endocrine system Flashcards
what is the endocrine system
system of glands that produce hormones to enable cells to communicate in order to maintain homeostasis in the body
what is a hormone
chemical messenger that enable cells to communicate
what 3 ways does the endocrine system elicit a response
endocrine = secreted into bloodstream and act on distance cells
paracrine = act on nearby cells
autocrine = act on same cell
what is autocrine
form of signaling in which a cell secretes a hormone or a chemical substance that binds to the receptors on the same cell, leading to functional changes in the cell
what is paracrine
allows cells to communicate with each other by releasing signaling molecules that bind to and activate surrounding cells.
what is endocrine
secretes into bloodstream to act on distant cells
what is neuroendocrine
secreted by neurone into blood stream and act on distant cells
what can happen when hormones lose control
fatigue, hair loss/excess growth, acne, weight gain etc
what are the 3 classes of hormones
steroid hormones
peptide/proteins
amino acid derived
what are steroid hormones/ process of making it
a group of hormones derived from cholesterol that act as chemical messengers in the body.
precursor (e.g cholesterol) then
processed to active hormone (e.g cortisol)
then secreted into blood and is transported bound to binding protein (e.g tester one)
then free active hormone is able to pass through cell membrane to exert effect
difference between peptide and protein hormones
Peptide hormones consist of short chains of amino acids, whereas protein hormones are longer polypeptides
explain the production of the peptide/protein hormones
- first synthesised in the RER as an inactive precursor
- further processed in Golgi and secretory vesicles
- secreted by exocytosis into circulating blood
describe process of amino acid derived hormones
- tyrosine enters cell
- processed by enzymes to dopamine via precursor
- dopamine transported to secretory vesicles and converted to norepinephrine
- increased intracellular calcium levels mean secretory vesicles fuse with membrane and hormones can diffuse into bloodstream
whats the precursor for steroid hormones
cholesterol
what are 2 forms of patters for hormone release
episodic secretion
diurnal secretion
what 3 types of hormones are bound to transport molecules in plasma
t3 t4 thyroxin-binding globulin
thyroid hormones
steroid hormones
what are the 3 main roles of transport molecules for hormones
- extend biological half-life
- increase plasma conc of smaller hormones
- modulatory (alteration) effect of biological function
if hormones are circulating in the bloodstream, why dont they affect cells all the time
hormone receptors must be compatible
what are hormone receptors
specific shaped on cell surface or within wall allowing hormones to bind
difference between water-soluble and lipid-soluble hormones and how they pass through cell membrane
water-soluble= bind to cell surface receptors and message passed via signal transduction (conversion)
lipid-soluble= pass directly through cell membrane and translocate to nucleus bound to intracellular receptor
how do amino acid derived and peptide/protein hormones cause signalling (as they cant diffuse into the cell)
- they bind to the receptor on the cell
- there are intracellular receptors on the target cell which are often associated with the receptor
- this involves a G-protein
- the g-protein is next to an enzyme (adenylyl cyclase)
- this converts ATP into cyclic AMP (cAMP)
- cAMP is known as a second messenger as it signals a cascade of events that change the enzymatic activity of the cell to cause the target cell response
give examples of some hormones that use the cAMP second messenger system
AHD, glucagon, ACTH
explain how the steroid hormone causes signalling
- steroid hormones are lipophilic so they can freely move through the cell membrane
- they can bind to a receptor in the cell or move into the nucleus where I makes a hormone-receptor complex
- this complex causes a change in gene activity
- this increases transcription and mRNA production so increase in protein production
give some examples of hormones that can diffuse through cell for signalling
testosterone, estrogen, progesterone
what is an endocrine axes
series of endocrine glands that signal to each other in sequence
stimulus
gland A
hormone A
gland B
hormone B
gland C
hormone C
effect on target cells
what is positive and negative feedback in endocrine system
A positive feedback loop in the endocrine system is when release of a hormone initiates actions that lead to an additional release of that hormone. Unlike a negative feedback loop, a positive one is not looking to reach homeostasis (stability).
negative: If an endocrine gland senses that there is too much of one hormone in the body, it will initiate changes to decrease production of that hormone. And if there’s not enough of the hormone, the body will increase production of that hormone. You can think of it as your body’s attempt to self-regulate and self-correct.
what is the major player in hormonal regulation (in brain)
hypothalamus
what is the duty of the hypothalaus
- controls most of the endocrine autonomic and behavorial functions of body
- controls pituitary hormone release
what are the 2 compartments of the pituitary gland
anterior and posterior pituitary gland
what is the function of the anterior pituitary gland
- controls activity of other endocrine glands
- controls growth
- stimulates production of oestrogen and progesterone
- ovulation and pregnancy
- testorone production and spermatogenesis
what is the function of the posterior pituitary gland
store and releases two hormones: oxytocin and antidiuretic hormone (ADH, or vasopressin)
what the difference between primary and secondary endocrine disorders
primary= originating in peripheral of endocrine gland itself
secondary= under/overstimulating by tropic gland
what is a product of excess thyroid
hyperthyroidism
a swelling in your neck caused by an enlarged thyroid gland (goitre)
an irregular and/or unusually fast heart rate (palpitations)
twitching or trembling.
warm skin and excessive sweating.
red palms of your hands.
loose nails.
a raised, itchy rash – known as hives (urticaria)
patchy hair loss or thinning.
product of thyroid deficiency
tiredness.
weight gain.
depression.
being sensitive to the cold.
dry skin and hair.
muscle aches.
