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• Endocrine system


  The collection of glands of an organism that secrete hormones directly into the circulatory system to be carried towards a distant target organ
• Endocrine system


  • Maintains homeostasis
  • Communicates through gap junctions, neurotransmitters, paracrine hormones, and hormones
• Enzymes


  Biological catalysts that speed up biochemical reactions without causing them to alter
• Hormones


  Chemicals, like steroids or peptides, created by a component of an organism and transmit messages to other organs or tissues to provoke cellular responses
• The body has four principal mechanisms of communication between cells: gap junctions, neurotransmitters, paracrine hormones, and hormones
• Hormones travel in the bloodstream to other tissues and organs to provoke cellular responses
• Endocrine glands


  Organs that are traditional sources of hormones
• Hormones


  Chemical messengers transported by the bloodstream that stimulate physiological responses in cells of another tissue or organ
• Hypothalamus


  Shaped like a flattened funnel, forms floor and walls of third ventricle of the brain, regulates primitive functions of the body
• Many functions of the hypothalamus are carried out by the pituitary gland
• The hypothalamus is not an exocrine gland
• Pituitary gland


  Suspended from the hypothalamus by the infundibulum, housed in the sella turcica of the sphenoid bone, pea-sized gland
• Pituitary gland


  Composed of two structures with independent origins and separate functions: the adenohypophysis (anterior pituitary) and the neurohypophysis (posterior pituitary)
• The adenohypophysis arises from the hypophyseal pouch, an outgrowth of the pharynx
• The neurohypophysis is a downward growth from the brain
• Adenohypophysis


  Linked to the hypothalamus by the hypophyseal portal system, hypothalamic hormones regulate the adenohypophysis cells
• Neurohypophysis


  Nerve tissue, not a true gland, contains nerve cell bodies from the hypothalamus that pass down the stalk and secrete hormones stored in the neurohypophysis
• Hypothalamic hormones


  • Gonadotropin-releasing hormone
  • Thyrotropin-releasing hormone
  • Corticotropin-releasing hormone
  • Prolactin-inhibiting hormone
  • Growth hormone-releasing hormone
  • Somatostatin
• Anterior pituitary hormones


  • Follicle-stimulating hormone
  • Luteinizing hormone
  • Thyroid-stimulating hormone
  • Adrenocorticotropic hormone
  • Prolactin
  • Growth hormone
• Hypothalamic-releasing and -inhibiting hormones travel in the hypophyseal portal system from the hypothalamus to the anterior pituitary
• Hormones secreted by the anterior pituitary
• Hypothalamo–hypophyseal tract


  Pathway that hypothalamic neurons use to secrete hormones into the posterior lobe of the pituitary gland
• Neurohypophysis


  Posterior lobe of the pituitary gland
• Adenohypophysis


  Anterior lobe of the pituitary gland
• Hypothalamic hormones


  • Gonadotropin-releasing hormone
  • Thyrotropin-releasing hormone
  • Corticotropin-releasing hormone
  • Prolactin-inhibiting hormone
  • Growth hormone–releasing hormone
  • Somatostatin
• Anterior lobe hormones


  • Follicle-stimulating hormone
  • Luteinizing hormone
  • Thyroid-stimulating hormone (thyrotropin)
  • Adrenocorticotropic hormone
  • Prolactin
  • Growth hormone
• Hypothalamic-releasing and -inhibiting hormones

  Travel in hypophyseal portal system from hypothalamus to anterior pituitary
• Oxytocin (OT)


  Stored and released by posterior pituitary, stimulates labor contractions and milk flow
• Antidiuretic hormone (ADH)


  Stored and released by posterior pituitary, increases water retention and prevents dehydration
• Posterior pituitary does not synthesize oxytocin and ADH, they are produced in the hypothalamus
• Two hypothalamic hormones regulate the anterior pituitary
• Six hypothalamic hormones are released from the posterior pituitary
• TRH, CRH, GnRH, and GHRH are releasing hormones that affect anterior pituitary secretion
• PIH (prolactin inhibiting hormone) and somatostatin are inhibiting hormones
• PIH inhibits secretion of prolactin
• Oxytocin (OT) and antidiuretic hormone (ADH) are stored and released by the posterior pituitary
• The right and left paraventricular nuclei produce ADH, and the supraoptic nuclei produce OT
• The posterior pituitary does not synthesize OT and ADH, they are produced in the hypothalamus
• Acyclic alkanes


  General formula (CnH2n+2)

  
• Nomenclature


  1. The name is simply derived from the Greek (or Latin) prefix for the particular number of carbons in the alkane

  2. Methane, ethane, propane, butane, and pentane are used for alkanes containing respectively one, two, three, four, and five carbon atoms