Download Hormones in action

Hormones in action
How hormones work
 hormones come into contact with essentially all cells in the body, they
produce a specific effect on particular cells.
 Target cells have receptors that the hormone recognises and bind to,
triggering a response inside the cell.
 Each hormone can only effect specific cells that have the correct
receptor.
 Hormone reach's target cell, two ways they bind to the receptor/reaction.
 Depends on whether they are water soluble or fat soluble hormones.
For example thyroid gland
 Thyroid stimulating hormone can only bind with cells of the thryroid
hormone.
 Could be compared with radio waves, every one is in range but needs the
right frequency to interpret the sound.
Target cells and receptors
 Hormones can have several different target cells.
 Do not always react the same way.
 Insulin stimulates liver cells to store glucose but also causes adipose cells to store
fatty acids.
 Agonists act like the "normal" hormone, although perhaps more or less potently.
Natural hormones are themselves agonists and, in many cases, more than one
distinct hormone binds to the same receptor. For a given receptor, different agonists
can have dramatically different potencies.
 Antagonists are molecules that bind the receptor and block binding of the agonist,
but fail to trigger intracellular signalling events. Antagonists are like certain types
of bureaucrats - they don't themselves perform useful work, but block the activities
of those that do have the capacity to contribute. Hormone antagonists are widely
used as drugs.
Prostaglandins
 Hormone like substance.
 Act in a similar way to hormones, act locally do not travel far through blood
stream.
 Released by cell membranes, many different effects.
 Many organs are capable of producing prostaglandins
 involved in pain and the response to injury.
 Prostaglandins are also involved in regulating the contraction and
relaxation of the muscles in the gut and the airways.
Triggers for hormone release
 Some endocrine glands are stimulated by presence/abcence of certain
minerals or nutrients in the blood, for example low calcium levels stimulate
the parathyroid gland to release parathyroid hormones.
 Gland then releases pyrathyroid hormone
 In cases release of hormones is triggered by the nervous system.
 Medulla, part of the suprarenal gland, which releases adrenaline/
epinephrein when stimulated by nerve fibres from the sympathetic nervous
system
Hormone regulation
 Hormone levels need to be regulated within certain levels.
 This is usually achieved with negative feedback mechanisim.
 Much like a thermostat found in typical households, aiming to maintain
room temperature by monitoring surrounding environment with sensors.
 To cold = boiler turns on till set temperature is reached then shuts off
 Hypothylimus/pituritary complex is the thermostat, hormone level in the
blood is equivalent to air temperature
 Hormone level drop = endocrine gland “turns on” hormones are released
to reach desired level then “shuts off”
Thyroid gland
 Butterfly shaped gland
 Composed of gas sacs called follicles
 Produces two separate hormones triiodothyronine and thyroxine
(thyroid hormone. TH )
 Virtually all receptors in the body have receptors for TH.