INTRODUCTION TO ENDOCRINE Flashcards
what is the endocrine system responsible for?
growth and development
sex differentiation
metabolism
adaptation to changing environment ( regulation of digestion, use and storage of nutrients, electrolyte and water metabolism, reproductive functions)
how does the endocrine system work?
the endocrine system uses chemical substances called hormones ( amides, peptides, steroids’) to produce a physiological response
how do hormones work?
hormones function as chemical messengers
how do hormones function as chemical messengers?
they move through the blood to distant target sites of action
they can also act locally as paracrine or autocrine messengers for local effect
where are hormones present?
most are present in body fluids at all times in greater or lesser amounts as needed
what is the function of the endocrine gland?
releases endocrine hormones into circulating blood which influence function of a distanced targeted special cells e.g. thyroid hormone synthesized in thyroid gland and released into circulation
what is the function of the paracrine cell?
paracrine is secreted into extracellular fluid which affect nearby cells of a different type e.g. action of sex steroids on the ovaries
what is the function of the autocrine cell?
endocrines are secreted by the cells into extracellular fluids and affect functions of the same cells that produced it. e.g. insulin from pancreatic beta cells can inhibit the release from the same cell. e.g. arometers are inhibitors which prevent estrogen generation in breast cancer
what are neuroendocrine?
secreted by neurons into the circulating blood and inflame the functions of the target cells at other locations e.g. cytokines into extracellular fluid
what can peptides function as?
auto/para/endocrine hormones e.g. interleukins and other lymphokines that are secreted by helper cells and act on other cells of the immune system
what are cytokine hormones also called?
endokines
how does a synaptic transmission work?
it is a biological process which the neurons communicate with a target cell across a synapse
this involves the release of neurotransmitters binding to post synaptic receptors
what is conducted during neurotransmission?
conduction from one nerve cell to another or from one nerve cell to muscle
what does the endocrine system rely on?
relies on the signalizing molecules called hormones to accept responses from target cells which are synthesized in a specialized gland and travel through the blood stream or intracellular fluids
what is the difference between endocrine signaling and synaptic signaling?
endocrine- hormone mostly acts on cells distanced from synthesis
synaptic is conduction of neurotransmitters from one nerve cell to another or to a muscle
what are the characteristics of hormones?
a single hormone can exert various effects in different tissues
a single function can be regulated by several hormones
give an example where a single hormone exerts it effects on different tissues
estradiol (oestradiol)- produced in ovart acts on:
1-ovaran follicle- promote maturation
2-uterus to stimulate growth and maintain the cyclic changes in uterine mucosa
3-mammary gland to stimulate ductal growth
4-hypothalmic-pituitary system to regulate the secretion of gonadotropins and prolactin’s
5-bone to maintain skeletal integrity
6-general metabolic process to affect adipose tissue distribution
give an example of how a single function can be regulated by several hormones
lipolysis
catecholamines/ insulin/ glucagon/ cytokines/ tumor necrosis factor-a
what is the mechanism of action of hormones?
hormones interact with high-affinity receptors which are linked to one or more effector systems in the cell
how do hormones with receptor located on the surface of the cell work?
these act through second-messenger mechanisms
how do hormones with receptors located inside the cell work?
they modulate the synthesis of enzymes, transport proteins or structural proteins
what are the 3 classes of the the hormones according to their structure?
amines
peptides and proteins
steroids
give an example of amines and their associated glands
adrenaline and noradrenaline- synthesized in adrenal medulla and same effects as sympathetic stimulation
- T3 and t4- synthesized in thyroid gland- inc rate of chem reaction and inc rate of metabolism
give examples of peptides and proteins and their associated glands
insulin- islets of Langerhans- promotes glucose entry in many cells- controls carbohydrates metabolism
- Growth hormones’- synth in ant pituitary – stim protein synth and growth of most cells and tissues
give examples of steroids and their associated glands
all synthesized in adrenal cortex
- Cortisol- control met of protein carbs and fats- also anti-inflammatory effects
- Aldosterone- sodium reabsorption/ hydrogen ion ion sec
- Small amount of testosterone synthesized in adrenal and gestersone -male sex characteristics
what are the three actions hormones have when released into the blood stream?
1-circulate as free unbound molecules- usually peptide hormones and protein hormones
2-circulate as hormones attached to transport carriers- steroid and thyroid ( synth in liver)
3 intra/extracellular -termination of hormone function
what affects response of a target cell to a hormone?
number of receptors present
affinity of receptors for hormones
what is up regulation?
up regulation is an increase of the number of receptors on the target tissue making the cell more sensitive to target tissue/ increase uterine in 3rd trimester of pregnancy -promoting the contraction of muscles in the uterus
what is down regulation?
down regulation is a decrease in the number of receptors in target cells e.g. less sensitive or insulin may be downregulated -diabetes
what affects the affinity of receptors for their hormones?
ph of bodily fluids- affects the affinity of insulin receptors
how do the cell surface receptors produce the hormone response?
they use a first messenger> g protein> effector protein> cAMP> second messenger> target cell response
what happens in protein and polypeptide hormone receptors?(lipophilic)
usually unable to enter cell- bind to receptor complex
cellular response- transductor system mainly by cAMP- rapid response as the second messenger usually modulates existing proteins
the changes triggered by the peptide hormone-open and close membrane channnels so modulate metabolic enzymes for transport protein
why do some transport proteins have a longer effect?
because they activated genes and direct synthesis of new proteins
give examples of hormone receptors leading to interactions of second messengers?
glucagon/ insluin/ adrenaline/ parathyroid hormone/ TSH/ ACTH/ FSH/ LH/ ADH/ secretin
what is the difference when there is a lipophilic steroid hormone?
diffuses into target cell, binds and activated intracellular receptor
this way the nucluse chromatin binds to the region in the DNA
what is the exception to the way the steroid lipiophilic hormone binds to the DNA?
THR- always bind to DNA even in the absense of the thyroid hormone- this promotes the translocation of mba to produce mrna
this is translated into a specific protein molecule which promote the metabolic activities and sometimes synthesis of export
how do steroid hormones get transported in the blood and how does it work on its intraceular receptors?
1- corticosteroid binding to prevent from enzyme degradation- longer half life
2- binding complex - goes to nucleus
3- hormone receptor complex binds to dna
4-produces mrna and moves back to cytoplasm
5-translation- new cell process
6- some steroid hormones bind to membrane- second messenger system
what are examples of hormones that bind in intracellularly?
oestrogen testosterone progesterone adrenal cortical hormones thyroid hormones
how are hormone levels controlled?
affected by diurnal fluctuations that vary with the sleep wake cycle- GF and ACTH
secreted in complicated cyclic manner- female sex hormones
mech that monitor glucose/ water and ADH,. and hypothalmic-pituitary target cell
what is the role of the hypothalamus?
coordinating center of the brain for endocrine, behavioral and autonomic nervous system function.
what hormones does the hypothalamus regulate?
anterior: GHRH, somatostatin, dopamine, THR, CHR, GnRH,
posterior- ADH, oxytocin
how do you monitor the changing levels of hormone levels?
positive and negative feedback
level of the substance the hormone regulates
what is positive feedback? give an example
breast feeding
1-child is hungry- cries and mothers hypothalmus stimulated
2- sends impulses to the posterior
3-posterior releases ocytocin
4- ocytocin stimulates milk ejection from breast
5- stim in nerve of breast
6- sucking -muscles of breast contract to produce milk
give an example of negative feedback and how it works
stimulation for glucogen diminishes- diabetes
normal levels- 90mh/100ml
when would your blood glucose levels decline?
after skipping meal
what happens when your glucose levels rise?
after eating meal beta cells of the pancreases stimulate to release insulin into the blood and body cells take up more glucose
what diseases would be classified by hormone excess?
primary / secondary gland production
what endocrine disease would clasify as hormone deficiency?
primary gland failure
secondary to deficient tropic hormone
what endocrine disesases are due to hormone hypersensitivity?
failure of activation of hormone
target organ resistance
what are the 4 classes of endocrine disease classification?
hormone excess
hormone deficiency
hormone hypersensitivity
non-functioning tumours
what tests would you carry out to investiagte hormone levels?
blood,urine tests stimulation and suppression tests genetic tests imaging biopsy
