Endocrine Flashcards
what are homeostatic mechanisms?and whats homeostasis
and where de thes mechanisms exist?
- homeostatic mechanisms act to counteract changes in internal environment
- homeostasis = dynamic equilibrium
- cell = e.g regulating ca2+ conc
- tissue = balance beween cell proliferation and cel death
- organ = kidney regulates ion concs
- organism = temp control
characteristics of a control system diagram
- communication:
- endocrine and nervous system
- hormones released locally are under paracrine control
- or self effecting once they release substances like autocrine control
- peripheral nervous system divided into afferent (“going to brain; sensory) branch and efferent (going away from brain; motor)
- control centre:
- determine the reference set point
- 2 control centres ; hypothalamus and the the medulla oblongata in the brain stem
- hypothalamus controls the endocrine system whilst medulla oblongata controls ventillation and CVS
- receptors:
- detect stimuli and pass info through afferent pathways
- effector:
- agents that cause change and they are communicated by the efferent pathway
- feedback:
- has an effect on the control centre (reference set point)
- in negative feedback: change from normal causes series of changes that return state back to norm
- positive feedback: causes an increase in effect
what controls our biological rhythm?
when our clocks dont match up whats that called?
suprachiasmatic nucleus is the natural biological clock , (bunch of neurones). in controls our 24 hour cycle but it is affected by our Zeitgebers (environmental cues like like)
mismatch in environmental clock and biological clock causes jet lag
hormone melatonin released by pineal gland is importnt for setting clock
examples of biological rhythm
- temp changes throughout the day
- cortisol levels are highest when you wake up and low at midnight (decrease throughout the day) so write the time it was taken
- menstural cycle
set point
can vary like core body temp
what cells secrete hormones? and what are the cells that hormones act on called?
- endocrine gland
- target cells
if hormones are secreted what is the factor that controls whethere they are effective or not?
what does lipophilic hormones mean?
how is this different for lipophilic hormones?
whats the conc of hormone in the blood
blood concentration of the hormone
steroid based + thyroid hormone
they bind specifically or non-specifically to proteins in the blood and so in this case its the free hormone conc that matters
10^-10 and 10^-9 M
hormones from the heart liver stomach placenta placenta adipose kidney
- ANP BNP
- IGF1
- GASTRIN GHRELIN
- INHIBIN, PLACENTAL LACTOGEN
- LEPTIN
EPO RENIN CALCITRIOL
are some hormones neurotransmitters
yes
classificationS of hormones
- peptides ( insulin/glucagn/Grwth hormone)
- amino acid derivatives (amines) ; adrenaline/nor (tyrosine)/thyroid(tyrosine)/melatonin (tryptophan) {all water soluble but thyroid hormone is lipid soluble and travels using thyroxine-binding globulin TBG}
- glycoprotein ; large protein molecules w carbohydrate side chain e.g. LH/FSH/TSH water soluble
- steroid: derived from cholesterol, sterogenic tissue converts cholesterol to different hormones: (cortisol/testerstone/oestrogen/aldosterone) all lipidsoluble and need transporters
how are peptide, and steroid hormones stored and give examples?
also which hormone doesnt follow this pattern?
peptide
- store their hormones in discrete storage vesicles within the cell prior to secretion:
- just like insulin: which once synthesised is marginated into vesicles and only released via exocytosis in response to kATP channels closing(d high ATP)
- noradernaline stored
- *steroid
- steroid producing tissue dont store the hormone they store the precursor CHOLESTEROL as cholesterol esters in the form of lipid droplets
the thyroid hormone is an exception ; because its stored outside the cell in the form of protein colloid
how are protein and steroid hormones transported
protein are water soluble so travel in the blood okay but steroid hormones aren’t and so require specific carriers
what form is active
- freeform is bioogiall active
hormone level factors
- rate of production -rate of delivery - rate ofdegradation
conc hormones in the blood and give example
v low - thyroxine = 10-30pmol/L
where do water soluble receptors bind and give examples
- cell surface - AD/NR coupled adenylal cylase - Insulin /Tyrosine kinase wc udergoes dimerisation (except insulin since already dimerised, then undergo autophosphorylation , recruitment of adapter P and signalling complex, activate PK, phosphorylate target P
steroid hormones
- act as transcription factors - through the lipid membrane - bind to cytoplasmic receptor wc directs it to nucleus and enters it - binds to receptor on DNA and affects the expressionof a gene OR can bind to pre-bound receptor like how thyroid hormone relieves repression of the gene transcription - once the hormone is bound toDNA it is called a HRE hormone response ee element in the promoter region of specific genes
which is faster lipid soluble or water soluble?
- water b the receptors are already existent and present b in lipid soluble the hormone must act on the DNA and this gene expression takes time (minutes-hours)
control of appetite
- arcuate nucleaus in the hypothalamus ,
- it contains primary neurones that sense metabolite and hormone levels;
- seconadry neurones in other areas of the hypothalamus recieve inputs from the arcurate primary neurone and co-ordinate a response via the vagus nerve.
- primary neruones in the arcuate nucleus are divided into: excitatory and inhibitory subtypes.
+ regions of brain stem control appetite
whats POMP
it is releasd by inhibtory neurone (anorexigenic) to supress the appetite.
it is a pro hormone and is cleaved ito many hormones:
- ACTH
- a-melanocyte stimulating hormone (a-MSH) wc act on melanocortin 4 recetpors that supress the appetite
- beta - edophin (B-endorphin) this gives a feeling of euphoria and tiredness after eating once you’ve eaten a meal
gherkin
- peptide hormone made by stomach, is released upon empty stomach
- and acts on the AgRP in the accurate nucleus of the hypothalamus
- eating food and filling the stomach will cause strecthing the stomach wall and will suppress this hormone
*
- eating food and filling the stomach will cause strecthing the stomach wall and will suppress this hormone
PYY
- peptide tyrosine tyrosine
- -PYY (pepide tyrosin tyrosine) is released by cells in the ileum and colon in response to food and act on the POMC(pro-opiomelanocortin) and have an inhibitory effect telling yo you’re full
- it works in opposition with ghrelin
- giving PYY to rats made them anorexia B blunted response in humans
leptin
- leptin (released by adipocytes) has 2 effects ;
- stimulates eating AgRP and inhibit POMC
- overall effect though is to suppress eating.. it also c expression of more uncoupling proteins in the mitochondria so more energy dissipated as heat -insulin ; instead of ATP heat
leptin disease?
- decrease of leptin production or insensitivity to leptin is associated with obesity
leptin resistance is the type of obesity
role of carrier proteins
- increase half life -readily accessible reserve -increase solubility of hormone in plasma
when does the development of the Endocrine System? and what describe the development of the pituitary gland?
- at 4 weeks gestation there are no endocrine glands
- at 5 weeks they begin to develop;
1. pituitary gland develops from the neurohypophyseal bud and hypophyseal pouch
why is there always a small conc of pit. hormones in the blood
they’re released continously via merocrine secretion
what is a gland
an epithelial cell or an aggregate of epithelial cells (tissue) that are specialised for the secretion of a substance
what’s a secretion
a substance or materials producted and released by a specialised cell or aggregate of cells (tissue)
how are glands classified
based off their structure
and how they release products
the types of glands
endocrine (ductless)
exocrine (ducted)
how are glands formed
- growth signal recieved
- proliferation of daughter cells occurs abd extracellular protein degradation enzyme produced
- epithelial cells invade space created
whats the rate of secretion of a hormone controlled by?
negative feedback
takes into account the hormones beinf excreted and broken down
tropic vs trophic hormones
tropic have other endocrine glands as their target cell (like CRH for release of cortisol, or GnRH for FSH to testerstrone)
where are the receptors in a lipophilic hormone and protein hormone
peptide on the cell surface membrane since they are lipophobic. as a result theres ussually a second messenger thats released like cAMP,Ca2=,IP3, DAG, cGMP
whilst steroid hormones are lipophilic and so can cross the membraene and so have nuclear/cytoplasmic receptors
how are petide and steroid hormones inactivated
- peptide hormones undergo extensive chemical changes and are degraded to amino acids that are reused for protein synthesis
- steroid hormones are inactivated by small changes to their chemical structure that increase their water solubility enabling them to be excreted via bile or urine more easily
whats the consequences of disorders of the endocrien system and give examples
- changes in the endocrine tissue c under secretion or proidcution of abnormal and ineffective hormone (adeonma)
- antiboidies destroying the effective conc of hormones and so v conc of effective hormones (Hashimoto)
- cahnges in responsiveness of target cells to the hormones d changes to receptors and/or post-receptor events (diabetes 2)
describe the arcuate nucleas
its primary. neurones within it are divided into excitatory adn inhibitory.
excitatory (orexigenic neruones) stimulate appetite via release of neuropeptide Y (NPY) and agouti-related peptie (AgRP)
inhibitory ((anorexigenic neruones) within the arcuate nucleas supress the appetite by releasing pro-opiomelanocortin (POMC)
Insulin
insulin supresses the appetite via same mechanism as leptin, and also decreae in effectiveness of insulin associated with leptin
amylin
- Amylin ; made by B cells of the pancreas
- , suppress eating by decreasing glucagon secretion and slowing gastric emptying ..
- PRAMLINTIDE is treatment for type 2 diabetes and contains it
other than controlling appetite what other things can tha arcuate nucleas sense
fatty acid and glucose levels in the blood
