Hormonal Communication Flashcards
what are hormones
.signalling molecules secreted by endocrine glands that affect target cells that contain complementary receptors on their plasma membrane
what are endocrine glands
.ductless glands that secrete hormones directly into the blood stream
.e.g. adrenal gland
what are exocrine glands
.glands that secrete substances into a duct that carries them to a particular target in the body
Where are adrenal glands located
.above the kidneys
what are adrenal glands composed of
.an outer adrenal cortex surrounding the inner adrenal medulla
what does the adrenal cortex do
.produces mineralocorticoids that target kidney to control the concentration of sodium and positum ions in the blood
.e.g. aldosterone
.also secretes glucocorticoids like cortisol and corticosterone which stimulate a increase in blood glucose concentration
what does the adrenal medulla do
secretes adrenaline in response to danger, stress or excitement
what is the pancreas endocrine function
.Islets of Langerhans secretes insulin from beta cells and glucagon from alpha cells into the blood
what is the pancreas exocrine function
.secretes digestive enzymes like amylase, trypsin and lipase to the duodenum via pancreatic tract
What do alpha and beta cells contain
.many ribosomes and RER to produce protein hormones
.Golgi apparatus to package hormones into vesicles and are secreted via exocytosis by secretory vesicles
.many mitochondria as they are very active
what happens when blood glucose is too high
.the rise is detected by beta cells
.insulin is secreted by beta cells, inhibiting the action of alpha cells
.insulin travels to target cell in the liver, fat and muscles
.insulin binds to receptors on the plasma membrane of the cells causing vesicles containing glucose transport proteins to fuse with cell membrane
.this increases permeability of the cells to glucose
.increasing the uptake of glucose into the cell
.glucose then converted into glycogen or fats used for respiration
what is the correct blood glucose range?
90mg per 100cm of blood
how is insulin secretion controlled
.beta cells contain potassium and calcium ion channels
.as P ions diffuse out of the cell, the inside becomes more negative(potential diff -70mV)
.as glucose conc increases, glucose diffuses into beta cells through channel proteins down the conc gradient
.ATP is produced from respiration of the glucose and causes P ion channels to close
.P ions diffuse out of cell so the potential inside becomes positive
.depolarisation occurs opening calcium ion channels and allowing Ca2+ to enter
.causing vesicles containing insulin to fuse with plasma membrane via exocytosis
what happens when blood glucose is too low
.alpha cells detect change and secrete glucagon, inhabiting the beta cells
.glucagon stimulates hepatocytes to convert glycogen into glucose(glycogenolysis)
.glucose diffuse out of the hepatocytes into the blood
.cells use fatty acids and amino acids for respiration instead
what is diabetes mellitus
.disease where the body cannot control the blood glucose levels
