Slide 1

The Endocrine SystemCh 34 ParrotCh 45 Advanced Biology

I. The Endocrine SystemA. Control Pathways and Feedback Loops1. Componentsa. stimulusb. receptor proteinc. chemical messengersd. target cellse. response

2. Control Pathwaysa. Simple Endocrine Pathway

b. Simple Neurohormone Pathway

c. Simple Neuroendocrine PathwayB. Components of Endocrine System1. Hormonesa. chemical messengers released into extracellular fluid in one part of the body, travel through the circulatory system, affects other parts of the bodyb. communicates regulatory messagesc. binds to specific chemical receptors on cell membranes or within cells

d. Travels throughout the body, but only affects target cells1) cells that have receptors for a particular hormonee. bodys response to hormones is slower and longer lasting than to the nervous systemf. Most endocrine functions depend upon two opposing hormones

2. Glandsa. an organ that produces and releases a substance or secretionb. exocrine glands1) release their secretions through ducts either out of body to digestive systemc. endocrine glands1) release hormones to blood3. Local Regulatorsa. convey messages between neighboring cells within seconds or millisecondsb. some have cell-surface receptors and some have intracellular receptors

c. Types of chemical compounds acting as local regulators1) many neurotransmitters2) cytokines immune system3) growth factors4) nitric oxidea) dilate and constrict blood vesselsb) kills some bacteriac) kills some cancer cells5) prostaglandinsa) cause uterus to contractb) help induce fever, inflammation, and intensify painc) regulate aggregation of plateletsd) dilate and constrict blood vessels

C. Hormone Action

17C. Hormone Action1. Steroid Hormonesa. produced from lipid cholesterolb. not water soluble hydrophobicc. steroids usually pass through the lipid bi-layers of cell membrane and to the nucleus where it changes the pattern of gene expression

d. Steroid actionA steroid hormone enters a cell by passing directly across the cell membraneOnce inside, the hormone binds to a receptor (found only in the hormones target cells) and forms a hormone-receptor complex

3) The hormone-receptor complex enters the nucleus of the cell, where it binds to regions of DNA that control gene expression4) This binding initiates the transcription of specific genes to messenger RNA (mRNA)

5) The mRNA moves into cytoplasm and directs protein synthesis

e. Steroids are powerful and long lasting2. Non-steroid Hormonesa. include proteins, small peptides, and modified amino acids or aminesb. water solublec. bind to receptors on cell membranes and cause the release of secondary messengers that affect cell activities

d. Nonsteroid action1) a nonsteroid hormone binds to receptors on the cell membrane2) the binding of the hormone activates enzymes on the inner surface membrane

3) These enzymes release secondary messengers such as calcium ions, nucleotides, and even fatty acids to relay the hormones message within the cell4) These secondary messengers can activate or inhibit a wide range of cell activities II. Glands of the Endocrine SystemA. Functions of Major Endocrine Glands1. Pituitary Glanda. secretes hormones that directly regulate many body functions or control the actions of other endocrine glandsb. anterior pituitary glandc. posterior pituitary gland

2. Hypothalamus a. attached to posterior pituitary glandb. links CNS and endocrine systemc. controls the secretions of the pituitary glandd. activities influenced by1) the level of hormones and other substances in the blood2) sensory information from CNS

e. Hormones1) antidiuretic hormonea) stimulates kidneys to absorb water2) oxytocina) stimulates contractions during childbirth3) releasing hormonesa) hormones released into the anterior pituitary gland causing it to release hormonesf. Tropic hormone1) a hormone that has another endocrine gland as a target

3. Adrenal glanda. release hormones to help body deal with stressb. corticosteroids1) produced by adrenal cortex2) more than two dozen hormonesa) aldosterone1 regulates blood volume and pressureb) cortisol1 helps control rate of metabolism of carbohydrates, fats, and proteins

c. Adrenal medulla1) sympathetic nervous system causes release of hormonesa) epinephrine (adrenaline) or norepinephrine1 increase heart rate, increase blood pressure, widen air passages, causes release of extra glucose2 example of how one chemical signal can have different effects

4. Pancreasa. exocrine gland1) releases digestive enzymesb. endocrine gland1) releases insulin and glycagon from islets of Langerhansa) beta () cells release insulinb) alpha () cells release glucagon

2) Insulin stimulates cells to take glucose out of blooda) liver and skeletal muscles store glucose as glycogen1 glycogen is a polysaccharide (it is the animal equivalent of starch in plants)b) in fat tissue, glucose is converted to lipids

3) When blood glucose drops, glycagon is released from pancreasa) stimulates liver and skeletal muscle cells to break down glycogen and release glucose into bloodb) causes fat cells to convert lipids into glucose

Type I Diabetes Mellitus1. Autoimmune disorder2. bodys immune system kills beta () cells3. thus, insulin is not produced

Type II Diabetes Mellitus1. Body cells do not respond to insulin2. Because insulin receptors do not respond properly3. Incidence increasing because of obesity

5. Thyroid and Parathyroid Glandsa. thyroxine1) increases metabolic rate of cells cells become more active, use more energy, and produce more heat2) iodine is needed for thyroxine production

3) Hyperthyroidisma) too much thyroxineb) nervousness, elevated body temperature, increased blood pressure, weight loss4) Hypothyroidisma) too little thyroxineb) low body temperature, lack of energy, weight gain

b. Calcitonin1) reduces blood calcium levels2) signals kidneys to reabsorb less calcium from filtrate, inhibits calcium absorption in small intestine and promotes calcium absorption into bones

c. Parthyroid hormone (PTH)1) released by 4 parathyroid glands on the back of the thyroid2) increases calcium levels in the blood3) promotes release of calcium from bone, reabsorption of calcium in kidneys and increase uptake of calcium from small intestine4) promotes proper nerve and muscle function and proper bone structure

6. Reproductive Glandsa. gonads1) testes and ovaries2) produce gametes (egg and sperm)3) secrete sex hormonesa) ovaries secrete estrogensb) testes secrete testosterone

B. Control of Endocrine Glands1. the endocrine system is regulated by feedback mechanisms that function to maintain homeostasis

2. Controlling Metabolism1 hypothalamus senses that thyroxine levels in blood are low2 hypothalamus releases thyrotropin-releasing hormone (TRH)3 TRH stimulates anterior pituitary gland to secrete thyroid-stimulating hormone (TSH)4 thyroid-stimulating hormone (TSH) stimulates thyroid gland to release thyroxine5 as thyroxine levels increase, thyrotropin-releasing hormone (TRH) and thyroid-stimulating hormone (TSH) release decreases6 release of thyroxine stops

3. Controlling Body Temperature1 hypothalamus senses that core body temperature is low2 hypothalamus releases thyrotropin-releasing hormone (TRH)3 TRH stimulates anterior pituitary gland to secrete thyroid-stimulating hormone (TSH)4 thyroid-stimulating hormone (TSH) stimulates thyroid gland to release thyroxine5 thyroxine increases oxygen consumption and increases cellular metabolism/cellular respiration6 the increase in metabolic activity, increase body temperature

4. Maintaining Water Balance1 - concentration of solutes in blood increases2 hypothalamus signals posterior pituitary gland3 posterior pituitary gland releases more antidiuretic hormone (ADH)4 more antidiuretic hormone (ADH) goes to kidneys via the blood5 kidneys slow down water removal6 you realize that you are thirsty and take a drink7 water is quickly absorbed into blood8 solute concentration in blood decreases9 hypothalamus signals posterior pituitary gland10 pituitary gland releases less antidiuretic hormone (ADH)11 less ADH goes to kidneys via the blood12 kidneys increase amount of water removed from blood

Temp