Fichas
Endocrine Y1&2
Fichas del conjunto (26)
- 1What is the difference from paracrine, autocrine and endocrine hormones ?Paracrine and autocrine are local hormones. Paracrine targets local cells where as autocrat targets itself.
Endocrine is a circulating hormone. - 2What makes up the pancreas?Most of the exocrine cells of the pancreas are arranged in clusters called acini and produce digestive enzymes which flow through ducts into the GI tract. Distributed among the acini are clusters of endocrine tissue called pancreatic islets (islets of Langerhans)
- 3Wha are the 4 types of endocrine cells in the pancreas and what do they secrete?Alpha cell (secretes glucagon)
Beta cell (secretes insulin)
Delta cell (secretes somatostatin)
F cell (secretes pancreatic polypeptide) - 4Primary control of insulin secretion and what is its affect on other cells?Increase in Blood glucose directly detected by β cells in the islets
1. Glucose enters the β cell (via GLUT 2)
2. Raised intracellular glucose fuels the formation of more ATP.
3. β cells have ATP-sensitive potassium channels
4. Raised levels of ATP block these channels and potassium accumulates within the cytoplasm to a level where they cause depolarisation of the cell membrane.
5. Depolarisation opens voltage-gated calcium channels.
6. Calcium floods into the cells from the extracellular fluid and triggers exocytosis of vesicles loaded with insulin.
7. Insulin stimulates uptake of glucose by muscle and fat cells, so the sugar level in blood and extracellular fluid drops, less sugar enters the β cells, they produce less ATP and finally potassium can flood out of the unblocked potassium channels, so restoring the membrane potential. = End of insulin secretion! - 5What controls insulin secretion(5)?Increase in Blood glucose directly detected by β cells in the islets
• GI hormones, GIP & GLP-1 (feed forward)
– anticipatory release of INSULIN is thought to prevent sudden surge in glucose absorption following a meal
• Parasympathetic activity – increase during &afterameal
• Sympathetic activity – decrease insulin secretion
•plasma amino acids after meal –increase INSULIN - 6What does insulin do?Insulin increases glucose uptake into cells
increases: Glucose oxidation, Glycogenesis, Lipogenesis, Protein synthesis
Overall effect = increased stores of glycogen, fat and protein - 7How does glucose move in and out of cells?Not lipid soluble so moves through specific
protein channels (GLUT transporters) - 8Do all cells require insulin in order to take glucose into the cell?No the cellular uptake of glucose is independent of insulin in
• Brain (GLUT 3),mammary gland, GI tract and kidney tubules (secondary active transport coupled to sodium transport) - 9Insulin and the CNS?• Tight control of glucose is essential for CNS function BUT neurones ARE NOT themselves sensitive to insulin
• Metabolism of CNS neurons relies almost 100% on glucose
– they have a steady state of transport of glucose into cells. i.e. cannot increase or decrease rate of transport.
• Level of glucose in CSF (cerebrospinal fluid/extracellular fluid of the CNS) is directly proportional to blood sugar.
– Excess glucose increases the osmolarity of CSF and draws water out of the neurons
– Too little glucose and the neurons starve.
Cells of the CNS are not sensitive to insulin - 10What is Glucagon about?• Alpha cells secrete and store active hormone • Water soluble polypeptide
• Half-life 4– 6 mins
• Binds to specific G-protein – coupled membrane receptor
• Glucagon is release when “glucose has gone” • plasma amino acids after meal
–increase Glucagon • Parasympathetic activity
–increase GLUCAGON
• Sympathetic activity
– increase GLUCAGON
Glucagon is catabolic and increases:Gluconeogenesis Glycogenolysis Ketogenesis - 11Does insulin or Glucagon dominate in the fasted state.Fasted state : GLUCAGON dominates
it increases Gluconeogenesis, Glycogenolysis, Ketogenesis
Fed state : INSULIN dominates it increases Glucose oxidation Glycogenesis Lipogenesis, Protein synthesis - 12What does somatostatin do?decreases Growth hormone
Paracrine inhibition of insulin & glucagon release - 13How are ketone bodies produced?Adipose tissue in fasted state breaks down fat stores. Fatty acids enter bloodstream. Liver uses β oxidation to break down fatty acids BUT not all acetyl coA can enter citric acid cycle & excess acetyl Co A forms ketone bodies such as acetone
β hydroxybutyrate - 14What are the two chemical classes of hormone? Lipid soluble hormones bind to receptors in the cytoplasm or nucleus of the cell
Water soluble hormones bind to receptors on the surface of the cell - 15How does calcium homeostasis occur?• Intestinal absorption
• renal excretion
• release & uptake from bone
Activated vitamin D3 increases
• Parathyroid hormone increases
• Calcitonin decreases - 16What does calcitriol do?• Lipid soluble.
• Transported bound to vitamin – D binding
globulin
• Binds intracellular receptors
• Overall effect is to increase the concentration of calcium in blood plasma
– Enhances Ca2+ uptake from small intestine – Increases renal reabsorption of calcium
– Increases mobilisation of calcium from bone
– The metabolism of vitamin D and thus the production of calcitriol is regulated - 17What does Parathyroid Hormone do?• Cells in the parathyroid gland directly detect very small decrease infree [Ca2+ ]
• PTH released
• Overall effect is to increase the concentration of calcium in blood plasma
– by affecting transport mechanisms in bone, the kidneys & indirectly (via VIT D) the intestine
increase absorption of Ca2+ from the GI tract, increase mobilisation of calcium from bone and decrease urinary excretion of calcium - 18Where is Calcitonin made?it is
made by the parafollicular (C-cells) of the thyroid gland - 19What does CALCITONIN do?increases Ca in the ECF stimulates secretion
Overall effect is to PREVENT HYPERCALCAEMIA - 20Where is the endocrine gland?Paired, lying beneath the peritoneum, cranio-medial to the corresponding kidney
- 21What are the zone of the adrenal gland and what do they secrete?Outer:Zona glomerulosa (MINERALOCORTICOIDS (aldosterone))
Zona fasciculata (GLUCOCORTICOIDS(cortisol))
Zona reticularis(ANDROGENS)
medulla(adrenalin and noradrenaline) - 22From the three zones of the adrenal gland what type of molecules are produced and what are they produced from?The cortex is subdivided into three zones, each of which secretes a different group of lipid-soluble steroid hormones (corticoids) all formed from the cholesterol molecule
- 23What do mineralcorticoides do and give an example?Regulate the concentrations of Na+ and K+ in
the blood (affects blood volume/pressure)
– Aldosterone is the major hormone in this group – Bound to corticosteroid-binding globulin (CBG)
and albumin in blood – Half life 20 mins
– Inactivated in the liver - 24What does aldosterone do and how is it regulated?• Causes a rapid increase in Na+ reabsorption & K+ secretion in principal cells of DCT and collecting duct in the kidney
• Similarly increases Na+ reabsorption in salivary glands & large intestine
• Increased Na+ is accompanied by reabsorption of water and thus INCREASES volume of ECF and INCREASES arterial blood pressure
• Two major regulators
– RAAS renin increases when arterial blood pressure falls.... ANP inhibits aldosterone secretion
– Plasma potassium directly affects aldosterone-producing cells (depolarises cell membrane) Elevation of potassium conc. by 0.1mM/l will increase aldosterone in plasma by 30%
Minor regulators
ACTH - required for secretion but minor role in regulation
Na in ECF – decrease in Na will moderately simulate aldosterone secretion - 25What are glucocorticoids and what do they do?• EffectCHO,lipid&proteinmetabolismCortisolisthe major hormone in this group
– Bound to CBG and albumin in blood
– Half-life 70 mins (3 – 4 times longer than aldosterone
because more tightly protein bound – Inactivated in the liver
• Glucocorticoids(mainlycortisol)regulatemetabolism by promoting gluconeogenesis in the liver &uptake of glucose by tissues other than brain. Increased blood sugar levels assist the body to cope with stress
• Stimulatesdegradationfat&protein
– Enhances lipolysis
– Causes breakdown of skeletal muscle proteins to provide
substrate for gluconeogenesis
allowing oxidation of fatty acids & amino acid for energy use and so preserving cell glucose
• Permissive action on other hormones
– Must be present for catecholaminesvasoconstriction – Normal activity of glucagon
• Suppresses immune system
– High concentration of cortisol can reduce/reverse
inflammatory & allergic responses ( immunosupression)
• Causes negative calcium balance - 26What are catecholamines and what do they do?• Adrenaline, noradrenaline & dopamine – Produced in adrenal medulla
– Derived from amino-acid tyrosine – Water-soluble
• Increase cardiac output –increase HR, contractility –increase blood pressure
• Redistribution of blood to skeletal muscles
• Increase the plasma glucose concentration – glycogenolysis
– gluconeogenesis
• increase breakdown of triglycerides and therefore increases plasma fatty acids
Información
- Descripción
- Veterinary Medicine Fichas sobre Endocrine Y1&2, creado por Heather M el 18/08/2018.
- Creado por
- Heather M
- Visitas
- 1
- Valoración