Hormal Regulation of energy Metbolism Flashcards
What are hormones
Chemical messengers, released from glands and organs, which can be transported around the body to regulate numerous processes
Describe the endocrine system
Hormonal signals to distant cells via the bloodstream to allow for whole-body communication between tissues.
Slower acting, but typically more prolonged.
What are examples of endocrine hormones
Insulin, testosterone, cortisol
Describe the paracrine system
Hormonal signals to nearby cells via extracellular/interstitial fluid that is often short-lived signal for transient signals.
Fast switching on and off of processes
What are examples of paracrine communication
Growth factors (IGF), nitric oxide
Describe the autocrine system
Hormonal signals to self or very nearby identical cells via extracellular/ interstitial fluid that allows for self regulation of cells
What are examples of the autocrine communication
Cancer cells, T-cells (regulate their own growth and activation)
How can hormones be classified
Hormones can be classified by system, site of release, structure, and function
What are peptide and protein hormones
Peptide and protein hormones – made of amino acids. Water-soluble. E.g., Insulin, growth hormone
What are steroid hormones
Steroid hormones – made from cholesterol. Lipid soluble. E.g., Cortisol, oestrogen, testosterone,
What are amino acids-derived hormones
Amino acid-derived hormones – from single AA. Water or lipid soluble. E.g., Adrenaline, thyroid hormones
What are lipid-derived hormones
Lipid-derived hormones – derived from fatty acids. Exclusive to paracrine system. E.g., prostaglandins.
How do glands know when to secrete hormones
Endocrine cascade
Describe the hypothalamus-pituitary-target organ axis
Stimulus from the environment > CNS activity > hypothalamus release of neuro-hormone > stimulate hormone release from pituitary gland > hormone acts on target tissue
What is the function of alpha and beta cells
Alpha (α) and beta (β) cells detect change in blood glucose concentration.
Direct stimulation of α and β trigger release of glucagon and insulin, respectively.
What also stimulates the release of glucagon and insulin
Other nutrients
Other hormones
Neural regulation
What does insulin promote
Storage (signals energy available)
What does glucagon promote
Release (signals energy needed)
Is insulin anabolic or catabolic
Insulin is anabolic (wants to make)
Is glucagon anabolic or catabolic
Catabolic (wants to break)
Describe the GPCR – Gαs AC – cAMP – PKA Pathway in the liver
Glucagon binds to the extracellular region of a G-protein coupled receptor (GPCR)…
The Gαs (alpha subunit of GPCR) is energised (by GTP). It dissociates and translocates to bind to adenylyl cyclase (AC). AC is now activated.
AC converts ATP to cAMP.
cAMP binds to regulatory subunits, activating protein kinase A (PKA)
Which enzyme converts glucose-1-phosphate to glycogen ( glycogenesis) in the liver
Glycogen synthase
Which enzyme converts glycogen to glucose-1-phosphate (glycogenolysis) in the liver
Glycogen phosphorylase
How does PKA activate glycogen phosphorylase in the liver
Phosphorylation of phosphorylase kinase to activate it, phosphorylase kinase can then phosphorylate and activate glycogen phosphorylase for glycogenolysis
How does PKA inactivate glycogen synthase in the liver
PKA phosphorylates PP1 which inhibits phosphorite in phosphatase, so glycogen synthase is not phosphorylated/ activated by phosphoprotein phosphatase
Why does this pathway not happen in skeletal muscle
Does not have specific G protein receptors
How is glycogen broken down in the muscle
Via adrenaline (or epinephrine, hormone, derived from tyrosine (AA))
Is adrenaline catabolic or anabolic
Catabolic (wants to break)
How does adrenaline liberate fuels for movement in skeletal muscle
Also acts via the GPCR – Gαs AC – cAMP – PKA pathway but via Specific β-adrenergic receptor instead
Describe the insulin signalling pathway (IR – IRS-1 – PI3K – PKB/Akt pathway)
Insulin receptor (IR) is a tyrosine kinase receptor
Tyrosine kinase receptor consists of Extracellular α-unit and transmembrane β-unit
Insulin binds to the a-unit binding and phosphorylating insulin receptor substrate 1 (IRS)
The phosphorylated IRS-1 bind and phosphorylates the phosphoinositide-3 kinase, or PI3 kinase (PI3K) complex
which add a phosphate to convert PIP2 to PIP3 at the cell membrane
PIP3 recruits and activates phosphoinositide-dependent kinase-1, or PDK1.
PDK1 phosphorylates and activates Akt or PKB.
Akt / PKB activates glycogen synthase through inhibiting the inhibition.
