Endocrine System Overview

The primary function of the endocrine system is to secrete hormones that regulate various metabolic functions of the body.

Hormones travel from endocrine cells to their target cells through the bloodstream.

The three main classes of hormones discussed are proteins/peptides, amines, and steroids.

<p>Peptide bonds connect amino acids to form peptide chains in protein/peptide hormones.</p> Signup and view all the answers

<p>According to the classical endocrine definition, a hormone must be a chemical signal secreted by a cell, transported by the blood, and act on distant target tissues.</p> Signup and view all the answers

<p>It helps monitor the patient's endogenous insulin production.</p> Signup and view all the answers

<p>Peptide hormones are secreted through exocytosis, where vesicles fuse with the plasma membrane, releasing their contents.</p> Signup and view all the answers

<p>Half-life is the time it takes for half of the hormone molecules to be inactivated or cleared. Short half-lives limit clinical utility.</p> Signup and view all the answers

<p>Most protein/peptide hormones are soluble in aqueous solutions like blood, allowing unbound circulation.</p> Signup and view all the answers

<p>Protein hormones like insulin are digested in the gastrointestinal tract (GIT), rendering oral administration ineffective.</p> Signup and view all the answers

<p>cholesterol</p> Signup and view all the answers

<p>smooth endoplasmic reticulum</p> Signup and view all the answers

<p>They bind to carrier proteins.</p> Signup and view all the answers

<p>cytoplasmic or nuclear receptors</p> Signup and view all the answers

<p>genomic effect to activate or repress genes for protein synthesis</p> Signup and view all the answers

<p>non-polar</p> Signup and view all the answers

<p>yes</p> Signup and view all the answers

<p>21-hydroxylase</p> Signup and view all the answers

<p>Tyrosine</p> Signup and view all the answers

<p>Thyroxine (T4) and Triiodothyronine (T3)</p> Signup and view all the answers

<p>Bound to plasma proteins</p> Signup and view all the answers

<p>Thyroid hormones can be administered orally, but catecholamines cannot be</p> Signup and view all the answers

<p>Intracellular receptors</p> Signup and view all the answers

<p>Preformed vesicles</p> Signup and view all the answers

<p>The biologically active form of the hormone</p> Signup and view all the answers

<p>Serves transport, provides reservoir, buffers acute changes in hormone secretion, slows clearance from plasma</p> Signup and view all the answers

<p>Glucagon and growth hormone both oppose insulin's blood glucose-lowering action, but they each use different mechanisms to do so.</p> Signup and view all the answers

<p>The combination of glucagon and epinephrine results in a higher blood glucose level than either hormone alone.</p> Signup and view all the answers

<p>A circadian clock is an internal biological timekeeper operating on a daily cycle; a circadian rhythm is the biological process that is regulated by the circadian clock.</p> Signup and view all the answers

<p>It indicates that the circadian rhythms persist even in the absence of external time cues, showing they are driven by internal mechanisms.</p> Signup and view all the answers

<p>The term is 'hormonal rhythm'. Hormonal rhythms can range from minutes to months.</p> Signup and view all the answers

<p>Modern activities like shift work can significantly disrupt the body's internal circadian clock.</p> Signup and view all the answers

<p>Lightheadedness, difficulty concentrating, and fatigue.</p> Signup and view all the answers

<p>Circadian means 'about a day'.</p> Signup and view all the answers

<p>The magnitude of a cell's response to a hormone is directly related to the number of available hormone receptors on the target cell. More receptors generally lead to a greater response, while fewer receptors result in a diminished response.</p> Signup and view all the answers

<p>Spare receptors are cell surface receptors that exist in excess of what is required to produce a maximal response. They allow a maximum response even when only 15-25% of the receptors are bound to a hormone.</p> Signup and view all the answers

<p>Receptor downregulation is when the number of receptors on a target cell is reduced through receptor internalization via endocytosis and/or decreased receptor synthesis. This often occurs in response to increased hormone levels, and it leads to a reduced sensitivity of the cell to the hormone.</p> Signup and view all the answers

<p>Receptor affinity is the strength of the interaction between the receptor and the hormone. High affinity means that a lower concentration of hormone is needed to produce the same response, making the cell more responsive.</p> Signup and view all the answers

<p>Endocytosis is the process by which cells engulf portions of their membrane, including receptors bound to hormones. This leads to a decrease in the number of receptors on the cell surface and is therefore involved in receptor downregulation.</p> Signup and view all the answers

<p>In complex endocrine pathways, hormones often serve as negative feedback signals. They act to inhibit the earlier steps of the pathway, ensuring that hormone levels are kept within a narrow range.</p> Signup and view all the answers

<p>Hormone receptors typically have a high affinity for their respective hormones. This high affinity ensures that receptors can bind to the hormone even when plasma hormone concentrations are low.</p> Signup and view all the answers

<p>Receptor upregulation refers to an increase in the number of receptors on the target cell. This can occur through increased receptor synthesis or decreased receptor degradation.</p> Signup and view all the answers