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The endocrine system plays a critical role in maintaining homeostasis and regulating various physiological processes through the secretion of hormones. Understanding its intricacies is crucial for comprehending how hormones influence bodily functions and responses.
Hypothyroidism, caused by iodine deficiency or thyroid inflammation, results in reduced thyroid hormone production. This condition leads to symptoms such as lethargy, decreased body temperature, slowed respiratory and heart rate, cold intolerance, and weight gain.
Aldosterone, primarily regulated by the renin-angiotensin-aldosterone system, plays a vital role in sodium and water balance, thus influencing blood pressure regulation.
Gigantism occurs due to excessive growth hormone release during childhood, leading to abnormal growth of bones and tissues before epiphyseal plate closure, resulting in abnormally tall stature.
Hyperthyroidism arises from an excess of thyroid hormones, causing symptoms such as heightened activity levels, increased body temperature, elevated respiratory and heart rates, heat intolerance, and weight loss.
Peptide hormones are charged and unable to pass through the plasma membrane, requiring binding to extracellular receptors to initiate intracellular signaling cascades.
Epiphyseal plates are regions of growing bones that seal shut during puberty, marking the end of longitudinal growth.
Tropic hormones regulate the function of other endocrine glands. The hypothalamus controls the pituitary gland through tropic hormones, allowing it to exert widespread effects throughout the body.
C-cells, also known as parafollicular cells, produce calcitonin, which helps regulate calcium levels in the blood by increasing excretion from the kidneys, decreasing absorption from the gut, and promoting calcium storage in bones.
Cortisol, a glucocorticoid hormone, enhances the synthesis of catecholamines, which are involved in the body's stress response.
Diabetics often experience polyuria (increased urination) and polydipsia (increased thirst) due to glucose being excreted in the urine, causing dehydration and increased fluid intake.
Follicular cells of the thyroid gland produce thyroid hormones (T3 and T4) through iodination of tyrosine residues, which are essential for regulating metabolism and growth.
Calcitonin decreases plasma calcium levels by enhancing calcium excretion from the kidneys, reducing absorption from the gut, and promoting calcium storage in bones.
Insulin produced by beta cells in the pancreas lowers blood glucose levels by promoting cellular uptake of glucose and storage as glycogen.
Somatostatin, secreted by delta cells in the pancreas, inhibits the release of several hormones, including insulin and glucagon.
Oxytocin operates via a positive feedback loop, where its release during childbirth stimulates uterine contractions, further promoting its own release until delivery is complete.
Steroid hormones are lipid-soluble and can pass through the plasma membrane to bind intracellular receptors, exerting slower but longer-lasting effects compared to peptide hormones.
ACTH (adrenocorticotropic hormone) stimulates the adrenal cortex to produce cortisol and other glucocorticoids, essential for stress response and metabolism.
FSH and LH (follicle-stimulating hormone and luteinizing hormone) act on the testes and ovaries, regulating gamete production and sex hormone secretion.
TRH (thyrotropin-releasing hormone) acts on the thyroid gland, stimulating the release of TSH (thyroid-stimulating hormone) to regulate thyroid hormone production.
The adrenal glands, located on top of the kidneys, produce hormones such as cortisol, aldosterone, and adrenaline, crucial for stress response and electrolyte balance.
The posterior pituitary stores and releases hormones (e.g., oxytocin, ADH), synthesized in the hypothalamus.
Thyroid hormones (T3 and T4) are synthesized from tyrosine and iodine atoms in follicular cells, crucial for metabolism regulation and growth.
Types of hormones include peptides (e.g., insulin), steroids (e.g., cortisol), and amino acid derivatives (e.g., epinephrine).
Direct hormones produced by the anterior pituitary include prolactin, endorphins, and growth hormone, which act directly on target tissues.
In summary, the endocrine system's intricate network of glands and hormones regulates various physiological functions, ensuring homeostasis and responding to internal and external stimuli effectively. Understanding these mechanisms is crucial for comprehending health and disease processes encountered in medical contexts like the MCAT.