Introduction to endocrine system Flashcards
What kind of feedback do endocrine glands show?
Negative feedback.
What are the three classes of hormones?
Amines/amino acids, peptides of proteins, or steroid hormones.
What is tyrosine?
An amino acid that can give rise to thyroid hormones but also adrenaline/noradrenaline.
What is an example of a protein hormone?
Insulin.
What is an example of a steroid hormone?
Sex hormones such as oestrogens, androgens, progestorones.
What do the pituitary, thyroid and adrenal glands all have in common?
They are regulated by the hypothalamus and the pituitary gland.
What does the medulla in the adrenal gland release?
Adrenaline and noradrenaline.
What does the adrenal cortex release?
Cortisol, corticosterone, cortisone, aldosterone and androgens.
What does the thyroid release?
Thyroxine, triodothyronine and calcitonin.
What does the hypothalamus release?
ADH and oxytocin.
What does the anterior pituitary gland release?
ACTH, TSH, GH, PRL, FSH, LH, MSH.
What does the pineal gland release?
Melatonin - hormone involved in regulating sleep and waking cycles and establishing the 24 hour rhythms.
What does the heart release?
Atrial natruiretic peptide.
What does the kidney release?
Renin and erythropoietin.
What is a major morphological feature of endocrine glands?
They are ductless.
What are features of endocrine glands?
They have a good supply, the secrete messengers directly into the circulation.
What is an example of a primary endocrine gland?
Pituitary glands, thyroid and adrenal.
What organs have secondary endocrine function?
The brain, heart, kidney and GI tract.
What is intracrine signalling?
Signalling within a cell (producing products that signal within the cell).
What is autocrine signalling?
Signalling where it releases something back on itself (the cell itself).
What is paracrine signalling?
Releasing things that affect neighbouring cells.
What is endocrine signalling?
When products are secreted into the bloodstream and can travel a distance to their target cells.
What is neuroendocrine signalling?
Modified nerve cells that can secrete hormones into the circulation directly and travel to distant target cells.
What are the four main areas in which hormones are important in?
Reproduction, growth and development, maintenance of internal environment and regulation of energy.
How can hormones act differently on different tissues?
Different tissue-specific effects, depending on the tissue.
What are catecholamines derived from?
Tyrosine?
What are some catecholamines?
Adrenaline and noradrenaline.
What are thyroid hormones derived from?
Tyrosine.
What are examples of thyroid hormones?
Thyroxine and triiodothyronine.
How is adrenaline formed?
Tyrosine is converted to L-DOPA via tyrosine hydroxylate which is then converted to dopamine via dopa decarboxylase. Dopamine is then converted to noradrenaline via dopamine-beta-hydroxylase. It’s then converted into adrenaline phenylethanolamine N-methyl transferase.
How are thyroid hormones synthesised?
Tyrosine and iodine combined to form mono-iodotyrosine.
How is thyroxine formed?
The combination of two di-iodotyrosine molecules.
How is triiodothyronine formed?
Di-iodotyrosine combines with mono-iodotyrosine.
What does adenylyl cyclase do?
It converts ATP to cAMP.
What does cAMP do?
It phosphorylates protein kinase to make it active which then phosphorylated
What happens to the phosphoproteins formed from PKA?
They will be packed into a lipid droplet from (LDL), go to the SER and mitochrondrion and diffuse into the blood.
What are peptides?
Short amino acid chains.
What are some examples of polypeptide hormones?
Insulin and prolactin.
What are some protein hormones?
Thyroid stimulating hormones, follicle stimulating hormone and growth hormone.
What are some short amino acid chain hormones?
ADH and oxytocin.
What is a prohormone?
It needs to be cleaved by digestive hormones to the final hormone product that can then be released into the bloodstream.
Where are peptide and protein hormones stored?
In secretory vesicles that are capable of being released straight away on demand.
What does the ability of a cell to respond to a hormone depend on?
The presence of receptors for that hormone on or in the target cell.
How can the number of receptors for a hormone be regulated?
Up-regulation or down-regulation.
What types of receptors can bind to hormones?
Cell surface receptors or intracellular receptors.
What happens when a hormone binds to cell surface receptors?
They activate an intracellular signalling cascade.
What happens when substances bind to intracellular receptors?
They activate gene transcription.
What hormones bind to intracellular receptors?
Corticosteroids.
What hormones activate cell surface receptors?
Insulin.
What are the two ways in which hormones can be released in response to a stimulus?
The stimulus can act on endocrine cells that causes a hormone to be released directly that acts on target cells, or the stimulus can act on a hypothalmic neurone and release a regulatory hormone that acts on the target endocrine organ to release a second hormone to act on the target cells and bring about the response.
What are features of the responses caused by hormones?
It is a relatively slow transfer of information, it can be long lasting and all the cells are contacted - specificity is determined by receptors.
What pattern do hormones regulated by the hypothalamus and pituitary gland show?
Circadian rhythm (24 hour rhythm) - the cycle starts at midday and goes through the evening.
What is hypo-secretion (example)?
When there is too little secretion of a hormone e.g. type 1 diabetes.
What is hyper-secretion (example)?
Too much secretion e.g. pancreatic endocrine tumour.
What is hypo-responsive (example)?
Cells are not as responsive as they should be e.g. type 2 diabetes.
What is hyper-responsive (example)?
Cells are too responsive to hormones e.g. TSH receptor constitutive activation e.g. hyper thyroidism.
Name some common endocrine problems.
Hyperthyroidism, type1/2 diabetes, renin-dependent hypertension.
