14 Flashcards
What is an endocrine gland and what does it do?
It is a group of cells that are specialised to secrete hormones
Where are hormones secreted into?
Bloodstream
What does pituitary gland produce and what does its hormones do?
GH (growth hormone) - controls growth of bones and muscles
FSH (follicle stimulating hormone) - growth and maturation of sperm and eggs
TSH (thyroid stimulating hormone) - triggers thyroid to release hormones.
What does the thyroid gland produce and what does its hormone do?
Thyroxine - controls basal metabolic rate and glucose used in respiration.
What hormone does adrenal gland secrete and what does its hormone do?
Adrenaline - triggers fight or flight
What hormone does pineal gland secrete and what does its hormone do?
Melatonin - affects reproductive development and daily cycles
What does thymus gland secrete and what does its hormone do?
Promotes production and maturation of WBC’s
What does pancreas secrete and what do its hormones do?
Insulin - converts glucose into glycogen in liver
Glucagon - converts glycogen back into glucose in liver
What do testes secrete and what does its hormone do?
Testosterone - controls sperm production and secondary sexual characteristics
What do ovaries secrete and what do its hormones do?
Oestrogen - controls ovulation and secondary sexual characteristics
Progesterone - prepares uterus lining for receiving embryo
What is a target cell?
When hormones bind to specific receptors found on membranes or in cytoplasm of cells in target organ.
What are steroid hormones?
Hormones which are lipid soluble and pass through the liquid component of cell membrane and bind to receptors in cytoplasm or nucleus.
What are non steroid hormones?
Hydrophilic so cannot pass directly through cell membrane and must bind to receptors on cell surface membrane.
Describe mechanism of action of steroid hormones
1) Lipid-soluble steroid hormone passes through cell membrane
2) Hormone binds with receptor
3) Hormone-receptor complex attaches to DNA
4) Hormone-receptor complex acts as transcription factor to facilitate or inhibit transcription of specific gene.
5) polypeptide synthesised by ribosomes and mRNA
What is the adrenal cortex?
Outer region of glands
What hormones do adrenal cortex secrete?
Vital hormones like cortisol and aldosterone
What is adrenal medulla?
Inner region of glands
What hormones does adrenal medulla produce?
Non essential ones like adrenaline
What are the three main types of hormone the adrenal cortex produce?
Glucocorticoids
Mineralocorticoids
Androgens
What do glucocorticoids do?
Help regulate metabolism through controlling how body converts fats, carbs and proteins to energy.
Includes cortisol which is a primary stress hormone
What do mineralocorticoids do?
Helps control blood pressure through maintaining salt and water levels .
Main hormone is aldosterone
What do androgens do?
Small amounts of male and female sex hormones are released
Relatively small impact compared to other sex hormones like testosterone
Still important especially during menopause
What system involves adrenal medulla?
Sympathetic system as adrenaline is used.
What does adrenaline do?
Increases heart rate,
sends blood quickly to muscles and brain, rapidly raises blood glucose levels by converting glycogen to glucose.
What does noradrenaline do?
Works with adrenaline,
Increases heart rate,
Widens pupils,
Widens air passage of lungs,
Causes vasoconstriction in non essential organs to increase blood pressure
What does an exocrine gland do?
Produces enzymes and releases them via duct into the duodenum
What three important enzymes does the pancreas release?
Amylases, lipases and proteases
What two main hormones does the pancreas produce?
Insulin and glucagon
What does insulin do?
Converts glucose to glycogen
What does glucagon do?
Converts glycogen to glucose
What are the islet of langerhans?
Small regions of endocrine tissue in exocrine tissue.
What are islets of Langerhans responsible for?
Produce the insulin and glucagon to be released into the blood cells
How do the islet of Langerhans appear under a microscope?
Lightly stained
Large spherical clusters
Endocrine pancreas
How does pancreatic acini appear under microscope?
Darker stained
Small berry like clusters
Exocrine pancreas
What do alpha produce and secrete in islet of Langerhans?
Glucagon
What do beta cells produce and secrete in islet of Langerhans?
Insulin
What colour do alpha cells stain?
Pink
What colour do beta cells stain?
Blue
What is glycogenolysis?
When glucagon from liver is broken down into glucose. This increases blood glucose conc.
What is gluconeogenesis?
When glucose is produced from non carbohydrate sources.
What factors increase blood glucose conc?
Diet - carbs are broken down in digestive system to release glucose which increase blood glucose conc when absorbed by bloodstream.
Glycogenolysis - glycogen is being converted back into glucose which will increase blood glucose conc.
Gluconeogenesis - glucose is produced from non carb sources which will increase blood glucose conc.
How is blood glucose conc decreased?
Respiration - some glucose is used by cells to release energy. However during exercise, more glucose is used for the body to generate more energy and so glucose levels decrease.
Glycogenesis - when glucose is converted to glycogen for storage and so blood glucose conc decreases
What ways does insulin lower blood glucose conc?
- increasing rate of absorption of glucose by cells
- increasing the respiratory rate of cells - this increases their need for glucose and causes a higher uptake of glucose from blood
- increasing glycogenesis rate - insulin stimulates liver to remove glucose from blood
- increasing rate of conversion of glucose to fat
- inhibiting release of glucagon from alpha cells of islet of langerhans
What cells contain insulin receptors?
Virtually all do but RBCs are a main exception.
Why does insulin have to constantly be excreted?
As it is constantly broken down by cells in the liver
What does insulin do?
Converts glucose to glycogen for storage
What does glucagon do?
Converts glycogen into glucose when BGC is low.
What cells have glucagon receptors?
Liver and fat cells
How does glucagon raise BGC?
- glycogenolysis
- increasing gluconeogenesis
-increasing amount of glucose absorbed by liver
What type of system are alpha and beta cells taking part in?
Negative feedback system
What are the steps in control of insulin secretion?
1) at normal BGC, potassium channels in beta cells plasma membrane are open and potassium ions diffuse out cell. Inside potential is -70 mV relative to outside.
2) when BGC rises, glucose enters the cell by a glucose transporter
3) glucose is metabolised inside mitochondria producing ATP
4) ATP binds to potassium channels causing them to close.
5) potassium ions can no longer diffuse out cell causing potential difference to reduce to around -30 mV and a depolarisation occurrs
6) depolarisation = v gated calcium channels open
7) calcium ions enter cells and cause secretory vesicles to release insulin via exocytosis
What is exocytosis?
The bulk transport of materials out of cells.vesicles containing material fuse with cell surface membrane and contents are release to outside of cell
