lab assessment,lab work,

Endocrine System Physiology4EXERCISEOBJECTIVES1. To define the following: hormones, target cell, negative feedback,metabolism, thyroxine, thyroid stimulating hormone (TSH), thyrotropinreleasing hormone (TRH), hypothalamus, hypothalamic pituitary portalsystem, portal vein, hormone replacement therapy, diabetes type I, dia-betes type II, glucose standard curve2.To give examples of how negative feedback loops regulate hormonerelease3.To explain the role of thyroxine in maintaining an animal’s metabolic rate4.To explain the effects of thyroid stimulating hormone (TSH) on ananimal’s metabolic rate5.To understand the role of the hypothalamus in the regulation of thyrox-ine and TSH production6.To understand how hypothalamic hormones reach the pituitary gland7.To understand how estrogen affects bone density8.To explain how hormone replacement therapy works9.To explain how fasting plasma glucose is used to diagnose diabetes10.To understand how levels of cortisol and ACTH can be used todiagnose endocrine diseases.
the endocrine system regulates the functioning of every cell, tissue, andorgan in the body. It acts to maintain a stable internal body environment,regardless of changes occurring within or outside of the body. Endocrinecells have the ability to sense and respond to changes via the excretion of spe-cific chemicals known as hormones.Hormones are carried in the blood, usu-ally attached to specific plasma proteins, and circulate around the body. Whenthe hormone-protein complex reaches a target cell(the cell at which a chemi-cal message is aimed), the hormone detaches from the protein and enters thecell to induce a specific reaction.Hormones work in different ways, depending upon their chemical structures.For example, polypeptide hormones,composed of chains of amino acids, workby first attaching to a protein receptor in the cell membrane, initiating a series ofreactions in the membrane resulting in cyclic adenosine monophosphate(cAMP)entering the cell. The entrance of this chemical into the cell induces the cell towork harder and faster. Steroid hormonesand thyroxine(a hormone secreted bythe thyroid, which we will be examining in detail shortly) enter the cell to attachto a cytoplasmic receptor. The hormone-receptor complex then enters the nucleusof the cell to attach to specific points on the DNA. Each attachment causes theproduction of a specific mRNA, which then moves to the cytoplasm to be trans-lated into a specific protein.Most regulation of hormone levels in the body is conducted by negativefeedback:if a particular hormone is needed, production of that hormone will bestimulated; if there is enough of a particular hormone present, production of thathormone will be inhibited. In a few very specific instances, hormonal output iscontrolled by positive feedbackmechanisms. One such instance is the output ofthe posterior pituitary hormone oxytocin.This hormone causes the muscle layerof the uterus, the myometrium,to contract during childbirth. Contraction of the.