Unit 5 - Hormonal Communication Flashcards
Exocrine gland
A gland that secretes their products into a duct that carries the molecule to where they are used
Define endocrine glands
Ductless glands that secrete 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: Thyroid-stimulating hormone FSH: Follicle-stimulating hormone LH: Luteinising hormone. GH: Growth hormone. Oxytocin ADH: Anti-diuretic hormone
What does the adrenal gland secrete?
Adrenaline Androgens Aldosterone Cortisol Noradrenaline
Name the two 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
What is the role of the Adrenal Medulla?
Manufacture and release non- essential hormones e.g. dopamine and adrenaline
Why must hormone target cells have SPP receptors on their cell surface membrane?
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 cell surface membrane 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 with 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 membrane
Binds to intracellular receptor
Hormone-receptor complex is mobilised toward nucleus
Complex binds to specific 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
Secretes 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 concentration is too high
How does insulin work?
Binds to receptors which activate a second messenger system
What does insulin do?
Increases 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 concentration
4-6 mmol dm3 or or 90mg per 100ml blood
When blood glucose concentration 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 concentration 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 mV
- 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 mV
- VG Ca2+ channels open in response to change in membrane potential allowing them 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 it would be digested by enzymes so not absorbed into bloodstream
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 is glucose removed in response to insulin?
- Liver & muscle
Acini are…
Groups of cells arranged around a tiny ductule
Function of aldosterone
Na+ reabsorption in the kidney
Water reabsorption
Control blood pressure
