Endocrine Flashcards
what’s included in the classical endocrine system?
Hypothalamus Pituitary gland Thyroid gland Parathyroid gland Adrenal glands Pancreas Testis Ovaries
Primary functions of the endocrine system?
Growth + development: hormone release plays primary and permissive role in development
Reproduction: regulate growth of sexual organs, pattern of sexual behaviour
Maintenance of Homeostasis: control ECF, electrolyte composition and bone, muscle, fat stores
Energy balance regulation: store energy and mobilise it when necessary, balancing food consumption and energy expenditure
Where do endo and exocrine glands secrete their products?
Endocrine glands secrete into interstitial fluid and then blood (pituitary; thyroid)
Exocrine glands secrete into ducts (salivary; sweat)
Define autocrine and paracrine hormones
bioactive messenger molecules
Autocrine: act on cells that released them (endothelial cells will secrete hormone that triggers development of endothelium)
Paracrine: act on cells adjacent to the cell that released it (neurotransmitters released at synapse, impact neighbouring cell)
Outline the processes of peptide hormone production
Synthesised in ribosomes
enzymatically cleaved in the ER
Packaged in secretory vesicles in the golgi apparatus
exocytosis (membrane-bound vesicles transported to cell membrane
In hormone context, describe a negative feedback loop
Gland A secretes hormone A
hormone A stimulates production of hormone B from gland B
hormone B triggers desired effect and inhibits production of hormone A
Outline the journeys of water soluble and lipid soluble hormones from production to target cell
Water soluble
Hormone produced, exocytosis occurs due to vesicles transporting hormone past the plasma membrane
transported freely in blood, picked up by receptors on surface of target cell
Lipid soluble
Diffuse freely across plasma membrane, require transport protein molecule to move through blood
diffuse across target cell membrane, modified by enzymes in target cells, nuclear receptors act as transcription factors
What do hormones bind to specifically?
Receptor site of glycoproteins
receptor specificity
2 types of cell receptors?
Cell surface + intracellular
Outline cell surface receptor pathway
Hormone binds to plasma membrane receptor
G protein pathway activated
Adenylate cyclase
ATP > cAMP
Activates protein kinases
They phosphorylate cellular proteins
lots of phosphorylated proteins cause physiological change
Outline intracellular receptor pathway
Hormone diffuses into plasma membrane
binds to receptors in cytoplasm or nucleus
hormone-receptor complex alters gene expression
Altered DNA formed
altered mRNA formed
messenger RNA directs synthesis of new specific proteins that bring about physiological changes
What are islets of langerhans, what are the 4 types?
Pancreatic cells that secrete glucagon and insulin
Alpha - Beta - Delta - F
What do alpha cells (pancreas) secrete and what does it do?
Secrete glucagon - raises blood glucose level by accelerating breakdown of glycogen into glucose in the liver (glycogenolysis)
converts other nutrients into glucose (gluconeogenesis)
What do beta cells (pancreas) secrete and what does it do?
Secrete insulin - decreases blood glucose level by accelerating movement of glucose into cells, converting to glucose to glycogen (glycogenesis)
inhibits gluconeogenesis and glycogenolysis
What is the GSIS mechanism?
Describe it
Glucose Stimulated Insulin Secretion
Glucose is transported into the cell by GLUT-2, a transporter protein
It is phosphorylated by glucokinase to become glucose-6-phosphate
Undergoes glycolysis, krebs, ETC in the mitochondria, ATP is produced
the change in ATP : ADP ratio triggers the closing of the ATP sensitive K+ channel proteins
This causes the cell membrane to depolarise if -55mV threshold is met (-70mV at rest)
Voltage dependent Ca2+ channels (CDCC) open, influx of Ca2+ into the cell
Ca2+ binds to vesicles (made by golgi) containing insulin, vesicles near membrane surface release insulin out of the cell
Blood insulin increases and therefore blood glucose decreases
2 characteristics of type 2 diabetes?
Characterised by:
Dysfunction of pancreatic b cells to produce and secrete insulin
Insulin resistance, inability of cells to respond to insulin
A common anti-diabetic drug affects the cell in what way that overrides a symptom of diabetes?
In a diabetic person, less insulin is being made, therefore less glucose is getting transported into the cells
Without glucose, the GSIS mechanism cannot occur
The antidiabetic drugs inhibit (close) the ATP gated K+ channels that would usually close due to the change in ATP:ADP ratio in the cell
Leading to the depolarisation of the membrane, the VDCC to open, Ca2+ influx and exocytosis of the insulin contained within the vesicles
What is the difference between GLUT2 and GLUT4
GLUT2 is found in the liver, pancreas etc
GLUT4 is found in the muscle, adipose, heart
GLUT 4 is not naturally found in the membrane, it is present on vesicles in the intracellular space
Someone is suffering with hypoglycaemia, what could counteract this and why?
Glucagon, as it increases blood glucose by stimulating gluconeogenesis and glucogenolysis (breakdown of glycogen to glucose)
Describe Type 1 Diabetes Mellitus
A lack of insulin secreting b pancreatic cells
Without insulin, Glucose cannot enter the cells, leads to high blood glucose levels
Also high volume of urine with high solute concentration
