M5, C14 Hormonal Communication Flashcards
define hormones
chemical messengers that carry a signal to a target organ or tissue
define endocrine glands
glands that secrete a hormone directly into the blood.
they have no tubes or ducts
What is the simple hormonal pathway
endocrine gland -> blood -> receptor on target tissue
define target cells
only specific cells have complementary receptors for the hormone
this means that hormones can travel around in the blood and only affect the correct target tissue
what are the two types of hormone
non-steroid / protein
steroid
how do steroid hormones interact with the target cell
it’s lipid soluble so pass through lipid component of the cell membrane and bind to steroid hormone receptors to form hormone-receptor complex
the receptors are present in cytoplasm or nucleus
a hormone-receptor complex is formed and acts as a transcription factor which in turn facilitates or inhibits the transcription of a specific gene
how do non-steroid hormones interact with the target cell
they are hydrophilic so can’t pass directly through the cell membrane
they bind to specific receptors on the cell-surface membrane on target cell
triggers a cascade reaction mediated by chemicals called second messengers
What are the 2 glands in the pancreas?
Exocrine
Endocrine
What’s the function of the exocrine gland in the pancreas?
Produces digestive enzymes and pancreatic juice which are secreted into ducts which lead to the pancreatic duct.
They then go to the duodenum (top part of small intestine)
What are the 3 main digestive enzymes the exocrine gland produces in the pancreas?
Amylases (break down starch into simple sugars)
Proteases (break down protein into amino acids)
Lipases (break down lipids into fatty acids and glycerol)
What is the function of the endocrine gland in the pancreas?
Produces the hormones insulin and glucagon.
They control blood glucose concentration.
Where is endocrine tissue found in the pancreas?
Within exocrine tissue there are small regions of endocrine tissue called islets of Langerhans. This is where the hormones are produced and secreted.
What is the structure of the islets of Langerhans in the pancreas?
What do the different cells produce?
There are 2 different types of cell: Alpha cells (produce and secrete glucagon) Beta cells (produce and secrete insulin)
Alpha cells are larger and more numerous than beta cells.
On a microscope how could you differentiate between the alpha and beta cells in the islet of Langerhans?
Using differential staining
E.g. staining beta cells blue and alpha cells pink
What is the structure of the endocrine tissue in the pancreas?
Within islets of Langerhans
Lightly stained
Large, spherical clusters
What is the structure of the exocrine tissue in the pancreas?
Pancreatic acini
Darker stained
Small berry-like clusters
define negative feedback
any change to the optimum condition will result in a series of events leading to the reversal of the change
what do these terms mean?
lysis
genesis
neo
lysis: to split/breaking down
genesis: forming/creating
neo: new
how does the body react when blood glucose concentration levels rise
- beta cells secrete insulin into the bloodstream.
- insulin binds to glycoprotein receptor causing a change in tertiary structure of glucose transport protein channels so more glucose enters cells. There is a higher uptake of blood glucose from blood.
- rate of glycogenesis is increased. liver stimulated to remove glucose from blood. glycogen is stored in liver and muscle cells.
- glucose is converted into fat
- release of glucagon from alpha cells is inhibited
- insulin in constantly secreted because enzymes in the liver break it down.
- when levels lower again, beta cells detect it and insulin secretion is reduced
how does the body react when blood glucose concentration levels fall
- alpha cells detect fall and glucagon is secreted into bloodstream
- glucagon receptors are on liver and fat cells
- glycogenolysis - liver breaks down its glycogen into glucose and release into blood.
- glucose that’s absorbed into liver is reduced
- gluconeogenesis - increasing conversion of amino acids and glycerol into glucose in the liver
- when levels rise again, alpha cells detect this and secretion of glucagon is reduced
how is the potential difference maintained in beta cells when blood glucose concentration is normal
potassium ion channels are open and potassium ions diffuse out of the cell
causes the inside of the cell to have a potential difference of -70mV
How is insulin secreted from beta cells?
When blood glucose concentration increases, glucose enters the cell via glucose transporter due to facilitated diffusion.
The glucose is metabolised inside mitochondria to produce ATP.
The ATP binds to ATP sensitive potassium ion channels.
The potassium ion channels close and potassium ions remain inside the cell causing the inside pd to become -30mV.
This causes boltage-gated calcium ion channels to open and calcium ions enter the cell (diffusion).
This causes vesicles containing insulin to release the insulin by exocytosis.
what causes type 1 diabetes
who normally gets it
beta cells don’t produce insulin
may be caused by and autoimmune response where the body attacks its own beta cells
normally begins in childhood
what causes type 2 diabetes
beta cells don’t produce enough insulin OR a person’s body cells don’t respond properly to insulin
glycoprotein insulin receptor on cell membrane doesn’t work properly.
cells lose responsiveness to insulin so don’t take up enough glucose.
due to excess body weight, inactivity or overeating of carbohydrates
risk of getting it increases with age
