasing Hormone |

| thyroid stimulating hormone TSH: |

|What is the function of TSH? (what is its target organ?) |

|What hypothalamic hormones affect its release? Thyrotropin-Releasing Hormone (TRH) |

|How are these hormones from the hypothalamus regulated? As the level of circulating thyroid hormones fall, the hypothalamus puts out TRH. When the levels|

|of circulating thyroid hormones are at correct level, the hypothalamus stops putting out TRH. |

| adrenocorticotropic hormone ACTH: |

|What is the target organ for ACTH? Adrrenal Cortex What hormones does it affect the release of? Cortisol |

|What is the name of the hormone from the hypothalamus that controls ACTH’s release? Corticotropin-releasing Hormone (CRH) |

| follicle stimulating hormone FSH: |

|What are the target organs for FSH? Gonads |

|What effect does it have on the males? Testes start to produce sperm |

|On females? Ovaries begin to produce eggs and to produce and release estrogens |

|What hormone from the hypothalamus affects its release? Gonadotropin-Releasing Hormones |

| luteinizing hormone LH: |

|What does it do? Causes ovulation and formation of corpus luteum in the ovary which then begins to release estrogen and progesterone |

|How is it different in males than in females? In males it stimulates the testes to release testosterone |

| |

|What is its controlling hormone from the hypothalamus called? Gonadotropin-releasing hormone |

| Posterior pituitary: |

|The posterior lobe consists of __nerve__ fibers and supporting _neuroglial cells arising in the |

|hypothalamus. |

|What structure actually produces the hormones released by the posterior pituitary?hypothalamus |

| antidiuretic hormone ADH: |

|What is the function of this hormone? Causes the kidneys to conserve water |

| |

|What disorder may result if enough ADH isn’t secreted? Diabetes insipidus |

| oxytocin: |

|What are the functions of this hormone ? causes contraction of the uterus walls during childbirth and milk-letdown during breast feeding |

| Thyroid Gland: |

|The thyroid gland is located below the _larynx___ and consists of two broad __lobes_____ connected by an |

|___isthmus__. |

|The thyroid consists of secretory parts called _follicles___ filled with hormone-storing |

|__colloid__. |

| thyroxine T4: How many iodines does it contain? four |

|triiodothyronine T3: How many iodines? three |

| |

|What is the function of these two hormones? They regulate metabolism |

| |

|How does TSH affect their release? TSH stimulates the thyroid to release T3 and T4 |

|How do they affect the release of TSH? When these hormones are at the correct level, the release of TSH is inhibited |

| |

|What is a goiter and what may cause one? A goiter is an enlarged thyroid gland that is usually caused by lack of iodine. Without iodine, the thyroid |

|cannot make T3 and T4, and thus nothing inhibits the release of TSH which continues to over stimulate the thyroid |

|calcitonin: |

|What is the function of this hormone? Lowers blood levels of calcium and phosphate ions |

| |

| |

|What part of the thyroid secretes it? It is secreted by extrafollicular cells of the thyroid |

| Parathyroid Glands: |

|How many are there and where are they found? Four: located on the back of the thyroid gland |

| parathyroid hormone PTH: |

| |

|What is the function of this hormone? Increases blood calcium levels |

|How does it achieve this function? Stimulates osteoclasts in bone which break down bone tissue and rlease calcium into the blood: it also influences|

|the kidneys to conserve calcium |

| |

|How is it related to calcitonin from the thyroid? PTH and Calcitonin have opposite effects and work together to maintain the correct levels of calcium |

|ions in the blood |

| Adrenal Gland: |

|The adrenal glands sit atop the __kidneys_____ enclosed in a layer of ___fat__. |

| Adrenal medulla: |

|The adrenal medulla is made up of modified __post-ganglionic neurons__ that are connected to the _sympathetic___ |

|nervous system. The hormones secreted are the same as neurotransmitters of this system but are called hormones |

|because they are secreted into the __body fluids and blood stream_____. |

| epinephrine & norepinephrine: |

|What affect do these have on the body? Similar effects to those of the sympathetic division of the autonomic nervous system |

|What are they secreted in response to? Stress and “fight or flight” situations |

| adrenal cortex: |

|The adrenal cortex makes up most of the adrenal glands and consists of ___epithelial_____ cells in three layers— |

|an outer, middle, and an inner zone. Several groups of hormones are secreted by the cortex. |

| |

| mineralocorticoids - aldosterone: |

|This hormone controls the levels of _sodiun__ ions by conserving them in the __kidneys____. |

|Why is this important? Important in homeostasis of the body |

| |

|Which zone secretes mineralocorticoids? Outer zone |

| glucocorticoids: |

|These hormones influence the metabolism of glucose, protein, and fat in response to conditions that __stress__ |

|the body and require a greater supply of __glucose___ in the bloodstream. |

|How does negative feedback control the release of these hormones? CRH from hypothalus causes pituitary to release ACTH. ACTH in turn stimulates release |

|of glucocorticoids. Glucocorticoids inhibit further release of CRH |

| |

|What else can trigger their release? Stress , injury, or disease |

| |

|Name an important Gluccocorticoid. cortisol |

| |

|Which zone secretes these hormones? Middle zone |

| sex hormones: |

|Sex hormones, produced in the ___inner____zone, are mostly of the _male_____ type but can be |

|converted to __female___ hormones in the skin, liver, and adipose tissues. |

|b. These hormones supplement those released by the gonads and may stimulate early development of reproductive organs. |

| pancreas: |

|The pancreas secretes hormones as an _endocrine__ gland, and digestive juices to the digestive tract as an |

|___exocrine___ gland. |

|Where is the pancreas located? Behind and beneath the stomach |

|Its endocrine portions are the islets of __langerhans__ that include two cell types--_alpha__ |

|cells that secrete glucagon, and __beta___ cells that secrete insulin. |

| |

|Glucagon __increases__ the blood levels of glucose by stimulating the breakdown of |

|_glycogen____and the conversion of noncarbohydrates into ___glucose___. |

|What controls the levels of glucagon in the blood? Declining blood sugar levels |

|Insulin __decreases___ the blood levels of glucose by stimulating the liver to form __glycogen___ |

|increasing __protein__ synthesis, and stimulating adipose cells to store _fat_. |

|What controls the blood levels of insulin? High blood sugar levels |

| Pineal gland: |

|The pineal gland, near the upper portion of the thalamus, secretes _melatonin___-, which is involved in the |

|regulation of __circadian_______________________ rhythms of the body. |

| Thymus gland: |

|The thymus gland, lying between the lungs under the __sternum____, secretes _thymosin______ that |

|affect production and differentiation of T lymphocytes that are important in _immunity_______________________. |

| Reproductive Glands |

|The ovaries produce what two hormones? Estrogen and progesterone |

|What does the placenta produce? Estrogen, progesterone, and gonadotropin |

|The testes produce __testosterone____. |

| Digestive Glands Other Hormone Producing Organs |

|The digestive glands secrete hormones associated with the processes of digestion. |

|The __heart___ secretes atrial natriuretic peptide affecting sodium and the kidneys secrete |

|__erythropoietin_____ for blood cell production. |

| |

| Stress: |

|Factors that serve as stressors to the body produce stress and threaten ___homeostasis_______________. |

|Stress may be physical, psychological, or some combination of the two. |

|What effects on the body does physical stress have? Threatens the survival of tissues |

| |

|What does psychological stress result from ? real or perceived dangers |

| |

|Responses to stress are designed to maintain homeostasis. |

|The _hypothalmus____ controls the general stress syndrome, which involves increased sympathetic |

|activity and increased secretion of which hormones? Cortisol, glucagon, growth hormone, and antidiuretic hormone. |

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