Calcium ions Cyclic-AMP (cAMP)- first messenger activates G protein, activates kinase enzyme adenylate cyclase which converts ATP to ring shaped molecule. Phosphate group attaches in phosphorylation. Single hormone, one effect in one target tissue and different effects in other target tissues. Phosphodiesterase inactivates cAMP converting AMP Hormones released where there is a large amount of capillaries, enter bloodstream, hormones circle freely and travel when bound to transport protein Intracellular Receptors Receptors are inside cytoplasm or nucleus, used for lipid-soluble hormones Hormones cross plasma membrane, form hormone-receptor complex- activates or inactivates specific genes which alters the rate of mRNA transcription which will change the function of the cell Hormone Secretion Enter blood throughout body Freely circulating hormones short-lived Inactivated when: o Diffuse to target cells and bind to receptors o Absorbed and broken down in liver and kidneys o Broken down by enzymes in plasma membrane or interstitial fluid If bound to transport protein they stay in circulation longer, equilibrium Lipid/Steroid hormones are able to diffuse across membranes Control Negative feedback o Humoral Stimuli- changes in composition of extracellular fluid, stimuli’s triggers production of hormone direct or indirect to effect or reduce intensity of stimulus o Hormonal Stimuli- changes in levels of circulating hormones o Neural Stimuli- neural stimulation of neuroglandular junction through neurotransmitters, neurotransmitter arrives at neuroglandular junction, involves activity of hypothalamus
Hypothalamus and Endocrine Control Hypothalamus- highest level of endocrine control, link between nervous and endocrine systems Coordinating centers regulates by: o Hypothalamus secretes two hormones directly into general circulation: ADH and oxytocin- transported along axons posterior of pituitary gland o Hypothalamus secretes releasing and inhibiting hormones to control anterior pituitary secretions Releasing Hormones- stimulate synthesis and secretion of one or more hormones in anterior lobe Inhibiting Hormones- prevent synthesis and secretion or pituitary hormones, hormones released by anterior lobe of pituitary gland control other endocrine glands o Hypothalamus contains ANS centers that control adrenal medullae through sympathetic innervation. ANS control endocrine cells of the adrenal medullae through sympathetic innervation 10.3 Pituitary Gland Hypophysis o Protected by sella turcica of sphenoid bond o Hangs from hypothalamus connected by slender stalk call infundibulum Anterior and posterior are structured differently Nine hormones are secreted, peptide hormones o 7 anterior lobe o 2 posterior lobe o All use cAMP second messenger and mind to membrane receptors Anterior Lobe of Pituitary Gland Adenohypophysis Endocrine cells surrounded by extensive capillary network hormones and they secrete
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