Bio 245 Klesath Exam 1 NCSU Questions and Answers | 2025 Update | 100% Correct.

3 reflex mechanisms that stimulate hormone secretion – CORRECT ANSWER 1. Hormonal Stimulation: stimulus for release of hormones by the binding of another hormone (e.g. the TSH from anterior pituitary binds to thyroid gland to release TH) 2. Humoral Stimulation: release of hormone in response to change of blood nutrient levels (e.g. blood glucose levels rise so insulin is released from pancreas, or fall and glucagon is released) 3. Neural Stimulation: direct stimulation from nervous system to endocrine gland (e.g. epinephrine and norepinephrine by adrenal medulla during fight or flight) Hormonal Stimulation – CORRECT ANSWER Stimulus for release of hormones by the binding of another hormone (e.g. the TSH from anterior pituitary binds to thyroid gland to release TH) Humoral Stimulation – CORRECT ANSWER Release of hormone in response to change of blood nutrient levels (e.g. blood glucose levels rise so insulin is released from pancreas, or fall and glucagon is released) Neural Stimulation – CORRECT ANSWER Direct stimulation from nervous system to endocrine gland (e.g. epinephrine and norepinephrine by adrenal medulla during fight or flight) Steroids – CORRECT ANSWER Lipid soluble molecules synthesized by cholesterol 1. Gonads (Estrogen, Progesterone, Testosterone) 2. Adrenal Cortex hormones (Corticosteroids like cortisol, mineralocorticoids, aldosterone) Biogenic Amines – CORRECT ANSWER Modified amino acids, water soluble (except thyroid) 1. Catecholamines (epinephrine and norepinephrine) 2. Thyroid Hormone → lipid soluble 3. Melatonin Proteins – CORRECT ANSWER Most hormones, small chains of amino acids, water soluble1. Small peptides and large polypeptides 2. Glycoproteins Local Hormones – CORRECT ANSWER DO NOT circulate in blood, so only affect either same cell that produced them (autocrine) or neighboring cells (Paracrine) 1. Eicosanoids: synthesized through enzymatic cascade, Phospholipase A2 removes fatty acid from phospholipid within the plasma membrane → Prostaglandins Prostaglandins – CORRECT ANSWER Famous eicosanoid • Are diverse group: synthesized by most tissues in the body • Stimulate pain receptors, reduce fever, increase inflammatory response Lipid soluble hormones – CORRECT ANSWER Can cross membrane, but needs carrier protein while circulating in blood, once unbound they can enter the nucleus a. Has a longer half-life because protected by carrier proteins b. Once inside the cell, hormone binds to intracellular receptor either in nucleus or cytosol c. Once bound, forms a hormone-receptor complex which interacts with DNA directly in regions called Hormone Response Element (HRE) d. Initiates transcription/translation and production of a new protein Water soluble hormones – CORRECT ANSWER Travel free in blood so shorter half-life, cannot enter plasma membrane so binds to a membrane bound receptor a. Second messengers begin a signal transduction pathway, which can cause an amplified signal G protein activation by water-soluble hormones – CORRECT ANSWER a. Hormone binds to G-Protein and activates it when GDP→ GTP b. Active G-Protein is released and receptor moves along inside plasma membrane, either to activate or inhibit other intracellular cascades Adenylate Cyclase – CORRECT ANSWER a. Hormone binds to G-Protein and activates it when GDP→ GTP b. Active G-Protein is released and receptor moves along inside plasma membrane c. Using ATP, cAMP is created and activates protein kinase A, which will phosphorylate things → Small concentration of hormone can have large effect on cellPhospholipase C – CORRECT ANSWER i. Phospholipase C is enzyme activated by G-protein ii. Splits into PIP2 and second messengers, DAG and IP3 iii. DAG activates kinase C iv. IP3 leaves membrane and causes increase in Ca2+ in cytosol which can directly affect or act as 3rd messenger Upregulation – CORRECT ANSWER When the amount of hormones is small, then the number of receptors increase in order to increase the sensitivity and obtain more of the hormones → Occurs with changes in development, cell cycle, and cell activity