The Endocrine System Flashcards
What hormones are released by the anterior pituitary gland?
GH, TSH, adreno-corticotropic hormone, LH, FSH, prolactin
What hormones are released by the posterior pituitary gland?
Oxytocin, ADH (vasopressin)
What hormones are released by the hypothalamus?
Thyrotropin-Releasing hormone (TRH), Corticotropin-Releasing hormone (CRH), Gonadotropin-releasing hormone (GnRH), Prolactin-releasing hormone (PRH), Prolactin-inhibiting hormone (PIH) (dopamine), Growth-hormone releasing hormone
(GHRH), Growth-hormone inhibiting hormone (GHIH)
(somatostatin) (SS)
State the functions of the endocrine system.
Regulates metabolism and H2O and electrolyte balance, Induces adaptive changes to help cope with stressful situations, Promotes smooth, sequential growth and development, Controlling reproduction, Regulating red blood cell production, (along with the autonomic nervous system) controlling and integrating activities of both the circulatory and digestive systems.
Which stalk connects the hypothalamus and the pituitary gland?
The infundibular stalk
Describe the embryology of the pituitary gland.
The posterior pituitary is an epithelial structure that develops from Rathke’s pouch, a depression in the roof of the embryo’s mouth. The anterior pituitary is a neural structure that develops from the floor of the midbrain.
How is oxytocin and ADH produced?
ADH: When ECF is hypertonic and H2O must be conserved in the body or when ECF is hypotonic and H2O must be expelled from the body, the secretion of ADH is controlled using negative feedback. Reduced activity of hypothalamic osmoreceptors inhibits ADH secretion and vice versa.
What are the roles of ADH?
ADH controlled variable water reabsorption occurs in the final stages of the tubules in the kidney. Controls blood volume.
Describe the mechanism of action of ADH in water metabolism.
While 65% of the water volume’s absorption is obligatory in the proximal tubules, the distal tubules reabsorption of water is vasopressin-controlled. For H2O absorption to occur in the kidneys, an osmotic gradient must occur across the tubules and the tubular segment must be permeable to H2O. The distal and collecting tubules are impermeable to H2O except in the presence of ADH. Vasopressin reaches the basolateral membrane of the tubular cells lining the distal and collecting tubules through the circulatory system and binds with the V2 receptor specific to it. This binding activates the cAMP (cyclic adenosine monophosphate) secondary-messenger system within the cell. cAMP increases the opposite luminal membrane’s permeability to H2O by promoting the insertion of AQP-2 (aquaporin) water channels into the membrane. This membrane is impermeable to water in the absence of vasopressin. Water enters the tubular cell from the tubular lumen through the inserted water channels. Water exits the cell through AQP-3/4 permanently positioned at the basolateral border, and then enters the blood in this way being reabsorbed.
Describe the mechanism of action of ADH in blood volume.
Baroreceptors in the heart’s left atria detect stretch, the vagus nerve and CN IX then sends a signal to the hypothalamus resulting in less ADH release in the posterior pituitary and so less water reabsorption, leading to less volume of water in blood.
How is ADH supplemented clinically?
Vasopressin is used in emergency vasodilatory (septic) shock. It effects vasoconstriction. Felypressin is used in this manner to enhance the duration of local anesthetic.
Desmopressin (specific for V2 receptors, renal) reduces enuresis, replaces deficiency in central diabetes inspidus and increases release of von Willeband factor and factor VIII.
Terlipressin (V1 specific, vascular) controls variceal bleeding due to splanchnic shock and is used as a vasopressin substitute.
What is the function and target cells of oxytocin?
Oxytocin targets the uterus and the mammary glands in which it causes increased contractility and milk ejection respectively.
eWhich part of the pituitary synthesises hormones.
The anterior pituitary
What are the different cell types found in the anterior pituitary?
Somatotrophs make GH.
Thyrotropes make TSH.
Corticotropes make ACTH.
Gonadotropes make FSH and LH.
Lactotrophs make prolactin.
What are the factors affecting anterior pituitary hormone secretion? What are the 7 hypophysiotropic hormones?
Hypothalamic hormones and feedback by target gland hormones. Thyrotropin RH, Corticotropin RH, gonadotropin (GnRH), GHRH, somatostatin (GHIH), PRH, dopamine (PIH).
Describe the vascular link between the hypothalamus and the anterior pituitary. (1st factor)
Hypophysiotrophic hormones produced by neurosecretory hormones in the hypothalamus enter the hypothalamic capillaries. These hypothalamic capillaries rejoin to produce the hypothalamic-hypophyseal portal system, a vasular link to the anterior pituitary. The portal system branches into the capillaries of the anterior pituitary. The hypophysiotropic hormones, which leave the blood across the anterior pituitary capillaries, control the release of anterior pituitary hormones. When stimulated by the appropriate hypothalamic releasing hormone, the anterior pituitary secretes a given hormone into the capillaries. The anterior pituitary capillaries rejoin to form a vein, through which the anterior pituitary hormones leave for ultimate distribution throughout the body by systemic circulation.
Describe the hierarchical chain of command and negative feedback in endocrine control.
Describe the release of GH.
It is released in pulses. It is released from the anterior pituitary in several bursts in the early morning. Its secretion is simulated in deep sleep. It spikes in the 1st 2 hours of sleep. It is high in puberty, lower in adults, nearly non-existent in those aged above 50.
