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Download Concept 45.2: Hormones and other chemical signals bind to
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Paracrine Signaling by Local Regulators • In paracrine signaling, nonhormonal chemical signals called local regulators elicit responses in nearby target cells • Types of local regulators: – Neurotransmitters – Cytokines and growth factors – Nitric oxide – Prostaglandins • Prostaglandins help regulate aggregation of platelets, an early step in formation of blood clots LE 45-6 Hypothalamus Pineal gland Pituitary gland Thyroid gland Parathyroid glands Adrenal glands Pancreas Ovary (female) Testis (male) Concept 45.2: Hormones and other chemical signals bind to target cell receptors, initiating pathways that culminate in specific cell responses • Hormones convey information via the bloodstream to target cells throughout the body • Three major classes of molecules function as hormones in vertebrates: – Proteins and peptides – Amines derived from amino acids – Steroids • Signaling by any of these hormones involves three key events: – Reception – Signal transduction – Response Epinephrine (also known as Adrenaline) Epinephrine (also known as Adrenaline) Tyrosine (an amino acid) LE 45-3 SECRETORY CELL SECRETORY CELL Hormone molecule VIA BLOOD Hormone molecule VIA BLOOD Signal receptor TARGET CELL TARGET CELL Signal transduction pathway OR Signal receptor Cytoplasmic response DNA Signal transduction and response mRNA DNA NUCLEUS Nuclear response NUCLEUS Receptor in plasma membrane Synthesis of specific proteins Receptor in cell nucleus Intracellular Receptors for Lipid-Soluble Hormones • Steroids, thyroid hormones, and the hormonal form of vitamin D enter target cells and bind to protein receptors in the cytoplasm or nucleus • Protein-receptor complexes then act as transcription factors in the nucleus, regulating transcription of specific genes LE 4-9 Estradiol Female lion Testosterone Male lion LE 45-3 SECRETORY CELL SECRETORY CELL Hormone molecule VIA BLOOD Hormone molecule VIA BLOOD Signal receptor TARGET CELL TARGET CELL Signal transduction pathway OR Signal receptor Cytoplasmic response DNA Signal transduction and response mRNA DNA NUCLEUS Nuclear response NUCLEUS Receptor in plasma membrane Synthesis of specific proteins Receptor in cell nucleus LE 45-4 different cell responses Different receptors Epinephrine Epinephrine Epinephrine a receptor receptor receptor Glycogen deposits Vessel constricts Intestinal blood vessel Vessel dilates Skeletal muscle blood vessel Different intracellular proteins Glycogen breaks down and glucose is released from cell Liver cell different cell responses LE 45-3 SECRETORY CELL SECRETORY CELL Hormone molecule VIA BLOOD Hormone molecule VIA BLOOD Signal receptor TARGET CELL TARGET CELL Signal transduction pathway OR Signal receptor Cytoplasmic response DNA Signal transduction and response mRNA DNA NUCLEUS Nuclear response NUCLEUS Receptor in plasma membrane Synthesis of specific proteins Receptor in cell nucleus cAMP (cyclic Adenosine Monophosphate) Which of the following statements about hormones is correct? – A. Steroid and peptide hormones produce different effects but use the same biochemical mechanisms. – B. Steroid and peptide hormones produce the same effects but differ in the mechanisms that produce the effects. – C. Steroid hormones affect the synthesis of proteins, whereas peptide hormones affect the activity of proteins already present in the cell. – D. Steroid hormones affect the activity of certain proteins within the cell, whereas peptide hormones directly affect the processing of mRNA. – E. Steroid hormones affect the synthesis of proteins to be exported from the cell, whereas peptide hormones affect the synthesis of proteins that remain in the cell.
