About This Chapter Hormones The classification of hormones Control of hormone release Hormone interactions Endocrine pathologies Hormone evolution
Hormones: Function Control Rates of enzymatic reactions Transport of ions or molecules across cell membranes Gene expression and protein synthesis
Hormones Have Been Known Since Ancient Times Diseases of endocrine system have been documented Classic steps to identify an endocrine gland and the hormone they produce: Remove the suspected gland Replace the hormone Create hormone excess
Figure 7.1 An endocrine disorder in ancient art
Figure 7.2-2 Hormones
ifgure 7.2-3 Hormones
Figure 7.2-4 Hormones
Figure 7.2-5 Hormones
Figure 7.2-1 Hormones
Hormones Cell-to-cell communication molecules Chemical signals Secreted by a cell or group of cells into the blood Transported by blood Distant target tissue receptors Growth factors act at short distance Activates physiological response at low concentrations Ectohormones are released into the environment Pheromones: Elicit physiological or behavioral response on other organisms of the same species
Hormones Cellular mechanism of action Depends on binding to target cell receptors Initiates biochemical responses Hormone action must be terminated Half-life indicates length of activity
Hormones: Classification by Chemical Class Peptide or protein hormones Steroid hormones Amino acid derived or amine hormones
Hormones: Peptides or Proteins Preprohormone Large, inactive precursor Prohormone Smaller, inactive Proteolytic, post-translational modification Peptide/protein hormones Transport in the blood and half-life Bind surface membrane receptors Cellular response through signal transduction system
Figure 7.3 Peptide Hormone Synthesis and Processing
Figure 7.3 Peptide Hormone Synthesis and Processing Slide 1 mrna Preprohormone Ribosome Endoplasmic reticulum (ER) Messenger RNA on the ribosomes binds amino acids into a peptide chain called a preprohormone. The chain is directed into the ER lumen by a signal sequence of amino acids. Signal sequence Prohormone Transport vesicle Enzymes in the ER chop off the signal sequence, creating an inactive prohormone. The prohormone passes from the ER through the Golgi complex. Golgi complex Secretory vesicle Active hormone Secretory vesicles containing enzymes and prohormone bud off the Golgi. The enzymes chop the prohormone into one or more active peptides plus additional peptide fragments. Cytoplasm Peptide fragment ECF Release signal The secretory vesicle releases its contents by exocytosis into the extracellular space. Plasma Capillary endothelium To target The hormone moves into the circulation for transport to its target.
Figure 7.3 Peptide Hormone Synthesis and Processing Slide 2 mrna Preprohormone Ribosome Endoplasmic reticulum (ER) Messenger RNA on the ribosomes binds amino acids into a peptide chain called a preprohormone. The chain is directed into the ER lumen by a signal sequence of amino acids. Cytoplasm ECF Plasma Capillary endothelium
Figure 7.3 Peptide Hormone Synthesis and Processing Slide 3 mrna Preprohormone Ribosome Endoplasmic reticulum (ER) Messenger RNA on the ribosomes binds amino acids into a peptide chain called a preprohormone. The chain is directed into the ER lumen by a signal sequence of amino acids. Signal sequence Prohormone Enzymes in the ER chop off the signal sequence, creating an inactive prohormone. Cytoplasm ECF Plasma Capillary endothelium
Figure 7.3 Peptide Hormone Synthesis and Processing Slide 4 mrna Preprohormone Ribosome Endoplasmic reticulum (ER) Messenger RNA on the ribosomes binds amino acids into a peptide chain called a preprohormone. The chain is directed into the ER lumen by a signal sequence of amino acids. Signal sequence Prohormone Transport vesicle Enzymes in the ER chop off the signal sequence, creating an inactive prohormone. The prohormone passes from the ER through the Golgi complex. Golgi complex Cytoplasm ECF Plasma Capillary endothelium
Figure 7.3 Peptide Hormone Synthesis and Processing Slide 5 mrna Preprohormone Ribosome Endoplasmic reticulum (ER) Messenger RNA on the ribosomes binds amino acids into a peptide chain called a preprohormone. The chain is directed into the ER lumen by a signal sequence of amino acids. Signal sequence Prohormone Transport vesicle Enzymes in the ER chop off the signal sequence, creating an inactive prohormone. The prohormone passes from the ER through the Golgi complex. Golgi complex Secretory vesicle Active hormone Secretory vesicles containing enzymes and prohormone bud off the Golgi. The enzymes chop the prohormone into one or more active peptides plus additional peptide fragments. Cytoplasm Peptide fragment ECF Plasma Capillary endothelium
Figure 7.3 Peptide Hormone Synthesis and Processing Slide 6 mrna Preprohormone Ribosome Endoplasmic reticulum (ER) Messenger RNA on the ribosomes binds amino acids into a peptide chain called a preprohormone. The chain is directed into the ER lumen by a signal sequence of amino acids. Signal sequence Prohormone Transport vesicle Enzymes in the ER chop off the signal sequence, creating an inactive prohormone. The prohormone passes from the ER through the Golgi complex. Golgi complex Secretory vesicle Active hormone Secretory vesicles containing enzymes and prohormone bud off the Golgi. The enzymes chop the prohormone into one or more active peptides plus additional peptide fragments. Cytoplasm Peptide fragment ECF Release signal The secretory vesicle releases its contents by exocytosis into the extracellular space. Plasma Capillary endothelium
Figure 7.3 Peptide Hormone Synthesis and Processing Slide 7 mrna Preprohormone Ribosome Endoplasmic reticulum (ER) Messenger RNA on the ribosomes binds amino acids into a peptide chain called a preprohormone. The chain is directed into the ER lumen by a signal sequence of amino acids. Signal sequence Prohormone Transport vesicle Enzymes in the ER chop off the signal sequence, creating an inactive prohormone. The prohormone passes from the ER through the Golgi complex. Golgi complex Secretory vesicle Active hormone Secretory vesicles containing enzymes and prohormone bud off the Golgi. The enzymes chop the prohormone into one or more active peptides plus additional peptide fragments. Cytoplasm Peptide fragment ECF Release signal The secretory vesicle releases its contents by exocytosis into the extracellular space. Plasma Capillary endothelium To target The hormone moves into the circulation for transport to its target.
Figure 7.3a Peptide Hormone Synthesis and Processing
Figure 7.3b Peptide Hormone Synthesis and Processing
Figure 7.3c Peptide Hormone Synthesis and Processing
Figure 7.4 Peptide hormone receptors and signal transduction
Hormones: Steroid Cholesterol-derived Made only in a few organs: adrenal glands and gonads Lipophilic and easily cross membranes Made as needed, not stored Bind carrier proteins in blood Longer half-life Cytoplasmic or nuclear receptors Genomic effect to activate or repress genes for protein synthesis Slower acting Cell membrane receptors Nongenomic responses
Figure 7.5a Steroid Hormones
Figure 7.5b Steroid hormones act primarily on intracellular receptors. Slide 1 Blood vessel Steroid hormone Cell surface receptor Most hydrophobic steroids are bound to plasma protein carriers. Only unbound hormones can diffuse into the target cell. Rapid responses Protein carrier Nucleus Steroid hormone receptors are in the cytoplasm or nucleus. Cytoplasmic receptor Nuclear receptor Some steroid hormones also bind to membrane receptors that use second messenger systems to create rapid cellular responses. DNA Interstitial fluid Cell membrane Endoplasmic reticulum Transcription produces mrna The receptor-hormone complex binds to DNA and activates or represses one or more genes. Activated genes create new mrna that moves back to the cytoplasm. New proteins Translation Translation produces new proteins for cell processes.
Figure 7.5b Steroid hormones act primarily on intracellular receptors. Slide 2 Blood vessel Most hydrophobic steroids are bound to plasma protein carriers. Only unbound hormones can diffuse into the target cell. Protein carrier Nucleus Interstitial fluid Cell membrane
Figure 7.5b Steroid hormones act primarily on intracellular receptors. Slide 3 Blood vessel Steroid hormone Most hydrophobic steroids are bound to plasma protein carriers. Only unbound hormones can diffuse into the target cell. Protein carrier Nucleus Steroid hormone receptors are in the cytoplasm or nucleus. Cytoplasmic receptor Nuclear receptor Interstitial fluid Cell membrane
Figure 7.5b Steroid hormones act primarily on intracellular receptors. Slide 4 Blood vessel Steroid hormone Cell surface receptor Most hydrophobic steroids are bound to plasma protein carriers. Only unbound hormones can diffuse into the target cell. Rapid responses Protein carrier Nucleus Steroid hormone receptors are in the cytoplasm or nucleus. Cytoplasmic receptor Nuclear receptor Some steroid hormones also bind to membrane receptors that use second messenger systems to create rapid cellular responses. Interstitial fluid Cell membrane
Figure 7.5b Steroid hormones act primarily on intracellular receptors. Slide 5 Blood vessel Steroid hormone Cell surface receptor Most hydrophobic steroids are bound to plasma protein carriers. Only unbound hormones can diffuse into the target cell. Rapid responses Protein carrier Nucleus Steroid hormone receptors are in the cytoplasm or nucleus. Cytoplasmic receptor Nuclear receptor DNA Some steroid hormones also bind to membrane receptors that use second messenger systems to create rapid cellular responses. Interstitial fluid The receptor-hormone complex binds to DNA and activates or represses one or more genes. Cell membrane
Figure 7.5b Steroid hormones act primarily on intracellular receptors. Slide 6 Blood vessel Steroid hormone Cell surface receptor Most hydrophobic steroids are bound to plasma protein carriers. Only unbound hormones can diffuse into the target cell. Rapid responses Protein carrier Nucleus Steroid hormone receptors are in the cytoplasm or nucleus. Cytoplasmic receptor Nuclear receptor DNA Some steroid hormones also bind to membrane receptors that use second messenger systems to create rapid cellular responses. Interstitial fluid The receptor-hormone complex binds to DNA and activates or represses one or more genes. Cell membrane Transcription produces mrna Activated genes create new mrna that moves back to the cytoplasm. Translation
Figure 7.5b Steroid hormones act primarily on intracellular receptors. Slide 7 Blood vessel Steroid hormone Cell surface receptor Most hydrophobic steroids are bound to plasma protein carriers. Only unbound hormones can diffuse into the target cell. Rapid responses Protein carrier Nucleus Steroid hormone receptors are in the cytoplasm or nucleus. Cytoplasmic receptor Nuclear receptor Some steroid hormones also bind to membrane receptors that use second messenger systems to create rapid cellular responses. DNA Interstitial fluid Cell membrane Endoplasmic reticulum Transcription produces mrna The receptor-hormone complex binds to DNA and activates or represses one or more genes. Activated genes create new mrna that moves back to the cytoplasm. New proteins Translation Translation produces new proteins for cell processes.
Hormones: Amino Acid Derived, or Amine Derived from one of two amino acids Tryptophan; melatonin Tyrosine: catecholamines (epinephrine, dopamine) and thyroid homones
Hormones: Amino Acid Derived, or Amine Amine hormones: Examples Melatonin Catecholamines Epinephrine Norepinephrine Dopamine Thyroid hormones
Figure 7.6 Amine hormones Tyrosine is the parent amino acid for catecholamines and thyroid hormones. FIGURE QUESTION Determine how each catecholamine molecule differs from the tyrosine molecule. Catecholamines are made by modifying the side groups of tyrosine. Thyroid hormones are synthesized from two tyrosines and iodine (I) atoms. Dopamine Thyroxine (Tetraiodothyronine, T 4 ) Norepinephrine Epinephrine Triiodothyronine (T 3 )
Endocrine Reflex Pathways Stimulus Sensor Input signal Integration Output (efferent) signal (hormone in blood) Targets Response physiological action Negative feedback Simple endocrine reflexes use endocrine cells as receptors Many endocrine reflexes involve the nervous system Neurohormones are secreted by neurons in blood
Figure 7.7a Simple endocrine pathways
Figure 7.7b Simple endocrine pathways