Endocrine System- All notes Flashcards
What are the types of intercellular messenger system?
-neurotransmission, neuroendocrine, endocrine, paracrine and autocrine
What is the endocrine system?
-Gland in the system secretes a neurotransmitter which gets released into he bloodstream to travel to the target cell
What are the features of hormones?
-glands that secrete them directly into the bloodstream to be carried to target cells or tissues away from the endocrine gland
What are the types of hormone?
-Peptide, steroidal, tyrosine containing and eicosnaoids
What are the differences between types of hormones?
-Structural (chemical) difference change the synthesis, storage, transportation and biological functions of hormones
What are peptide hormones?
-Chains of an amino acid that can be small or larger and are mostly secreted from the hypothalamus, pituitary gland, pancreas and GIT
What is the synthesis of peptide hormones ?
-Similar to any protein syntesis; transcription / translation- preprohormone-prohormone-hormone-secretory glands
Where are peptide hormones stored?
-Within the vesicles in the cell
How are peptide hormones release?
-Exocytosis
How are peptide hormones transported?
-They are hydrophilic so freely circulate in the blood vessel, no plasma protein bonding so short half-life
What are steroidal hormones?
-Hormones that have cholesterol as the base e.g. cortisol and sex hormones
How are steroidal hormones synthesised?
-Enzymatic conversion of precursor (cholesterol base) molecules into hormone
How are steroidal hormones released into the bloodstream?
-Stimulus increased precursor level and enzyme activation so molecules simply diffuse across membrane and bind with plasma protein until needed
How are steroidal hormones transported?
-Travel in the bloodstream joined with a a carrier protein in an inactive state until it is needed and released. Lipophilic so has a hard life of hours to days
What is a tyrosine containing hormone?
-A hormone that has tyrosine as the base such as thyroid hormones
How are tyrosine containing hormones released?
-Stimulus required then simple diffusion across membrane
How are tyrosine containing hormones transported ?
-Lipophilic, binds with a plasma protein in the blood with weak reversible bonds to give a half life of hours to days
What are eicosanoids?
-Hormones that are synthesised by stereo- and regional’s-specific peroxidation of arachidonic acid (membrane lipid) as the precursor and lipase as the enzyme that dictates production
How are eicosanoids released?
-Stimulus required as poorly diffuse across cell membrane
How are eicosanoids transported?
-Required an anionic transporter. Hav a half life of seconds and is limited to autocrine and paracrine effects
How do peptide hormones function?
-Hormones interact with the cell surface receptors which then stimulates a response inside the cell which leads to a physiological response
How do steroidal hormones work?
-They are diffused across the cell membrane or even into the nucleus to interact with either a cytosolic or nuclear receptor which then produces specific protein and biological effects
How are hormones metabolised?
-Enzymes in the liver, blood and kidney then excreted in the urine
How does the negative feedback axis of hormonal homeostasis work?
-Endocrine glad releases a hormone which acts directly on target cells. If the target cell is receiving too much or too little hormone, it will send a message to the gland to reduce or increase production
How does the hypothalamus pituitary axis work?
-Hypothalamus relates CRH which acts on the anterior pituitary gland which releases trophic hormone ACTH which acts on peripheral endocrine gland which produces cortisol which acts on target cells
How is the hypothalamus -pituitary axis regulates?
-Feedback loop can go back to any point in the axis to increase or decrease production of certain hormone
Why is the sleep/wake cycle clinically significant when testing for hormone levels?
-Hormone levels will naturally fluctuate significantly within the sleep/wake cycle so depending on the time of day, certain hormones will be higher or lower than normal
What happens if the …. is hyper secretion in hypothalamus -pituitary axis?
-Type 1 diabetes
What is a primary defect in hypothalamus -pituitary axis?
-Anything wrong with the PEG
What is a secondary defect in hypothalamus-pituitary axis?
-Senses there is not enough cortisol as PEG isn’t producing any so produces more ACTH that can not be used
What can you deduce if there is too much ATCH in blood?
-Issue with PEG
What are some causes of hyper secretion?
-Tumour or Immunological
What are some causes of hypo secretion?
-Genetic, immunological, destruction of gland by disease or trauma
How can you diagnose an endocrine disorder?
-Signs and symptoms, hormone levels (bloods), imaging