7 metabolism homeostasis Flashcards
what is the biological rhythm?
rather than a set point its a steady value that varies over time, circadian rhythm
e.g) hormone cortisol varies - peak at 7am and through at 7pm
jet lag is controlled by what?
melatonin - released from pineal gland
What are the 4 different classifications of hormones
peptides - insulin
glycoproteins - LH/FSH
amino acid derivatives - TH/adrenaline
steroids - cortisol/aldosterone
anterior pituitary gland releases what hormones?
Thyroid simulating (TSH)
Growth hormone (GH)
Follicle stimulating hormone (FSH)
luteinising hormone (LH)
prolactin
physiological and metabolic pathway- insulin
promotes fuel storage post meal
glucose stored as glycogen, FA synthesis, AAs uptake and protein synthesis
physiological and metabolic pathway - glucagon
mobilises fuels and maintains blood glucose levels during fasting
activates gluconeogenesis and glycogenolysis
physiological and metabolic pathway - adrenaline
mobilises fuel storages during acute stress
stimulates glucose production
physiological and metabolic pathway - cortisol
allows changing environments during stress
AAs mobilisation, gluconeogenesis and lipogenolysis
where is the control centre located?
arcuate nucleus within the hypothalamus
hormones that stimulate appetite
ghrelin
hormones that suppress appetite
leptin
peptide YY
examples of primary neurons
excitatory (OREXIGENIC) - stimulates appetite; releases NPY and AgRP peptides
inhibitory (ANOREXIGENIC) - suppress appetite; releases POMC (cleaved to α-MSH) and CART
biological need of having food because we are hungry…system?
episodic homeostatic system
involves having food because we feel like having food…system?
hedonic regulatory system (reward)
What are some weight loss therapies?
bariatric surgery
pharmacology (GLP-1)
dietary changes
increase in physical activity
what 3 components must the control system have and what are their requirements to maintain homeostasis?
control centre (hypothalamus) - must be able to compare a value to specific point
effector - must be able to change controlled variable
receptor - must be able to monitor a controlled variable
what are circadian hormones maintained by?
cortisol
negative feedback
decreases effect from stimulus
positive feedback
increases effect from stimulus
difficult to stop
system communications
paracrine - hormone acts locally
autocrine - hormone acts on releasing cell
endocrine - hormone acts at distant tissue
examples of endocrine glands
pituitary/pineal/thyroid - head and neck
adrenal/pancreas/kidney - abdomen
gonads/uterus/placental - pelvis
how are hormones synthesised?
as preprohormone or prohormone and stored in vesicles
eg) preproinsulin
functions of pancreas
exocrine - produces digestive enzymes
endocrine - produces polypeptide hormones
How are inactive polypeptide and glycoprotein hormones activated
Through cleavage
Hormone structure defines what (4)
How it is made
How it is transported in blood
How it interacts with receptors
How it is inactivated
How are steroid hormones classified
Number of carbon atoms
Number of double bonds
Different side chains
How is glucagon secreted
Synthesised in RER
Transported to Golgi
Packed into secretory vesicles
Secretory granules move to cell surface of alpha cells
Release contents into blood via exocytosis
How is hormone secretion controlled
Endocrine cells stimulated chemically to release hormones
How is insulin stimulated
Feeding
How is the exchange between ICF and ECF controlled
membrane transport
How is the pancreas developed
Ventral pancreatic bud combines with dorsal pancreatic bud and forms main pancreatic bud
What are amino acid derivative hormones derived from
Tyrosine
What are examples of amino acid derivative hormones
Thyroid hormones
Adrenaline
What are glycoprotein hormones
2 polypeptide chains (alpha and beta) with carbohydrate side chains
What are hormones
Chemical signals produced in the endocrine glands that travel in the bloodstream to affect other tissues
What are peptides hormones inactivated to
Degraded to amino acids
What are polypeptide hormones
Single chain polypeptides that vary in length
What are pro-hormones
Pre-cursors of polypeptide and glycoprotein hormones
What are some examples of glycoprotein hormones (4)
Thyroid stimulating hormone
Follicle stimulating hormone
Luteinizing hormone
Human chorionic gonadotropin
What are some examples of polypeptide hormones
Thyrotropin releasing hormone
Glucagon
Insulin
Growth hormone
What are some examples of positive feedback in the body(3)
Blood clotting cascade
Ovulation
Lactation
What are steroid hormones
Derived from cholesterol
What are the 2 different hormones that can be produced from cholesterol ester
Progestogens
7 dehydrocholesterol
What are the components of a control system
Receptor
Control centre
Effector
What are the components of ECF
Interstitial fluid
Circulating fluid
Specialised compartments
What are the effect of glucagon on glucagon target tissues
Liver-glycogenolytic
Liver-gluconeogenic
Liver-ketogenic
Adipose-lipolytic
What are the hormone secreting sections in the head and neck(4)
Pituitary gland(posterior and anterior)
Thyroid glands
Parathyroid gland
Pineal gland
What are the hormone secretory sections in the pelvis
Gonads (Ovary and testes)
Uterus
Placenta
What are the hormones secretory sections in the abdomen(4)
Adrenal cortex
Pancreas
Kidney
Gut
What are the role of somatostatins
Inhibit islet secretions
What are the steps for insulin synthesis
Insulin gene transcribed to mRNA
Insulin mRNA move to Ribosomes
N-terminal sequence formed
mRNA translated to preproinsulin
Signal cleaved
Proinsulin formed
Proinsulin transport to Golgi to be cleaved to mature insulin and C peptide
Insulin and C peptide put into vesicles
What are the target tissues of glucagon
Liver and adipose
What are the target tissues of insulin(3)
Skeletal muscle
Liver
Adipose
What can progestogens be converted to
Androgens
Glucocorticoid
Mineralcorticoids
What does binding of glucagon on G-protein coupled receptor activate
Production of cAMP
What does cAMP activate in glucagon action
Protein kinase A
C-AMP response element binding transcription factor
What does cAMP activate in glucagon action
Protein kinase A
C-AMP response element binding transcription factor
What does glucagon bind to on a cell
G protein coupled receptor
What does the control centre use to change the controlled variable
Effector until the set point is reached
What happens to inactivation of steroids and amino-acid derivative hormones
Small change in structure
Recycled
Excreted
what hormones does the endocrine portion of pancreas produce(3)
insulin and glucagon
somatostatin
pancreatic polypeptide
What is a transmembrane dimer
2 identical subunits spanning cell membrane
what is an annular pancreas
rare condition in which the second part of the duodenum is surrounded by a ring of pancreatic tissue continuous with the head of the pancreas
What is ICF
Fluid inside the cells
What is negative feedback
Effect of the response to stimulus is to decrease the effect
Effector switched off when switched point is reached
What is positive feedback
Response of stimulus is to increase effect
Effector not switched off and goes out of control
What is required as a signal for insulin to be secreted
Intracellular calcium
What is required with chemical communication
Cell producing chemical messenger
Target cell that has receptors for that specific receptor
What is steroid polarity wise
Hydrophobic
What is the action of a hormone if it can cross the cell surface membrane
Bind to receptors located inside the cell
Receptor-hormone complex move
Binding leads to metabolic changes
What is the action of a hormones if it cannot cross the cell surface membrane
Binds to receptor of the cell surface
Activates second messenger system
Exert metabolic effects
What is the composition of the transmembrane dimer subunit
1 alpha and 1 beta chain connected by disulphide bond
What is the effect of insulin on insulin sensitive tissue
Liver and muscle glycogenic
Liver anti-gluconeogeneic
Adipose anti-lipolytic
Liver anti-ketogenic
Increase in protein synthesis
What is the function of Ghrelin
Regulate appetite
hunger
What is the function of the endocrine gland for the pancreas
Produce polypeptide hormones
What is the function of the exocrine gland of the pancreas
Produce digestive enzymes (amylase,lipase,protease)
What is the most common control of hormone secretion
Control by “Tropic” hormones
What is the pancreas divided into anatomically
Head
Body
Tail
What is the pancreas divided into histologically
Endocrine and exocrine gland
What is the polarity of adrenaline
Hydrophillic
What is the polarity of thyroid
Hydrophobic
What is the precursor of glucagon
Pre-proglucagon
What is the process of activation of insulin receptor
Conformational change in receptor
Alpha chain wrap insulin
Beta chains move together
Beta chain active tyrosine kinase
Phosphorylation cascade
Activation of signalling pathways
What is the process of insulin secretion
High blood glucose
Glucose transport into beta cell via GLUT2 (facilitated diffusion)
Increase plasma glucose in beta cell
Membrane depolarisation
Influx of Calcium ions
Increased cAMP
Calcium ion trigger exocytosis of insulin containing secretory granules
What is the purpose of hormone transport
Good for coordinated multiple responses
What is the purpose of nervous communication
Rapid communication from point to point that is initiated by a chemical signal or a change
What is the role of the control system
Controls variables by maintaining them at an optimal level
What is the role of the endocrine pancreas
Maintain blood glucose at a constant and optimal level
what is the role of trophic hormones
stimulate growth (cell size/number) in the target tissue
Control production of another hormone
What occurs as a result of activation of insulin receptors
Increased GLUT4 expression
Increased glucose uptake
What type of contact when cells are close
Local diffusion of chemicals messengers
What type of contact when cells are far apart
Chemical messengers in the blood
Electrical transmission
What type of contact when cells are touching
Cell surface chemicals
What type of feedback is hormone secretion
negative feedback
What type of receptor is insulin receptor
Tyrosine kinase receptor
when is glucagon stimulated
Fasting
Where does inactivation of hormones occur
Target tissue
Liver
Where is adrenaline stored
Vesicles in adrenal medulla
Which hormones must bind to proteins
Steroids
Thyroid hormones
Which hormones can be transported in the blood(3)
Polypeptide
Glycoprotein
Adrenaline
