The Endocrine System

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The Endocrine System

• By Karl, Manny, Alondra, and Joseph

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The Endocrine System

• The endocrine system includes all of the glands
  of the body and the hormones produced by those
  glands. The glands are controlled directly by
  stimulation from the nervous system as well as by
  chemical receptors in the blood and hormones
  produced by other glands. By regulating the
  functions of organs in the body, these glands
  help to maintain the bodys homeostasis. Cellular
  metabolism, reproduction, sexual development,
  sugar and mineral homeostasis, heart rate, and
  digestion are among the many processes regulated
  by the actions of hormones.

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Hypothalamus and Pituitary Gland

• The hypothalamus regulates the internal
  environment.
• Example through the autonomic system it helps
  control heartbeat, body temperature, and water
  balance.
• Control the glandular secretions of the pituitary
  gland (hypophysis).
• A small pituitary glad is about 1cm in diameter
  and is connected to the hypothalamus by a stalk
  like structure.
• The pituitary consist of the posterior pituitary
  portion (neurohypophysis) and the anterior
  pituitary portion (adrenohypophysis)

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Posterior Pituitary

• Neurosecretory cells (neurons in hypothalamus)
  produce the antidiuretic hormone (ADH) and
  oxytocin.
• These hormones pass through the axons into the
  posterior pituitary where they are stored in axon
  endings.
• The hypothalamic hormone, antidiuretic hormone,
  and oxytocin are produced in the hypothalamus but
  are released into the bloodstream from the
  posterior pituitary.

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Antidiuretic hormone and Oxytocin

• ADH (antidiuretic hormone also known called
  vasopressin) also called vasopressin is released
  from the posterior pituitary
• Upon reaching the kidneys, ADH causes more water
  to be reabsorbed into kidney capillaries.
• as the blood become dilute once again ADH is no
  longer released
• an additional effect of ADH is to raise blood
  pressure by vasoconstruction of blood vessels
  through out the body
• inability to produce ADH causes diadetes
  insipidus (watery urine) in which a person
  produces copious amounts of urine with a
  resultant loss of ions from the blood
• oxytocin which is the other hormone made in the
  hypothalamus cause uterine contraction during
  childbirth and milk letdown when a baby is
  nursing

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Anterior Pituitary

• The portal system of two capillary networks or
  beds connected by a vein lies between the
  hypothalamus and the anterior pituitary
• The hypothalamus controls the anterior pituitary
  by providing hypothalamic-releasing hormones and
  hypothalamic-inhibiting hormones

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Hormones that affect other glands

• Three hormones produced by the anterior pituitary
  have an effect on other glands
• Thyroid-stimulating hormone (TSH) stimulates the
  thyroid to produce the thyroid horomones
• Adrenocorticotropic hormone (ACTH) stimulates the
  adrenal cortex to produce its hormones
• Gonadotropic Hormones stimulates the gonads, the
  testes in the males, and the ovaries in females
  to produce gametes and sex hormones
• The hypothalamus the anterior pituitary and
  other glands controlled by anterior pituitary are
  all involved in self-regulating negative feedback
  mechnism that maintain stable condition

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Effects of other hormones

• Other hormones produced by the anterior Pituitary
  do not affect other endocrine glands
• Prolactin (PRL) is produced at the beginning of
  the 5th month of a pregnancy
• It causes the mammary glands in the breast to
  develop milk
• Growth Hormones (GH) somatotropic hormone
  stimulates protein synthesis with in cartilage
  bone and muscle

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Effects of growth hormones

• If to little GH is produced during childhood they
  have pituitary dwarfism which are characterized
  by perfect proportions but small stature
• If to much GH is secreted then the person ca
  become a giant, which usually have poor health
  become secondary effect on blood sugar level

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Thyroid and parathyroid glands

• Thyroid Gland is a large gland located in the
  where it is attached trachea just below the
  larynx
• Is Composed f a large number of follicles each a
  small spherical structure made of thyroid cells
  filed with triiodothyronine which contains three
  iodine atom
• Thyroxine which four iodine atoms

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Effects of thyroid hormones

• The thyroid gland actively acquires iodine to
  produce triiodothyronine and thyroxine.
• If iodine is lacking in a diet the Thyroid glands
  are unable to produce thyroid hormones
• Constant stimulation by the anterior pituitary
  results in the thyroid enlarging, resulting in a
  simple, or endemic, goiter.
• Thyroid hormones do not have single target
  organs instead they stimulate all cells of the
  body to metabolize at a faster rate
• Congenital hypothyroidism undesecretion of
  thyroid hormone
• Hypothyroidism stocky and short in extreme cases
  since infancy or childhood.
• For adults with this condition its called
  mixedema, which is characterized by lethargy,
  weight gain, loss of hair, slower pulse rate,
  lowered body temperature, and thickness and
  puffiness of the skin.
• Hyperthyroidism oversecretion of thyroid hormone
  
• The thyroid gland is overactive and a
  exophthalimic goiter forms.
• Hyperthyroidism can also be caused by a thyroid
  tumor which is determined as a lump.
• Treatment is surgery with administration of
  radioactive iodine.

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Calcitonin

• Calcitonin a hormone secreted by the thyroid
  gland when the blood calcium level rises
• Primary effect is to bring the deposit of calcium
  in the bones (osteoclasts)
• Low calcium level stimulates the release of
  parathyroid hormones by the parathyroid glands
• Calcitonin can be used therapeutically in adults
  to reduce the effects of osteoporosis.

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Parathyroid glands

• Parathyroid Glands causes the blood phosphate
  level to derease and the ionic blood calcium
  level to increase
• The antagonistic actions of calcitonin from the
  thyroid gland and parathyroid glands maintain the
  blood calcium level within normal limits
• When insufficient parathyroid hormone production
  leads to a dramatic drop in blood calcium level,
  hypocalcmic tenani makes the body shake from
  continuous muscle contraction.
• The effect is brought by increased excitability
  of the nerves, which initiates nerve impulses
  spontaneously and without rest (severe cases can
  be fatal)

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Adrenal Glands

• The adrenal glands are a pair of roughly
  triangular glands found immediately superior to
  the kidneys. The adrenal glands are each made of
  2 distinct layers, each with their own unique
  functions the outer adrenal cortex and inner
  adrenal medulla.
• Adrenal cortex The adrenal cortex produces
  many cortical hormones in 3 classes
  glucocorticoids, mineralocorticoids, and
  androgens.
• 1. Glucocorticoids have many diverse functions,
  including the breakdown of proteins and lipids to
  produce glucose. Glucocorticoids also function to
  reduce inflammation and immune response.
• 2. Mineralocorticoids, as their name suggests,
  are a group of hormones that help to regulate the
  concentration of mineral ions in the body.
• 3. Androgens, such as testosterone, are produced
  at low levels in the adrenal cortex to regulate
  the growth and activity of cells that are
  receptive to male hormones. In adult males, the
  amount of androgens produced by the testes is
  many times greater than the amount produced by
  the adrenal cortex, leading to the appearance of
  male secondary sex characteristics.

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Adrenal Medulla

• The adrenal medulla produces the hormones
  epinephrine and norepinephrine under stimulation
  by the sympathetic division of the autonomic
  nervous system. Both of these hormones help to
  increase the flow of blood to the brain and
  muscles to improve the fight-or-flight response
  to stress. These hormones also work to increase
  heart rate, breathing rate, and blood pressure
  while decreasing the flow of blood to and
  function of organs that are not involved in
  responding to emergencies.

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Pancreas

• The pancreas is a large gland located in the
  abdominal cavity just inferior and posterior to
  the stomach. The pancreas is considered to be a
  heterocrine gland as it contains both endocrine
  and exocrine tissue. The endocrine cells of the
  pancreas make up just about 1 of the total mass
  of the pancreas and are found in small groups
  throughout the pancreas called islets of
  Langerhans. Within these islets are 2 types of
  cellsalpha and beta cells. The alpha cells
  produce the hormone glucagon, which is
  responsible for raising blood glucose levels.
  Glucagon triggers muscle and liver cells to break
  down the polysaccharide glycogen to release
  glucose into the bloodstream. The beta cells
  produce the hormone insulin, which is responsible
  for lowering blood glucose levels after a meal.
  Insulin triggers the absorption of glucose from
  the blood into cells, where it is added to
  glycogen molecules for storage.

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Adipose Tissue

• Adipose tissue produces the hormone leptin that
  is involved in the management of appetite and
  energy usage by the body. Leptin is produced at
  levels relative to the amount of adipose tissue
  in the body, allowing the brain to monitor the
  bodys energy storage condition. When the body
  contains a sufficient level of adipose for energy
  storage, the level of leptin in the blood tells
  the brain that the body is not starving and may
  work normally. If the level of adipose or leptin
  decreases below a certain threshold, the body
  enters starvation mode and attempts to conserve
  energy through increased hunger and food intake
  and decreased energy usage. Adipose tissue also
  produces very low levels of estrogens in both men
  and women. In obese people the large volume of
  adipose tissue may lead to abnormal estrogen
  levels.

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Other thyroid glands

• The body has many other endocrine glands, such as
  the testes in males and ovaries in females. The
  thymus and pineal glands produce hormones. Some
  tissues within organs produce hormones and/ or
  growth factors. Individual body cells produce
  local messenger chemicals called prostaglandin.
• Testes and Ovaries
• The testes are located in the scrotum, and the
  ovaries are located in the pelvic cavity. The
  testes produce androgens (i.e. testosterone),
  which are the male sex hormones. The ovaries
  produce estrogens and progesterone, the female
  sex hormones. The hypothalamus and pituitary
  gland control the hormonal secretions of these
  organs. (See page 208)

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Cont.

• Androgens
• Puberty is the moment in life when sexual
  maturation occurs. The greatly increased
  testosterone secretion during this time
  stimulates the growth of the penis and the
  testes. Testosterone also brings about and
  maintains the male secondary sex characteristics
  that develop during puberty, including the growth
  of a beard, axillary hair, and pubic hair. It
  prompts the larynx and vocal cords to enlarge,
  causing the voice to change. Its partially
  responsible for the muscular strength of males.
  This is why some athletes take large amounts of
  anabolic steroids. (See page 220). Testosterone
  also stimulates oil and sweat glands in the skin
  therefore its largely responsible for acne and
  body odor. Another side effect of testosterone is
  baldness. Genes for baldness are probably
  inherited by both sexes, but baldness is seen
  more in males due to the presence of
  testosterone.
• Estrogen and Progesterone
• The female sex hormones have many effects on the
  body. In particular, estrogens secreted during
  puberty stimulate the growth of the uterus and
  the vagina. Estrogen is necessary for ovum
  maturation and its largely responsible for the
  secondary sex characteristics in females,
  including female body hair and fat distribution.
  The pelvic girdle is wider in females than it is
  in males, resulting in a larger pelvic cavity.
  Both estrogen and progesterone are needed for
  breast development and for regulation of the
  uterine cycle, which includes monthly

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Thymus Gland

• The lobular thymus gland, which lies just beneath
  the sternum, reaches its largest size and is most
  active during childhood. (See figure 10.1). When
  lymphocytes pass complete development in the
  thymus, theyre transformed into thymus-derived
  lymphocytes, or T-lymphocytes. The lobules of the
  thymus gland are lined by epithelial cells that
  secrete hormones called thymosins. This hormone
  aids in the differentiation of lymphocytes packed
  inside the lobules.

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Pineal gland

• The pineal gland, which is located in the brain,
  produces the hormone melatonin, primarily at
  night. (See figure 10.1). Melatonin is involved
  in our daily sleep-wake cycle normally we grow
  sleepy at night when melatonin levels increase
  and awake once daylight returns and melatonin
  levels decrease. (See figure 10.15). Daily
  24-hour cycles such are this are called circadian
  rhythms. Circadian rhythms are controlled by an
  internal timing mechanism called a biological
  clock. Based on animal research, it appears that
  melatonin also regulates sexual development.
  Its also been noted that children whose pineal
  gland has been destroyed due to a brain tumor
  experience early puberty.
• Hormones from Other Tissues
• We previously mentioned that the heart produces
  atrial natriuretic hormone (see page 214). The
  kidney also influences the cardiovascular system
  function by producing the hormone erythropoietin
  (EPO), which stimulates red blood cell
  reproduction by the bone marrow.

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Leptin

• Leptin is a protein hormone produced by adipose
  tissue. Leptin acts on the hypothalamus, where
  its signals satiety- that the individual has had
  enough to eat. Oddly, the blood of obese
  individuals may be rich in leptin. It may be
  possible that the leptin that they produce is
  ineffective because of a genetic mutation, or
  else their hypothalamic cells lack a suitable
  number of receptors for leptin.

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Growth factors

• Many different types of organs and cells produce
  peptide growth factors, which stimulate cell
  division and mitosis. Some, like lymphokines are
  released into the blood others diffuse into
  nearby cells. These growth factors include
• Granulate and macrophage colony-stimulating
  factor (GM-CSF) is secreted by many different
  tissues. GM-CSF causes bone marrow stem cells to
  form either granulocyte or macrophage cells (both
  are forms of white blood cells), depending on
  whether the concentration is high.
• Platelet derived growth factor is released from
  platelets and from many other cell types. It
  helps in wound healing and causes an increase in
  the number of fibroblasts, smooth muscle cells,
  and certain cells of the nervous system.
• Epidermal growth factor and nerve growth factor
  stimulate the cells indicated by their names, as
  well as many others. These growth factors are
  also important in wound healing.
• Tumor angiogenesis factor stimulates the
  formation of capillary networks and is released
  by tumor cells. One treatment for cancer is to
  halt the activity of this growth factor.

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Prostaglandins

• Prostaglandins are potent chemical signals
  produced within cells by arachidonate, a fatty
  acid. Prostaglandins arent distributed in the
  blood. Instead, they work close to where theyre
  produced. In the uterus, prostaglandins cause
  muscles to contract and are involved with the
  pain and discomfort of menstruation. They also
  mediate the effects of pyrogens, chemicals that
  are believed to reset the temperature regulatory
  center in the brain. For example, aspirin reduces
  body temperature and controls pain because of its
  effect on prostaglandins. Some prostaglandins can
  reduce gastric and have been used to treat
  ulcers. Others lower blood pressure and have been
  used to treat hypertension. And others still
  inhibit platelet aggregation and have been used
  to prevent thrombosis (the formation of
  stationary clots in blood vessels). However,
  different prostaglandins have contrary effects,
  and its very difficult to standardize their use.

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Effects of Aging

• Thyroid disorders and diabetes are the most
  significant endocrine problems affecting health
  and function as we age. Both hypo- and
  hyperthyroidism are seen in the elderly. Graves
  disease is an autoimmune disease that targets the
  thyroid, resulting in symptoms of cardiovascular
  disease, increased body temperature and fatigue.
  A person may also experience weight loss of as
  much a 20 pounds, depression and mental
  confusion. Hypothyroidism (myxedema) may fail to
  be diagnosed because they symptoms may simply be
  attributed to the process of aging (hair loss,
  mental deterioration, and skin changes). The true
  incidence of IDDM (insulin-dependent, commonly
  referred to as Type-1 diabetes) diabetes among
  the elderly is unknown. Its symptoms can be
  confused with those of other medical conditions
  that are present.. As in all adults, NIDDM
  (non-insulin-dependent, mellitus type-2 diabetes)
  diabetes is associated with being overweight and
  often can be controlled by proper diet.

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Medical focus

• Side Effects of Anabolic Steroids
• The story amazed major league baseball across the
  world baseball sluggers - homerun hitters who
  had set new records for baseball were
  implicated in a scandal involving abuse of
  anabolic steroids. In testimony before the U.S.
  House of Representatives in March 2005, Mark
  McGwire of the St. Louis Cardinals, denied using
  steroids during his baseball career, and stood by
  his hitting records. However, other players, most
  notably, Jose Canseco and Jason Giambi, admitted
  using PEDs (performance-enhancing drugs). During
  the hearings, Congressional officials announced a
  ten-game suspension for players who texted
  positive for steroids. Many legislators
  questioned whether the records created by those
  who tested positive should be allowed to stand.
  The most tremendous concern to the general
  public, is the increased use of steroids by teens
  wanting to bulk up quickly, probably wanting to
  be just like the athletes they admire. Anabolic
  steroids are synthetic forms of testosterone.
  Taking doses 10 to 100 times the amount
  prescribed by doctors for illnesses promotes
  larger muscles when the person also exercises.
  Trainers were probably the first to acquire
  steroids for weight lifters, body builders, and
  other athletes, like professional baseball
  players. However, being on steroids can have
  adverse effects. Men experience decreased sperm
  counts and decreased sexual desire due to
  reduction of the size of the testis. Some develop
  an enlarged prostate, or grow breasts. On the
  other hand, women can develop male sexual
  characteristics, such as hair on their chests and
  faces, balding, and most experience and abnormal
  enlargement of the clitoris. Some stop ovulation
  and/or menstruating, sometimes permanently.
  Researchers predict that two or three months of
  high-dosage use of steroids as a teen can cause
  death by 30 or 40. Steroids have been linked to
  heart disease in both sexes and implicated in the
  deaths of young athletes from liver cancer and
  kidney problems. Steroids cause the body to
  retain fluid, which results in increased blood
  pressure. Users normally try to get rid of
  steroid bloat by taking large doses of
  diuretics (A diuretic is any substance that
  promotes the production of urine. All diuretics
  increase the excretion of water from bodies,
  although each class does so in a distinct way). A
  young California weight lifter had a fatal heart
  attack after using steroids, and the post-mortem
  report showed a lack of electrolytes, salts that
  help regulate the heart. And lastly, steroid
  abuse has psychological effects, like depression,
  hostility, aggression, and eating disorders.
  Unfortunately, these drugs cause the user to feel
  invincible. One particular abuser had his friend
  record him as he drove his car at 40 miles an
  hour into a tree. (Look at fig 10B). The FDA
  (Federal Food and Drug Administration now bans
  most steroids, and steroid use has been banned by
  the National Collegiate Athletic Association
  (NCAA), the National Football League (NFL), and
  the International Olympic Committee (IOC).

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Homeostasis

• The endocrine system works alongside of the
  nervous system to form the control systems of the
  body. The nervous system provides a very fast and
  narrowly targeted system to turn on specific
  glands and muscles throughout the body. The
  endocrine system, on the other hand, is much
  slower acting, but has very widespread, long
  lasting, and powerful effects. Hormones are
  distributed by glands through the bloodstream to
  the entire body, affecting any cell with a
  receptor for a particular hormone. Most hormones
  affect cells in several organs or throughout the
  entire body, leading to many diverse and powerful
  responses.

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Hormonal regulation

• The levels of hormones in the body can be
  regulated by several factors. The nervous system
  can control hormone levels through the action of
  the hypothalamus and its releasing and inhibiting
  hormones. For example, TRH produced by the
  hypothalamus stimulates the anterior pituitary to
  produce TSH. Tropic hormones provide another
  level of control for the release of hormones. For
  example, TSH is a tropic hormone that stimulates
  the thyroid gland to produce T3 and T4. Nutrition
  can also control the levels of hormones in the
  body. For example, the thyroid hormones T3 and T4
  require 3 or 4 iodine atoms, respectively, to be
  produced. In people lacking iodine in their diet,
  they will fail to produce sufficient levels of
  thyroid hormones to maintain a healthy metabolic
  rate. Finally, the number of receptors present in
  cells can be varied by cells in response to
  hormones. Cells that are exposed to high levels
  of hormones for extended periods of time can
  begin to reduce the number of receptors that they
  produce, leading to reduced hormonal control of
  the cell.

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