Paracrine Signaling by Local Regulators

1. 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

2. Prostaglandins help regulate aggregation of platelets, an early step in formation of blood clots

4. Hypothalamus Pineal gland Pituitary gland LE 45-6 Thyroid gland Parathyroid glands Adrenal glands Pancreas Ovary (female) Testis (male)

5. 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

6. Signaling by any of these hormones involves three key events: • Reception • Signal transduction • Response

7. Epinephrine(also known as Adrenaline)

8. Epinephrine(also known as Adrenaline) Tyrosine (an amino acid)

9. SECRETORY CELL SECRETORY CELL LE 45-3 Hormone molecule Hormone molecule VIA BLOOD VIA BLOOD Signal receptor TARGET CELL TARGET CELL Signal transduction pathway Signal receptor OR Cytoplasmic response DNA Signal transduction and response mRNA DNA NUCLEUS Nuclear response Synthesis of specific proteins NUCLEUS Receptor in plasma membrane Receptor in cell nucleus

10. 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

11. Estradiol LE 4-9 Female lion Testosterone Male lion

13. SECRETORY CELL SECRETORY CELL LE 45-3 Hormone molecule Hormone molecule VIA BLOOD VIA BLOOD Signal receptor TARGET CELL TARGET CELL Signal transduction pathway Signal receptor OR Cytoplasmic response DNA Signal transduction and response mRNA DNA NUCLEUS Nuclear response Synthesis of specific proteins NUCLEUS Receptor in plasma membrane Receptor in cell nucleus

14. different cell responses Different receptors LE 45-4 Epinephrine Epinephrine Epinephrine  receptor  receptor a receptor Glycogen deposits Vessel dilates Glycogen breaks down and glucose is released from cell Vessel constricts Skeletal muscle blood vessel Liver cell Intestinal blood vessel Different intracellular proteins different cell responses

15. SECRETORY CELL SECRETORY CELL LE 45-3 Hormone molecule Hormone molecule VIA BLOOD VIA BLOOD Signal receptor TARGET CELL TARGET CELL Signal transduction pathway Signal receptor OR Cytoplasmic response DNA Signal transduction and response mRNA DNA NUCLEUS Nuclear response Synthesis of specific proteins NUCLEUS Receptor in plasma membrane Receptor in cell nucleus

16. cAMP (cyclic Adenosine Monophosphate)

17. 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.