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The Endocrine Sytem Second controlling system of the body ◦ Nervous system is the fast-control system Uses chemical messengers (hormones) that are released into the blood Hormones control several major processes ◦ ◦ ◦ ◦ ◦ Reproduction Growth and development Mobilization of body defenses Maintenance of much of homeostasis Regulation of metabolism Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid glands Thymus Adrenal glands Pancreas Ovary (female) Testis (male) Figure 9.3 Chemical Make-up Hormones are classified chemically as ◦ Amino acid–based, which includes Proteins Peptides Amines ◦ Steroids—made from cholesterol ◦ Prostaglandins—made from highly active lipids Mechanisms of Hormone Action Hormones affect only certain tissues or organs (target cells or target organs) Target cells must have specific protein receptors Hormone-binding alters cellular activity Steroid hormone Nucleus Cytoplasm 1 Receptor protein 2 3 Hormonereceptor complex 4 DNA mRNA 5 New protein Plasma membrane of target cell 6 (a) Steroid hormone action Figure 9.1a Nonsteroid hormone (first messenger) Cytoplasm Enzyme ATP 3 1 2 Receptor protein Plasma membrane of target cell Second cAMP messenger 4 Effect on cellular function, such as glycogen breakdown (b) Nonsteroid hormone action Figure 9.1b Control of Hormone Release Hormone levels in the blood are mostly maintained by negative feedback A stimulus or low hormone levels in the blood triggers the release of more hormone Hormone release stops once an appropriate level in the blood is reached Hormonal Stimuli of Endocrine Glands Most common stimuli Endocrine glands are activated by other hormones Releasing hormones secreted into portal circulation Hypothalamus Anterior pituitary Posterior pituitary Hypophyseal portal system Adrenocorticotropic hormone (ACTH) Growth hormone (GH) Bones and muscles Prolactin (PRL) Follicle-stimulating Thyrotropic hormone (TH) hormone (FSH) and luteinizing Mammary hormone (LH) glands Thyroid Adrenal cortex Testes or ovaries © 2012 Pearson Education, Inc. Figure 9.4 Optic chiasma Axon terminals Hypothalamic neurosecretory cells Hypothalamus Arterial blood supply Posterior lobe Capillary bed Venous drainage Anterior lobe of the pituitary © 2012 Pearson Education, Inc. ADH Oxytocin Kidney tubules Mammary glands Uterine muscles Figure 9.6 Hypothalamus Part of the brain that sits above the pituitary They work together Anterior Pituitary 1. Growth hormone 2. Adrenocorticotropic hormone - ACTH 3. Thyroid stimulating hormone - TSH Posterior Pituitary 1. Antidiruetic hormone (ADH) – promotes re-absorption of water in kidney – increases BP 2. Oxytocin – uterine contractions Adrenal Glands Respond to ACTH by producing: 1. Glucocorticoids (cortisone) – produce glucose in blood through fatty acid breakdown, inhibit inflammation. 2. Mineralocorticoids (aldosterone) – promote uptake of sodium and chloride in kidneys, water follows, increase BP 3. Epinephrine - emergency hormone Decreased Na+ or increased K+ in blood Stress Hypothalamus Decreased blood volume and/or blood pressure Corticotropinreleasing hormone Anterior pituitary Increased ACTH blood pressure or blood volume Kidney Renin Indirect stimulating effect via angiotensin Angiotensin II Direct stimulating effect Heart Atrial natriuretic peptide (ANP) Inhibitory effect Mineralocorticoidproducing part of adrenal cortex Enhanced secretion of aldosterone targets kidney tubules © 2012 Pearson Education, Inc. Increased absorption of Na+ and water; increased K+ excretion Increased blood volume and blood pressure Figure 9.12 Short term Stress More prolonged Hypothalamus Releasing hormones Nerve impulses Spinal cord Corticotropic cells of anterior pituitary Preganglionic Adrenal sympathetic medulla fibers ACTH Adrenal cortex Mineralocorticoids Glucocorticoids Short-term stress response Catecholamines 1. Increased heart rate 2. Increased blood pressure (epinephrine and 3. Liver converts glycogen norepinephrine) to glucose and releases glucose to blood 4. Dilation of bronchioles 5. Changes in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity 6. Increased metabolic rate © 2012 Pearson Education, Inc. Long-term stress response 1. Retention of sodium 1. Proteins and fats converted to and water by kidneys glucose or broken 2. Increased blood down for energy volume and blood 2. Increased blood pressure sugar 3. Suppression of immune system Figure 9.13 Thyroid Stimulated by Thyrotropin releasing hormone (TRH) from the hypothalamus which stimulates TSH from anterior pituitary. 1. Thyroxine (iodine) Maintains metabolism Hyperthyroidism – high metabolic rate, nervous, irritable Hypothyroidism – low met. Rate, slow, sluggish, overweight 2. Calcitonin – takes up calcium from blood to bones Disorders of the endocrine system Goiter – iodine deficiency, thyroxin production declines The hypothalamus secretes TRH, but has no effect Results in enlargement of the thyroid Grave’s disease – antibodies in the immune system mistakenly bind to TSH receptors on the thyroid gland stimulating more thyroxin production hyperthyroidism Parathyroids Rest on the thyroid 1. Parathyroid hormone – releases calcium from bone to blood Opposite of calcitonin Bone remodeling Calcitonin Calcitonin stimulates calcium salt deposit in bone. Thyroid gland releases calcitonin. Stimulus Rising blood Ca2+ levels Calcium homeostasis of blood: 9–11 mg/100 ml BALANCE BALANCE Stimulus Falling blood Ca2+ levels Thyroid gland Osteoclasts degrade bone matrix and release Ca2+ into blood. Parathyroid glands PTH Parathyroid glands release parathyroid hormone (PTH). Figure 9.10 Bone growth Bone grows in length because: 1 Cartilage grows here. 2 Cartilage is replaced by bone here. 3 Cartilage grows here. 4 Cartilage is replaced by bone here. © 2012 Pearson Education, Inc. Bone remodeling Growing shaft is remodeled as: Articular cartilage Epiphyseal plate 1 Bone is resorbed here. 2 Bone is added by appositional growth here. 3 Bone is resorbed here. Figure 5.6 Pancreas Islets of Langerhans – produce insulin and glucagon 1. Glucagon stimulates glycogen to break into glucose molecules and be released into the blood 2. Insulin decreases the glucose in the blood Uptake of glucose from blood is enhanced in most body cells Insulin-secreting cells of the pancreas activated; release insulin into the blood Insulin Tissue cells Glucose Glycogen Pancreas Elevated blood sugar level Liver takes up glucose and stores as glycogen Stimulus Blood glucose level (e.g., after eating four jelly doughnuts) Stimulus Blood glucose level (e.g., after skipping a meal) Blood glucose rises to homeostatic set point; stimulus for glucagon release diminishes Liver breaks down glycogen stores and releases glucose to the blood Blood glucose falls to homeostatic set point; stimulus for insulin release diminishes Low blood sugar level Glucagon-releasing cells of pancreas activated; release glucagon into blood Glucose Glycogen Liver Glucagon Figure 9.15 thermoregulation Ectotherm vs. endotherm Cooling by evaporation Warming by metabolism – shivering and metabolizing fat Vasodilation and vasoconstriction of blood vessels Ex. In hot environments, animals increase blood flow to their ears to release heat and in cold do the opposite. Countercurrent exchange – warm blood is traveling to extremities. Hibernation, blubber, hair, basking,… Reproductive Systems Female Ovaries – produce eggs (ova) and secrete estrogen and progesterone Stimulated by FSH and LH Male FSH – stimulates sperm production LH – stimulates interstitial cells to produce testosterone Suspensory ligament of ovary Uterine (fallopian) tube Ovarian blood vessels Broad ligament Fundus Lumen (cavity) of uterus of uterus Ovary Infundibulum Fimbriae Ovarian ligament Body of uterus Ureter Uterine blood vessels Uterosacral ligament Cervix Uterine tube Round ligament of uterus Endometrium Myometrium Wall of Perimetrium uterus Cervical canal Vagina (b) Figure 16.8b Menstrual Cycle Phase 1 Follicular phase (10 days) Anterior pituitary secretes FSH and LH FSH – follicle stimulating hormone LH – luteinizing hormone Follicle grows – releases estrogen which causes uterine lining to thickenendometrium Estrogen also causes ant. Pit. To release LH The luteal surge causes ovulation Growing follicles Primary follicle Degenerating corpus luteum Blood vessels Antrum Corona radiata Mature vesicular (Graafian) follicle Germinal epithelium Corpus luteum Developing corpus luteum Ruptured follicle Ovulation Secondary oocyte Figure 16.7 Ovulation – release of the egg from the ovary ends the follicular phase. Ova floats into fallopian tube (oviduct) Phase 2 Luteal phase Follicle has released the egg and changes into the corpus luteum Corpus luteum continues to secrete estrogen and now begins to produce progesterone Progesterone increases vessels and glands in uterus After about 13-15 days, if fertilization and implantation have NOT occurred the corpus luteum shuts down Phase 3 Menstruation Uterus reabsorbs some of the tissue created in the endometrium The rest sheds off and is passed out of the body Male Reproductive system Ureter Urinary bladder Prostatic urethra Pubis Seminal vesicle Ampulla of ductus deferens Membranous urethra Ejaculatory duct Rectum Prostate Bulbourethral gland Urogenital diaphragm Erectile tissue of the penis Spongy urethra Shaft of the penis Ductus (vas) deferens (a) Epididymis Testis Scrotum Glans penis Prepuce External urethral orifice Figure 16.2a