Endocrine Physiology Quiz

Anterior Pituitary Hormones

• 7 major stimulatory hormones released by the anterior pituitary:
  • Adrenocorticotropic hormone (ACTH): targets adrenal cortex, increases steroidogenesis (cortisol and androgenic hormones)
  • Melanocyte-stimulating hormone (MSH): targets pigment cells, promotes melanin secretion and lipotropin
  • Thyroid-stimulating hormone (TSH): targets thyroid, increases thyroid hormone production and iodine uptake
  • Growth hormone (GH): targets muscle, bone, and liver, essential for normal tissue growth and maturation

Hormone Characteristics

• Specific rates and rhythms of secretion
• Operate within feedback systems (positive or negative) to maintain optimal internal environment
• Affect only target cells with appropriate receptors, initiating specific cell functions or activities
• Excreted directly by the kidneys or deactivated by the liver for renal excretion

Hormone Types

• Steroids: cortisol from adrenal cortex, estrogen, progesterone from ovaries, testosterone from testes
• Amino acids: tyrosine and thyroxine from thyroids, catecholamines from adrenal medulla
• Proteins: peptides like insulin from pancreas

Hormone Regulation

• Chemical factors (blood sugar or calcium levels)
• Endocrine factors (hormone from one endocrine gland controlling another)
• Neural control
• Negative feedback is the most common type, maintaining hormonal secretion within a physiologic range

Hormone Circulation

• Water-soluble hormones (insulin, pituitary, hypothalamic, parathyroid, norepinephrine, and epinephrine) circulate in free, unbound forms, with short-acting response and catabolized by circulating enzymes
• Lipid-soluble hormones (cortisol, adrenal androgens, aldosterone, estrogens/progesterone, testosterone) circulate bound to a carrier protein, with rapid and long-lasting response

Target Cells

• Recognize and bind with high affinity to hormones, initiating a signal
• Up-regulation: low concentrations of hormones increase the number of receptors per cell
• Down-regulation: high concentrations of hormones decrease the number of receptors

Hypothalamus

• Connected to anterior pituitary by portal blood vessels
• Connected to posterior pituitary by a nerve tract (supraopticohypophsial tract)
• Produces hormones: PIF (dopamine), TRH, GnRH, somatostatin, GRF, CRH, and Substance P

Posterior Pituitary Hormones

• Antidiuretic hormone (ADH, arginine vasopressin): controls plasma osmolality, causes water reabsorption in kidneys
• Oxytocin: causes uterine contractions and milk ejection, serves as co-factor with vitamin D to increase calcium absorption

Endocrine Pancreas

• Produces hormones glucagon and insulin
• Houses the islets of Langerhans, with different cell types secreting various hormones:
  • Alpha cells: secrete glucagon
  • Beta cells: secrete insulin and amylin
  • Delta cells: secrete somatostatin and gastrin
  • F cells: secrete pancreatic polypeptide

Insulin

• Synthesized from proinsulin in beta cells
• Anabolic hormone, promotes synthesis of proteins, lipids, and nucleic acids
• Facilitates glucose uptake into cells, controlling blood glucose levels
• Regulated by chemical, hormonal, and neural control
• Secretion promoted by increased blood glucose levels, amino acids, and parasympathetic stimulation
• Secretion diminishes with low blood glucose levels, high insulin levels, and sympathetic stimulation

Other Hormones

• Prolactin: targets breast, functions in milk production, with effects on reproductive and immune functions
• Luteinizing hormone (LH): targets granulosa cells in women, Leydig cells in men, functions in ovulation, progesterone production, testicular growth, and testosterone production
• Follicle-stimulating hormone (FSH): targets granulosa cells in women, Sertoli cells in men, functions in follicle maturation, estrogen production, and spermatogenesis

Explore the characteristics of hormones in endocrine physiology, including autocrine, paracrine, and endocrine signaling. Learn about the specific rates of secretion, feedback systems, target cells, and the effects of hormones on cell functions.