block C - endo and reproduction Flashcards
why study endocrine pysiology?
because endocrine diseases are very common, examples are diabetes mellitus, thyroid disease and PCOS. drugs affecting this system are very commonly used
what is PCOS?
polycystic ovary syndrome - excess androgen
what are the two chemical ways you can distingish hromones?
peptide Vs steroid hormones
peptide hormones typically cause short- term effects and steroid hormones typically cause long-term effects
what is an example of a peptide hormone and how is its structure regulated?
insulin-its structure is regulated by disulphide bridges
what are some examples of steroid hormones?
cortisol and testosterone
what is an example of a ‘steroid-like hormone’?
thyroxine
what determines the charcteristics of a hormone?
the amino acid sequence
what are some of the characteristic actions of peptide hormones?
they have a rapid onset of action
they’ve got a rapid offset of action
they’re secreted in ‘bursts’ when required
what are the characteristic actions of steroid hormones?
slow onset of action
slow offset of action
secreted to maintain ‘constant’ plasma hormone concentration
how would you explain the differences between steroid and peptide hormone in terms of speed of on and offset?
it depends on their two different mechanisms
peptide is faster
what are peptide hormones involved in controlling in short-term regulation?
glucose
water
calcium
peptide hormones are secreted when they’re needed, when does this stop?
secretion is terminated when desired physiological correction is achieved
how does the control of blood glucose affect hormone secretion?
islets of langerhas cells are sensitive the to the glucose concentration in the blood and they will secrete insulin if its too high and glucagon if its too low
what are the cell types in islets of langerhas?
A ( or alpha) cells - glucagon
beta-cells - insulin
d-cells
why is insulin needed?
it is key to getting glucose into cells and helps to lower blood glucose levels
where is glucose stored in the body and what form does it take?
its stored in the liver as glycogen
what happens when blood glucose is low?
the A cell is a source of glucagon and this helps to mobilise glycogen from storage places like the liver and add the glucose back into the circulation
why is the one hormone to raise the glucose level and another one to lower it?
because it provides much tighter control than just one
what is the parathyroid hormone?
its a hormone produced in small glands beside the thyroid gland and it raises the calcium blood concentration
how is parathyroid hormone concentration regulated?
if theres low Ca2+ concentrations, the parathyroid cells release the hormone to elevate blood Ca2+ levels
what is the aim of the secretion of hormones with long-term regualtion?
their main aim is to maintain the concentration of hormone within certain physiological limits
what are the main parts of the brain involved in controlling long term regulation hormones?
the hypothalamus and the pituitary gland
what is the main control centre for:thyroxine; cortisol; sex hormones?
thyroxine - thyroid
cortisol- adrenal cortex
sex hormones- gonads (ovaries/testes)
where are hypothalamic hormones secreted form?
they’re secreted into the median eminence in the hypothalamus
how do hypothalamic hormones reach the anterior pituitary to control its secretion?
some of them come down from the median eminence through the long portal vessels into the anterior lobe
what does thyrotrophin releasing hormone cause?
it causes the release of thyrotropin, corticotrophin, growth hormone and gonadotrophins are all controlled in the same way
what are examples of inhibitory factors produced in the hypothalamus?
- dopamine inhibits the production of prolactin
- somatastosin inhibits the production of growth hormone
how does the system maintain the concentraition of hormones within physiological limits?
through negative feedback mechanisms
explain the negative feedback mechanism of thyrotrophin?
TRH brings about the secretion of thyrotropin, which causes the thyroid gland to produce thyroxine which then negatively feeds back
this keeps the thyroxine concentration within certain limits
what is the negative feedback mechanism of cortisol?
CRH releases corticotrophin, then the adrenal gland then releases cortisol (to deal with stress and reduce inflammation) then cortisol feedsback to CRH
what does stress do to cortisol secretion?
it causes a marked increase in cortisol secretion and bring about an essential survival response i.e. in terms of injury or to escape from a life threatening situation
what do thyroid hormones do?
they set the metabolic level of the body
what is essential for growth and development?
thyroid hormones
sex hormones
insulin
growth hormone
what is the other name of growth hormone?
somatrotrophin
what is growth hormone needed for?
- it promotes growth, especially in young people
- in late adult life, lack of growth hormone is associated with immune secretion
- its important in Ca2+ and phosphate retention
- increased protein synthesis
- increase in blood glucose
- increased circulating free fatty acids
what are effects of growth on an individual?
- elongation of the bones
- the epiphysis is a cartilage plate in the bone and the growth occurs until teenage years
- the epiphyseal plate is where cartilage forms and actively proliferating cartilage tissue (chondrocytes)
- as the chondrocytes move further down the bine, the cartilage is converted into bone by osteoblasts at the shaft end of the plate
- finally the ephyseal plate then becomes converted into bone and no more growth of the bone can take place
how can growth hormone affect the growth of bones?
it can promote the conversion of cartilage to bone at shaft edge of the plate and in general promote cartilage to bone production
how does growth hormone affcect the growth of muscle?
it promotes the transfer from the liver of glucose from glycogen and lipids, helping to grow muscle
how does growth hormone affet adipose tissue growth?
it accelarates lipolysis in the adipose tissue, which leads to increased circulating free fatty acids.
then reduced tissue glucose uptake
how does growth hormone work indirectly?
it goes to the liver, then insulin like growth factor-1 (IGF-1) to promote growth
how is growth hormone regulated?
its secreted from the pituitary, its production is promoted by the availability of amino acids, low blood glucose, exercise and stress (chronic stress inhibits growth hormone though)
what hormones allow and inhibit the production of growth hormone?
growth hormone releasing hormone and somatostatin (growth hormone release inhibitory hormone)
IGF-1 also gives negative feedback on the production of growth hormone
grehlin has a complex role in glucose production
what are the conceqences of growth hormone deficiency?
if growth hormone deficiency comes before epiphyseal closure= dwarfism
IGF-1 deficiency= dwarfism