Endocrine Flashcards
When does concentration of metabolites need to be altered rapidly
increase in rate of glycolysis during exercise
Reduce rate of glycolysis after exercise
Increase rate of gluconeogenesis after exercise
What is Km
Michealis constant
substrate concentration at which half the enzyme molecules are associated with the substrate
What tissue are GLUT1 transporters in and what Km do they need
red blood cells and some other tissues 3mM
What tissues are GLUT2 transporters in and what Km do they need
Liver, pancreas 17mM
What tissue is GLUT3 transporters in and what Km do they need
brain, 1.4mM
What tissues are GLUT4 transporters in and what Km do they need
muscle and adipose tissues, 5mM
Why is glucose absorption through GLUT3 always constant
because the brain need fuel, low Km allows their to be a constant flow unless starved
What happens when glucose gets into the cell
it is phosphorylated into glucose-6-phosphate by hexokinase or glucokinase
Differences and similarities between nervous system and endocrine system
nervous system releases neurotransmitters to local areas whereas endocrine system releases hormones into the bloodstream to target organs
Both are directly connected by the hypothalamus and pituitary
What is signal transduction
process of converting one type of signal into another
Four types of signals?
neuronal, contact-dependent signalling, paracrine, endocrine
Describe neuronal signalling
action potentials are transmitted electrically along a nerve axon, when the signal reaches the nerve terminal it causes a release of neurotransmitters onto adjacent cells
Describe contact-dependent signalling
cell-surface-bound signal molecule binds to a receptor protein on an adjacent cell. no molecules are released
(A communicating junction links the intracellular compartments of two adjacent cells, allowing transit of relatively small molecules.)
Paracrine
signals are released by cells in the extracellular fluid in their neighbourhood and act as local mediators
Endocrine
hormones are secreted into the bloodstream and are widely distributed throughout the body
Describe cell surface receptors
extracellular molecules are usually large and hydrophilic (peptides and proteins) so they cannot cross the plasma membrane
therefore they bind to cell surface receptors which generate intracellular secondary messenger signalling molecules
(most common type of receptor)
Describe intracellular receptors
some small extracellular hydrophobic molecules can pass through target cells plasma membrane and bind to the intracellular receptors in the cytosol or nucleus than then regulate things such as gene transcription
True/false: cells can receive and respond to many signals simultaneously
true
What is apoptosis
cell programmed death
What are processes that rely on altered protein function and how fast are they
movement, secretion and metabolism
fast (
What are processes that rely on altered protein synthesis and how fast are they
differentiation, growth and division
slow (minutes to hours)
Three types of effector proteins
metabolic enzyme (alters metabolism) cytoskeletal protein (alters cell shape or movement) transcription regulator (alters gene expression)
What are the three main types of cell surface receptors
ion channel coupled receptors
G protein coupled receptors
enzyme coupled receptors
What is another name for ion channel coupled receptors
transmitter-gated ion channels
Describe an ion channel coupled receptor
they are responsible for transmission of signals across synapses in the nervous system signal molecules (such as acetylcholine) cause the receptors to open in response to binding , causing a change in the electrical potential across the cell membrane so a chemical signal is transduced (converted into another form) into a electrical signal
Describe G protein coupled receptors
they are transmembrane proteins
the extracellular portion of the GPCR bind to signalling molecules
cytoplasmic portion binds to the G protein
What are the two most common enzyme targets of G protein coupled receptors
adenylyl cyclase and phospholipase C
What does adenylyl cyclase do (in related to GPCRs)
catalyses the formation of the secondary messenger signalling molecule cAMP
What does phospholipase C do (in relation to GCPRs)
produces the second messengers inositol triphosphate (IP3) and diacylglycerol (DAG)
What does inositol triphosphate do
promotes the accumulation of cytosolic Ca2+ (calcium ions) which is another common second messenger
What is the effect of adrenaline on skeletal muscle
Adrenaline activates a GPCR which activated a G protein that activates adenylyl cyclase which produces cAMP (a secondary messenger)
increase in cAMP activates protein kinase A (PKA) which phosphorylates and activates phosphorylase kinase
this activates glycogen phosphorylase (enzyme that breaks down glycogen)
This all occurs within seconds
What are the thyroid glands lateral lobes connected by
the isthmus
What does the thyroid gland form the floor of
the pharynx
Where are the parathyroid glands located
behind the lateral lobes of the thyroid gland
four glands (two superior and two inferior)
approximate diameter of 12mm each
Where does T3 and T4 synthesis occur (thyroxine)
in the thyroid follices
Describe T3 and T4 synthesis
Thyroglobulin (precursor for T3 and T4) is produced by thyroid follicular cells
iodine is actively absorbed from bloodstream by iodine trapping (sodium is co-transported with iodine from basolateral side of membrane into the cell and is then concentrated in the follicular cells by about 30 times)
through reaction with enzyme called thyroperoxidase, tyrosine is bound to thyroglobulin to form monoiodotyrosine (MIT) and diiodotyrosine (DIT)
linking two moieties of DIT produce T4 and one MIT and one DIT produce T3
Describe dietary intake of iodine
absorbed first into the extracellular pool
then removed from their by the thyroid or kidneys
thyroid contains huge iodine store in colloid
Describe cretinism (Congenital iodine deficiency syndrome)
neurological deficits
small stature and immature appearances
puffy face and hands
delayed puberty
What is hypothyroidism, describe it in adulthood
under active thyroid gland insidious onset (very gradual) low BMR and cold sensitivity bradycardia slow, hoarse voice lethargy and slow movements constipation menstrual abnormalities one weight gain dry thickened skin slowing of mental function
What is hyperthyroidism, describe it
over active thyroid gland
nervousness, restlessness, tremors or anxiety
tachycardia and palpitations
Increased appetite but associated with weight loss
tiredness
increased number of bowel movements per day
decreases menstruation
most common type is Graves disease with characteristic eye signs (bulging eyes, redness and retracting eyelids)
what are the biological roles of calcium
blood coagulation
neuromuscular excitability, neurotransmitter release and hormone secretion
membrane ion transport (and permeability to sodium ions)and second messenger functions
enzyme regulations
contraction (including skeletal and cardiac muscle)
what three hormones is plasma calcium concentration precisely controlled by
parathyroid hormone (PTH) (counter-regulatory hormone)
calcitonin (Counter-regulatory hormone)
vitamin D
What do counter regulatory hormones do? what does this mean in the examples of PTH and calcitonin
any deviations have considerable impact with severe consequences
hypercalcaemia (high calcium levels) trigger the release of calcitonin
Hypocalcamia (low calcium levels) trigger the release of PTH
If calcium levels decrease in the blood plasma then what happens
increase in parathyroid gland (chief cells)
which then increase the levels of PTH which then increase the levels of calcium
If calcium levels rise too much in the blood plasma then what happens
increase in thyroid parafollicular C cells
which increase calcitonin release which decreases the levels of calcium
What hormone regulates the calcium homeostasis minute by minute and what hormone is more in case of emergency
minute by minute is PTH
emergency is calcitonin
What is hypocalcaemia caused by and what are some symptoms
caused by hypoparathyroidism following accidental removal or damage to parathyroid glands during thyroid surgery
symptoms include: increased neuromuscular excitability, twitching, muscle cramps, tetany, carpopedal spasm, coma and death
What is hypercalcaemia associated with and what are some symptoms
with primary hyperparathyroidism and malignancy
symptoms of stones, bones and groans
slowing of nerve impulses, sluggish reflexes and muscle weakness, mood and cognitive dysfunctions may also see polydipsia and polyuria
in extreme cases can cause neurotoxicity, coma and death
What is a PCHR (personal child health record) used for
family and birth related information routine screening immunisations growth advice and support early education
Three factors that influence growth
nutrition
genetics
environment
Difference between hypertrophy and hyperplasia
hypertrophy = increase is size of cells hyperplasia = increase in number of cells
What is GHRH, describe it
growth hormone releasing hormone
Produced in the hypothalamus and secreted from nerve endings into the portal system
is an anterior pituitary peptide hormone
can cause growth in most tissues that grow, promotes differentiation of some cell types
binds to GH receptors in target tissues
works often in combination with insulin-like-growth-factor-1 (IGF-1)
Describe growth hormone (GH) secretion
it is periodic - think circadian rhythms things that promote secretion: sleep acute stress hypoglycaemia exercise
Metabolic actions of the growth hormone
increase in amino acid uptake increase in protein synthesis decrease in protein catabolism decrease in lipogenesis increase in lipolysis decrease in glucose uptake and oxidation increase in blood glucose (stimulate gluconeogeneis and glycogenolysis)
what does endocrine mean? exocrine?
endo- internal secretion, secrete hormones directly into bloodstream upon stimulation
exo- secrete into glands (Such as salivary glands, sweat glands, and glands of GI tract)