ENDOCRINE SYSTEM

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ENDOCRINE SYSTEM

• Endocrine glands secrete chemical messages into
  the blood stream that affects distant specific
  target tissues
• Endocrine Glands are small in size (less than
  1/10th and kg total) but big in maintaining
  homeostasis.
• HORMONES- chemical messengers released into the
  blood stream that direct activities in the bodys
  cells
• FUNCTIONS
• Reproduction
• Growth and development
• Body defense system
• Maintain electrolyte, water, and nutrient balance
• Regulate cellular metabolism

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3 CLASSES OF HORMONES

• 1. Amino acid based- proteins, peptides, and
  amines
• 2. Steroids- built around a core of cholesterol
  (hydrophobic does not dissolve in water)-sex
  hormones and adrenal hormones
• 3. Prostaglandins fatty acid based- act locally
  at site of release

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How do hormones work?

• TARGET CELLS or TARGET ORGANS- hormones must
  attach to specific protein receptors on the
  plasma membrane
• When hormone binds it typically changes the cell
  in one of the following ways-
• 1. Changes plasma membrane permeability or
  electrical state
• 2. Synthesis of proteins or enzymes in the cell
• 3. Activate or deactivate enzymes in the cell
• 4. Stimulation of mitosis (cell division)

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STEROIDS- hydrophobic- so therefore fat soluble

• Page 281
• STEP 1 diffuses through plasma membrane
• STEP 2 enters the nucleus
• STEP 3 binds to specific receptor proteins in
  nucleus
• STEP 4 binds to specific sites of DNA
• STEP 5 activates genes
• STEP 6 genes make new proteins

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NONSTEROIDAL HORMONES- not fat soluble

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• STEP 1 binds to receptor on plasma memb
• STEP 2 sets off a series of reactions that
  activate enzyme
• STEP 3- produces a second messenger molecule
• STEP 4- produces cells predicted reaction to the
  hormone

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Types of endocrine glands

• HORMONAL- glands prodded into action due to
  hormones
• NEURAL- glands prodded into action due to neural
  stimulation
• HUMORAL- changing blood levels of certain ions
  (Ca) for example prods the glands into action

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NEGATIVE FEEDBACK SYSTEM

• Negative feedback limits amount of hormone that
  is released

Hypothalamus
Blood
Levels OK ?
Set point

• Yes?

• No?

Hypothalamus releases a
"Releasing Hormone"
Pituitary gland releases "Tropic
hormone"
Peripheral gland releases its hormone
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Structure and function of Endocrine glands

• PITUITARY GLAND (HYPOPHYSIS)- Master endocrine
  gland- located in the sella turcica of the skull
  consists of 2 functional areas
• ANTERIOR PITUITARY- secretes the 4 tropic
  hormones- activates other endocrine glands
• POSTERIOR PITUITARY- serves as a storage area for
  two hormones to be used when activated by the
  neurons of the hypothalamus

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ANTERIOR PITUITARY

• Secretes 4 tropic hormones
• Receives hormones from hypothalamus called
  regulating factors
• Growth hormone (GH)
• TROPHIC HORMONES
• Thyroid stimulating hormone (TSH)
• Adrenocorticotropic hormone (ACTH)
• Gonadotropins
• Follicle stimulating hormone (FSH)
• Luteinizing hormone (LH)

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GROWTH HORMONE

• (increases amino acid transport into cells and
  increases protein synthesis, mitosis, and
  cartilaginous bone growth)
• Growth hormone acts on liver and bone
• Overproduction of (GH) will result in gigantism.
  Or if occurs after long bone formation has
  completed Acromegaly will occur
• Underproduction of (GH) will result in pituitary
  dwarfism

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Growth Hormone
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Thyroid stimulating hormone

• Controls production of metabolic regulatory
  hormones from thyroid gland

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Adenocorticotropic hormone

• Controls adrenal cortex production of
  corticosteroid hormones

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Follicle Stimulating Hormone

• females FSH promotes synthesis of estrogen and
  development and growth of follicles in ovaries to
  become oocyte(s)
• males FSH promotes production of sperm in
  testes

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Luteinizing Hormone

• Luteinizing Hormone
• 1) females promotes sex hormone production and
  release of oocyte from follicle
• 2) males promotes sex hormone production

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Posterior lobe of pituitary

• Anti-Diuretic Hormone (ADH)- causes collecting
  ducts of nephron to re-absorb more water from
  urine
• Oxytocin- Causes contraction of uterine smooth
  muscle (i.e. LABOR!!!) Release (post-partum)
  causes contraction of milk ducts in mammary
  glands

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THYROID GLAND

• Located ate the base of the throat just inferior
  to the Adams apple
• Two large lobes joined by an isthmus
• Produces- Thyroxine and Calcitonin
• Thyroxine- stimulates metabolism- contains
  iodine
• People with not enough iodine in their diet get
  GOITERS. Negative feedback loop tells thyroid to
  keep producing but lack of iodine makes the
  molecule nonfunctional

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Thyroid

• Goiter

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Thyroid Gland

• Hypothyroidism- Cretinism- dwarfism occurs in
  early childhood
• In adults results in MYXEDEMA- physical or mental
  sluggishness

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Thyroid Gland

• Hyperthyroidism- high metabolic rate, intolerance
  of heat, rapid heartbeat, nervous behavior
• GRAVEs DISEASE- thyroid enlarges and eyes bulge

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Thyroid gland

• CALCITONIN- decreases blood calcium levels by
  causing calcium to be deposited into bones
• Hyposecretion- lead to decalcification in elderly
  adults

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PARATHYROID GLAND

• PARATHYROID HORMONE- regulates calcium level in
  blood- when low it decalcifies bone to add to
  blood supply
• - If blood calcium levels fall too low then
  neurons become irritable and overactive.
• -Hyperparathyroidism- causes massive bone
  destruction-

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Adrenal Cortex

• Mineralcorticoids- regulate salt and potassium
  in the blood
• ALDOSTERONE- high levels in the blood reclaim
  sodium and allow potassium out in urine
• When sodium is absorbed then water will flow
  smoother
• Hyposecretion- ADDISONS DISEASE- sodium and
  water are lost from the body- skin appears bronze
  and muscles become weak
• Hypersecretion- excessive water and sodium
  retained- potassium severely lost-

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Adrenal Cortex

• CORTISONE- promote normal cell metabolism-
  resists long-term stressors-
• Have anti-inflammatory and pain inhibitors
• Hypersecretion- CUSHINGS SYNDROME- buffalo
  hump

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Adrenal Cortex

• ANDROGENS- male sex hormones
• hypersecretion- masculinization regardless of
  sex
• -ESTROGEN- female sex hormones- production of
  female characteristics

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ADRENAL MEDULLA

• EPINEPHRINE (ADRENALINE) AND NOREPINEPHRINE-
• Prolongs the effects of the sympathetic nervous
  system
• Hyposecretion- no major effects

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PANCREAS

• INSULIN- acts on all body cells and increases
  their ability to take glucose in through cell
  membrane
• Takes glucose out of blood
• Without insulin- glucose will be lost out urine
  along with excess water- dehydration- DIABETES
  MELLITUS

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PANCREAS

• 3 COMMON SIGNS OF DIABETES
• 1. excessive urination
• 2. excessive thirst
• 3. hunger due to inability to take in sugars

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PANCREAS

• GLUCAGON- adds glucose to blood- stimulates
  liver to breakdown glycogen into glucose
• Hyposecretion / hypersecretion- no important
  disorders

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PINEAL GLAND

• MELATONIN- sleep trigger establishes the
  day/night cycle
• Coordinates hormones of fertility

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THYMUS

• THYMOSIN- programs certain lymphocytes
• Thymus stores T cells until they mature

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OVARIES

• ESTROGENS- stimulate secondary sex
  characteristics in women-
• ESTROGEN AND PROGESTERONE- prepares the uterus
  to receive a fertilized egg- Menstrual Cycle
• Prepares breasts for milk production
• Helps maintain pregnancy
• HYPOSECRETION- inhibits womans fertility
• menopause
• Hypersecretion- increased breast cancer and
  ovarian cancer

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TESTES

• ANDROGENS- male sex hormones
• TESTOSTERONE- causes male sex characteristics
• Production of sperm
• Hyposecretion- sterility

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PLACENTA

• HUMAN CHORIONIC GONADOTROPIN- stimulates the
  production of more estrogen and progesterone
• Home pregnancy tests test for Human chorionic
  gonadotropin