Hormonal Communication Flashcards
What is a hormone
Chemical messenger released by endocrine glands that travels in the bloodstream and acts on target cells
What are the two type of hormones what does this mean
Peptide - Lipid insoluble can’t diffuse through phospholipid bilayer
Steroid - Lipid soluble can diffuse through phospholipid bilayer
Explain the sequence of a peptide hormone
Binds to a specific receptor on the cell surface membrane
Activates a g-protein which activates adenylyl cyclase
This enzyme converts ATP into cAMP
Results in a cascade of events
e.g. adrenaline
What is the primary and secondary messenger in a peptide hormone sequence
Primary - Hormone
Secondary - cAMP
Explain the sequence of a steroid hormone
The hormone diffuse through the phospholipid bilayer and binds to a specific receptor in the cell
This has a direct effect on the DNA in the nucleus as gene transcription is altered
What are the adrenal glands
Endocrine gland located on top of the kidney
Made of an adrenal cortex (outside) and an adrenal medulla (inside)
Describe the adrenal cortex
Zona
Glomerulusa - mineral corticoids e.g. aldosterone
Fasciculata - glucocorticoids e.g. cortisol
Reticularis - precursor molecules
These are in response to stress
Increased blood volume and pressure
Increased Na+ uptake in kidneys
Increased fat and lipid breakdown
Describe the adrenal medulla
Involved in fight of flight response Secretes adrenaline Glycogenolysis Relax smooth muscle Increased stroke volume/heart rate Vasoconstriction of non essentail organs Pupils dilate Pilo erection Peristalsis inhibited
What is the pancreas
It is an exocrine and endocrine gland
Describe the exocrine function of the pancreas
Secretes ‘pancreatic juices’ that contain digestive enzymes into small intestine
They include amylase, trypsin, NaHCO3 and lipase
The acinus are small group of cells surrounding the tubules
They are grouped in small lobules separated by connective tissue
Intralobular ducts – pancreatic ducts – duodenum
Describe the endocrine function of the pancreases
Contains clusters called the Islets of Langerhans
Made of Alpha and Beta cells
The alpha cells secrete glucagon and beta cells secrete insulin
What is the role of the alpha cells what happens following this
Secretes glucagon that acts on the liver cells when blood glucose levels are too low
Glycogenolysis - glycogen to glucose
Gluconeogenesis - fatty and amino acids to glucose
Rate of respiration is lowered as you don’t want glucose being used up
What is the role of the beta cells what happens following this
Secretes insulin that acts on the liver and muscle cells when blood glucose levels are too high
Glycogenesis - glucose to glycogen
rate of respiration increased
Describe the events of high blood glucose detection by the Beta cells
There’s a build up of glucose outside the beta cell
It diffuses down the concentration gradient though a GLUT protein channel
The glucose is phosphorylated to make ATP
This ATP binds to ligand gated K+ ions and it closes
The build up of K+ ions causes the cell to depolarise
Voltage gated Ca2+ ions open and vesicles containing insulin fuses with the cell surface membrane
The insulin is released by exocytosis and diffuses down the concentration gradient into nearby blood capillaries
Describe the actions of a liver or muscle cell when insulin has been secreted
Insulin binds to a specific receptor on the cell surface membrane
This activates a G-protein and this activates adenylyl cyclase
This enzyme converts ATP to cAMP which is a secondary messenger
This cascade of events results in vesicles containing glut proteins to fuse with the cell surface membrane
Glucose has built up outside the cell and diffuses down the concentration gradient into the cells
Glycogenesis, lipogenesis and respiration all occurs
