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Balance mechanisms
Physiology Block D:Support Systems
| Question | Answer |
|---|---|
| what are the 3 possibilities for food after it is ingested, digested and absorbed | use it for energy use it to make something new store it for later ( use stored, or broken down) |
| what are the two functional metabolic states of the body | absorptive/ fed state;post absorptive /fasted state |
| what is the absorptive/fed state | nutrients entering blood from GI tract - anabolic pathways |
| what is the postabsorptive or fasted state | no more nutrients from GI tract - catabolic pathways |
| what is the main source of energy in absorptive/ fed states | carbohydrates - glucose |
| what is glucose used for in the body | used for cell energy ATP main source of energy for most cells stored as glycogen, converted to triglycerides, stored as fat |
| how is glucose stored in the body | glycogen: glycogenesis in the liver and skeletal muscle fat: triglycerides; lipogenesiss in liver, stored in adipose tissue |
| glycogenesis | only way carbohydrates are stored glucose to G6P to glycogen |
| lipogenesis | converted glucose to fatty acids glucose to pyrubate to acetyl CoA to fatty acids combine with glycerol to form triglycerides |
| what is the main source of energy in the absorptive or fed state | proteins - amino acids use for protein synthesis (liver and other tissues) convert to triglycerides, stored as fat AA to acetyl CoA to fatty acids |
| what are the 4 lipoproteins | chylomicrons (CM) very low density lipoproteins low density lipoproteins high density lipoproteins |
| lipoprotein lipase | in capillary endothelium, remove fatty acids from triglyceride |
| fatty acids in fed state | used as energy source in fed state |
| triglycerides in fed state | reassembled and store in adipose tissue in fed state |
| CM remnant transport in fed sate | cholesterol transported to liver where CM is degraded |
| VLDL transport in fed sate | triglycerides from liver to adipocytes |
| LDL transport in fed sate | cholesterol to tissue |
| HDL transport in fed sate | cholesterol to liver |
| when there is decreased blood supply of nutrients to add more the body must.... | glygogenolysis - glycogen to glucose in liver; lipolysis - stored triglycerides to fatty acids and glycerol; protein catabolism - protein to amino acids |
| in relation to the brain why is it important to maintain plasma glucose levels | normally only uses glucose for energy production |
| what are 3 ways to get more glucose in the body | glycogenolysis - use liver glycogen stores; create new glucose - gluconeogenesis (liver), amino acids, lactate, pyruvate, glycerol; glucose sparing - tissues switch to more fatty acids to switch to more fatty acids |
| what happens after prolonged starvation | lipolysis - fatty acids in the liver are converted into ketone bodies |
| ketoacidosis | ketones in the blood greatly decrease the pH of the blood |
| what is the hormonal control of absorptive states | insulin - beta cells of endocrine pancreas |
| what is the hormonal control of postabsorptive states | glucagon - alpha cells of endocrine pancreas |
| in the abosorptive state what processes increase | glucose oxidation; glycogen synthesis; fat synthesis; protein synthesis |
| in teh postabpsorptive state, what processes increase | glycogenolysis gluconeogenesis ketogenesis |
| what increases insulin plasma levels | increased plasma glucose increased plasma amino acids GIP, GLP-1 parasympathetic stimulation |
| what decreases insulin plasma levels | sympathetic stimulation plasma epinephrine |
| what increases glucagon plasma levels | decreased plasma glucose levels; increased plasma amino acids |
| hyperglycemia | insulin secretion increases and glucagon secretion decreases insulin effects dominate glucagon effects |
| describe how insulin is secreted from the beta cells | high glucose levels causes higher glucose entry which increases metabolism and ATP production; potassium channels close which depolarizes the cell opening Calcium channels which release insulin |
| what happens when plasma insulin levels increase | target cell - hepatocytes, skeletal muscle, adipocytes insulin binds to receptors on cell membrane substrates phosphorylated changing their actions second messenger pathways change transcription or activity of enzymes change in metabolism |
| how is glucose transported in skeletal muscle and adipocytes | when there is no insulin there are no transporters; insulin binds to receptor which signals transduction cascade - exocytosis so glucose can enter cell |
| how else will put transporters in the membrane | exercising muscle |
| describe glucose transport liver hepatocytes | glucose moves down its concentration gradient; hexokinase-mediated conversion of glucose to G6P keeps intracellular glucose low |
| hypoglycemia | glucagon secretion increases, insulin secretion decreases glucagon only affects the liver |
| what is the sympathetic nervous system's response to hypoglycemia | noreepinephrine and epinephrine - inhibit insulin secretion glucagon secretion; directly affect liver, skeletal muscle and adipose tissue |
| describe how each of the following make glucose liver, adipocytes, skeletal muscle | liver - glycogenolysis, gluconeogenesis adipocytes - lipolysis skeletal muscle - glycogenolysis |
| what is cortisol's role in the hypoglycemia | required for gluconeogenesis and lipolysis to occur (stress hormone) |
| describe type 1 diabetes mellitus | elevated blood glucose levels autoimmune disorder - immune system attacks beta cells inadequate secretion of insulin by beta cells of pancreas cannot move glucose out of blood into tissues so glucagon dominates |
| describe type 2 diabetes mellitus | insulin secreted in response to increased blood glucose, target cells no longer respond to insulin insulin resistance |
| calcium is necessary for what processes | neurotransmitter release; muscle contraction; second messenger; blood clotting factors |
| how does calcium get into plasma | dietary calcium absorbed into ECF; in the bone calcium is resorbed - remodelled; in the kidney calcium is reabsorbed - reclaimed |
| osteoblasts | deposit calcium into bone extracellular matrix build bone |
| osteoclasts | resorb calcium from bone into plasma breakd- low palsm own bone so calcium can enter blood stream |
| what 3 hormones regulate plasma calcium | parathyroid hormone calcitriol calcitonin |
| calcitriol | vit D acitvated in kidney by PTH modifies the activity of bone cells, important for the formation of new bone regulates calcium levels in the blood by helping the body to absorb calcium from food and by preventing calcium loss from the kidneys |
| PTH | parathyroid hormone - glands secrete PTH due to low plasma calcium concentration |
| calcitonin | c cells in thyroid glands secrete calcitonin due to high plasma calcium concentration actions opposite to PTH only has a minor role in normal regulation |
| osteoporosis | to much resorption of bone |
| what is metabolism output | heat, work, stored energy |
| what leads to energy input | hunger, satiety, other factors |
| what leads to energy output | heat - unregulated byproduct of work and temp regulation; work - membrane transport, mechanical work (movement, chemical work (synthesis); storage - chemical bonds, ATP |
| metabolic rate = | total energy expenditure/time kcal or calorie |
| calorie | amount of heat required to raise the temp of 1L of H2O by 1 degree celcius |
| BMR | metabolic rate of subject at rest physically and mentally at a comfortable room temperature in teh post absorptive state ( no food for at least 12 hours) |
| direct calorimetry | measure change in temp foods - fat 9kcal/g carbs/ protein 4 kcal/g |
| indirect calorimetry | measure O2 consumption metabolic rate = kcal/hour O2 used L/hour x 4.8 kcal/L |
| what affects metabolic rate | age gender lean muscle mass exercise food hormones |
| what type of hormones are most important for BMR | thyroid, epinephrine |
| what increases BMR | food induced thermogenesis - rapid increase muscle activity - largest increase |
| what controls food intake | hypothalamus - feeding(hunger) center - tonically active; satiety center - inhibits feeding centre; neuropeptide Y; leptin |
| tonically active | slow continuous activity |
| neuropeptide Y | brain neurotransmitter stimulates food intake |
| leptin | produced by fat cells inhibits NPY in animals |
| input + production = | loss (heat) |
| what are heat gain and heat loss mechanisms | radiation - both; conduction - both; convection - loss only; evaporation - loss only |
| what is the ideal core temperature for the body | 37 |
| how does the body decrease body temp | skin temperature signals peripheral thermoreceptors sending signals to hypothalamus |
| how does the body increase body temp | core temperature signals core thermoreceptors which signal hypothalamus |
| how does the hypothalamus respond when it's too cold | increase heat production: shivering, voluntary muscle activity decrease heat production: vasoconstriction of skin arterioles |
| how does the hypothalamus respond when it's too hot | decrease heat production - decrease muscle activity increase heat loss - vasodialtion of skin arterioles sweating |
| hypothermia | abnormally low core temperature |
| hyperthermia | abnormally high core temperature |
| heat exhaustion | severe dehydration; core temp 38-39 |
| heat stroke | more severe, higher temp mortality 50% |
| what causes a fever | infection; bacteria release toxins; response- immune cells release pyrogens; increase hypothalamic thermostat setpoint; FEVER; increase heat production - decrease heat loss; increase core temp to new set point |
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