Ch 45: Endocrine System

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Ch 45 Endocrine System
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Endocrine System

• All of the hormone secreting cells
• Endocrine Glands
• Secrete hormones
• Ductless (secrete into bloodstream)
• Signal Transduction Pathway
• Most hormones bind to receptor proteins in
  membrane and cause intracellular response

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Chemical Messages (signal-transduction pathways)
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Signal Transduction Pathways

• Activates a series of molecules within the cell
  after signal is received
• Allow for small amounts of a hormone to have a
  large effect

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Intracellular Hormones

• Some hormones will bind to interior receptors and
  mediate a response
• Generally, these act in the nucleus and stimulate
  a transcription factor (make some enzymes)

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Human Endocrine System

• Tropic hormones Stimulate other endocrine cells
  to secrete hormones
• Humans have nine endocrine glands

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Hypothalamus

• Combines the endocrine and nervous systems
• Nuerosecretory cells produce hormones
• Releasing hormones stimulate the anterior
  pituitary
• Inhibiting hormones prevent the anterior
  pituitary from secreting hormones

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Anterior Pituitary
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Posterior Pituitary

• Stores and secretes hormones produced by the
  hypothalamus

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Major Hormones
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More Hormones
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Antidiuretic Hormone (ADH)

• Promotes retention of water by the kidneys.
• Secretion regulated by water/salt balance
• Secreted by post. pituitary after production in
  hypothalamus

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Anterior Pituitary Hormones

• Growth hormone
• Stimulates growth and metabolism
• Gigantism excessive GH during development
• Hypopituitary dwarfism childhood GH deficiency

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Anterior Pituitary Hormones

• Prolactin
• stimulates milk production and secretion
• Gonadotropins
• Follicle-stimulating hormone (FSH)
• production of sperm and ova
• Luteinizing hormone (LH)
• stimulates ovaries and testes

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Anterior Pituitary Hormones

• Thyroid-stimulating hormone (TSH)
• stimulates thyroid gland
• Melanocyte-stimulating hormone
• may play a role in fat metabolism
• Endorphins
• inhibit pain perception
• mimicked by heroin and other opiates

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Pineal Gland

• Near center of the mammalian brain
• Secretes melatonin
• Involved in biological rhythms associated with
  reproduction
• Secretion regulated by light/dark cycles

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Thyroid Gland

• Two lobes locatedon the ventral surfaceof the
  trachea
• T3 (triiodothyronine) and T4 (thyroxine) hormones
  stimulate and maintain metabolic activity
• Secretion of T3 and T4 regulated by TSH hormone
  secreted by anterior pituitary

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Thyroid Gland
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Thyroid Gland

• Animation of Thyroid Secretion
• Animation of Thyroid Regulation
• Goiter Animation

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Thyroid Gland

• Iodine deficiencies lead to goiter (swelling of
  thyroid gland (why salt is iodized)
• Hyper- and Hypothyroidism results from too much
  or too little T3/T4
• Also secretes calcitonin
• Lowers blood calcium levels

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Parathyroid Glands

• four parathyroid glands embedded in the surface
  of the thyroid gland
• parathyroid hormone (PTH)
• Raises blood calcium levels
• break down bone
• reabsorb by kidney
• PTH and calcitonin are antagonistic

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Regulation of Calcium Levels
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Pancreas

• Endocrine (into blood) and exocrine (into ducts)
• Exocrine bicarbonate ions and digestive enzymes
• Endocrine insulin and glucagon
• Islets of Langerhans

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Insulin

• Secreted by beta cells
• Lowers blood glucose levels
• Stimulates all body cells (except brain cells) to
  take up glucose
• Regulated by glucose in blood (negative feedback).

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Diabetes

• Low or no insulin production
• High blood sugar levels
• Sugar in urine
• Severe diabetes leads to fat usage in cell.
  respiration and ultimately death (dec. blood pH
  due to acidic metabolites)
• Type I Autoimmune disorder, present in
  childhood, treated with insulin injections
• Type II Target cells less responsive over time
  to insulin. 90 of cases, usually over 40.

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Glucagon

• secreted by alpha cells
• raises blood glucose levels
• liver and skeletal muscle breakdown glycogen
  stores
• regulated by glucose in blood (negative feedback)

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Blood Sugar Regulation
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Adrenal Glands

• Adrenal glands
• Adjacent to the kidneys
• The adrenal cortex is the outer portion
• The adrenal medulla is the inner portion
• Epinephrine (adrenaline) and norepinephrine
  (noradrenaline)
• Secretion regulated by the nervous system in
  response to stress

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Response to Stress (Fight or Flight)

• Epinephrine and norepinephrine
• Raises blood glucose level and blood fatty acid
  level
• Increase metabolic activities
• Increases heart rate and stroke volume and
  dilates bronchioles
• Shunts blood away from skin, digestive organs,
  and kidneys, and increases blood flow to heart,
  brain, and skeletal muscle

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Testes (testosterone)

• Androgen type of steroids
• sperm formation
• promote development and maintenance of male sex
  characteristics
• regulated by FSH and LH

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Ovaries

• Estrogen and progesterone (steroids)
• Estrogens
• uterine lining growth
• female sex characteristics
• Regulated by LH and FSH
• Progesterone
• Uterine lining growth
• Reg. by LH and FSH