Endocrine/Repro Flashcards
define endocrine
the source cell sends out a signal molecule/hormone that acts on a specific receptor
define autocrine
an autocrine cells releases a signalling molecule/hormones that acts on autocrine receptors on the cell that released the hormone
define paracrine
a cell signalling molecule/hormone released by a paracrine cell acts on a nearby target cell
local action
examples are renal autoregulation and neuromuscular junctions
define endocrine systems
an endocrine cell releases the cell signalling molecule that circulates through the blood to a distant target cell
what are endocrine glands?
a collection of glands that secrete hormones directly into the circulatory system to be carries toward a distant target
where is the right lobe of the pancreas found?
within the meso-duodenum
where is the left lobe of the pancreas found?
within a deep leaf of the greater omentum
is the pancreas an endocrine or exocrine gland?
both
what are the clusters of exocrine cells in the pancreas called?
acini
what are acini?
clusters of exocrine cells in the pancreas
what do acini produce?
digestive enzymes that flow through ducts into the GI tract
what are islets of Langerhans?
areas/clusters of endocrine tissue distributed among the exocrine tissue of the pancreas
what are the four types of endocrine cell in an islet of Langerhans and what do they do?
alpha cell- secretes glucagon
beta cell- secretes insulin
delta cell- secretes somatostatin
F cell- secretes pancreatic polypeptide
how is insulin produces and released?
beta cells synthesise pro-hormone called PROINSULIN
converted to active insulin by removal of inactive peptide water soluble polypeptide
binds to specific tyrosine kinase membrane receptor
what is the primary control of insulin secretion?
an increase in blood glucose concentration
where is blood glucose concentration detected?
by beta cells in the islets of Langerhans
what are the four further ways of controlling insulin?
GI hormones in feed-forward mechanism - anticipatory release of insulin before a meal
Parasympathetic activity - increase during and after a meal
Sympathetic activity - decreases insulin activity
Increase in plasma amino acids after a meal - increases insulin secretion
how does glucose move in and out of cells?
moves through specific protein channels called GLUT transporters
insulin increases the expression og GLUT 4 transporters
do all cells require insulin in order to take glucose into the cell?
no
cellular uptake of glucose is independent of insulin the brain (through GLUT 3) and mammary glands, GI tract and kidney tubules through secondary active transport with sodium
when is insulin the dominant hormone? is it anabolic or catabolic?
dominant in a fed state
anabolic
when is glucagon the dominant hormone? is it anabolic or catabolic?
dominant in the fasted state
catabolic
how does the liver respond to insulin?
Respond to insulin by increasing uptake of glucose via insertion of GLUT 4 transporters in their cell membrane within seconds.
No transporters = no glucose uptake so these cells will be starved of energy if there is insufficient insulin.
Glucose converted to glucose-6-phosphate, glycogen or fat.
what does a decrease in blood glucose concentration result in i the hepatocytes?
hepatocytes make glucose and transport out into the blood using GLUT 2 transporters
detected by beta cells in the pancreas, leads to a decrease in insulin in the plasma
what does an increase in the blood glucose concentration lead to in the hepatocytes?
increased glucose in the plasma, detected by beta cells, increased insulin in the plasma
glucose concentration reverses and glucose enters the hepatocytes using GLUT 2 transporter. Insulin stimulates hexokinase to maintain a low intracellular concentration of glucose.
how do animal ovarian cycles differ from that of humans?
animals don’t menstruate
shorter follicular phase (this is where menses would be in human)
shorter in total - average 21 days
what is oestrus?
animals signalling when they are able to become pregnant
what is the difference between the length of the cycle and the length of oestrus?
length of the cycles is referring from one oestrus period to the next
oestrus is the length of time where the sperm will survive to fertilise the ovum
when does LH peak?
at the end of oestrus
when does oestrogen peak?
towards the start of oestrus
when does progesterone peak?
around day 10 for a few days
what hormone can you administer to an animal to stimulate ovulation?
GnRH drives the hypothalamus which then releases an LH surge that stimulates ovulation
why is glucose control important for CNS function?
metabolism of CNS relies almost entirely on glucose
steady state of transport of glucose into cells
what are the four functions of insulin and what is its overall effect?
increased glucose oxidation
increased glycogenesis
increased lipogenesis
increased protein synthesis
overall - increased stores of glycogen, fat and protein
where is glycogen from and is it stored?
from alpha cells in islet of Langerhans
stored as active hormone in the alpha cells
what other things control glucagon?
increase in plasma amino acids after a meal stimulates secretion
parasympathetic activity stimulates secretion
sympathetic activity stimulates secretion
Why does an increase in plasma amino acids after a meal stimulate the
release of both insulin & glucagon?
It prevents post prandial hypoglycaemia in carnivores
are there more alpha or beta cells in an islet of Langerhans?
beta cells (insulin)
what causes type 1 diabetes?
inadequate insulin secretion
what causes type 2 diabetes?
abnormal target cell responsiveness
what are the clinical signs of diabetes?
hyperglycaemia
polydipsia and polyuria
ketoacidosis
how does diabetes mellitus cause polydipsia and polyuria?
hyperglycaemia caused as glucose cannot enter insulin-dependent cells
glucose is freely filtered into the nephron
ability of the kidneys to reabsorb filtered glucose is exceeded when the concentration of plasma glucose is above 10 – 12mM/l renal threshold for glucose reabsorption is exceeded
glycosuria causes an osmotic diuresis
increase in urination
ECF decreases and plasma osmolarity increases
thirst centre in hypothalamus is stimulated
what is polydipsia and polyuria?
polydipsia - increase in thirst
polyuria - increase in urination
in the liver, which biochemical process is stimulated by glucagon?
gluconeogenesis
what would cause an increase in insulin secretion?
increase in parasympathetic stimulation of the pancreas
