Whats the difference between endocrine and exocrine glands
- ENDOCRINE:
- Contains cells that produce a hormone and release it straight into blood
- Ductless
- EXOCRINE:
- Produce a chemical which isn’t directly released into the blood
- Have a duct which carries secretion to another place
Describe the characteristics of protein/non-steroid hormones (e.g. insulin)
- Not able to cross cell surface membrane so DONT enter cell
- Hydrophillic so can’t pass through plasma membrane
- Bind to specific receptors on membrane of target cells
- Triggers a cell signalling cascade in cell
- Often requires second messengers
Describe the characteristics of steroid hormones (e.g. progesterone)
- Can pass through cell surface membrane and enter cell
- Acts upon the DNA in the nucleus
- Pass through plasma membrane and binds to steroid specific receptor in cytoplasm/ nucleus
- Forms hormone-receptor complex that acts as a transcription factor for a gene
- Acts to facilitate or inhibit a specific gene
Whats the function of the adrenal cortex
- Uses cholesterol to produce certain steroid hormones (e.g. mineralocorticoids, glucocorticoids and androgens)
Describe what mineralocorticoids are.
ALDOSTERONE:
- helps control blood pressure by maintaining the balance between salt and H2O conc in the body
- its release is mediated by kidney
Describe what glucocorticoids are.
CORTISOL:
- involved in regulation of metabolism
- helps regulate blood pressure and cardiovascular function in response to stress
CORTICOSTERONE:
- works with cortisol to regulate immune response and suppress inflammatory reactions
Describe what androgens are
- Hormones are converted elsewhere in body to female and male hormones however these are steroid hormones so are also produced in much larger amounts by the ovaries and testes
Whats the function of the adrenal medulla
- Hormones here are released when the sympathetic nervous system is stimulated
- Occurs when the body is stressed
- produces peptide (catacoholamine) hormones
Describe the action of hormones
- hormones act as first messengers because it carries the chemical message from the endocrine gland to the receptor o the target cells.
- This then activates an enzyme in the cell which catalyses the production of a molecule inside the cell called a signalling molecule
- the signalling molecule is the second messenger as it activates a cascade of reactions inside the cell
Whats adrenaline?
- hormone that increases heart rate by sending blood quickly to muscles and brain
- Also rapidly raises blood glucose conc levels by converting glycogen to glucose in the liver
- first messenger that is an amino acid derrivative and can’t enter target cell
Whats noradrenaline?
- Works with adrenaline in response to stress producing effect such as increasing heart rate, widening of pupils , widening of air passages and narrowing of blood vessels in non-essential organs
What are the actions of adrenaline?
- Triggers the liver cells to undergo glycogenolysis so glucose is released into bloodstream
- Allows respiration to increase so more energy is available for muscle contraction
What is cyclic AMP?
- second messenger that not only relays signal molecules but amplifies their strength
- cAMP is made from ATP by the enzyme andenylyl cyclase which is found on inner side of plasma membrane
- Adenylyl cyclase is activated when first messengers e.g. hormones active adenylyl cyclase stimulatory G-protein coupled receptors
- When activated the adenylyl cyclase convert ATP to cAMP which then activates protein kinase enzymes
How does adrenaline work?
- Its a first messenger that binds to specific receptors and activates an enzyme in the membrane called adenylyl cyclase
- this then catalyses the production of a second messenger called cyclic AMP from ATP and activates a cascade making more glucose available to the cell 9by catalysing breakdown of glucose to glycogen
Describe the structure of adrenal glands
- Has inner part (medulla) and outer (cortex) that have diff functions
- Have good blood supply
- On the top of the kidneys
Describe the structure and function of the pancreas/islets of langerhans
- gland under the stomach
- composed largely of exocrine tissue
- produces digestive enzyme and pancreatic juice which are secreted into duodenum via pancreatic duct
- has endocrine tissue called islets of Langerhans –> found in clusters around blood capillaries and secrete hormones directly into blood
- IoL made up of two types of cell (alpha and beta)
Difference between alpha and beta cells
ALPHA: - bigger and more numerous - Makes glucAgon BETA: - smaller (nucleus takes up more room) - makes insulin
- A stain can be used to identify each
Difference between endocrine and exocrine tissue
ENDO (islets of langerhans) - Lightly stained - Large spherical clusters - Produce and secrete hormones EXO (pancreatic acini) - Darker stained - Small, berry-like clusters - Produce and secrete digestive enzymes
How does insulin work?
- lowers blood glucose conc
- increases permeability of cell membranes to glucose so cells take up more
- also activates enzymes that convert glucose into glycogen so its stored in cytoplasm (by glycogenesis)
- also increases rate of respiration of glucose esp in muscle cells
How does glucagon work?
- raises blood glucose conc
- activates enzymes that break down glycogen into glucose (glycogenolysis)
- Also promotes formation of glucose from fatty acids and amino acids (glyconeogenesis)
- also decreases rate of respiration of glucose in cells
What happens when theres a rise in blood glucose conc
- pancreas detects change and beta cells secrete insulin and alpha cells stop secreting glucagon
- insulin bind to effectors and liver and muscle cells respond to decrease in blood glucose conc (e.g. glucogenesis)
Describe the control of insulin secretion by beta cells
HIGH BLOOD GLUCOSE CONC DETECTED
- more glucose enters beta cells by facilitated diffusion causing rate of respiration to increase
POTASSIUM ION CHANNELS CLOSE
- Rise in ATP triggers K+ ion channels in plasma membrane to close and so K+ ions can’t enter beta cell so build up outside cell making inside of beta cell less negative
- plasma membrane of beta cell depolarised
CALCIUM ION CHANNELS OPEN
- Depolarisation triggers Ca+ ion channels to open so Ca+ enter beta cell
- This causes vesicles to move and fuse with the beta cell membrane releasing insulin by exocytosis
What is Type 1 diabetes
-auto-immune disease where body attacks + destroys beta cells meaning people can’t produce insulin
- Can result in death if untreated
- risk slightly increased if theres family history
- can lead to HYPERglycaemia and HYPOglycaemia
HYPER = blood glucose conc too high (longterm effects)
HYPO = blood glucose conc too low (act drunk/ can lead to coma)
What is Type 2 diabetes
- inability to produce enough insulin or respond to insulin
- usually acquired later in life than type 1
- linked with obesity and poor diet
- risk is increased in certain ethnic groups (asian, african) and if theres family history of it
