Physiology Flashcards
Endocrine glands are different from exocrine glands as…
Endocrine glands DONT have ducts, exocrine glands do.
Cortisol, progesterone, testosterone are all examples of which chemical class of hormone?
Steroid
Amino acid modified hormones are derived from what? (2)
1) Tyrosine
2) Tyramine
Thyroid hormones and adrenaline are examples of which class of hormones (chemically)?
Modified amino acids
Somatostatin is released from which cell type in the Islet of Langerhans?
Delta
Paracrine signalling enters the circulation. True/false?
False
Most endocine control occurs with high/low concentration of hormone. This signal is typically amplified/repressed as it reaches the target site?
Low hormone
Amplification
All hormones are agonists. True/false?
False - antagonist hormones exist
Amines are hydrophilic/phobic?
Hydrophilic
Amines tend to be synthesised as needed/before in batches & stored?
Before and stored in vesicles
Steroids are hydrophilic/phobic?
Hydrophobic
Steroids are different from amines and proteins in that they…
Are synthesised and secreted upon demand (not pre-fabricated)
The rate-limiting step in conversion of cholesterol to steroid is which step?
Pregnenolone
How are steroids transported in the blood?
Carrier bound (inactive 90%); those which are free (10%) are biologically active
What are the functions of specific carrier proteins for any given hormones? (3)
1) Increase amount of hormone transportable in blood
2) Provides a reservoir of that hormone
3) Extends the half-life of that hormone
Cortisol carrier protein is called
Cortisol binding globulin
Thyroxine binding globulin (TBG) binds mostly to which thyroid hormone preferentially?
T4 (thyroxine)
General carrier protein examples (2)
1) Albumin
2) Transthyretin
The half life of amines (e.g. adrenaline) is generally hours/minutes/seconds?
Seconds
Protein hormones half a typical half-life of minutes/hours/seconds?
Minutes
Steroids have a typical half-life of hours/minutes/days & why?
Hours - due to extensive protein binding
Amines typically activate what hormone receptor class?
G-protein coupled (Gs, Gi and Gq related)
Receptor kinases are typically activated by which class of hormone?
Protein
Steroids typically activate which class of receptor?
Nuclear receptor
Thyroxine activates what type of receptor?
Nuclear receptor
What’s the “initial” protein involved in G-coupled receptor signalling?
Gs (activates adenyl cyclase which converts ATP to cAMP, activating PKA which causes cellular effects)
Which enzyme converts IP3 to PIP2?
Phospholipase C
Give an example of a hormone which signals via PKC/IP3 G-coupled receptors? (2)
GRH, angiotensin II
Give an example of a hormone which signals via cAMP/PKA G-coupled receptors? (2)
Adrenaline
Glucagon
PLC and IP3 signalling is calcium dependent/independent?
Dependent
cAMP/PKA signalling is calcium dependent/independent?
Independent
List the anterior pituitary hormones (6)
1) ACTH
2) GH
3) FSH
4) LH
5) Prolactin
6) TSH
List the posterior pituitary hormones? (2)
1) ADH
2) Oxytocin
The parathyroid glands produce which hormone(s)?
1) PTH
2) Calcitonin
The pineal gland produces which hormone?
Melatonin
The intermediate pituitary produces which hormone?
Melanotrophin-stimulating hormone (MSH)
The intermediate pituitary is often considered part of the anterior/posterior pituitary?
Anterior
The adrenal cortex produces which hormones?
Glucocorticoids (inc. cortisol), aldosterone
Remember: cortex is divided into GFR zones. Tip for remembering what is made where is “Blood, Sugar, Sex” (from superficial to deep)
- G = Blood (aldosterone)
- F = Sugar (cortisol)
- R = Sex (weak androgens)
Adrenal Medulla produces which hormones (2)?
- Adrenaline
- Noradrenaline
Remember, “Blood, Sugar, Sex” for cortex –> goes onto “Magic” for medulla (adrenaline = “magic feeling”)
In pregnancy, the placenta is a major source of which hormone?
hCG
Alpha cells in the pancreas secrete…
Glucagon
Beta cells in the pancreas secrete…
Insulin
The beta-cells of the pancreas are focused where?
Around the central blood vessels
Insulin is synthesised in the RER/SER?
RER
Insulin is produced as multiple precursor chains. True/false?
False - one large prehormone chain.
“Pre-proinsulin” contains what?
Two polypeptide chains linked with disulphide bonds. It contains a signal peptide.
Proinsulin contains what?
Insulin + attached C-peptide
Lispro is an example of ultrafast/slow insulin
Ultrafast
Lispro is often used as a monotherapy for T1DM. True/false?
False - extremely short acting and so won’t establish lasting glucose control
Glargine is a synthetic insulin. True/false?
True - a recombinant analogue
Glargine can be used a single-dose insulin because
It precipitates in subcutaneous tissue, giving a peakless rise in insulin concentration in the blood
Glucose enters beta-cells through which receptor?
GLUT-2
Glucose is phosphorylated in beta-cells by which enzyme?
Glucokinase
What’s the normal Km of glucokinase?
5mM (anything above this triggers insulin release)
Glucose is converted to which substrate by glucokinase?
Glucose-6-phsophate
How many ATPs are generated by complete oxidative phosphorylation?
36
How does ATP production by glucokinase (indirectly) lead to insulin release?
Increased ATP opens K channels, leading to greater intracellular voltage. This in turn opens voltage-gated calcium channels, leading to depolarisation and release of insulin granules.
Release of insulin is triphasic/biphasic/ monophasic?
Biphasic
The “readily releasable pool” refers to what?
The 5% of insulin granules that are immediately available for release
K-ATP channels consist of two proteins; what are they?
Pore subunit “Kir6” and sulphonylurea receptor “SUR1”
How do sulfonylurea drugs trigger insulin release?
They block the SUR1 channel in the beta-cell K-ATP channel which increases cellular potential (depolarisation), leading to calcium influx and release of insulin
SUR drugs are 1st or 2nd line therapy for T2DM?
2nd line
Mutation of Kir6.2 in neonatal diabetes commonly responds to SUR drugs, true or false?
True
Describe a drug which opens the SUR channel?
Diazoxide (leads to out-flow of potassium which means no insulin is secreted)
Insulin is a catabolic / anabolic hormone?
Anabolic
Describe the effects of insulin (NOT liver related) (4)
1) Amino acid uptake by muscle
2) DNA and protein synthesis
3) Growth
4) Glucose uptake in muscle and adipose tissue
Describe the effect insulin has on the liver (2)
Lipogenesis and glyocgen synthesis (store)
True/false: insulin triggers lipolysis and gluconeogenesis?
False - it inhibits these as the body is assumed to be in a glucose-rich state
The insulin receptor is what type of receptor?
Tyrosine kinase
Donohue Syndrome is a rare, autosomal dominant/recessive condition resulting in a mutation of which receptor?
Recessive - insulin receptor
Rabson-Mendenhall Syndrome classical sign
Acanthosis nigricans
Rabson-Mendenhall Syndrome classical triad of symptoms
1) Insulin resistance
2) Hyperglycaemia
3) Compensatory hyperinsulinaemia
What are the macrovascular complications of diabetes? (2)
IHD, stroke
What are the microvascular complications of diabetes? (3
- Retinopathy
- Neuropathy
- Nephropathy
Describe Charcot’s foot
Occurs due to loss of peripheral nerve sensation; the foot has become so damaged over time the joints destabilise. Neuropathic arthropathy.
What types of neuropathy are there (4)
1) Peripheral
2) Autonomic
3) Proximal
4) Focal
Gastroparesis would be considered which type of neuropathy in DM?
Autonomic (delay in stomach motility)
Thyroid hormones have major effects on which functions (5)
1) Metabolism
2) Growth
3) Development
4) Reproduction
5) Behaviour
What effect do thyroid hormones have on thermogenesis?
Increase (around 30% of temperature regulation is directly attributable to thyroid hormones)
Thyroid hormone has what effect on BG & insulin?
Raises both
Thyroxine has what effect on fat?
Increases FA oxidation
In the fetal brain, thyroid hormones are vital for which process?
Myelinogenesis
Do thyroid hormones have any role in sympathetic nervous transmission?
Yes - they increase responsiveness to both adrenaline and noradrenaline (sympathetic neurotransmitter)
How is HR influenced by thyroid status? (hint: why do beta-blockers work in hyperthyroid?)
Thyroid hormones sensitise the nerves to the actions of adrenaline and noradrenaline (sympathetic transmitter) - so will increase HR
Deiodinase enzyme is only present in the liver & kidney, T/F?
False (3 types; type 1 is found in the liver/kidney)
Where is deiodase type 2 found? (3)
Heart, skeletal muscle, thyroid/pituitary
Where is deiodase type 3 found?
Mostly in fetal tissue
The TSH receptor is what type of receptor?
G-coupled protein
Which compartment is biggest, ICF or ECF?
ICF
Body water is mostly contained within which compartment?
ICF
The majority of sodium is stored within which compartment?
ECF
Potassium is mostly stored within which compartment?
ICF
Sodium follows water everywhere, T/F?
False - water follows sodium everywhere
In hyponatraemia, which compartment will have a noticeable drop in fluid?
ECF
Sodium is controlled by gluco/mineralo-corticoids?
Mineralocorticoids
Too much sodium causes which compartment to expand (ICF/ECF)?
ECF
Hypernatraemia should be treated with which medication
Loop diuretic
Diabetic ketoacidosis is likely to cause a sudden, acute reduction in which fluid compartment?
ECF
