The Endocrine System

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The Endocrine System

• H1 Hormonal Control

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• Endocrine System a system of glands that secrete
  hormones to regulate body function
• HORMONES chemical messengers or regulators
• - they are released by cells in one part of the
  body and affect cells in other parts of the body
  to speed up or slow down processes.
• Endocrine Hormones are produced in endocrine
  glands and secreted directly in the blood and
  distributed by the circulatory system.

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Makes hormones and regulates the pituitary gland
Pineal gland (makes serotonin which regulates
sleep patterns)
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Endocrine Gland
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How do Hormones Signal Cells?

• Note Hormones do not affect ALL cells
• Depends on whether or not that cell has a
  receptor for the particular hormone.
• (TARGET CELLS are the cells hormones act on)
• There are 2 types of hormones
• 1. Steroid Hormones
• 2. Protein Hormones

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Steroid Hormones

• made from cholesterol (lipid) Complex ring of C,
  H, and O
• Soluble in fat but NOT water so can dissolve
  through cell membrane
• Inside the cell they bind to receptor in the
  cytoplasm or nucleus to form the hormone-receptor
  complex

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Steroid Hormones

• The receptor-hormone complex can then switch
  certain genes on or off by promoting or
  inhibiting the transcription of genes
• ex sex hormones
• ex cortisol (stimulates the conversion of amino
  acids to glucose by the liver and decreases
  expression of insulin)

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Steroid Hormones
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Steroid Hormones
SECRETORY CELL
HORMONE
TARGET CELL
RECEPTOR
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Protein Hormones

• Made of chains of amino acids or modified amino
  acids
• Soluble in water but insoluble in fats (cant
  dissolve through cell membrane)
• Ex insulin, growth hormone

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Protein Hormones

• The protein hormones attach to receptor sites on
  the cell membrane
• The hormone-receptor complex leads to the release
  of a secondary messenger in the cell that can
  spread throughout the cell and relay messages
• Ex of secondary messengers Ca2 and cyclic
  adenosine monophosphate (cyclic AMP)
• Secondary messengers then activate enzymes in the
  cell.

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Protein Hormones
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Animations

• http//highered.mheducation.com/sites/0072437316/s
  tudent_view0/chapter47/animations.html

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Control Systems

• The body relies on the nervous system and the
  endocrine system for control of organs and
  tissues
• The nervous system allows the body to adjust
  quickly to environmental changes
• The endocrine system is designed to maintain
  control over longer durations

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Hypothalamus

• The hypothalamus in the brain is part of both the
  nervous system and the endocrine system
• As an endocrine gland it creates hormones that
  either
• a) are stored in the (posterior) pituitary gland
• b) control the release of hormones from the
  (anterior) pituitary gland

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Pituitary Gland (The Master Gland)

• master gland because it controls the other
  endocrine glands
• (However, it is controlled by the hypothalamus)
• Located at the base of the brain connected to
  the hypothalamus by a stalk
• The pituitary produces and
  stores hormones
• The hypothalamus stimulates
  their release when necessary

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Posterior Lobe

• Stores and releases hormones that are actually
  made by the neurosecretory cells of the
  hypothalamus
• The hormones travel from the hypothalamus to the
  pituitary via specialized nerve cells
• They are stored in the pituitary and released
  into the blood when necessary
• (The hypothalamus will send a nerve response to
  have the hormones released)
• Ex ADH (antidiuretic hormone), oxytocin

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Posterior Lobe

• Ex ADH release
• Hypothalamus creates ADH and stores it in
  pituitary gland
• Osmoreceptors in hypothalamus recognize osmotic
  pressure (solute concentration of blood)
• Impulses are sent to pituitary to increase or
  inhibit the release of ADH into blood stream
  accordingly

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Anterior Lobe

• Produces its own hormones
• However, the hypothalamus regulate their release
  with inhibiting or releasing hormones made by the
  hypothalamus
• The inhibiting and releasing hormones are
  transported to the anterior lobe of the pituitary
  via specialized nerve cells
• This stimulates the release of pituitary hormones
  which will travel through the blood to target
  cells

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Anterior Lobe

• Ex TSH and TRH
• The anterior lobe produces and stores TSH
  (thyroid stimulating hormone)
• TSH is released by the anterior lobe when the
  hypothalamus releases TRH (thyroid releasing
  hormone)

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Ie cortisol
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Hormone Target Organ Primary Function  
Thyroid Stimulating Hormone (TSH) Thyroid Gland Releases hormones made in the thyroid (such as thyroxine)
Adrenocorticotropic Hormone (ACTH) Adrenal Cortex Stimulates the release of hormones involved in the stress response (such as cortisol)
Somatotropin (STH) also known as Growth Hormone (GH) Most body cells Promotes growth
Follicle Stimulating Hormone (FSH) Gonads (ovaries and testes) Females stimulates follicle development in the ovaries Males Promotes the development of sperm cells in the testes
Luteinizing Hormone (LH) Gonads (ovaries and testes) Females stimulates ovulation and the formation of the corpus luteum Males stimulates the production of testosterone
Prolactin Mammary Glands Maintains milk production in lactating females
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Posterior Pituitary Hormones
Hormone Target Organ Primary Function
Antidiuretic Hormone (ADH) kidneys Increases water reabsorption in the kidney
Oxytocin Uterus, mammary glands Initiates strong uterine contractions Triggers milk release in lactating females