5.1.4 - Hormonal Communication Flashcards
Exocrine gland
A gland that secretes their products into a duct that carries the molecule to where they are used
Endocrine gland
A ductless gland that secretes hormones directly into the blood
Examples of endocrine glands
Pituitary
Adrenal
Pancreas
Examples of exocrine glands
Mammary
Gastric
Salivary
Pancreas
Why is the pancreas both endo/exocrine
Releases hormones e.g. insulin and glucagon directly into the blood stream but also releases digestive enzymes e.g. trypsin into ducts
What does the pituitary gland secrete
TSH
LH
ADH
What does the adrenal gland secrete
Adrenaline
Types of hormones
Lipid soluble hormones (steroid hormones)
Peptide hormones
What are steroid hormones derived from
Cholesterol
Hormones released by cortex of adrenal glands
Mineralocorticoids
Glucocorticoids
Androgens
Vital to life e.g. cortisol and aldosterone
What do mineralocorticoids do
Help control the conc. of minerals e.g. aldosterone
What do glucocorticoids do
Help control the metabolism of carbs and proteins
Adrenal Medulla
Manufacture and release non- essential hormones e.g. dopamine and adrenaline
Why must hormone target cells have spp receptors on their csm
So that the correct hormone can bind and no other molecule will be able to bind and have the same effect
First vs. second messengers
1st bind to csm and have an effect by activating a 2nd messenger, this is what actually affects the activity of the cell
Why are steroid hormones able to enter the cell
Interacts w/ phospholipid bilayer and dissolve as they are lipid soluble
How do hormones act as secondary messengers
Hormones bind to spp cell surface receptor
Stimulates production of a messenger molecule e.g. cAMP
cAMP activates or inhibits enzyme pathways
How do hormones act as gene activators
Hormone permeates any membrane
Binds to intracellular receptor
Hormone-receptor complex is mobilised toward nucleus
Complex binds to spp regions of DNA
Leads to increase/decrease in translation -> protein synthesis
Endocrine part of the pancreas
Islets of Langerhans
alpha cells secrete glucagon
beta cells secrete insulin
INTO bloodstream
Exocrine part of pancreas
Pancreatic acini
Secretes digestive enzymes INTO DUCT which drains into the pancreatic duct which empties in duodenum
What does insulin act on
Hepatocytes
Muscle cells
Adipose tissue
Brain cells
When is insulin secreted
When blood glucose conc is too high
How does insulin work
Binds to receptors which activate a second messenger system
What does insulin do
Increase glucose uptake into cells by facilitated diffusion
Increase respiration rate (glycolysis)
Glycogen conversion (glycogenesis) in hepatocytes and muscle cells
Lipogenesis
What does glucagon work on
`Hepatocytes and muscle cells
Has spp receptors
When is glucagon secreted
When blood glucose is too low
What does glucagon do
Glycogen breakdown (glycogenolysis)
Decrease glucose uptake
Converting fatty acids and amino acids to glucose (gluconeogenesis)
Normal glucose conc
4-6 mmol dm3
When blood glucose conc rises
Detected by beta cells in islets of Langerhans
Secretes more insulin
Hepatocytes and muscle cells remove glucose from blood and convert to glycogen (glycogenesis)
Blood glucose falls
-ve feedback
When blood glucose conc falls
Detected by alpha cells in islets of Langerhans
Pancreas secretes more glucagon
Hepatocytes and muscle cells convert glycogen to glucose and release it in to bloodstream (glycogenolysis)
Blood glucose conc rises
-ve feedback
Describe how insulin secretion is controlled
VG K+ channels in plasma membrane open and K+ diffuses out of beta cell and inside has pd of -70
Blood glucose conc. increases and glucose enters cell
Glucose is phosphorylated then metabolised to form ATP
Presence of extra ATP causes ligand-gated K+ channels to close
K+ cannot diffuse out so membrane potential reduces to only -30
VG Ca2+ open to response in change in membrane potential - Ca move in
Ions cause vesicles to release insulin (exocytosis) into bloodstream
Processes that lower blood glucose
Glycolysis
Glycogenesis
Lipogenesis
Processes that increase blood glucose conc
Gluconeogenesis
Glycogenolysis
Causes of type 2 diabetes
Obesity Poor diet Insufficient exercise Diet high in sugar Genetics
Insulin resistance
Symptom of Type 2 diabetes
When the body doesn’t respond to insulin
Hyperglycaemia
High blood glucose
What can long-term hyperglycaemia lead to
Modification of diff proteins e.g. collagen in blood vessels –> angina and heart failure
Also affects peripheral nerves (poor blood circulation)
Causes of Type 1 diabetes
Majorly genetically linked but environmental factors such as an infection which causes the immune system to destroy beta cells w/ similar antigens
Hypoglycaemia
Excessive, abnormal thirst
Frequent urination
Tiredness
Glucose is excreted in urine instead of being used in body
Why are Type 1 diabetics frequently dehydrated
Glucose increases osmolarity so more water is lost in urine
How does the metabolism of a Type 1 diabetic adapt
More glycogenolysis and gluconeogenesis occurs
Body produces ketones and fatty acids for respiration, increases acidity of blood
Treatment for diabetes
Insulin injection
Insulin pump
Islets of Langerhans transplant (donors must match )
Exercise –> decreases insulin resistance
Drugs when diet therapy fails
Why are the islets of Langerhans surrounded in an extensive network of blood vessels
Shorter diffusion distance for glucose inthe blood
Where is glycogen stored
In muscle and liver tissue
What is gluconeogenesis a result of
Fasting
Starvation
Stress
Which hormones stimulate gluconeogenesis
Adrenaline and glucocortoids
Advantages of using insulin from genetically modified bacteria
Exact copy of human insulin, faster and more effective
Less chance of develpoing tolerance to insulin
Lower chance of rejection
Lower risk of infection
More ethical
Why cant insulin be taken orally
Insulin is a protein and if taken orally cannot be reabsorbed into the bloodstream during ultrafiltration at glomerulus
Why is there a delay in the increase of insulin conc following increases in blood glucose conc
Increase has to be detected by beta cells
Takes time depolarise beta cells and release insulin
How does increased heart rate raise blood pH
Removes more CO2 and in turn makes the blood less acidic
Prevents cell damage
Where do hormones travel in the blood
Blood plasma
Tissue that secretes glycogen and insulin
Pancreatic
In which tissues are glucose removed from in response to insulin
Liver
Muscle
Acini
Groups of cells arranged around a tiny ductule
Function of aldosterone
Na+ reabsorption in the kidney
Water reabsorption
Control blood pressure
