The Endocrine System

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The Endocrine System

• Anatomy and Physiology

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Endocrine System

• Endocrine organs secrete hormones directly into
  body fluids (blood)
• Hormones are chemical messengers that only affect
  target cells that have a special receptor on the
  cell surface

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Hormones

• Are of two types steroid and nonsteroid, usually
  peptide (protein)
• Steroid hormones may enter the cell through the
  cell membrane, but nonsteroid hormones cannot

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Nonsteroid hormones

• These hormones, usually proteins, cannot get
  through the cell membrane.
• They must attach to a receptor on the outside of
  the membrane
• They use a 2nd messenger system to get the
  message into the cell, to achieve the desired
  response

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Pass it on!
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2nd messenger system
A chain reaction
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Endocrine Glands
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Control of Hormones

• Most often controlled by negative feedback
• This means a gland or system is sensitive to the
  concentration of the substance it secretes, or a
  product it controls

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Control of Hormones

• If high levels of a hormone or product are
  detected, then the gland is inhibited (shut off)
• If low levels are detected, more must be needed,
  so the gland is not inhibited (allowed to turn on)

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Control of Hormones

• What turns on and off each gland varies
• Some have many steps involved, like a chain
  reaction

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Control of Hormones
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Control of Hormones
Growth hormone is controlled by a releasing and
an inhibiting hormone. Which one is secreted in
greater concentration determines whether GH is
released or not.
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Control of Hormones
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Hypothalamus controls Pituitary
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Hypothalamus controls Pituitary
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Hormones of the Pituitary
Master gland
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Growth Hormone

• Stimulates cell growth and division
• Under-secretion can be dwarfism, with correct
  proportions and normal mental development
• Over-secretion can be gigantism

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61 normal males hand
Twelve year olds hand
Twelve years old 65
Gigantism
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Hypopituitary Dwarfism
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Posterior Pituitary
Vasopressin is also called ADH antidiruetic
hormone
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Thyroid Gland

• Secretes three hormones
• Thyroxine (T4), Triiodothyronine (T3)
• Calcitonin

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Thyroid Hormones

• T3 and T4 control metabolism
• Undersecretion in childhood could cause
  cretinism in adults called myxedema with
  sluggishness, obesity
• Oversecretion can be Graves disease

Graves disease
Cretinism
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Goiter

• Enlarged thyroid gland
• Caused by lack of iodine
• Iodine is required to make T4, and if not
  present, the thyroid keeps working to the point
  of enlargement, yet cannot make T4

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Thyroid Control

• TRH (TRF) from hypothalamus to pituitary
• TSH from pituitary to thyroid
• T3 and T4 (thyroxine) from thyroid
• Negative feedback

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Parathyroid

• Parathyroid gland secretes parathyroid hormone
  (PTH)
• PTH increases blood calcium and decreases blood
  phosphate
• Parathyroid gland can sense level of calcium in
  the blood

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Parathyroid

• Osteoblasts are cells that build bone
• Osteoclasts are cells that break down bone to
  release calcium
• If calcium is low in the blood, PTH stimulates
  osteoclasts
• If calcium is high in the blood, PTH inhibits
  osteoclasts
• Controlled by the parathyroid glands, sensing the
  amount of blood calcium

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Parathyroid
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Parathyroid

• Your body sacrifices bone tissue to maintain
  correct levels of calcium in the blood.

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Thyroid helps with calcium

• The thyroid gland also helps with calcium
  regulation
• It secretes calcitonin, which decreases level of
  blood calcium by encouraging the kidney to
  excrete calcium and inhibiting osteoclasts
• PTH and calcitonin are opposites

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Adrenal Hormones

• Adrenal glands on each kidney
• Inner part is called medulla
• Outer part is called cortex
• Each section produces different hormones

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Adrenal Hormones

• Cortex produces cortisol (hydrocortisone)
• Stimulates carbohydrate metabolism
• Reduces inflammation
• Stimulates muscle growth

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Cortisol from Adrenal cortex

• Undersecretion leads to Addison disease, can be
  fatal by disturbing electrolyte balance
• Oversecretion is Cushing syndrome, alters
  carbohydrate and protein metabolism, and
  electrolyte balance

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Adrenal Hormones

• Cortex also produces aldosterone
• Acts on kidney to increase uptake of sodium
• Essential for survival because of its role in
  water and solute balance

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Adrenal Hormones

• Medulla produces epinephrine, also called
  adrenaline
• Fight or Flight
• Increases heart rate, blood pressure, glucose
  level, and blood flow to heart and lungs

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Pancreas

• Functions as both endocrine and exocrine gland
• Endocrine hormones are insulin and glucagon
• Exocrine digestive enzymes

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Pancreas
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Pancreas

• Special clusters of cells called the Islets of
  Langerhans secrete hormones
• Alpha cells secrete glucagon
• Beta cells secrete insulin

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Pancreas

• Glucagon stimulates the liver to break down
  glycogen into glucose
• Stimulated by low blood sugar

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Pancreas

• Insulin stimulates the liver to form glycogen and
  promotes the absorption of glucose into cells
• Lowers blood sugar
• Stimulated by high blood sugar

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Diabetes Mellitus

• Lack of insulin
• Cells are starving cannot get glucose into the
  cell without insulin, thus weight loss is a
  symptom
• Kidneys try to get rid of excess sugar,
  increasing urine output and thirst

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Diabetes Mellitus
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Diabetes Mellitus
High blood sugar damages blood vessels, leading
to complications Complications includecoronary
artery disease, retinal damage, kidney damage,
and problems from poor circulation in the
peripheral areas