Endocrine system Flashcards
What is the main function of the endocrine system?
To produce and release chemical messengers (hormones)
What is the difference between endocrine and exocrine systems?
ENDOCRINE ->No open contact with exterior // No ducts // Produce hormones which are secreted into the blood//// EXOCRINE -> Open contact with exterior// Ducts // Ducts carry secretions to surface
What is the function of the pineal gland?
Maintain sleep schedule
What is the role of the hypothalamus?
oversees internal body conditions// receives stimuli from receptor // monitors chemical and physical characters of blood // secretes hormones which regulate pituitary function
What is the role of the pituitary gland?
to receive signals from the hypothalamus then send these signals to other organs within the endocrine signal
Where is the pituitary gland located ?at connects the hypothalamus an the pituitary gland?
infundilnulum
What is the two components of the hypothalamus and their function?
hypothalamo-hypophysialk tract->connect the hypothalamus with the posterior pituitary // hypothalamhypohysial portal -> connects anterior pituitary with hypothalamus
How does growth factors occur? (using the hypothalamus and the pituitary gland)
- Hypothalamus releases GHIH hormone through the portal blood // 2. Reaches anterior pituitary gland which then produces the growth hormone // 3. Growth hormone is then sent throughout the entire body via blood vessels stimulating growth
What is meant by an axis in the endocrine system?
glands sending signals to each other in a sequence
What makes up the thyroid galnd?
many follicles (sphere simple cuboidal epithelial cells ) //4 small glands on posterior of the thyroid gland are composed of parathyroid cells and oxyphil cells//
What are the components of the suprarenal gland and their functions?
INNER MEDULLA - makes epinephrine (Adrenaline ) and norepinephrine // OUTER CORTEX - makes steroid hormones
What is Cushing’s syndrome ?
a hormonal disorder that occurs when the body produces too much cortisol (a hormone that helps the body respond to stress) // resulting in excessive sweating and weight gain
What is the two main functions of the pancreases?
Acts as an exocrine gland - acini produces pancreatic juice , moves into small intestine and breaks down compounds // endocrine - pancreatic islets secrete hormones into circulation
What are the 3 types of cells in pancreatic islets ? Where are they found?
Beta / Alpha / Delta// all found lining exocrine ducts
What is the function of beta pancreatic islet cells?
RELEASES- Insulin TARGETING -liver, skeletal muscle, adipose tissue// REPSONSE = Increased uptake and use of glucose and amino acids
What is the function of alpha pancreatic islet cells?
RELEASES- insulin // TARGETING - primarily liver// RESPONSE = increases breakdown of glycogen , release of glucose in the circulatory system
What is the function of delta pancreatic islet cells?
RELEASES - somatostatin // TRAGETS - alpha and beta cells / RESPONSE - inhibits insulin an glucagon secretion
What are the 3 layers of the adrenal cortex?
ZONA GLOMERULOSA // ZONA FASCICULATA // ZONA RETICULARSIS
What steroid hormones are produced from what sections of the adrenal cortex?
ZONA GLOMERULOSA -> aldosterone // ZONA FASCICULATA -> cortisol // ZONA RETICULARSIS-> androstenedione
What are the two ways cells communicate?
- Direct membrane to membrane contact // Synthesis and release of messengers (more common)
What are the 4 types of messengers cells use to communicate?
- Hormones // Small chemicals // Antibodies //
Neurotransmitters
What are the 4 structural classes of hormones?
PEPTIDE (water soluble / hydrophilic / bind to cell surface receptor)// STEROID ( made from cholesterol / water-insoluble / hydrophobic / require carrier proteins //AMINE (made of amino acids e.g. Melaine and serotonin )
Briefly explain the processes of cell signalling
- Synthesise of signalling molecule in the signalling cell
- Release of signalling molecule by the signalling cell
- Transport of signalling molecule to target cell
- Detection of signalling molecule by a specific receptor protein on or in the target cell
- Change in target cell function triggered by receptor -signal complex
- Inactivation / removal of signalling molecule
What are the 4 extracellular molecules which are involved in cell signalling?
ENODCIRNE// PARACRINE // AUTOCRINE // PROTEN EXPRESSION INTERACTIONS
What is endocrine signalling?
long-range signalling // glands produce a hormone which travels through the body to a target cell e.g. insulin
What is paracrine signalling?
- Short-range// cells produce messengers and these messengers are sent in the extracellular fluid where it reaches the target cell // e.g. neurotransmitters
What is autocrine signalling?
- Very - short range// Cell releases messenger, the target is found within the same cell but In a different location // e.g. growth factor
What is membrane contact cell signalling?
roteins expressed on the surface of the signalling cell interact with receptor proteins expressed on the surface of the target cell via direct contact // e.g. signalling of T cells in immune system
What is signalling transduction?
the process by which cells receive and respond to signals from their environment//interactions between signals and membrane receptors
What are the 4 main cell receptor types?
Nuclear/ G-protein// Ligand-gated ion channel // kinase -linage receptor
Briefly explain a inotropic channel (liganded-gated channel receptor).
expressed on electrically excitable cells e.g. nerve and muscle // Binding of signalling molecule leads to conformational change in the receptor which results in the opening of a central ion pore , resulting ion flux causes change in the membrane potential (increases or decreases dependent on ion)// Ion flux is driven by the electrochemical gradient of the permeant ions
- e.g. Acetylcholine
What is the structure of an ion channel ?
4 subunits and a pore
Briefly explain a G-protein coupled receptor.
Many cell-surface receptors that are couple to trimeric signal-transducing G proteins
- Require energy (GDP-> GTP)
- Trimeric = composed of 3 subunits (alpha, beta and gamma) // Ligand binding to a G protein-coupled receptor activates the associated G protein which in turn activates and inhibits a downstream enzyme to generate an intracellular secondary message // G protein activation and complex formation are part of a cycle
Briefly explain the kinase-linked receptor.
Large and diverse group of membrane receptors // Primary respond to protein membrane Consists of :
Ø Extracellular ligand-binding domain
Ø Single transmembrane helix
Ø Intracellular domain (often enzymatic ) – - may have protein kinase activity + no enzyme activity but interacts via intracellular effector enzymes (uses adaptor proteins)
- e.g. insulin
Briefly explain the nucellar receptor.
Regulate gene transcription // Known as nuclear receptors , some are located in the cytosol //Migrate to nucleus upon ligand binding // Can recognize foreign molecules // Induce expression of enzymes needed for metabolizing foreign substances
What are the two types of nuclear receptor?
Type I (cytoplasmic) and Type II (nuclear), based on their location and ligand(binding of a molecule to a protein) binding behaviour.
Why is amplifying signals important?
EFFICENCY-> allows cells to respond to low concentrations of signalling molecules// SPEED-> rapidly spreads the signal across the ell// CONTROL + REGULTION -> enables fine-tuned responses //
What are the three main categories of hormones based on chemical structure?
PROTEIN AND POLYPEPTIDE// STEROID / DERIEVED FROM AMINO ACIDS (thyroid and catecholamines )
What are the mechanisms of biosynthesis, storage, release and transport of protein hormones?
BIOSYNTHESIS - in advance in pituitary gland //STORAGE - in vesicles within the cell //
RELEASE - via exocytosis /TRANSPORT- dissolved in plasma// EXAMPLE - insulin , GH, TSH // CHEMICAL NATURE - hydrophilic
What are the mechanisms of biosynthesis, storage, release and transport of steroid hormones?
BIOSYNTHESIS - on demand from reaction pathways in the adrenal cortex, ovaries, testes and placenta // STORAGE - not stored prior to secretion// RELEASE - simple diffusion//
TRANSPORT- bound to plasma proteins// EXAMPLES - cortisol and oestrogen (sex hormones) // CHEMICAL NATURE - hydrophobic
What are the mechanisms of biosynthesis, storage, release and transport of thyroid hormones?
BIOSYNTHESIS - from tyrosine within the thyroid// STORAGE - stored as colloid in thyroid follicles //RELEASE - via transport protein
TRANSPORT- bound to plasma proteins// EXAMPLE - thyroxine // CHEMICAL NATURE - hydrophobic
Give examples of negative feedback control of hormone secretion.
response driven -> based on direct effect of hormones in action // e.g. blood calcium level change as secretions of hormone from the endocrine tissue alters the response of controlled variables // ENOCRINE GALND(pancreatic beta-islet cells) -> HROMONE (insulin) -> TRAGET ORGAN (liver and muscles) -> PHYSIOLOGICAL EFFECT(increase glucose uptake and glycogen synthesis) -> CIRCULATING COMPONENT (blood glucose)
Give examples of positive feedback control of hormone secretion.
increases the action / e.g CHILDBIRTH
1. uterus contractions push baby’s head against the cervix// 2. stretch sensitive nerve cells in cervix send signal to CNS // 3 oxytocin is released causing contractions of muscles in uterus wall // 4. uterus dilates
Give examples of feed-forward feedback control of hormone secretion.
the stimuli causes an effect before the action of the feedback occurs // e.g. MORNING CORTISOL SURGE // 1. suprachiasmatic nucleus in hypothalamus acts as the body clock// 2. SCN signals to hypothalamus before down // 3. hypothalamus releases corticotropin releasing hormone(CRH) // 4. CRH stimulates the release of ACTH from anterior pituitary gland // 5. ACTH drives cortisol releases from adrenal gland // 5. wake state is achieved
What are the main properties and action of ADH?
controls water reabsorption in kidneys via increasing membrane permeability to water in the collecting ducts of the renal tubules // use ADH V2 receptors located on the basolateral membrane of collecting tubules in cell of kidneys
What are the main properties and action of aldosterone ?
controls sodium reabsorption in kidneys// synthesised in the adrenal cortex // stimulated via decreased blood volume and pressure
What is the integrated control of body salt (sodium ) and water concentrations?
1.HYPOTHALAMUS - sense changes in blood osmolarity, synthesises and releases ADH(antidiuretic hormone) // PITUITARY GLAND - releases ADH due to signals from hypothalamus // 3. KIDNEYS - regulates excretion and reabsorption based on hormonal signals// 4. ADRENAL GLAND- secretes aldosterone promoting reabsorption in kidneys
When is natriuretic peptides (ANP) released and what do they result in?
released by the heart in response to increased atrial stretch // increases sodium and water excretion in the kidneys
What are the mechanisms of biosynthesis, storage, release and transport of catecholamine hormones?
BIOSYNTHESIS - from tyrosine and amine groups in the adrenal medulla //STORAGE - in secretory vesicles //RELEASE - via exocytosis//
TRANSPORT- freely dissolved // EXAMPLE - Adrenal medulla // CHEMICA NATURE - hydrophilic
Where are hormones synthesised?
1.TRANSCRIPTION - occurs in cell nucleus // 2. RIBOSOMES - synthesis peptide chains creating pre-prohormones (contains signal peptide)// 3. ENDOPLASMIC RETICULUM - signal peptide is removed leaving a pro hormone // 4. GOLGI BODY - vesicle packages are prepared , modification occurs// 5. EXOCYTOSIS of the hormone into the target cell as an active hormone
What is the mechanism of peptide hormones?
peptides reach the target cell and activate a protein receptor creating a signal cascade
How are steroid hormones synthesised ?
Enzymes synthesis and cholesterol is transported into the mitochondria// they are then transported via plasma proteins after diffusion through the cell
What is diabetes insipidus?
a pathological condition in which the hypothalamus does not produce ADH //
What is liddle’s syndrome?
A genetic disorder where sodium, calcium channels have much longer levels of activity in the apical membrane than usual// high blood pressure caused by increased sodium transport into the blood increasing water reabsirbtion
What feedback system controls most hormones?
negative
What are the 3 layers of the adrenal cortex?
ZONA GLOMERULOSA -> clusters of small cells there is few lipids and aldosterone is regulated here by angiotensin 2 and potassium // ZONA FASCICULATA- > large cells arranged in cords , cortisol is regulated by ACTH// ZONA RETICULARIS-> smaller cells arranged randomly , adrenal and androgen are regulated by ACTH and other factors
What is the movement and action of cortisol?
transported via plasma bound to corticosteroid-binding globulin (CBG)-> targets cell receptor in cytoplasm -> initiates and represses gene expression// maintains blood glucose levels through being a catabolic and stimulating the break down of glucose, lipids and muscles
What can cause high levels of cortisol?
physical stress e.g. surgery // emotional stress e.g. fear// metabolic stress e.g. acute hypoglycaemia / infection and inflamation
What can cortisol be therapeutically used to treat?
MAINLY FOR INFLAMATORY OR IMMUNOSUPRESSION DISEASES: -
// Adrenal insufficiency (Addison’s Disease) // e.g. Asthma, eczema, arthritis, inflammatory bowel disease, prevention of transplant rejection
What is the histology of thyroid gland?
composed of numerous spherical follicles line by cubiodal epithelial cell // filled with colloid and thyroblobium which stores the thyroid hormones// high vascularised
Why is iodine important in thyroid glands?
synthesises thyroid hormones
What does endemic and thyrota refer to in reference to diseases?
ENDEMIC = constant low level of disease // THYROTA = constant inflammation of the thyroid
How is the thyroid hormone syntehsied?
from tyrosine an amino acid // 1. iodine is uptake// 2. iodine is then oxidised // 3. oxidised iodine binds to thyroglobulin protein// 4.iodtryosines are couples together by TPO to form T4 and T3 which are then stored in thyroid follicles .
What does T3 and T4 hormone refer to?
T4 = tetraiodothyronine -> 2 tyrosine + 4 iodine // T3= triiodothyronine -> 2tyrosine + 3 iodine// T4 is converted to T3 in the cell due to T3 having higher physiological activity
What is the main function of the thyroglobulin?
synthesis and storage of T3 and T4
What is the action of T3 and T4 ?
Both enter cell by ATP-dependent carrier // in absence of hormones T3 and T4 bind to DNA resulting in transcription and formation of multiple mRNA// acts via nuclear receptors
What regulates the release of thyroid hormones ?
axis driven , negative feedback loop// TRH is released from the hypothalamus stimulating TSH production // when TSH is released from the pituitary gland secreating T3and t4
What is congenial hypothyroidism ?
inadequate thyroid hormone production in new born due to underdeveloped thyroid gland
How is congenial hypothyroidism tested for?
neonatal screening test // testing for TSH levels being high resulting in T3 and T4
Where is cortisol produced?
Zona fasciculata in the adrenal cortex
What is the function of thyroid hormones?
increases oxygen consumption // increases sodium, potassium ATPase activity / provides substrates for metabolism
What is hyperthyroidism?
excessive production and activity of thyroid hormones// results in high metabolic rate , memory decline, dry skin, constipation, irregular heavy periods, joint pain , depression, fatigue
What is diffuse toxic goiter?
an autoimmune disorder where antibodies to the TSH receptor stimulate thyroxine secretion
What is toxic nodular goitre?
caused by benign tumour or malignant adenoma
What drugs can be used to reduce issues of hyperthyroidism?
RADIOACTIVE IODINE // THIOUREYLENE DRUGS (reduce synthesis ) // IODINE (reduces synthesis at gland and blood supply to the gland) // HORMONE REPLACMENT THEAPHY (levothyroxine and liothyronine )
What is type 1 diabetes ?
autoimmune disease where the immune system attacks insulin-producing cells
What is type 2 diabetes ?
insufficient insulin secretion for blood glucose regulation
What are some treatments of type 1 diabetes ?
aim = insulin replacement therapy // recombination human insulin -> insulin is inserted into E.coli // monitor serum glucose -> administer specific amounts of insulin
What is some treatments for diabetes 2?
diet and exercise // ANTIDIABETIC DRUGS -> insulin
What are the main categorise of antidiabetic drugs?
insulin sensitisers (increase sensitivity of insulin in muscles) // insulin secretagogues (stimulates release of insulin from pancreases) // insulin mimetics (enhances and mimics action of incretin hormone) // glucose reabsorption inhibitors (encourages renal excretion)
What is the action of metformin?
treatment for T2D // reduces hepatic glucose synthesis / increases glucose uptake in skeletal muscle / reduces carbohydrate absorption in the gut/ increases expression of glucose transporters in skeletal muscles
What is the action of thiazolidendiones?
IMPORVES INSULIN SENSITIVITY / reduces hepatic glucose output// increases glucose uptake into skeletal muscle// reduces blood glucpse, insulin and FFAs
What is the action of sulphonylureas and meglitinides ?
ENHANCES INSULIN SECREATION FROM BETA CELLS // only works in pancreatic beta cells are functional // involves the depolarisation of beta-cell membrane and enhances secreation from vesicles
What are incretin hormones?
metabolic hormones secretes in the GI tract and inhibits glucagon release therefore reducing absorption of nutrients by slowing gastric emptying
What is the action of gilptins?
are competitive inhibitors for DDP-4 enzyme and therefore reduce synthesise of GLP-1 and GIP// reduces blood glucose by inhibiting GGP4 enzyme reducing glucagon release and increasing insulin release
What is the action of GLP-1 receptor agonistic?
mimic action of GLP-1 (stimulating insulin secretions) // slows gastric emptying // E.G. semaglutide
What is the action of gliflozins?
blocks sodium -gated co-transporters on convoluted tubule of nephrons / results in lost of excretions of blood glucose
What drug can be used to replace cortisol?
Oral hydrocortisone// prednisone // dexamethasone
What drug can be used to replace aldosterone?
oral fludrocortisone
What is cushioning disease?
over production of cortisol in the adrenal cortex // results in tumours in pituitary gland and adrenal gland //
What drug can be used to replace androgen?
Oral dehydroepiandrosterone
Where are sex hormones produced?
gonads
What are some actions of oestrogen?
maturation of reproductive organs // development of secondary sexual characteristics // accelerated linear growth // closure of epiphyses
How does the contraceptive pill prevent pregnancy?
inhibits GnRH release from hypothalamus // inhibits FSH release from pituitary gland // inhibits LH release from pituitary gland// reduces likelihood of implantation
