HUMB1000 Lecture Notes - Lecture 29: Melanocyte, Neural Crest, Pituitary Gland
Document Summary
Released by cells and have a local effect on same cell type from which chemical signals released: paracrine. Released by cells and affect other cell types locally without being transported in blood: neurotransmitter. Produced by neurons secreted into extracellular spaces by presynaptic nerve terminals; travels short distances; influences postsynaptic cells: endocrine. Produced by cells of endocrine glands, enter circulatory system, and affect distant cells. Characteristics of the endocrine system: body control system where regulation requires duration rather than speed, glands that secrete chemical messengers (hormones) into circulatory system (blood, hormone characteristics. Acts on target tissues elsewhere in body: hormone secretion can be: Sudden release due to stimulus e. g. , adrenaline in response to stress. Small variations over long periods e. g. , thyroid hormones. E. g. , estrogen & progesterone during menstrual cycle: target cells respond to a hormone because they have the correct receptor. May use same chemical messenger as neurotransmitter and hormone.