Jaymie TicknorContemporary Biology 1112 Sect. 8533 and 5 December 2013Lecture #23Chapter #20 PowerpointThe Endocrine System - Hormones: endocrine system is an internal system of regulation and communication involving hormones and the glands that secrete them; one of the most complicated and complex systems in the bodyHormones are chemicals that travel through the body and act as signals to generate a response from target cellsHormones travel through the blood and interact with target cells in two ways: they bind to receptors on the cell’s surface (protein hormones) and they diffuse across the cell membrane (steroid is a fat like substance that can easily go across the membrane)Protein hormones: cannot cross cell membranes, instead it binds to a membrane receptor; this triggers a chain reaction, called signal transduction, inside the cell that tells the cell what to do; relay molecules inside cell to send a signalSteroid hormones: bind to receptors inside the cell to trigger the target cellSex hormones are the steroid hormones responsible for male and female anatomical developmentEndocrine glands: groups of cells or organs distributed throughout the brain and body that secrete hormonesThyroid secretes calcitonin to lower blood calcium levels; located at base of neck; secretes thyroid hormones T3 and T4, which act on most cells of the body (in almost every tissue type) to increase metabolic activity; secretes calcitonin, which acts on the bone to help lower blood calcium levels (signals bone to increase uptake/storage of calcium)Parathyroids secrete parathyroid hormone to raise blood calcium levels; located on the backside of the thyroid gland; secretes parathyroid hormone (PTH), which acts on the bone, digestive tract, and kidneys to raise blood calcium levels; signals bone to release calcium from storage into the blood; signals increased absorption of calcium in the digestive tract; signals increased reabsorption of calcium in the kidney (thus decreased secretion/excretion of calcium)Thymus secretes thymosin, which stimulates T cells of the immune system; located just above the heart; secretes thymosin and thymopoietin, which helps immune cells (T cells) mature; most active during infancy/childhood, atrophies (shrivels up) during adulthoodPancreas secretes insulin and glucagon to regulate blood glucose levels; secretes hormones insulin and glucagon, which assist in maintaining normal blood sugar level; Insulin: lowers blood glucose levels (generally secreted after a meal); Glucagon: increases blood glucose levels (generally during periods of fasting, not eating)Hypothalamus secretes gonadotropin-releasing hormone (GnRH); tells the pituitary gland what to secrete; regulates body temperature, affects hunger, thirst, and reproductionPituitary gland responds to GnRH by secreting the pituitary gonadotropins-follicle-stimulating hormone (FSH) and luteinizing hormone (LH); FSH stimulates sperm production for men, stimulates egg cell development for women; LH stimulates testosterone production for men and stimulates ovulation for womenSecretes a wide variety of hormones:Antidiuretic hormone (ADH) regulates water absorption by the kidneysThyroid stimulating hormone (TSH): causes thyroid to secrete T3 and T4Follicle stimulating hormone (FSH): involved in egg and sperm productionLuteinizing hormone (LH): involved in ovulation and testosterone productionProlactin: involved in breast milk productionOxytocin: involved in breast milk release and increasing uterine contraction during laborGrowth hormone (GH): bone growthAdrenal glands: sit atop kidneys; secrete epinephrine in response to stress or excitement; secrete glucocorticoids, which raises blood glucose levels and promotes fat breakdown; secrete mineralocorticoids, which help regulate levels of sodium and potassium in the blood; also synthesizes testosterone and estrogen (little levels)Pineal gland: located in the brain (behind the thalamus); secretes melatonin, which helps to regulate sleep-wake cyclesTestes: secrete testosterone; sperm production, hair thickness and distribution, muscle mass, and voice deepening; sperm production is more efficient at temperatures lower than body temperature; testes outside of body cavityOvaries: produce and secrete estrogen and progesterone; menstruation, maturation/release of egg cells, breast development, pregnancy, and menopause; production of egg cells begins in uteroPuberty: begins sperm production in males and egg production in females; age 8-13 years old for female, 9-14 for malesSkeletal System: functions include: supports the body, protects internal organs, aids movement, maintains mineral homeostasis, and produces red blood cells, white blood cells and platelets in bone marrow located in most bonesHuman skeleton is composed of 206 bones divided into 2 units: Axial skeleton: ribs, spine, skull; Appendicular skeleton: limbs, pelvic, and pectoral girdlesJoints in the skeleton allow for a variety of movements: ball and socket joint (hip), hinge joint (knee); pivot joint (neck)Bone is a living, dynamic tissue that varies depending on function: Compact bone: densely packed, forms the hard, outer shell of bones; Spongy bone: loosely pack, porous, honeycomb-like interior; Bone Marrow: interior of spongy bone, produces blood cells;bones have blood vessels inside and along their surfaceBones act as a reservoir of the body’s calcium; they can store excess calcium or release it as neededOsteoblasts: remove calcium from blood during bone deposition processOsteoclasts: add calcium to blood by breaking down and reabsorbing bone tissueBones are in a continuous process of remodelingParathyroid hormone (PTH) triggers bone resorption of calciumCalcitonin triggers bone deposition of calciumFemales typically have wider hips, smaller frontal bones, larger femur bone to support hips, and smaller jaw compared to males3 types of muscle in human body: skeletal, cardiac, smooth; muscles are composed of bundles of muscle fibers arranged in parallel; muscle fibers are cells; cells are made of filaments, also parallel; the parallel stripe arrangements of fibers gives skeletal muscle its characteristic striated appearance; piece of muscle, inside is single muscle fiber/cell, inside is myofibril, inside is myosin and actin (Z disc where actin is anchored); one Z disc to another is one sarcomere (one unit of muscle contraction and movement)General process of “sliding filament model” of muscle contraction: myosin