The Endocrine System

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The Endocrine System

• Dr. Tamie Lieto

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Endocrine

• Endowithin
• Krino separate
• The word implies that intercellular chemical
  signals are produced within and secreted from
  endocrine glands, but that the chemical signal
  have effects at locations that are away from or
  or separate from the endocrine glands that
  secrete them. The chemical signals are
  transported by way of the blood

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Hormones

• Hormones the intercellular chemical signals
  that are secreted by the endocrine glands
• Hormone means set in motion because hormones
  set things in motion
• Hormones are distributed in the blood to all
  parts of the body BUT only certain tissues called
  Target tissues respond

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Regulation of Hormone Secretion

• Negative Feed Mechanism based on the following
  blood levels of chemicals
• eg glucose and insulin
• hormones
• eg some hormones control other
  hormones
• Nervous System
• eg epinephrine is released from
  adrenal medulla because of nervous stimulation

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Endocrine Glands and Their Hormones

• Look at Table 10.3 Endocrine Glands, Hormones
  and their Target Tissues

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Classification of Hormones

• Proteins/ Amino Acids
• thyroid
• posterior pituitary
• Lipids
• Steroids
• Eicosanoids

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Pituitary Gland

• The pituitary gland is located posterior to the
  optic chiasm and beneath the hypothalamus.
• It is connected to the hypothalamus by a stalk
  called the infundibulum
• It is divided into anterior and posterior parts
• It is part of the Hypothalamus Pituitary Axis

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Pituitary Gland
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Pituitary

• The Pituitary Gland is divided into
• Anterior and Posterior Parts
• Hormones from the pituitary control control the
  function of many other endocrine glands
• such as the ovaries , testes, thyroid gland and
  adrenal coortex
• Also secretes hormones that affect growth, kidney
  function, birth and milk production by the breast
• Release of Hormones from the Pituitary is under
  the control of the Hypothalamus

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Hormones secreted by the Pituitary

• Growth Hormone- stimulates growth of bone and
  organs by increasing protein synthesis
• It resists protein breakdown during food
  deprivation and promotes fat breakdown instead
• Growth hormone is under the control of Growth
  hormone releasing factor (GHRF) and Growth
  Hormone Inhibiting Factor)

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Hormones secreted from the pituitary gland

• AnteriorPituitary
  Posterior Pituitary
• 
  Antidiuretic Hormone
• Growth Hormone
  Oxytocin
• Thyroid stimulating hormone
• (TSH)
• Adrenocorticotrophic hormone
• ( ACTH)
• Melanocyte Stimulating hormone
• Luteinizing Hormone
• Follicle Stimulating Hormone
• Prolactin

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Growth Hormone (GH)

• Growth Hormone- increases protein synthesis
  and growth of tissue and organs, breakdown of
  lipids, and release of fatty acids, increase
  blood glucose levels
• Target Tissue Most Tissue

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Deficient of Growth HormonePituitaryDwarfism
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Excess Growth HormoneGigantism

• Exces growth hormone can
• result from hormones secreting
• tumors of the pituitary gland

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Acromegaly

• IF growth hormone continues to be in excess after
  the growth plates are closed bones will grow
  wider . This condition is called acromegaly

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Thyroid Stimulating Hormone (TSH)

• Thyroid Stimulating Hormone (TSH)
• Target tissue binds to the receptors on the
  thyroid gland and causes the thyroid gland to
  secrete thyroid hormone
• Too much TSH over stimulates the
  Thyroid gland ( enlarges)
• Too little TSH under stimulates the
  Thyroid gland (Shrinks)
• TSH is under the control of the Thyroid
  Releasing Hormone released form the
  hypothalmus

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Adrenocorticotropic Hormone ACTH

• Adrenocorticotropic Hormone
• Target Tissue Binds to receptors on the
  adrenal cortex gland and stimulates release of
  the Glucocorticoid hormones such as cortisol
• Target Tissue Binds to melanocytes in
  the skin and increase skin pigmentaion
• ACTH is under the control of the ACTH
  releasing hormone secreted by the hypothalmus

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Gonadotropins

• Target Tissue Bind to the receptors on the
  gonads(ovaries and testes)
• Luteinizing Hormone
• Follicle Stimulating Hormone
• Under control by the GNRH or gonadotropin
  releasing hormones of the hypothalamus

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Luteinizing Hormone (LH)

• Females- target tissue ovary, promotes ovulation
  and progesterone in the ovary
• Males- target tissue testis, causes
  testosterone synthesis and supports sperm cell
  production in testis
• t

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Follicle Stimulating Hormone (FSH)

• -Female
• Target tissue Follicles in ovary.
  Promotes follicle maturation and estrogen
  secretion in ovary.
• - Male
• Target tissue- Seminiferous tubules in
  male causing Sperm production

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Prolactin

• Female-
• Target Tissue receptors in the breast and
  ovary
• Helps promote breast development during
  pregnancy and stimulates the production of milk.
  Prolongs progesterone secretion following
  ovulation and during pregnancy.
• Male - Target tissue-testis increses
  sensitivity to LH
• Under control of the releasing hormones from the
  hypothalamus

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Site of Prolactin Action is the Mammary Gland
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Melanocyte Stimulating Hormone (MSH)

• Target Tissue MSH binds to receptors on the
  skin and increase the production of melanocytes
  causing them to synthesize melanin
• Causes the skin to darken
• Under the control of releasing hormones that
  increase or decrease its production

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Antidiuretic Hormone

• ADH
• Target Tissue binds to receptors in the kidney
  that increase water reabsorption by kidney
  tubules. This results in less water loss as
  urine.

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Oxytocin

• Target Tissue Binds to membrane bound receptors
  in uterus and mammary glands.
• Causes contraction of the smooth muscle in the
  uterus and milk let down in breast

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The Thyroid

• made up of two lobes connected by a
  narow band called the ithmus
• lobes are on either side of the trachea
• highly vascular
• contains follicles filled with the protein
  hormone
• Secretes Thyroid Hormone

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Thyroid Hormone

• Target Tissue most cells of the body
• regulates your rate of metabolism
• also important for growth and
  development
• The thyroid gland requires iodine to synthesize
  thyroid hormone
• deficiency of iodine in the diet can lead
  to thyroid hormone deficiency
• regulation is through feed back
  mechanism Fig10.14

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Hypothalamus-Pituitary- Thyroid Axis
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• Lack of thyroid hormone is called Hypothyroidism

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• Excess amout of thyroid hormone can lead to
• GRAVES DISEASE

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Parathyroid Gland

• Four glands that are embedded in the posterior
  wall of the thyroid
• Secretes
• Parathyroid hormone
• Calcitonin
• hormones which regulates calcium metabolism

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Parathyroid Hormone

• Target tissue bone and kidney
• PTH binds to membrane bound receptors of
  cells and increases the absorption of calcium
  from the intestines which increases active
  Vitamin D
• PTH also causes the resorption by incresing
  the rate of bone breakdown by osteoclasts of bone
  tissue to release Ca (calcium) into the
  circulation and decreases the rate at which Ca is
  lost in the urine
• PTH acts on tissue to raise blood Calcium
  Levels to normal

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Calcitonin

• Target Tissue Bone
• Decreases the rate of bone breakdown,
  prevents large increase in blood calcium levels
  following a meal

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Adrenal Gland

• Divided into
• Adrenal Cortex (outer)
• Glucocorticoids (cortisol)
• Aldosterone
• Adrenal Androgens
• Adrenal Medulla
• Epinephrine and Norepinephrine

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Layers of the Adrenal Gland
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Arenal Cortex Hormones

• Mineralocorticoids- Aldosterone regulation of
  NA and K and water balance.
• Glucorticoids- Cortisol decreases inflammation,
  increases glucose
• Adrenal Androgens DHEA- axillary and pubic hair
  in females

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Excess Adrenal Androgens (DHEA) in females
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Cushing Syndrome ( excess cortisol)
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The Pancreas

• Both Endocrine and Exocrine Gland
• The Endocrine part
• pancreatic Islets which secrete
• insulin (beta cells)
• glucagon( alpha cells)

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Pancreatic Islet cells
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Blood Glucose control

• Under the control of insulin and glucagon
• It is very important to maintain blood glucose
  levels within a normal range of values.
• A decline in blood glucose level below its normal
  range causes the nervous system to malfunction
  because glucose is the nervous systems main
  source of energy

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Insulin

• Insulin is released from the beta cells primarily
  in response to the elevated blood glucose levels
  and increased parasympathetic stimulation that is
  associated with the digestion of a meal.
• Increased blood levels of certain amino acids
  also stimulate insulin secretion.
• Decreased insulin secretion results from
  decreasing blood glucose and from stimulation by
  the sympathetic division of the nervous system
  This allows blood glucose to be conserved to
  provide the brain with glucose.

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Glucagon

• Binds to receptors on liver cells and causes the
  release of glucose from glycogen
• The glucose is then released in the blood to
  increase blood glucose levels
• Glucagon secretion is reduced after a mealb

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Diabetes Mellitus Two Types

• Type I - secretion of too little insulin
  from the pancreas
• - onset childhood, very thin , require
  insulin
• Type 2 - insufficient numbers of insulin
  receptors on target cells or defective
  recepetors
• - adult onset, usually overweight, can
  take medications that help increase endogenous
  insulin activity.

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Diabetes Mellitus Type I The signs and symptoms

• As a result, tissues can not take up glucose
  and the blood becomes Hyperglycemic
• Satiety center responds as if there is no
  glucose and patients feeel hungry
• Excess glucose is secreted in urine and they
  become dehydrated
• Fats and protein become energy source and body
  wasting occurs

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Table 10.4

• Effects of Insulin and Glucagon on Target Tissue

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Testes and Ovaires

• Testes secrete testosterone- growth of male and
  development of male reproductive structures,
  muscle enlargement, hair, voice change and male
  sexual drive
• Ovaries secrete estrogen and progesterone- female
  characteristics
• Both are under control of FSH and LH form the
  pituitary

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Pineal Gland

• Small gland superior and posterior to the
  thalamus
• Secretes a hormone called melatonin which
  decreases LH and FSH by decreasing GNRH which may
  help regulate the onset of puberty by acting on
  the hypothalmus

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Thymus

• Secretes thymosin which enhances the ability of
  the immune system
• Thymosin helps in the production of the white
  cells ( called T cells)

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Other Hormones

• Prostaglandins- role in inflammation
• Erythropoietin-comes from kidney and stimulates
  red blood cell production
• HCG ( human chorionic gonadotropin) secreted by
  the placenta during pregnancy to maintain the
  pregnacy.

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Age Related Changed in the Endocrine System

• Age related changes include a gradual decrease
• GH inpeople who do not exercise
• Melatonin
• Thyroid Hormone
• Reproductive Hormones
• Thymus Hormones
• Increase in Diabetes

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