lecture 11 - endocrine system Flashcards
what is intracellular communication?
message transmitted directly from cell to cell, specificity depends on anatomical location
what is the endocrine system?
endocrine cells within endocrine glands release hormones which are conveyed by the blood stream and act on distant cells
what are the 3 classes of hormones?
steroids, peptides, amino acids
what is the synthesis of steroid hormones?
- Don’t store them, produce them on demand
- Release a hormone to raise blood levels
– drops off and reattaches – free hormone that can get across membranes - Act on intracellular receptors which then bind to DNA (hormone response elements) and regulates gene transcription
- If change the gene expression within a cell you change the cell or tissues functions
- Have slow long lasting effects
what is the steroid hormone action on receptors?
- DNA binding domain
- Hinge region
- Hormone binding site
- Transcription activating domain
- Inhibitory protein complex
when can a receptor not bind to DNA?
if no hormone is present
what are peptide hormones?
- Synthesised as preprohormones and stored prior to release
- Act on cell surface receptors then via 2nd messenger systems to cause effect in target cells – alters cell function
what are amino acid hormones?
- Mostly synthesised from tyrosine
- Stored for instant release
- Diff modes of action (Thyroid has intracellular receptor and others act at the cell surface)
what is the action of amino acids on receptors?
- Receptor on cell surface, hormone binds to it
- Triggers 2nd messenger pathways – increase production of things
- Add phosphate groups onto proteins
- Hormone effects have to be reversable
- Change activity of cellular protein
- Effect of these hormones is multiple and rapid
- Some effects are fairly short term – metabolism
what is feedback control?
- Response – drop in blood glucose but don’t want it to drop too far
what is negative feedback control?
- Other brain area inputs – hypothalamus – can tell us our hydrated state, whether we’ve exercised or not – trying to get back to our ideal levels
what is the hypothalamic-pituitary axis?
- Site of interaction between the nervous and endocrine systems. Exerts control over several endocrine glands and physiological activities
what is the posterior pituitary?
posterior lobe is of neural origin and know as the neurohypophysis. It consists of axons and nerve endings of neurones whose cell bodies reside in the hypothalamus
what is the anterior pituitary?
anterior lobe originates from Rathke’s pouch and is known as the adenohypophysis, it consists of endocrine tissue – tissue migrates up towards and then meets the posterior pituitary
what is a growth hormone?
- Released in response to growth hormone releasing hormone from the hypothalamus
- Release inhibited by growth hormone -inhibiting (somatostatin) from the hypothalamus
- Stimulates growth, cell production and regeneration
what are acute metabolic actions of GH?
- Release fatty acids from adipose tissue and enhances their conversion to acetyl- CoA
- Reduced glucose metabolism and uptake into cells, especially the liver
- Increased gluconeogenesis in the liver
- Increased production of insulin- like growth factor (IGF-1) – hepatic
what is a thyroid?
- Rich blood supply
- Usually 2 pairs of parathyroids on rear of the thyroid
- Functional units of the thyroids are the follicles
- Single layer of cells surrounding a pool of colloid
- Production and storage of thyroid hormones in colloid
- Size of the thyroid varies with its state of stimulation
- C cells secrete calcitonin – involved in calcium homeostasis
what is cushings syndrome?
excess cortisol, results from a pituitary tumour
what are features of cushings syndrome?
weight gain, hypertension, acne etc
