Lecture 22- Endocrine 2 Flashcards
What is the posterior pituitary?
-comprises the posterior lobe of the pituitary gland and is part of the endocrine system., -it is a collection of axonal projections from the hypothalamus that terminate behind the anterior pituitary gland. It is where neurohypophysial hormones are stored and released.
What hormones are secreted in the posterior pituitary?
-secreted by the hypothalamus but stored in the posterior pituitary -posterior hormones= have a main job to do and connected to other hormones action -OXYTOCIN=Uterine contractions; lactation -VASOPRESSIN=Stimulates water retention; raises blood pressure by contracting arterioles, induces male aggression(also called antidiuretic hormone)
How is the hypothalamus connected to the posterior and anterior pituitary?
-hypothalamus directly linked to the posterior pituitary -the hypothalamus connects to a blood vessel that goes to anterior pituitary
What is the anterior pituitary?
-The anterior pituitary regulates several physiological processes including stress, growth, reproduction and lactation. - The anterior pituitary itself is regulated by the hypothalamus
Which hormones does the anterior pituitary produce?
-Growth hormone -Thyroid-stimulating hormone -Adrenocorticotropic hormone -Prolactin -Follicle-stimulating hormone -Luteinizing hormone
What does Oxytocin do?
-posterior pituitary hormone -Small peptide Functions: = uterine smooth muscle contraction = myoepithelial contraction (ie milk let down) =Maternal behavioral modifications -linking with stress the first letting of milk= triggered by oxytocin -feel good hormone -should be a natural thing -can be induced by an injection
What does Vasopressin do?
-posterior pituitary hormone =also called (AntiDiuretic hormone) -increases water retention in the kidneys -Causes arteriolar smooth muscle contraction -important for water retention
What does the thyroid stimulating hormone do?(TSH)
(anterior pituitary hormone) -stimulates the thyroid glands to produce the thyroid hormones (T3 and T4) -they stimulate metabolism in nearly all tissues of the body
What does the ACTH (adrenocortical hormone) do?
(anterior pituitary hormone) -stimulates adrenal cortex to release cortisol that controls metabolic actions and stress response
What does the growth hormone (GH) do?
-anterior pituitary hormone -stimulates the liver to make somatomedins(they make things grow) -make bones, soft tissues= grow! -another pathway is that it influences lot of other tissues metabollicaly
What are the Hypothalamic stimulatory & inhibitory peptides?
-Growth hormone-Releasing hormone - Thyrotropin-releasing hormone -Corticotropic-Releasing hormone -Gonadotropic-Releasing hormone -Prolactin-Releasing hormone -Prolactin-Inhibiting hormone
How does communication between the hypothalamus and the anterior pituitary occur?
-Communication between the hypothalamus and the anterior pituitary occurs through chemicals (releasing hormones and inhibiting hormones) that are produced by the hypothalamus and delivered to the anterior pituitary through blood vessels in the infundibulum. The releasing and inhibiting hormones are produced by specialized neurons of the hypothalamus, called neurosecretory cells. The hormones are released into a capillary network (primary plexus) and transported through veins (hypophyseal portal veins) to a second capillary network (secondary plexus) that supplies the anterior pituitary. The primary plexus and the hypophyseal portal veins are in the infundibulum and the secondary plexus is in the anterior pituitary. The hormones then diffuse from the secondary plexus into the cells of the anterior pituitary, where they initiate the production of specific hormones by the anterior pituitary. The releasing and inhibiting hormones secreted by the hypothalamus and the hormones produced in response by the anterior pituitary are listed in Table 1. Many of the hormones produced by the anterior pituitary are tropic hormones (tropins), hormones that stimulate other endocrine glands to secrete their hormones.
How does communication between the hypothalamus and the posterior pituitary occur?
-Communication between the hypothalamus and the posterior pituitary occurs through neurosecretory cells that span the short distance between the hypothalamus and the posterior pituitary (through the infundibulum). Hormones produced by the cell bodies of the neurosecretory cells are packaged in vesicles and transported through the axon, and stored in the axon terminals that lie in the posterior pituitary. When the neurosecretory cells are stimulated, the action potential generated triggers the release of the stored hormones from the axon terminals to a capillary network within the posterior pituitary. Two hormones, oxytocin and antidiuretic hormone (ADH), are produced and released in this way.
Is there negative feedback between the hypothalamus and the anterior pituitary?
-yes -hormone from hypothalamus to the anterior pituitary and that stimulates release of another hormone targeting endocrine gland that then releases another hormone= this hormones acts as a negative feedback on the hypothalamus and the anterior pituitary
What are the characteristics of the Growth hormone (Somatotropin)?
-Protein hormone of about 190 amino acids -Synthesized and secreted by cells called somatotrophs=up in the anterior pituitary -Receptor = Tyrosine Kinase -Regulates growth & metabolism -Possible role in diminishing aging effects -important even for individuals who are not growing anymore= metabolism -Secreted in a pulsatile manner(=indicates= negative feedback cycle, -pulsating way = sign of regulatory system, -negative feedback being detected by the system) -Differences between males & females; stage of maturity
What happens in the body when blood amino acids rise or blood fatty acids decrease? and exercise and decrease in blood glucose?
-stimulates the hypothalamus to release Growth hormone releasing hormone (GHRH) -that stimulates the anterior pituitary to produce growth hormone that targets the liver and makes Somatomedins/IGF1 which promote growth= so a rise in cell division, rise in protein synthesis (that decreases the amino acids in blood) and increases bone growth -also the GH has metabolic effects via the liver and somatomedins = -increased fat breakdown= that increases the fatty acids in the blood -also decreases the glucose uptake by muscles -so the glucose in blood increases -IGF1= insulin growth factor 1 -good to measure if you want to know what is happening in the system
How does a bone grow due to the GH?
-makes IGF1 from somatomedins -increases proliferation of cartilage cells (chondrocytes) via IGF-1, resulting in long bone growth -increase in bone thickness - IGF1 also increases differentiation & proliferation of precursor muscle cells (myoblasts) -in the early development we can stimulate for more muscle cell development, once you are mature that cannot happen -growing bone= can see the wedge of the cartilage -growth of a bone= the epiphyseal plate
What happens when a person has too much growth hormone?
-what happens when you have so much extra growth hormone: depends on th elevel of maturity -he is out of proportion, stimulates growth but unequally -later once not growing as the epiphyseal plate not present anymore -growth hormone continues to have effects on individual= acromegaly= the enlarged bones= jaw etc. look like neandrethals -Tumourof somatotropes=so producing lot of growth hormone= they produce it -acromegaly= more likely to occur in animals
What can dwarfism be a result of?
-decrease in GHsecretion -decrease in GHRH - decrease in Tissue sensitivity
What is the adrenal gland?
-the top of the kidneys - responsible for releasing hormones in response to stress through the synthesis of corticosteroids such as cortisol and catecholamines such as epinephrine (adrenaline) and norepinephrine. -affect kidney function through the secretion of aldosterone
What does the adrenal gland cortex release?
-Mineralcorticoids(ALDOSTERONE) -Glucocorticoids(CORTISOL) -(Sex hormones)
What does the adrenal gland medulla release?
-Epinephrine -Norepinephrine
What does aldosterone do?
-adrenal cortex releases it -central role in the regulation of blood pressure mainly by acting on the distal tubules and collecting ducts of the nephron, increasing reabsorption of ions and water in the kidney, to cause the conservation of sodium, secretion of potassium, increased water retention, and increased blood pressure
What does cortisol do?
-adrenal cortex releases it -It is released in response to stress and a low level of blood glucocorticoids. Its primary functions are to increase blood sugar through gluconeogenesis; suppress the immune system; and aid in fat, protein and carbohydrate metabolism. It also decreases bone formation - released in response to stress, sparing available glucose for the brain, generating new energy from stored reserves, and diverting energy from low-priority activities (such as the immune system) in order to survive immediate threats or prepare for the exertion of rising to a new day. However, prolonged cortisol secretion (which may be due to chronic stress or the excessive secretion seen in Cushing’s syndrome) results in significant physiological changes -Cortisol circulates bound to corticosteroid-binding globulin Transcortin -Anti-inflammatory & Immunosuppressive effects Manifested at high concentrations -Permissive actions -Treat Ketosis in ruminants ␣ ␣ Anti-inflammatory -ketosis= abnormal fat metabolism in sheep, cattle and horses -has effects on the adipose tissue
