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