Unit 1: Extracellular Signalling Flashcards
what events occur when blood glucose concentration falls?
pancreas detects, glucagon released and carried o the liver in the blood, turns glycogen into glucose
what are the three stage in cell signalling?
reception, transduction and response
what are the two main forms of communication between cells in multicellular organisms?
hormones and neurotransmitters
what are hormones?
extra signalling molecules that are secreted by one tissue (endocrine organ) into the blood. The hormone circulates in the bloodstream until it reaches its target receptor or is broken down
what are the two main types of signalling hormone?
peptide hormones - hydrophilic - eg insulin, growth hormone, ADH
steroid hormones - hydrophobic - eg cortisol and testosterone
where is the receptor molecules for hydrophobic signalling molecules and why?
since hydrophobic signalling molecules can pass through the membrane by diffusion, their receptor molecules are within the cytoplasm or nucleus of the target cell.
how do hydrophilic signalling molecules reach receptors?
since they cannot pass through the membrane, their receptors are integral proteins (transmembrane)
what are the two types of signal transduction?
opening an ion channel at the cell surface
releasing a secondary messenger within the cytosol
what are peptide hormones?
small hydrophilic proteins
why is the action of peptide hormones highly specific?
the target cells have to have the appropriate receptors on their surface
what are neurotransmitters?
hydrophilic signalling molecules released during nervous communication
where are neurotransmitters released?
synaptic gap between a nerve cell and its neighbour
give examples of neurotransmitters
noradrenaline and acetylcholine
what is acetylcholine?
the neurotransmitter at the neuromuscular junction connecting motor nerves to muscles
what is noradrenalin?
neurotransmitter and stress hormone for fight or flight
what is the receptor for a steroid hormone?
gene-regulatory protein
describe the action of steroid hormone and gene-regulatory protein
when steroid binds to gene-regulatory protein, brings about a conformational change that activates the protein so it can bind to DNA and regulate transcription of specific genes.
what is cortisol?
steroid hormone made in the adrenal glands adjacent to the kidneys and its function is to regulate blood pressure, cardiovascular function and regulation of body’s carbs, proteins and fats, also has medicinal use
