Endocrine System By: Valentina Chen Period 2 1

Hormones and Glands Hormones → Chemicals released in one part of the body that travel through the bloodstream and affect the activities of cells in other parts of the body Target cells → Cells that have receptors for a particular hormone In general, the body’s responses to hormones are slower and longer-lasting than the responses to nerve impulses. Organ that produces and releases a substance or secretion 2 types: 1.Exocrine Gland→ Release secretions through ducts directly to the organs that use them 2.Endocrine Gland→ Release secretions directly into the bloodstream 2

Hormone Action 2 basic patterns of hormone action A.Steroid Hormone→ produced from cholesterol 1. Can cross cell membrane easily o Steps: a. Steroid hormone enters cell by passing through cell membrane b. Binds to steroid receptor protein to form hormone- receptor complex c. Hormone-receptor complex enters cell nucleus,where it binds to DNA control sequence d. Binding initiates transcription of specific genes to mRNA e. mRNA moves to cytoplasm and directs protein synthesis 2. Hormone receptor complexes work as regulators of gene expression- turn on or off whole sets of genes (Affect gene expression DIRECTLY!) B. Nonsteroid Hormones 1. Cannot pass through cell membranes of their target cells o Steps: a. Nonsteroid hormone binds to receptors on cell membrane b. Binding activates an enzyme on the inner surface of cell membrane c. Enzyme activates secondary messengers that carry the message of the hormone inside the cell d. Secondary messengers can activate or inhibit a wide range of other cell activities 2. Secondary messengers→ carry the message of the hormone inside the cell 3

Prostaglandins and Control of the Endocrine System All cells except red blood cells have been shown to produce small amounts of hormonelike substances called prostaglandins Prostaglandins are fatty acids /first discovered in prostate Affect only nearby cells and tissues and thus known as “local hormones” Causes smooth muscles to contract Aspirin helps to stop pain of headache by inhibiting the synthesis of prostaglandins Endocrine system regulated by feedback mechanisms that function to maintain homeostasis RECALL: Feedback inhibition occurs when an increase in any substance ”feeds back” to inhibit the process that produced the substance in the first place 4

Control of the Endocrine System Cont. A. Controlling Metabolism (example) 1. When the hypothalamus senses that the level of thyroxine in the blood is low, it secretes thyrotropin- releasing hormone (TRH) 2. TRH stimulates the anterior pituitary gland to secrete thyroid- stimulating hormone (TSH) 3. TSH stimulates the thyroid gland to release thyroxine 4. Increased levels of TRH and TSH inhibit TRH secretion by the hypothalamus 5. Thyroxine increases oxygen consumption and cellular metabolism/ increase in metabolic activity results help body to maintain its core temperature despite lower temperatures 5

Control of the Endocrine System Cont. and Complementary Hormone Action B. Maintaining Water Balance 1. Water deficit stimulates the release of antidiuretic hormone (ADH) kidneys to conserve water 2. Oversupply of water causes kidneys to eliminate the excess water as urine 3. Chain of command: Hypothalamus to pituitary to kidney Two hormones with opposite effects act to regulate part of the body’s internal environment Example: 1.PTH and calcitonin 2.Insulin and Glucagon 6

Pituitary Gland and Hypothalamus I.Pituitary Gland a. Location: Base of skull b. Structure: Bean-sized c. Hormones released: Refer to chart d. Targets & actions: Refer to chart e. Other info: Controls many other endocrine glands II.Hypothalamus a. Location: Above and attached to posterior pituitary b. Structure: Small and round c. Hormones released: Releasing hormones d. Targets & actions: Pituitary gland→ controls secretions e. Other info: Activity of hypothalamus influenced by levels of hormones in the blood and sensory information 7

Thyroid and Parathyroid Glands III. Thyroid Gland a. Location: Base of neck b. Structure: Bulbous, wraps around neck c. Hormones released: Thyroxine, calcitonin d. Targets & actions: Protein, Carbohydrates, Fat→ regulates metabolic rates e. Antagonistic effects: Dwarfism, mental retardation IV. Parathyroid Gland a. Location: Back surface of thyroid gland b. Structure: Small, round c. Hormone released: Parathyroid hormone (PTH) d. Target & action: Kidneys/organ systems→ maintains homeostasis of calcium levels in blood e. Antagonistic effects: Osteoporosis 8

Adrenal Glands (Cortex and Medulla) V. Adrenal Glands a. Location: On top of kidneys b. Structure: Pyramid-shaped A. Adrenal Cortex 1. Location: Outer layer of adrenal gland 2. Hormones released: Corticosteroids, Cortisol, Aldosterone 3. Targets & actions: Carbs, Fats, Proteins→ Helps control of metabolism Kidneys→ regulates reabsorption of sodium ions and excretion of potassium ions B. Adrenal Medulla 1. Location: Inner membrane of adrenal gland 2. Hormones released: Epinephrine, Norepinephrine Targets & actions: Heart, lungs→ increase heart rate, blood pressure, blood flow, widen passageways 9

Pancreas VII. Pancreas a. Location: In front of kidneys b. Structure: Long, tube-like c. Hormones released: Insulin, glucagon d. Targets & actions: Bloodstream→ maintains glucose levels in the blood e. Antagonistic effects: Diabetes mellitus→ condition where the pancreas fails to produce or properly use insulin o 2 types: 1. Type I diabetes Autoimmune disorder where one secretes little or no insulin 2. Type 2 diabetes Autoimmune disorder that produces low to normal amounts of insulin 10

Female and Male Reproductive Glands VIII. Female Reproductive Gland a. Location: Abdomen b. Structure: Ovaries c. Hormones released: Estrogen, Progesterone d. Targets & actions: Uterus→ prepares for fertilized egg Ovaries→ development of eggs IX. Male Reproductive Gland a. Location: Abdomen b. Structure: Testes c. Hormone released: Testosterone d. Target & action: Testes→ produces sperm, development of male secondary sex characteristics 11

Endocrine System Chart GlandHormoneTargetAction 1. Hypothalamus “Releasing hormones”Pituitary glandControls secretions of pituitary 2. Pituitary Gland (8) A. Posterior (2) 1. OxytocinUterusStimulates contractions of uterus during childbirth; releases milk in nursing mothers 2. Antidiuretic hormone (ADH)KidneysStimulates kidneys to reabsorb water from tubules B. Anterior (6) 1. Growth hormone (GH)CellsStimulates protein synthesis and growth in cells 2. Prolactin (PRL)BodyStimulates milk production in nursing mothers 3. Follicle-stimulating hormone (FSH) GonadsStimulates production of mature eggs and sperm 4. Luteininzing hormone (LH)Gonads; uterusStimulates ovaries and testes; prepares uterus for implantation of fertilized egg 5. Thyroid-stimulating hormone (TSH) ThyroidStimulates synthesis and release of thyroxine from thyroid 6. Adrenocorticotropic hormone (ACTH) Adrenal glandStimulates release of some hormones from adrenal cortex 12

GlandHormoneTargetAction 3. Thyroid Gland1. Thyroxine (T4)Protein, carbs, fatsIncreases metabolism & respiration 2. CalcitoninBone cellsReduces blood calcium 4. Parathyroid GlandParathyroid Hormone (PTH)BloodstreamMaintains calcium levels 5. Pancreas1. InsulinBloodstreamMaintains glucose levels 2. GlucagonLiver & muscle cells, fat Stimulates release of glucose and fatty acids 6. Adrenal Gland A. Adrenal Medulla 1. Epinephrine (Adrenalin)Heart, lungs, musclesIncreases heart rate, blood pressure, blood flow; widens air passageways 2. NorepinephrineHeartStimulates release of glucose B. Adrenal Cortex1. CorticosteroidsFats, proteins, carbsSteroid hormones 2. CortisolFats, proteins, carbsControls metabolic rates 3. AldosteroneKidneysRegulates reabsorption of sodium ions and excretion of potassium ions 7. Gonads A. Ovaries1. EstrogenUterusDevelopes eggs, prepares for fertilized egg 2. ProgesteroneUterusPrepares for embryo B. TestesTestosteroneTestes, BodyProduces sperm; develops secondary characteristics 8. ThymusThymosinLymph nodesStimulates T lymphocytes Endocrine System Chart Cont. 13