Chedy - theme 13 Flashcards
The fuel problem:
Brain needs a constant supply of glucose, but you can’t just be eating all the time. Blood glucose must be 70-110 mg / 100 mL
Effects of -glycemias:
Hypoglycemia: mild dysphoria, seizures, unconsciousness, permanent brain damage, death
Hyperglycemia: cell dehydration, glycation (spontaneous reaction between glucose and proteins, messing up the proteins), conversion from glucose to sorbitol causing cataracts
Energy storage: why is glycogen a good storage molecule?
Because it’s insoluble in water - doesn’t affect osmotic pressure
Sites of energy storage:
Glial cells (minor site), liver, muscle, fat
Energy storage in liver:
Hepatic glycogen is broken down early. The liver is the primary site of gluconeogenesis.
Energy storage in muscle:
Muscle cells are greedy and keep glucose for internal use only. They lack glucose-6-(p), so they can’t get glucose into the blood for transport. Stores AAs for gluconeogenesis in extreme starvation. Epinephrine from the adrenal medulla can power movement but can’t supply any other tissues with energy.
Energy storage in adipose:
Primary long-term energy source. Triglycerides can be broken down into fatty acids as an alternative energy source for non-glucose dependent tissues. Fatty acids CANNOT be used for gluconeogenesis - need that glycerol backbone.
Endocrine regulation of fuel metabolism: players
Pancreas, adrenal medulla, adrenal cortex, pit gland, thyroid gland
Pancreas and endocrine regulation:
Insulin and glucagon shift metabolic pathways between catabolic and anabolic. Islets of Langerhans have alpha (glucagon), beta (insulin), and gamma (somatostatin) subunits.
Endocrine and exocrine functions of the pancreas:
Endocrine - insulin and glucagon
Exocrine - production of digestive juices
Insulin:
Produced in high glucose. Controls blood glucose, fat, and AA concentration.
Somatostatin:
Inhibits insulin, glucagon, and itself.
Somatotropin is the weird nerd friend of insulin and glucagon who messes everything up.
Diabetes mellitus: general.
Prolonged high blood glucose. Acute complications: diabetic ketoacidosis, nonketotic hyperosmolar coma. Long term complications: cardiovascular disease, stroke, kidney failure, foot ulcers, eye damage. Sweet pee - excess glucose can’t be taken up by kidneys.
Diabetes type 1:
Insulin-dependent - pancreas fails to make enough insulin. Can be treated with insulin.
Diabetes type 2:
Non insulin-dependent - cells fail to respond to insulin; glucose can’t get into the cells. Caused by excessive body weight or lack of exercise.
Gestational diabetes:
Women without previous diabetes history develop high blood sugar during pregnancy.
Normal blood glucose curve:
Spikes after eating. Takes about two hours for concentration to return to normal. Glucose level is maintained for a day before it falls.
Insulin mechanism of action:
Binds cell surface receptors in adipose or muscle, activating glucose transporters.
Exercise and diabetes:
Muscle contraction stimulates localization of GLUT4 transporter to cell surface. Doctors recommend exercise for type 2 diabetes!
Metabolic effects of insulin:
Increases: glycogen synthesis, lipid synthesis and fatty acid esterification, AA uptake
Decreases: gluconeogenesis, proteolysis, lipolysis
Glucagon:
It’s like pancreas-specific epinephrine. A peptide hormone that increases blood glucose by breaking down glycogen or by gluconeogenesis.
Steroid hormones:
Pregnenolone is an inactive derivative of cholesterol. It is a precursor of progesterone, aldosterone, cortisol, and testosterone (which can be modified to estradiol).
Functions of aldosterone and cortisol:
Aldosterone is involved in the metabolism of minerals and ions. Cortisol is somehow involved in stress.
Adrenal glands: structure
Cortex (mesoderm) and medulla (ectoderm).
Adrenal cortex: structure
Composed of (from outside in): zona glomerulosa, zona fasciculata, zone reticularis.
Zona glomerulosa:
Involved in kidney regulation of ions
Zona fasciculata:
Produces glucocorticoids
Zone reticularis:
Somehow regulates sex determining hormones
Products of the adrenal medulla:
Catecholamines - epinephrine and norepinephrine
Products of the adrenal cortex:
Corticosteroids:
From glomerulosa - aldosterone (mineralocorticoid)
From fasciculata - cortisol and corticosterone (glucocorticoids)
From reticularis - androgen (sex steroid)
Glucocorticoids:
Catabolic hormones that promote gluconeogenesis in liver in times of stress. Act on bone, muscle, fat, and immune tissue to break them down. Present during fight/flight reactions when feeding/digestion are not available.
Cortisol stimulates the liver to synthesize glucose from AAs and glycerol.
Dual role of adrenal glands:
Promote glycogenolysis. When glycogen is used up, get glucose from other sources.
What is the most important organ for survival during starvation?
ADRENAL CORTEX!
Random detail: ACTH facilitates __ and __
Learning and behaviour