Endocrine control and metabolism Flashcards
State which process is at the core of energy metabolism?
“TCA cycle
FC:
- From TCA, ATP can be produced via ETC chain”
What is the central molecule in energy metabolism and why?
“Acetyl coA
- Any molecule that can be metabolized to Acetyl CoA
can be fed into the TCA.
- From TCA, ATP can be produced “
Name 5 examples of circulating nutrients?
“Circulating= Immediately availiable for energy metabolism
- Glucose
- Fatty acids (FA, FFA, NEFA)
- Amino acids
Originate from metabolic processes:
- Ketone bodies
- Lactate
NEFA= Non-esterified fatty acids”
Name 3 examples of stored nutrients?
“Glycogen
Triglycerides (TG, TAG)
Body proteins
“
State what concentration plasma glucose is kept constant at?
5 mmol L-1
Which metabolised nutrient does the brain depend on?
Metabolism of glucose
State critical range for hypoglycemia and its effects
” - ultimately coma and death
”
State what hyperglycemia is and its effects
“chronic exposure to raised glucose concentrations leads to protein damage via non-enzymatic glycation
- Glycation = addition of carb to protein
“
Why must glucose be constantly replensished?
“Majority of glucose is predominantly held in the ECF (40% of body weight / 2/3/ of water)
- Held at constant 5 mmoL-1
ICF has impermeable membranes to solutes like glucose
- But can be uptaken via transport
- When it does, it is immediately metabolised.
Different organs have different rate of glucose consumption e.g.
Brain: ~ 30 mmol hr -1 ,
Skeletal muscle:
~ 300 mmol hr -
So glucose will last minutes to couple of hours at max due to quick consuption from organs”
State two sources of plasma glucose?
“Diet (Up to 3000 mmol day-1)
Organs that can export glucose into the circulation
e..g liver.
FC: Liver can store or synthesise glucose from different forms”
“What prevents plasma glucose surging after a meal and
plummeting between meals?
“
“Hormones regulate the integration of carbohydrate, fat and protein metabolism to maintain constant plasma glucose levels.
“
State the two phases of metabolism and define them?
“Absorptive and fasting
Storage of nutrients in the absorptive phase (fed state)
Release of nutrients in the fasting phase (between meals, also called postabsorptive phase)
“
State the hormones which regulate metabolic pathways?
“Insulin
Counter-regulatory hormones
These promote energy storage or release
“
State the role of insulin in regulation of metabolic pathways?
“Signal of the fed state:
Promotes storage of nutrients/ Inhibits nutrient release
Decreases plasma glucose
“
“State the role of counter-regulatory hormones and state 4
examples?”
“Role (when plasma glucose falls)
- Promote nutrient release (for fuel)
- Raises plasma glucose
Examples
Glucagon
Adrenaline (epinephrine)
Cortisol
Growth hormone (somatotrophin)
“
Draw or describe the feedback system in the metabolic response to hypogylcemia?
“DIAGRAM IS ANSWER. THIS IS FC.
The immediate response is glucagon release from the pancreas. The fall in plasma glucose is detected in the pancreas itself, and the response is to turn up the rate of glucagon secretion, from pancreatic endocrine cells called alpha cells, to be considered later. Glucose is also sensed in the brainstem and hypothalamus, where a fall increases sympathetic outflow, which directly and indirectly stimulates hepatic glucose output.
Note that this is a –ve fb system. If plasma glucose falls the responses are such as to raise it. If plasma glucose rises these responses would be inhibited, reducing hepatic glucose output.
Note also that the –ve fb involves endocrine, neural, and neuroendocrine reflex loops. Purely endocrine: pancreas senses falling glucose, increases glucagon secretion, which in turn increases hepatic glucose output. Neuroendocrine reflex involves glucose sensing by neurons, sympathetic output to adrenal stimulating adrenaline secretion.
“
