Results for "Steroid Hormones"

Peptide Hormones vs Steroid Hormones

6- Kearns - Steroid Hormones

eukaryotes- transcription factors and steroid hormones

Adrenal gland and steroid hormones

Lecture 9 - Thyroid Hormones and Drugs, Gonadal Steroid Hormones and Drugs

The Endocrine System & Steroid Hormones

Normal adrenal function: adrenal gland and steroid hormones

Negative and Positive Feedback Loops Control hormone levelsNegative feedback loopHormone release stops in response to decrease in stimulus- Stimulus (eating) raises blood glucose levels- Pancreas releases insulin in response to elevated blood   glucose- Blood glucose decreases as it is used by the body or  stored in the liver - Insulin release stops as blood glucose levels normalize Positive feedback loop As long as stimulus is present, action of hormone continues- Infant nursing at mother’s breast→stimulates  hypothalamus→stimulates posterior pituitary- Oxytocin released→stimulates milk production  and ejection from mammary glands- Milk release continues as long as infant  continues to nurse The Major Endocrine OrgansThe major endocrine organs of the body include: the pituitary, pineal, thyroid, parathyroid, thymus, and adrenal glands, pancreas, and gonads (ovaries and testes)Endocrine glands - Ductless - Release hormones - Directly into target tissues - Into bloodstream to be carried to target tissuesHormones(Greek word hormone – to set into motion)     Pituitary Gland and Hypothalamus o The pituitary gland is approximately the size of a pea. o It hangs by a stalk from the inferior surface of the hypothalamus of the brain, where it is snugly surrounded by the sella turcica of the sphenoid bone. o It has two functional lobes – the anterior pituitary (glandular tissue) and the posterior pituitary (nervous tissue). o The anterior pituitary gland controls the activity of so many other endocrine glands (“master endocrine gland”) o The release of each of its hormones is controlled by releasing hormones and inhibiting hormones produced by the hypothalamus. o The hypothalamus also makes two additional hormones, oxytocinand antidiuretic hormone, which are transported along the axons of the hypothalamic nuerosecretory cells to the posterior pituitary for storage. They are later released into the blood in response to nerve impulses from the hypothalamus. Oxytocin o Is released in significant amounts only during childbirth and nursing. o It stimulates powerful contractions of the uterine muscle during sexual relations, during labor, and during breastfeeding. o It also causes milk ejection (let-down reflex) in a nursing woman. Antidiuretic Hormone (ADH) o ADH is a chemical that inhibits or prevents urine production. o ADH causes the kidneys to reabsorb more water from the forming urine; as a result, urine volume decreases, and blood volume increases. o In larger amounts, ADH also increases blood pressure by causing constriction of the arterioles (small arteries). For this reason, it is sometimes referred to as vasopressin. Anterior Pituitary HormonesThe anterior pituitary produces several hormones that affect many body organs. Growth Hormone (GH) o Its major effects are directed to the growth of skeletal muscles and long bones of the body o At the same time, it causes fats to be broken down and used for energy while it spares glucose, helping to maintain blood sugar homeostasis. ProlactinIts only known target in humans is the breast.After childbirth, it stimulates and maintains milk production by the mother’s breasts.Gonadotropic Hormones (FSH and LH) o Regulate the hormonal activity of the gonads (ovaries and testes) o In women, the FSH stimulates follicle development in the ovaries. o In men, FSH stimulates sperm production by the testes. o LH triggers ovulation of an egg from the ovary and causes the ruptured follicle to produce progesterone and some estrogen. o LH stimulates testosterone production by the interstitial cells of the testes. Pineal Gland The pineal gland is a small, cone-shaped gland that hangs from the roof of the third ventricle of the brain. Melatonin o The only hormone secreted from pineal gland in substantial amounts o Believed to be a “sleep trigger” that plays an important role in establishing the body’s sleep-wake cycle. o The level of melatonin rises and falls during the course of the day and night. o The peak level occurs at night and makes us drowsy o The lowest level occurs during daylight around noon. Thyroid Gland • The thyroid gland is located at the base of the throat, just inferior to the Adam’s apple. • It is a fairly large gland consisting of two lobes joined by a central mass, or isthmus. • The thyroid gland makes two hormones, one called thyroid hormone, the other called calcitonin. Thyroid Hormone o Referred to as body’s major metabolic hormone o Contains two active iodine-containing hormones, thyroxine (T4)and thriiodothyronine (T3) o Most triiodothyronine is formed at the target tissues by conversion of thyronine to triiodothyronine o Thyroid hormone controls the rate at which glucose is “burned”, or oxidized, and converted to body heat and chemical energy (ATP). o Thyroid hormone is also important for normal tissue growth and development, especially in the reproductive and nervous systems. Homeostatic Imbalance ➢ Without iodine, functional thyroid hormones cannot be made. ➢ The source of iodine is our diet (seafoods) ➢ Goiter is an enlargement of the thyroid gland that results when the diet is deficient in iodine. Hyposecretion of thyroxine may indicate problems other than iodine deficiency. If it occurs in early childhood, the result is cretinism. ▪ Results in dwarfism and mental retardation (if discovered early, hormone replacement will prevent mental impairment) Hypothyroidism occurring in adults results in myxedema ▪ Characterized by both physical and mental sluggishness (no mental impairment) ▪ Other signs are puffiness of the face, fatigue, poor muscle tone, low body temperature, obesity, and dry skin (Oral thyroxine is prescribed to treat this condition)   ➢ Hyperthyroidism generally results from a tumor of the thyroid gland. ➢ Extreme overproduction of thyroxine results in a high basal metabolic rate, intolerance of heat, rapid heartbeat, weight loss, nervous and agitated behavior, and a general inability to relax. Graves’ disease o A form of hyperthyroidism o The thyroid gland enlarges, the eyes bulge (exophthalmos) Calcitonin ➢ Second important hormone product of the thyroid gland ➢ Decreases the blood calcium ion level by causing calcium to be deposited in the bones Parathyroid Glands ➢ The parathyroid glands are tiny masses of glandular tissue most often on the posterior surface of the thyroid gland. ➢ Parathyroid hormone (PTH) is the most important regulator of calcium ion homeostasis of the blood. ➢ Although the skeleton is the major PTH target, PTH also stimulates the kidneys and intestine to absorb more calcium ions. Homeostatic Imbalance o If blood calcium ion level falls too low, neurons become extremely irritable and overactive. They deliver impulses to the muscles so rapidly that the muscles go into uncontrollable spasms (tetany), which may be fatal. o Severe hyperparathyroidism causes massive bone destruction. The bones become very fragile, and spontaneous fractures begin to occur. Thymus o Is located in the upper thorax, posterior to the sternum. o Large in infants and children, it decreases in size throughout adulthood. o By old age, it is composed mostly of fibrous connective tissue and fat. o The thymus produces a hormone called thymosin and others that appear to be essential for normal development of a special group of white blood cells (T lymphocytes) and the immune response. Adrenal Glands o The two adrenal glands curve over the top of the kidneys like triangular hats. o It is structurally and functionally two endocrine organs in one.   • it has parts made of glandular (cortex) and neural tissue (medulla) • The central medulla region is enclosed by the adrenal cortex, which contains three separate layers of cells. Hormones of the Adrenal CortexThe adrenal cortex produces three major groups of steroid hormones, collectively called corticosteroids: 1. Mineralocorticoids (aldosterone) ➢ Are produced by the outermost adrenal cortex cell layer. ➢ Are important in regulating the mineral (salt) content of the blood, particularly the concentrations of sodium and potassium ions. ➢ These hormones target the kidney tubules(Distal Convulating Kidney Tubles) that selectively reabsorb the minerals or allow them to be flushed out of the body in urine. ➢ When the blood level of aldosterone rises, the kidney tubule cell reabsorb increasing amounts of sodium ions and secrete more potassium ions into the urine. ➢ When sodium is reabsorbed, water follows. Thus, the mineralocorticoids help regulate both water and electrolyte balance in body fluids. 2. Glucocorticoids (Cortisone and Cortisol)  ➢ Glucocorticoids promote normal cell metabolism and help the body to resist long-term stressors, primarily by increasing the blood glucose level. ➢ When blood levels of glucocorticoids are high, fats and even proteins are broken down by body cells and converted to glucose, which is released to the blood. ➢ For this reason, glucocorticoids are said to be hyperglycemic hormones. ➢ Glucocorticoids also seem to control the more unpleasant effects of inflammation by decreasing edema, and they reduce pain by inhibiting the pain-causing prostaglandins. ➢ Because of their anti-inflammatory properties, glucocorticoids are often prescribed as drugs to suppress inflammation for patients with rheumatoid arthritis. ➢ Glucocorticoids are released from the adrenal cortex in response to a rising blood level of ACTH (Adrenocorticotropic hormone). 3. Sex Hormones ➢ In both men and women, the adrenal cortex produces both male and female sex hormones throughout life in relatively small amounts. ➢ The bulk of the sex hormones produced by the innermost cortex layer are androgens (male sex hormones), but some estrogens (female sex hormones) are also formed. Homeostatic Imbalance1. Addisson’s disease (hyposecretion of all the adrenal cortex hormones) ✓ Bronze tone of the skin (suntan) ✓ Na (sodium) and water are lost from the body ✓ Muscles become weak and shock is a possibility ✓ Hypoglycemia (↓ glucocorticoids) ✓ Suppression of the immune system 2. Hyperaldosteronism (hyperactivity of the outermost cortical area) ✓ Excessive water and sodium ions retention ✓ High blood pressure ✓ Edema ✓ Low potassium ions level (hypokalemia) 3. Cushing’s Syndrome (Excessive glucocorticoids) ✓ Swollen “moon face” and “Buffalo hump” ✓ High blood pressure and hyperglycemia (steroid diabetes) ✓ Weakening of the bones (as protein is withdrawn to be converted to glucose) ✓ Severe depression of the immune system 4. Hypersecretion of the sex hormones leads to masculinization, regardless of sex. Hormones of the Adrenal Medulla ➢ When the medulla is stimulated by sympathetic nervous system neurons, its cells release two similar hormones, epinephrine(adrenaline) and norepinephrine (noradrenaline), into the bloodstream. ➢ Collectively, these hormones are called catecholamines. ➢ The catecholamines of the adrenal medulla prepare the body to cope with short-term stressful situations and cause the so-called alarm stage of the stress response. ➢ Glucocorticoids, by contrast, are produced by the adrenal cortex and are important when coping with prolonged or continuing stressors, such as dealing with the death of a family member or having a major operation (resistance stage). Pancreatic Islets ➢ The pancreas, located close to the stomach in the abdominal cavity, is a mixed gland. ➢ The pancreatic islets, also called the islets of Langerhans, are little masses of endocrine (hormone-producing) tissue of the pancreas. ➢ The exocrine, or acinar, part of the pancreas acts as part of the digestive system. ➢ Two important hormones produced by the islet cells are insulin and glucagon. Insulin ➢ Hormone released by the beta cells of the islets in response to a high level of blood glucose. ➢ Acts on all body cells, increasing their ability to import glucose across their plasma membranes. ➢ Insulin also speeds up these “use it” or “store it” activities. ➢ Because insulin sweeps the glucose out of the blood, its effect is said to be hypoglycemic. ➢ Without it, essentially no glucose can get into the cells to be used. Glucagon ➢ Acts as an antagonist of insulin ➢ Released by the alpha cells of the islets in response to a low blood glucose levels. ➢ Its action is basically hyperglycemic. ➢ Its primary target is the liver, which it stimulates to break down stored glycogen to glucose and to release the glucose into the blood. Gonads ➢ The female and male gonads produce sex cells. ➢ They also produce sex hormones that are identical to those produced by adrenal cortex cells. ➢ The major differences from the adrenal sex hormone production are the source and relative amounts of hormones produced. Hormones of the OvariesBesides producing female sex cells (ova, or eggs), ovaries produce two groups of steroid hormones, estrogens and progesterone. 1. Estrogen (Steroid Hormone) ➢ Responsible for the development of sex characteristics in women (primarily growth and maturation of the reproductive organs) and the appearance of secondary sex characteristics at puberty. ➢ Acting with progesterone, estrogens promote breast development and cyclic changes in the uterine lining (the menstrual cycle) 2. Progesterone (Steroid Hormone) ➢ Acts with estrogen to bring about the menstrual cycle. ➢ During pregnancy, it quiets the muscles of the uterus so that an implanted embryo will not be aborted and helps prepare breast tissue for lactation. Hormones of the TestesIn addition to male sex cells, or sperm, the testes also produce male sex hormones, or androgens, of which testosterone is the most important. 3. Testosterone ➢ Promotes the growth and maturation of the reproductive system organs to prepare the young man for reproduction. ➢ It also causes the male’s secondary sex characteristics to appear and stimulates the male sex drive. ➢ It is necessary for continuous production of sperm. ➢ Testosterone production is specifically stimulated by LH. Other Hormone-Producing Tissues and OrgansPlacenta ➢ During very early pregnancy, a hormone called human chorionic gonadotropin (hCG) is produced by the developing embryo and then by the fetal parts of the placenta. ➢ hCG stimulates the ovaries to continue producing estrogen and progesterone so that the lining of the uterus is not sloughed off in menses. ➢ In the third month, the placenta assumes the job of the ovaries of producing estrogen and progesterone, and the ovaries become inactive for the rest of the pregnancy. ➢ The high estrogen and progesterone blood levels maintain the lining of the uterus and prepare the breasts for producing milk. ➢ Human placental lactogen (hPL) works cooperatively with estrogen and progesterone in preparing the breasts for lactation. ➢ Relaxin, another placental hormone, causes the mother’s pelvic ligaments and the pubic symphysis to relax and become more flexible, which eases birth passage. Developmental Aspects of the Endocrine System ➢ In late middle age, the efficiency of the ovaries begins to decline, causing menopause. o Reproductive organs begin to atrophy o Ability to bear children ends o Problems associated with estrogen deficiency begin to occur (arteriosclerosis, osteoporosis, decreased skin elasticity, “hot flashes”) ➢ No such dramatic changes seem to happen in men. ➢ Elderly persons are less able to resist stress and infection. ➢ Exposure to pesticides, industrial chemicals, dioxin, and pother soil and water pollutants diminishes endocrine function, which may explain the higher cancer rates among older adults in certain areas of the country. ➢ All older people have some decline in insulin production, and type 2 diabetes mellitus is most common in this age group. BLOOD ➢ It is the only fluid tissue in the body. ➢ A homogenous liquid that has both solid and liquid components. ➢ Taste, Odor, 5x thicker than water ➢ Classified as a connective tissue ❖Living cells = formed elements ❖Non-living matrix = plasma (90% water) Components •Formed elements (blood cells)are suspended in plasma •The collagen and elastin fibers typical of other connective tissues are absent from blood; instead, dissolved proteins become visible as fibrin strands during blood clotting •If a sample of blood is separated, the plasma rises to the top, and the formed elements, being heavier, fall to the bottom. •Most of the erythrocytes (RBCs) settle at the bottom of the tube •There is a thin, whitish layer called the buffy coat at the junction between the erythrocytes and the plasma containing leukocytes (WBCs) and platelets   Physical Characteristics and Volume • Color range ➢ Oxygen-rich blood is scarlet red ➢ Oxygen-poor blood is dull red • pH must remain between 7.35–7.45 • Slightly alkaline • Blood temperature is slightly higher than body temperature • 5-6 Liters or about 6 quarts /body   Functions and Composition of Blood 1. Transport of gases, nutrients and waste products 2. Transport of processed molecules 3. Transport of regulatory molecules 4. Regulation of pH and osmosis 5. Maintenance of body temp 6. Protection against foreign substances 7. Clot formation   Plasma • The liquid part of the blood; 90 percent water • Over 100 different substances are dissolved in this straw-colored fluid: ➢ nutrients ➢ electrolytes ➢ respiratory gases ➢ hormones ➢ plasma proteins; and ➢ various wastes and products of cell metabolism   • Plasma proteins are the most abundant solutes in plasma (albumin and clotting proteins) • Plasma helps to distribute body heat, a by-product of cellular metabolism, evenly throughout the body. Formed Elements Erythrocytes (RBCs) • Function primarily to ferry oxygen to all cells of the body. • RBCs differ from other blood cells because they are anucleate (no nucleus) • Contain very few organelles (RBCs circulating in the blood are literally “bags” of hemoglobin molecules ) •Very efficient oxygen transporters (they lack mitochondria and make ATP by anaerobic mechanisms) • Their small size and peculiar shape provide a large surface area relative to their volume, making them suited for gas exchange • RBCs outnumber WBCs by about 1,000 to 1 and are the major factor contributing to blood viscosity. • There are normally about 5 million cells per cubic millimeter of blood. • The more hemoglobin molecules the RBCs contain, the more oxygen they will be able to carry. • A single RBC contains about 250 million hemoglobin molecules, each capable of binding 4 molecules of oxygen. • Normal hemoglobin count is 12-18 grams of hemoglobin per 100 ml of blood • Men: 13-18g/ml Women: 12-16 g/ml   Homeostatic Imbalance Anemia • a decrease in the oxygen-carrying ability of the blood, whatever the reason is. • May be the result of (1) a lower-than-normal number of RBCs or (2) abnormal or deficient hemoglobin content in the RBCs.   Polycythemia Vera • An excessive or abnormal increase in the number of erythrocytes; may result from bone marrow cancer or a normal physiologic response to living at high altitudes, where the air is thinner and less oxygen is available (secondary polycythemia)     Formed Elements Leukocytes (WBCs) • Are far less numerous than RBCs • They are crucial to body defense • On average, there are 4,800 to 10,800 WBCs/mm3 of blood • WBCs contain nuclei and the usual organelles, which makes them the only complete cells in the blood. • WBCs are able to slip into and out of the blood vessels – a process called diapedesis • WBCs can locate areas of tissue damage and infection in the body by responding to certain chemicals that diffuse from the damaged cells (positive chemostaxis) • Whenever WBCs mobilize for action, the body speeds up their production, and as many as twice the normal number of WBCs may appear in the blood within a few hours. • A total WBC count above 11,000 cells/mm3 is referred to as leukocytosis. • The opposite condition, leukopenia, is an abnormally low WBC count (commonly caused by certain drugs, such as corticosteroids and anti-cancer agents) • WBCs are classified into two major groups – granulocytes and agranulocytes – depending on whether or not they contain visible granules in their cytoplasm.   Granulocytes Neutrophils ➢ Are the most numerous WBCs. ➢ Neutrophils are avid phagocytes at sites of acute infection. Eosinophils ➢ Their number increases rapidly during infections by parasitic worms ingected in food such as raw fish or entering through the skin. Basophils ➢ The rarest of the WBCs, have large histamine-containing granules. Histamine ➢ is an inflammatory chemical that makes blood vessels leaky and attracts other WBCs to the inflamed site   Agranulocytes Lymphocytes ➢ Have a large, dark purple nucleus that occupies most of the cell volume. ➢ Lymphocytes tend to take up residence in lymphatic tissues, such as the tonsils, where they play an important role in the immune response. ➢ They are the second most numerous leukocytes in the blood Monocytes ➢ Are the largest of the WBCs. ➢ When they migrate into the tissues, they change into macrophages. ➢ Macrophages are important in fighting chronic infections, such as tuberculosis, and in activating lymphocytes Platelets   ➢ They are fragments of bizarre multinucleate cells called megakaryocytes, which pinch off thousands of anucleate platelet “pieces” that quickly seal themselves off from the surrounding fluids. ➢ Normal adult has 150,000 to 450,000 per cubic millimeter of blood ➢ Platelets are needed for the clotting process that stops blood loss from broken blood vessels. ➢ Average lifespan is 9 to 12 days   Hematopoiesis • Occurs in red bone marrow, or myeloid tissue. • In adults, this tissue is found chiefly in the axial skeleton, pectoral andpelvic girdles, and proximal epiphyses of the humerus and femur. • On average, the red marrow turns out an ounce of new bloodcontaining 100 billion new cells every day. • All the formed elements arise from a common stem cell, thehemocytoblast, which resides in red bone marrow. • Once a cell is committed to a specific blood pathway, it cannotchange. • The hemocytoblast forms two types of descendants – the lymphoidstem cell, which produces lymphocytes, and the myeloid stem cell,which can produce other classes of formed elements.   Formation of RBCs • Because they are anucleate, RBCs are unable to synthesizeproteins, grow, or divide. • As they age, RBCs become rigid and begin to fall apart in 100 to 120 days. • Their remains are eliminated by phagocytes in the spleen, liver, and other body tissues. • RBC components are salvaged. Iron is bound to protein as ferritin, and the balance of the heme group is degraded to bilirubin, which is then secreted into the intestine by liver cells where it becomes a brown pigment called stercobilin that leaves the body in feces. • Globin is broken down to amino acids which are released into the circulation.The rate of erythrocyte production is controlled by a hormone called erythropoietin (from the kidneys) • Erythropoietin targets the bone marrow prodding it into “high gear” to turn out more RBCs. • An overabundance of erythrocytes, or an excessive amount of oxygen in the bloodstream, depresses erythropoietin release and RBC production. • However, RBC production is controlled not by the relative number of RBCs in the blood, but by the ability of the available RBCs to transport enough oxygen to meet the body’s demands   Formation of WBCs and Platelets   • The formation of leukocytes and platelets is stimulated by hormones • These colony stimulating factors (CSFs) and interleukins not only prompt red bone marrow to turn out leukocytes, but also enhance the ability of mature leukocytes to protect the body. • The hormone thrombopoietin accelerates the production of platelets from megakaryocytes, but little is know about how process is regulated. • When bone marrow problems or disease condition is suspected, bone marrow biopsy is done.   Hemostasis If a blood vessel wall breaks, a series of reactions starts the process of hemostasis (stopping the bleeding). Phases of Hemostasis 1. Vascular spasms occur. 2. Platelet plug forms. 3. Coagulation events occur.       Human Blood Groups • An antigen is a substance that the body recognizes as foreign; it stimulates the immune system to mount a defense against it. • The “recognizers” are antibodies present in plasma that attach to RBCs bearing surface antigens different from those on the patient’s RBCs.   ABO and Rh Blood Types The blood group system recognizes four blood types: • Type A, B, AB, and O • They are distinguished from each other in part by their antigens and antibodies. • Specific antibodies are found in the serum based on the type of antigen on the surface of the RBC   ABO and Rh Blood Types BLOOD TYPE Can Accept From Can Donate To A A, O A, AB B B, O B, AB AB A, B, AB, O AB O O O, A, B, AB   The Rh Factor Rh-Positive Rh-Negative Contains the Rh antigen -No Rh antigen   -Will make antibodies if given Rh-positive blood   -Agglutination can occur if given Rh-positive blood     Summary • Blood is responsible for transporting oxygen, fluids, hormones, and antibodies and for eliminating waste materials. • The major components of blood include the formed elements and plasma. • RBCs transport oxygen and carbon dioxide; WBCs destroy foreign invaders. • WBCs include granulocytes and agranulocytes. • Plasma is the liquid portion of unclotted blood. Serum is the liquid portion of clotted blood • Hemostasis includes four stages: blood vessel spasm, platelet plug formation, blood clotting, and fibrinolysis. • ABO and Rh types are determined by the antigen found on the RBCs

Intro to Neuroscience, Chapter 11: Sex and Emotions

Lecture 4- peptide and steroid hormones synthesis and

Steroid Hormones - Vitamin D

BIOCHEM part 6: Steroid Hormones and Vitamins

The Endoplasmic Reticulum (Er) Plays A Key Role In The Modification Osince The Rough Er Helps Modify Proteins That Will Be Secreted From The Cell, Cells Whose Job Is To Secrete Large Amounts Of Enzymes Or Other Proteins, Such As Liver Cells, Have Lots Of Rough Er. Smooth Er The Smooth Endoplasmic Reticulum (Smooth Er) Is Continuous With The Rough Er But Has Few Or No Ribosomes On Its Cytoplasmic Surface. Functions Of The Smooth Er Include: Synthesis Of Carbohydrates, Lipids, And Steroid Hormones Detoxification Of Medications And Poisons Storage Of Calcium Ions In Muscle Cells, A Special Type Of Smooth Er Called The Sarcoplasmic Reticulum Is Responsible For Storage Of Calcium Ions Which Are Needed To Trigger The Coordinated Contractions Of Muscle Fibers. There Are Also Tiny "Smooth" Patches Of Er Found Within The Rough Er. These Patches Serve As Exit Sites For Vesicles Budding Off From The Rough Er And Are Called Transitional Er . The Golgi Apparatus When Vesicles Bud Off From The Er, Where Do They Go? Before Reaching Their Final Destination, The Lipids And Proteins In The Transport Vesicles Need To Be Sorted, Packaged, And Tagged So That They Wind Up In The Right Place. This Sorting, Tagging, Packaging, And Distribution Takes Place In The Golgi Apparatus (Golgi Body), An Organelle Made Up Of Flattened Discs Of Membrane. Micrograph Of The Golgi Apparatus Showing A Series Of Flattened Membrane Discs In Cross-Section _image Credit: "The Endomembrane System And Proteins: Figure 3" By Openstax College, Biology (Cc By 3.0), Modification Of Work By Lousia Howard_ The Receiving Side Of The Golgi Apparatus Is Called The Cis Face And The Opposite Side Is Called The Trans Face. Transport Vesicles From The Er Travel To The Cis Face, Fuse With It, And Empty Their Contents Into The Lumen Of The Golgi Apparatus. As Proteins And Lipids Travel Through The Golgi, They Undergo Further Modifications. Short Chains Of Sugar Molecules Might Be Added Or Removed, Or Phosphate Groups Attached As Tags. Carbohydrate Processing Is Shown In The Diagram As The Gain And Loss Of Branches On The Purple Carbohydrate Group Attached To The Protein. Image Showing Transport Of A Membrane Protein From The Rough Er Through The Golgi To The Plasma Membrane. The Protein Is Initially Modified By The Addition Of Branching Carbohydrate Chains In The Rough Er; These Chains Are Then Trimmed Back And Replaced With Other Branching Chains In The Golgi Apparatus. The Protein, With Its Final Set Of Carbohydrate Chains, Is Then Transported To The Plasma Membrane In A Transport Vesicle. The Vesicle Fuses With The Plasma Membrane, Its Lipids And Protein Cargo Becoming Part Of The Plasma Membrane. _image Modified From "The Endomembrane System And Proteins: Figure 1" By Openstax College, Biology (Cc By 3.0), Modification Of Work By Magnus Manske_ Finally, The Modified Proteins Are Sorted (Based On Markers Such As Amino Acid Sequences And Chemical Tags) And Packaged Into Vesicles That Bud From The Trans Face Of The Golgi. Some Of These Vesicles Deliver Their Contents To Other Parts Of The Cell Where They Will Be Used, Such As The Lysosome Or Vacuole. Others Fuse With The Plasma Membrane, Delivering Membrane-Anchored Proteins That Function There And Releasing Secreted Proteins Outside The Cell. Cells That Secrete Many Proteins—Such As Salivary Gland Cells That Secrete Digestive Enzymes, Or Cells Of The Immune System That Secrete Antibodies—Have Many Golgi Stacks. In Plant Cells, The Golgi Apparatus Also Makes Polysaccharides (Long-Chain Carbohydrates), Some Of Which Are Incorporated Into The Cell Wall. Lysosomes The Lysosome Is An Organelle That Contains Digestive Enzymes And Acts As The Organelle-Recycling Facility Of An Animal Cell. It Breaks Down Old And Unnecessary Structures So Their Molecules Can Be Reused. Lysosomes Are Part Of The Endomembrane System, And Some Vesicles That Leave The Golgi Are Bound For The Lysosome. Lysosomes Can Also Digest Foreign Particles That Are Brought Into The Cell From Outside. As An Example, Let'S Consider A Class Of White Blood Cells Called Macrophages, Which Are Part Of The Human Immune System. In A Process Known As Phagocytosis, A Section Of The Macrophage’S Plasma Membrane Invaginates—Folds Inward—To Engulf A Pathogen, As Shown Below. Diagram Of Phagocytosis, In Which The Phagosome Generated By Engulfment Of A Particle Fuses With A Lysosome, Allowing Digestion Of The Particle. _image Credit: Modified From "The Endomembrane System And Proteins: Figure 4" By Openstax College, Biology (Cc By 3.0)_ The Invaginated Section, With The Pathogen Inside, Pinches Off From The Plasma Membrane To Form A Structure Called A Phagosome. The Phagosome Then Fuses With A Lysosome, Forming A Combined Compartment Where Digestive Enzymes Destroy The Pathogen. Vacuoles Plants Cells Are Unique Because They Have A Lysosome-Like Organelle Called The Vacuole. The Large Central Vacuole Stores Water And Wastes, Isolates Hazardous Materials, And Has Enzymes That Can Break Down Macromolecules And Cellular Components, Like Those Of A Lysosome. Plant Vacuoles Also Function In Water Balance And May Be Used To Store Compounds Such As Toxins And Pigments (Colored Particles). Lysosomes Vs. Peroxisomes One Point That Can Be Confusing Is The Difference Between Lysosomes And Peroxisomes. Both Types Of Organelles Are Involved In Breaking Down Molecules And Neutralizing Hazards To The Cell. Also, Both Usually Show Up As Small, Round Blobs In Diagrams. However, The Peroxisome Is A Different Organelle With Its Own Unique Properties And Role In The Cell. It Houses Enzymes Involved In Oxidation Reactions, Which Produce Hydrogen Peroxide ( ) As A By-Product. The Enzymes Break Down Fatty Acids And Amino Acids, And They Also Detoxify Some Substances That Enter The Body. For Example, Alcohol Is Detoxified By Peroxisomes Found In Liver Cells. Importantly, Peroxisomes—Unlike Lysosomes—Are Not Part Of The Endomembrane System. That Means They Don'T Receive Vesicles From The Golgi Apparatus. You Can Learn More About How Proteins Are Shipped To The Peroxisome In The Article On Protein Targeting.F Proteins And The Synthesis Of Lipids. It Consists Of A Network Of Membranous Tubules And Flattened Sacs. The Discs And Tubules Of The Er Are Hollow, And The Space Inside Is Called The Lumen. Rough Er The Rough Endoplasmic Reticulum (Rough Er) Gets Its Name From The Bumpy Ribosomes Attached To Its Cytoplasmic Surface. As These Ribosomes Make Proteins, They Feed The Newly Forming Protein Chains Into The Lumen. Some Are Transferred Fully Into The Er And Float Inside, While Others Are Anchored In The Membrane. Inside The Er, The Proteins Fold And Undergo Modifications, Such As The Addition Of Carbohydrate Side Chains. These Modified Proteins Will Be Incorporated Into Cellular Membranes—The Membrane Of The Er Or Those Of Other Organelles—Or Secreted From The Cell. If The Modified Proteins Are Not Destined To Stay In The Er, They Will Be Packaged Into Vesicles, Or Small Spheres Of Membrane That Are Used For Transport, And Shipped To The Golgi Apparatus. The Rough Er Also Makes Phospholipids For Other Cellular Membranes, Which Are Transported When The Vesicle Forms.

lipid soluble: Steroid hormones

Steroid Hormones

Steroid Hormones vs Non-Steroid Hormones

Part 9: Lipid-soluble Hormones (Steroid Hormones & Thyroid Hormones)

Chapter 17: The Endocrine System

Chapter 15: Lipids

fdjksl afdjs klejfsieofwjnervous system the body's speedy, electrochemical communication network, consisting of all the nerve cells of the peripheral and central nervous systems three critical features of the nervous system They receive input from the surrounding world. They process the info from the surroundings. They initiate responses to the internal and external environments, when necessary. neuron a nerve cell; the basic building block of the nervous system dendrites Branchlike parts of a neuron that are specialized to receive information. cell body Largest part of a typical neuron; contains the nucleus and much of the cytoplasm axon the extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands glial cell cells in the nervous system that support, nourish, and protect neurons nerves bundled axons that form neural "cables" connecting the central nervous system with muscles, glands, and sense organs how many neurons die everyday? 9,000 When neurons die can they be replaced? no what can kill neurons? alcohol intake, inhaling gas fumes neurons are what kind of cell eukaryotic what does the cell body contain nucleus, mitochondria, endoplasmic reticulum, and so on What does a dendrite do? receives information what does the axon do? carries impulses away from the cell body what does the cell body do? process information sciatic nerve nerve extending from the base of the spine down the thigh, lower leg, and foot How many more glial cells are there than neurons? 9x Do glial cells divide? yes glial cells act as a barrier for harmful things entering the brain blood brain barrier Blood vessels (capillaries) that selectively let certain substances enter the brain tissue and keep other substances out how is the blood brain barrier broken down hypertension, radiation, some infectious organisms sensory neurons neurons that carry incoming information from the sensory receptors to the brain and spinal cord. stimulations like temp, touch, taste, smell, light or sound motor neurons neurons that carry outgoing information from the brain and spinal cord to the muscles and glands Interneurons neurons within the brain and spinal cord that communicate internally and intervene between the sensory inputs and motor outputs. peripheral nervous system network of sensory cells modified to receive info from the environment and motor pathways that transmit signals to effectors, the muscles and glands capable of responding to that stimulus sensory pathway nerves coming from the sensory organs to the CNS consisting of afferent neurons motor pathways In the peripheral nervous system, common routes by which motor nerve impulses are transmitted. somatic nervous system the division of the peripheral nervous system that controls the body's skeletal muscles (voluntary) autonomic nervous system the part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). Its sympathetic division arouses; its parasympathetic division calms. (involuntary) sensory neurons alert the brain of a stimulus motor neurons help the brain to execute a response reflex signal that skips the brain, and goes to stimulate the motor neuron. direct sensory response autonomic nervous system helps us with homeostasis sympathetic nervous system the division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations parasympathetic nervous system the division of the autonomic nervous system that calms the body, conserving its energy dendrites recieve signals from external stimuli two ways dendrites receive stimuli through motor neurons and interneurons connecting with other neurons or directly from external stimulus resting potential of neuron its stable, negative charge when the cell is inactive action potential of neuron a very brief shift in a neuron's electrical charge that travels along an axon resting potential is produced as proteins within the neurons plasma membrane pump sodium ions out of the cell and potassium ions into the cell what ion goes into the cell potassium what ion goes out of the cell sodium how does the pumping of ions affect the charge of the cell? more positive on the outside more negative on the inside greater positive charge out of the cell makes the cell polarized when stimulated dendrites briefly open ion channels made of proteins which allow charged ions down the concentration gradient concentration gradient A difference in the concentration of a substance across a distance. when ion channels open the negative charge inside the cell is temporarily changed either decreasing or increasing changes in the cells electrical charge converge from the dendrites to the cell body when charges converge that is called action potential terminal buttons Small knobs at the end of axons that secrete chemicals called neurotransmitters axon terminals (terminal buttons) doe what i response to action potential release contents of vesicles, small sacks of chemicals inside the axon terminal into the space between cells which can influence nearby cells myelin sheath A layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next. as the action potential moves down the axon ion channels allow positively charged ions to rush in changing the charge to positive. other ion channels allow positively charged ions to rush out what restores the action potential ion channels letting the influx of positively charged ions to rush put Where are ion channels concentrated in the gaps in the myelin sheath fatty myelin is what color white fatty myelin shows up as white when tightly packed together regions of the brain with many cell bodies and dendrites appear what color gray multiple sclerosis myelin sheath destruction. disruptions in nerve impulse conduction little myelin causes the neurons to lose its ability to conduct electrical impulses which makes it harder for the brain to send signals to muscles synapse the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron at a synapse and neurons interacts with another cell What happens at a synapse? When a nerve impulse reaches the synapse at the end of a neuron, it cannot pass directly to the next one. Instead, it triggers the neuron to release a chemical neurotransmitter. The neurotransmitter drifts across the gap between the two neurons. sacs called vesicles release neurotransmitters into the synaptic cleft synaptic cleft The narrow gap that separates the presynaptic neuron from the postsynaptic cell. what happens when the action al potential reaches the axon terminal? little sacks called vesicles merge with axon cell membrane axon cell membrane presynaptic membrane the vesicles open and release chemicals called neurotransmitters neurotransmitters send a signal to the cell receiving the signal after sending a signal to a cell the neurotransmitters diffuse away and binds to nearby receptor sites after neurotransmitters diffuse the gates open in the post synaptic cell membrane and the signal enters the post synaptic cell after the signal enters a new neurotransmitter is released from the post synaptic cell receptors and is recycled or broken down what are neurotransmitters broken down by enzymes found in the synaptic cleft when a postsynaptic cell is a muscle cell it contracts when a postsynaptic cell is a gland it secretes how do neurotransmitters affect the neuron by causing it to fire on its own action potential or receives the likelihood of it firing on its own action potential what a neurotransmitter does to a neuron is decided by receptor the ability for neurons to not fire helps with filtering overwhelming sensory info such as a concert Acetylcholine A neurotransmitter that enables learning and memory and also triggers muscle contraction Acetylcholine is released by motor neurons at the point where they synapse with muscle cells Botulinum toxin an acetylcholine antagonist; prevents release by terminal buttons. most toxic substance known what does botox do blocks release of acetylcholine so less contractions in muscles =less wrinkles glutamine involved with learning and memory, more sensitive to glutamine, better memory and learning dopamine influences movement, learning, attention, and emotion. loss of is responsible for parkinson's. chief of happiness serotonin Affects mood, hunger, sleep, and arousal who makes serotonin more? men cocaine a powerful and addictive stimulant, derived from the coca plant, producing temporarily increased alertness and euphoria. tricks pleasure center in brain and binds with presynaptic membrane where dopamine is usually reabsorbed from the synaptic cleft. blocks reuptake sites dopamine remains in cleft repeatedly stimulating it prozac and zoloft block serotonin from being reabsorbed and recycled by presynaptic cells which prolongs it affect Selective Serotonin Reuptake Inhibitors (SSRIs) a group of second-generation antidepressant drugs that increase serotonin activity specifically, without affecting other neurotransmitters morphine and heroin mimic endorphins and bind to receptor sites. in high doses gives endorphins rush which causes euphoria. slows down respiratory rate and can be fatal nicotine mimics acetylcholine by binding to the same receptors and release adrenaline and other stimulating chemicals. rapid surges the rapid depletions of these chemicals make smokers want another cigarette drugs become addictive because the body's think that there is more natural amounts of usual neurotransmitters. reduces sensitivity to drugs, needing more to have the same reaction DRD4 gene that encodes a certain class of dopamine receptor. It can be mutated for those seeking sensation, altering the mesolimbic pathway and the way sensations are rewarded caffeine a mild stimulant found in coffee, tea, and several other plant-based substances cellular waste products takes form of a variety of molecules such as adenosine adenosine when binds with receptor reduces the likelihood of a neuron initiating an action potential as more adenosine binds with more receptors we feel tired when we sleep cellular waste products are reabsorbed and recycled effects of alcohol slowed down reactions slurs speech by blocking receptors for glutamate, provides buzz by blocking dopamine reuptake, blocks pain by stimulating the release of endorphins, increases feeling of happiness by modifying the efficiency of serotonin receptors muscles generate force through contraction skeletal muscle is attached to bones by connective tissue and is controlled by individual neurons attached to each muscle fiber cardiac muscles causes the heart to pump blood blood through the body smooth muscle, involuntary, surrounds blood vessels and many internal organs which help to move blood, move food through digestive system myofibrils cylindrical organelle within muscle cells that can contract; contains repeating units, called sarcomeres in which the contraction takes place Sarcomere the fundamental unit of muscle contraction , made of actin myosin actin protein of muscle tissue; makes up the thin filaments myosin protein of muscle tissue, making up the thick filaments muscle fiber contraction Results from a sliding movement where the actin and myosin filaments merge using ATP. Globular portions of the myosin filaments can form cross-bridges with actin filaments. Reaction between actin and myosin filaments generates the force of contraction. First step of sarcomere contraction detach, link between myosin and a parallel action filament is broken as a molecule of ATP bonds to myosin Second step of sarcomere contraction reach, as the atp breaks down, energy released alters the shape of the myosin into a higher energy shape and myosin now reaches farther down the actin filament Third step of Sarcomere contraction reattach, the myosin reattaches to the actin filament at this new location Fourth step of Sarcomere contraction pull back, the myosin then snaps back to its original shape, pulling the actin filament as it does so and shorting the fiber relaxed sarcomere Actin & Myosin myofilaments lie side by side contracted sarcomere the Z lines are close together duration between contraction and relaxation is called twitch fast twitch muscle fibers that react quickly and fatigue quickly slow twitch type of muscle that contracts slowly and is fatigue resistant Oxytocin peptide hormone, produced in neurons within the hypothalamus and released by the posterior pituitary, influences trust in others, increases the social attachments, directs the ejection of breast milk, and contractions in the uterus during childbirth synthesis site of oxytocin hypothalamus target tissues of oxytocin uterus and mammary glands effect of oxytocin Effects uterus - uterine contractions during labor, direct myometrium, other effects are on limbic system in both men and women increased by touch - reflects on bonding and trust hormones chemical messengers that are manufactured by the endocrine glands, travel through the bloodstream, and affect other tissues two systems for carrying out communication nervous and endocrine endocrine system the body's "slow" chemical communication system; a set of glands that secrete hormones into the bloodstream endocrine cells produce regulatory hormones target cells cells that have receptors for a particular hormone endocrine glands Glands of the endocrine system that release hormones into the bloodstream endocrine gland examples pituitary, thyroid, parathyroid, adrenal, pineal hormones help regulate homeostasis pheromones Chemical signals released by an animal that communicate information and affect the behavior of other animals of the same species. such as sexual reproduction and territory marking step one of how a hormone affect a certain cell signal is sent by a hormone being released from a gland step two of how a hormone affects a certain cell signal is received, although the hormone has no effect on most tissues it comes in contact with, cells with the right receptor in their cytoplasm or on their plasma membrane receives the signal step three of how a hormone affects a certain cell cell responds, hormone binds to receptor, causes response in target cell, can be change in gene expression in nucleus, can cause cell to start or stop producing a certain protein, alter rate of producing protein amines hormones adrenaline, hormones that are synthesized from single amino acids polypeptide hormones insulin and glucagon, chains of amino acids steroid hormones estrogen and testosterone, lipids lipid Energy-rich organic compounds, such as fats, oils, and waxes, that are made of carbon, hydrogen, and oxygen. most amines and polypeptide hormones are — while lipids are not water soluble amines and polypeptide hormones — pass through memebrane cannot lipids —pass through membranes can amines and polypeptide hormones bind to receptors embedded within the cell membrane which can influence inside the cell steroids hormones bind to receptors within the cytoplasm or nucleus of the cell, always passes into nucleus once a steroid is in the nucleus it binds to DNA, influencing gene expression paracrine receptors target cell receptors for a specific hormone can be nearby hormones secreted by glands in one part of the body are able to regulate cell function in another part of the body Prostaglandins Modified fatty acids that are produced by a wide range of cells. dilation or construction of blood vessels and affecting tissue inflammation what does asprin do Inhibits prostaglandins, decreases inflammation, and slows transmission of pain to site of injury Hypothalamus underside of brain, functions as liaison between the nervous and endocrine systems and it receives input from neurons throughout the brain and rest of body. sends out appropriate hormones to regular nearly every aspect of the organisms physiology, including body temp, hunger. thirst, and water balance pituitary gland The endocrine system's most influential gland. Under the influence of the hypothalamus, the pituitary regulates growth and controls other endocrine glands. posterior pituitary gland also known as the neurohypophysis; it is made up of nervous tissue/neurons and stores and secretes 2 hormones made by the hypothalamus (oxytocin and ADH); it is controlled by action potentials from the hypothalamus antidiuretic hormone (ADH) influences the absorption of water by kidney tubules anterior pituitary produced many hormones such as TSH, LH, FSH, prolactin, ACTH Thyroid Stimulating Hormone (TSH) causes thyroid to produce thyroxine, important in cellular respiration Follicle-stimulating hormone (FSH) stimulates development of follicles in ovaries and sperm maturation Lutenizing hormone (LH) triggers ovulation and stimulates testosterone production, works with FSH prolactin stimulates mammary glands to produce milk Adrenocorticotropic hormone (ACTH) Stimulates adrenal glands to produce cortisol and other stress related hormones Corticotropin-releasing hormone (CRH) Promotes secretion of adrenocorticotropic hormone (ACTH) growth hormone several effects, stimulating liver to release chemicals that spur growth of bones, cartilage, and other tissues excessive production of growth hormone during childhood can cause extreme growth called gigantism increased exposure to growth hormone in adulthood results in hands, face, feet growing unusually absence of growth hormone dwarfism how is pituitary dwarfism treated if caught early? shots of human growth hormone pineal gland secretes melatonin regulates sleep cycles thyroid gland releases thyroxine, influences the rate and efficient of cellular metabolism, regulates calcium levels in blood parathyroid glands regulate calcium levels in blood adrenal glands release adrenaline and cortisol (prepares body for action), regulate organisms response to stress. sit right above kidneys. pancreas releases insulin and glucagon, maintains blood glucose levels wishing a narrow range gonads release the sex steroids, including testosterone, estrogen, and progesterone, responsible for numerous physical, behavioral, and emotional features, including much sexual behavior, development, and growth Under active thyroid fatigue and weight gain overactive thyroid jitteriness, rapid heartbeat, weight loss, irritability when iodine intake is low, the thyroid is unable to produce thyroxine which causes thyroid to swell Calcitonin Lowers blood calcium levels insulin A hormone produced by the pancreas or taken as a medication by many diabetics negative feedback A primary mechanism of homeostasis, whereby a change in a physiological variable that is being monitored triggers a response that counteracts the initial fluctuation. positive feedback Feedback that tends to magnify a process or increase its output. endocrine disrupters Chemicals that disrupt normal hormone functions Polychlorinated biphenyls (PCBs) A group of industrial compounds used to manufacture plastics and insulate electrical transformers, and responsible for many environmental problems. Phthalates found in cosmetics, deodorants, and many plastics used for food packaging, children's toys, and medical devices. Cause kidney & liver damage, cancer, and low sperm counts. Bisphenol A (BPA) a substance widely used in plastics and to line food and drink cans, which has raised health concerns because it is an estrogen mimic endocrine disrupters effect on mammals reproductive harm endocrine disrupters effect on fish reproductive functioning endocrine disrupters effect on invertebrates defective shells, masculinization of female genitalia, reducing fertility oxytocin posterior pituitary, uterus, breast, brain, reduce stress, more trusting "love hormone" antidiuretic hormone (ADH) posterior pituitary, kidneys, water retention in kidneys Thyroid Stimulating Hormone (TSH) anterior pituitary, thyroid, stimulates production of thyroxine, important in cellular respiration Follicle-stimulating hormone (FSH) anterior pituitary, ovaries, testes, stimulates ovary development and sperm maturation prolactin anterior pituitary, mammary glands, milk production growth hormone anterior pituitary, liver and other organs, stimulates release of chemicals that spur growth of bones, cartilage, and other tissues cortisol and adrenaline adrenal glands, smooth, cardiac, skeletal muscle, blood vessels, cell throughout body, imitates response to stress, regulates response to long term stress melatonin pineal gland, brain, regulate sleep cycle thyroxine thyroid, cells throughout body, influenced metabolic spew and efficiency calcitonin and parathyroid hormone thyroid, bones, causes bones to pick up excess calcium in blood insulin pancreas, liver, adipose tissue, skeletal muscle, take up glucose in blood which reduces its level glucagon pancreas, liver, adipose tissue, concert stored glycogen into glucose estrogen, testosterone, progesterone gonads, cells uterus, breasts, balls, puberty, pregnancy, sperm production, egg production heritable sensory autonomic neuropathy condition in which afflicted individual cannot feel pain sensory neurons affected by skin and joints affected by syphilis Interneurons are affected by parkinsons motor neurons are affected by polio Oligodendrocytes Type of glial cell in the CNS that wrap axons in a myelin sheath. Microglia Act as phagocytes, eating damaged cells and bacteria, act as the brains immune system astrocyte release gliotransmitters by expcytosis to send signals to neighboring neuron connectomes Map of the network of connections between neurons in the human brain resting potential -70 mV action potential +30 mV (depolarized) Channelopathies diseases and disorders that are the result of ion channel dysfunction Tetrodotoxin -Poisoning can result from ingestion of poorly prepared puffer fish (exotic sushi) -Highly potent toxin that binds fast voltage-gated Na+ channels in cardiac and nerve tissue, preventing depolarization - blocks action potential without changing resting potential (same mechanism as Lidocaine) -Causes nausea, diarrhea, paresthesias, weakness, dizziness, loss of reflexes. -Treatment is primarily supportive. epilepsy potassium channel mutations, muscle weakness the synapse excitatory neurotransmitters chemicals released from the terminal buttons of a neuron that excite the next neuron into firing inhibitory neurotransmitters chemicals released from the terminal buttons of a neuron that inhibit the next neuron from firing GABA An inhibitory neurotransmitter in the brain. caffeine — glutamine and — GABA activity increases, decreases Alcohol — GABA activity and — Glutamate activity increases, decreases functions of muscle generate movement, force, heat, homeostasis 2 mutates copies of them upstairs gene causes excess muscle build up muscle is composed of bundles of muscle fibers bundles of muscle fibers are composed of muscle fibers muscle fibers are composed of myofibrils myofibrils are composed of actin and myosin actin and myosin are composed of sarcomere slow fiber muscle is dark mest fast fiber muscle is light meat motor unit A motor neuron and all of the muscle fibers it innervates rigor mortis stiffness after death caused by lack of ATP, muscle remains in a state of contraction acromegaly abnormal enlargement of the extremities during adulthood when exposed to excess growth hormone Addison Disease low levels of cortisol, autoimmune disease, depression, dizziness, low blood glucose, low blood pressure chronic stress excess cortisol, high blood glucose, obesityfdwkqfejifijeoiefowojk