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BLOOD GLUCOSE (normal 90mg/dL or 3.9-5.6mmolL-1), MARIN, Glucose…
BLOOD GLUCOSE (normal 90mg/dL or 3.9-5.6mmolL-1)
HYPOGLYCEMIA (<70mg/dL)
Low glucose impairs cellular energy (less ATP produced), damages the brain which is reliant, causes dizziness, shaking, fainting, coma, seizure, neurological damage
Results from overproduction of insulin (cells have too much glucose, low blood levels), skipping meals (insufficient intake), strenuous exercise, or medication
CHEMICAL RESPONSE
Release of adrenaline from adrenal medulla
Sweating, heart palpitations, chills, anxiety. hunger, fatigue, numbness
Release of glucagon and cortisol from adrenal glands
Raises glucose levels by releasing stored glycogen form the liver and stimulates glucose production
Hypothalamus senses low blood glucose levels
Hunger as hypothalamus signals to eat and replenish
Treatment: consuming carbohydrates or IV glucose/glucogen injections depending on severity
HYPERGLYCEMIA (>140mg/dL)
Low insulin, excessive carbohydrates, high stress, steroids, or inactivity as too much glucose enters bloodstream
When stress hormones (cortisol, adrenaline) are released, it signals the liver to release more glucose through glyconeogenesis
Beta pancreatic cells
Release insulin into blood
Body cells increase uptake of glucose
Short term symptoms: excessive thirst, excessive urination, fatigue, confusion
Excessive urination (polyuria) arises because kidneys filter glucose, which is osmotically active, and so carries water with it as it is expelled (causes glycosuria)
Long term: damage to blood vessels, kidneys (nephropathy), nerves (neuropathy), and eyes (retinopathy), and increased risk of heart disease
HORMONES
Somostatin (pancreatic α-cells)
Moderates/inhibits glucagon and insulin release, contributing to glucose balance
Cortisol (adrenal cortex)
Raises blood sugar by increasing gluconeogenesis (formation of glucose from non-carbohydrate substrates) and counteracting effects of insulin
Epinephrine/adrenaline (adrenal medulla)
Rapidly raises blood glucose during stress by promoting glycogenolysis (breaking down of stored glycogen into glucose)
Thyroxine (thyroid gland)
Increases glucose absorption through the gut and mobilizes glucose stores to raise blood sugar
Blood glucose (blood sugar)
Main source of energy for brain processes like thinking and memory as well as to generate action potentials, maintain ion gradients, and synthesize neurotransmitters. ATP produced from glucose powers activities in organs and muscles like digestion and contraction. Glucose is stored in the liver and muscles as glycogen until needed.
Provides fuel for cell processes by being converted into ATP for example, respiration: C6H12O6 + 6O2 --> 6CO2 + 6H2O + ATP
Gained by eating carbohydrate-rich food like bread, fruit, dairy, and potatoes, which are broken down by digestive enzymes into C6H12O6 (note: most sugar we eat is sucrose, a compound of fructose and glucose)
REGULATION
Insulin, from pancreatic β-cells
Lowers blood glucose by increasing uptake into skeletal muscle/fat tissue as glycogen, stored in the liver
Insulin spikes after carbohydrate-rich meals because blood glucose has risen
Facilitates entry of potassium into cells from the blood (activates Na+ - K+ ATPase pump)
Insulin is used to treat hyperkalemia (high blood potassium)
Glucagon from pancreatic α-cells
Increases blood glucose by causing glucose to be released from liver stores of glycogen into the blood (breakdown of glycogen: glycogenolysis)
Glucagon increases after fasting as blood glucose is low
Pancreas
Sensor and regulator that releases insulin if glucose is high and glucagon if insulin is low
Produces and secrets insulin and glucagon
β-cells are found in 'islets of Langerhans', clusters of endocrine cells (α, β, and δ) in the pancreas that are vital for metabolism and homeostatic control in the bloodstream
Hormone called somatostatin regulates release of insulin and glucagon to maintain glucose balance and prevent large fluctuations
Glycogen is a complex carbohydrate polymer of many glucose molecules, stored in the liver and muscles for when the blood store of glucose is depleted
CONNECTIONS
Negative feedback
Glucagon raises glucose
Cortisol and adrenaline raises glucose
Insulin lowers glucose
Somatostatin balances glucose
Thermoregulation influences glucose demand
Positive feedback does not occur in glucose regulation as it amplifies change instead of reverting to the previous state
MARIN
Glucose Homeostasis
,
Insulin and glucagon
, Control of Glucose ,
Glucose and Glucagon
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