bio chp#04

• Chemical coordination


  Cell-to-cell communication is crucial to the control of movement, growth, reproduction, and the maintenance of homeostasis
• Neurotransmitters


  Chemical messengers between neurons
• Pheromones


  Chemicals secreted by an organism in minute amounts to stimulate particular reaction from another organism of the same species
• Hormones


  Chemical messengers secreted by specialized tissues called glands, that are transported in the blood stream
• Chemical categories of hormones

  • Peptide and Protein hormones
  • Amino acid derivate hormones
  • Steroid hormones
• Peptide and Protein hormones

  Hormones composed of chains of amino acids ranging from a few to over a hundred amino acids in length
• Amino acid derivate hormones


  Hormones manufactured by enzymatic modification of specific amino acids
• Steroid hormones


  Hormones manufactured by enzymatic modifications of cholesterol
• Hormone specificity


  Determined by receptors on target cells
• Hydrophilic (polar) or protein nature hormones


  Cannot cross the cell membrane, instead they react with protein receptors protruding from the outside surface of target cell membrane
• Lipophilic (non-polar) steroid and thyroid hormones


  Able to diffuse into the cell membrane and bind to receptors inside the cell
• Second messenger system


  When the hormone binds to the receptor, the shape of the receptor is altered, triggering a series of biochemical reactions that alter the activity of cell
• cAMP


  A mononucleotide that regulates many cellular activities, often called a second messenger
• Steroid and thyroid hormones

  Bind to protein receptors in the nucleus, the receptor-hormone complex binds to DNA and initiates the transcription of messenger RNA from specific genes
• Endocrine system


  Includes all of the glands and patches that secrete hormones
• Exocrine glands


  Glands that excrete their products into particular ducts or into the gut
• Hypothalamus


  Part of the brain that contains clusters of specialized cells called neurosecretory cells, which secrete hormones that regulate the activity of the pituitary gland
• Hypothalamic releasing and inhibiting hormones

  • Thyrotropin releasing hormone (TRH)
  • Corticotropin releasing hormone (CRH)
  • Gonadotropin releasing hormone (GnRH)
  • Growth hormone releasing hormone (GHRH)
  • Growth hormone inhibiting hormone (GHIH)
  • Prolactin inhibiting hormone (PIH)
  • Melanocyte inhibiting hormone (MIH)
• Pituitary gland


  Pea-sized gland that dangles from the hypothalamus, consists of two distinct lobes: the anterior pituitary lobe (adenohypophysis) and the posterior pituitary lobe (neurohypophysis)
• Hormones produced by the anterior pituitary

  • Adrenocorticotropic hormone (ACTH)
  • Melanocyte stimulating hormone (MSH)
  • Growth hormone (GH) OR Somatotropic hormone (STH)
  • Prolactin
  • Thyroid Stimulating hormone (TSH)
  • Luteinizing hormone (LH)
  • Follicle stimulating hormone (FSH)
• Thyroid-stimulating hormone (TSH)


  Stimulates thyroid gland to produce thyroxin
• Luteinizing hormone (LH)


  Stimulate gonads (testes/ovaries) for production of steroid hormone estrogen and progesterone from ovaries and testosterone from testes
• Follicle stimulating hormone (FSH)


  Stimulate development of ovarian follicles in females. In males it is required for the development of sperm
• Gonadotropins (GnTH)


  FSH and LH are called gonadotropins because they stimulate the activities of the male and female gonads
• Posterior pituitary contains the ending of two types of neurosecretory cells whose cell bodies are found in the hypothalamus
• Antidiuretic hormone (ADH)


  Helps prevent dehydration by increasing the permeability to water of the collecting ducts of nephrons in the kidney
• Oxytocin


  Stimulates uterine contractions during labour and stimulates breast tissue contractions to promote lactation after childbirth
• Oxytocin plays a significant part in social interaction and human behaviour
• Tri-iodothyronine (T3)


  Thyroid hormone with 3 atoms of iodine, less potent than T4
• Tetra-iodothyronine (T4) or thyroxin


  Thyroid hormone with 4 atoms of iodine, secreted in greater amount but less potent than T3
• Calcitonin


  Peptide hormone that plays role in maintaining proper levels of calcium (Ca++) in the blood
• When blood Calcium concentration rises too high, calcitonin stimulates the uptake of calcium into bones, thus lowering its concentration in the blood
• Parathormone or parathyroid hormone (PTH)


  Peptide hormone produced by the parathyroid gland that stimulates the release of calcium from bones into the blood
• Falling levels of calcium in the blood

  Causes the parathyroid gland to release PTH
• A normal blood calcium level is important for the functioning of muscles, including the heart, and for proper functioning of the nervous and endocrine system
• Glucagon


  Peptide hormone secreted by alpha cells in the pancreas that raises blood sugar levels
• Insulin


  Peptide hormone secreted by beta cells in the pancreas that lowers blood sugar levels
• When blood glucose rises (e.g. after a meal)

  Insulin is released, causing cells to take up glucose for energy or storage
• When blood glucose drops (e.g. after skipping breakfast)

  Glucagon is released, causing the liver to break down glycogen and release glucose into the blood
• Diabetes mellitus


  Condition in which blood glucose levels are high and fluctuate wildly due to defects in insulin production, release or reception