Endocrine

Question 1

what are homeostatic mechanisms?and whats homeostasis

and where de thes mechanisms exist?

Answer 1

• 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

Question 2

characteristics of a control system diagram

Answer 2

• 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

Question 3

what controls our biological rhythm?

when our clocks dont match up whats that called?

Answer 3

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

Question 4

examples of biological rhythm

Answer 4

• 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

Question 5

set point

Answer 5

can vary like core body temp

Question 6

what cells secrete hormones? and what are the cells that hormones act on called?

Answer 6

• endocrine gland
• target cells

Question 7

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

Answer 7

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

Question 8

hormones from the heart liver stomach placenta placenta adipose kidney

Answer 8

• ANP BNP
• IGF1
• GASTRIN GHRELIN
• INHIBIN, PLACENTAL LACTOGEN
• LEPTIN

EPO RENIN CALCITRIOL

Question 9

are some hormones neurotransmitters

Answer 9

yes

Question 10

classificationS of hormones

Answer 10

• 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

Question 11

how are peptide, and steroid hormones stored and give examples?

also which hormone doesnt follow this pattern?

Answer 11

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

Question 12

how are protein and steroid hormones transported

Answer 12

protein are water soluble so travel in the blood okay but steroid hormones aren’t and so require specific carriers

Question 13

what form is active

Answer 13

• freeform is bioogiall active

Question 14

hormone level factors

Answer 14

• rate of production -rate of delivery - rate ofdegradation

Question 15

conc hormones in the blood and give example

Answer 15

v low - thyroxine = 10-30pmol/L

Question 16

where do water soluble receptors bind and give examples

Answer 16

• 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

Question 17

steroid hormones

Answer 17

• 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

Question 18

which is faster lipid soluble or water soluble?

Answer 18

• 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)

Question 19

control of appetite

Answer 19

• 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

Question 20

whats POMP

Answer 20

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

Question 21

gherkin

Answer 21

• • 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
    *

Question 22

PYY

Answer 22

• 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

Question 23

leptin

Answer 23

• 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

Question 24

leptin disease?

Answer 24

• decrease of leptin production or insensitivity to leptin is associated with obesity

leptin resistance is the type of obesity

Question 25

role of carrier proteins

Answer 25

- increase half life -readily accessible reserve -increase solubility of hormone in plasma

Question 26

when does the development of the Endocrine System? and what describe the development of the pituitary gland?

Answer 26

- 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

Question 27

why is there always a small conc of pit. hormones in the blood

Answer 27

they're released continously via merocrine secretion

Question 28

what is a gland

Answer 28

an epithelial cell or an aggregate of epithelial cells (tissue) that are specialised for the secretion of a substance

Question 29

what's a secretion

Answer 29

a substance or materials producted and released by a specialised cell or aggregate of cells (tissue)

Question 30

how are glands classified

Answer 30

based off their structure and how they release products

Question 31

the types of glands

Answer 31

endocrine (ductless) exocrine (ducted)

Question 32

how are glands formed

Answer 32

1. growth signal recieved 2. proliferation of daughter cells occurs abd extracellular protein degradation enzyme produced 3. epithelial cells invade space created

Question 33

whats the rate of secretion of a hormone controlled by?

Answer 33

negative feedback takes into account the hormones beinf excreted and broken down

Question 34

tropic vs trophic hormones

Answer 34

tropic have other endocrine glands as their target cell (like CRH for release of cortisol, or GnRH for FSH to testerstrone)

Question 35

where are the receptors in a lipophilic hormone and protein hormone

Answer 35

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

Question 36

how are petide and steroid hormones inactivated

Answer 36

* 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

Question 37

whats the consequences of disorders of the endocrien system and give examples

Answer 37

* 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)*

Question 38

describe the arcuate nucleas

Answer 38

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)**

Question 39

Insulin

Answer 39

insulin supresses the appetite via same mechanism as leptin, and also decreae in effectiveness of insulin associated with leptin

Question 40

amylin

Answer 40

* - 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

Question 41

other than controlling appetite what other things can tha arcuate nucleas sense

Answer 41

fatty acid and glucose levels in the blood