Hormonal Regulation Of Plasma Calcium And Calcium Metabolism
Regulation of Metabolism - Mt. SAC...Metabolic regulation by growth hormone • Regulation of...
Transcript of Regulation of Metabolism - Mt. SAC...Metabolic regulation by growth hormone • Regulation of...
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Regulation of MetabolismRegulation of MetabolismRegulation of Metabolism
By By Dr. Carmen Rexach Dr. Carmen Rexach
PhysiologyPhysiologyMt San Antonio CollegeMt San Antonio College
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Energy• Constant need in living cells• Measured in kcal
– carbohydrates and proteins = 4kcal/g– Fats = 9kcal/g
• Most diets are mixed
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Metabolic rate
• Measure MR– Direct = heat– Indirect =oxygen consumption
• Temperature– Influences chemical reactions– results in physiological response to change
• Physical activity = primary determinant of energy requirements– wt loss– wt gain
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Basal metabolic rate
• Conditions– 12 to 14 hours after eating– comfortable temperature– awake, but resting
• determinants– age, sex, surface area, thyroid
hormones, genetic components
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Anabolic requirements• Turnover rate = rate at which molecule is
broken down and resynthesized
• Requirements– essential amino acids for proteins and
essential fatty acids for fats– Water soluble and fat soluble vitamins– Minerals and trace elements
nutrient turnover requirementCarbohydratesproteinsfats
250g/day150g/day100g/day
150g/day35g/daynegligible
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Regulation of energy metabolism• Two sources
– absorbed nutrients– energy reserves
• Preferred energy sources– depends on available enzymes– brain = blood glucose; skeletal muscle = fatty acid
• Eating– Body fat and endocrine function– large habit component– Partially controlled by hypothalamus– Influenced by neurotransmitters, endorphins, intestinal
hormones• Hormonal regulation of metabolism
– absorptive state– postabsorptive state
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Energy regulation by islets of Langerhans
• Three cell types produce polypeptide hormones – Beta (β) cells = insulin
• Encourages cellular glucose uptake• In liver, activates glycogen synthetase• Encourages lipid synthesis• Stimulates the movement of amino acids into cells
– Alpha (α) cells = glucagon• Encourages liberation of reserves• Prevents glucose uptake by liver, muscle, adipose
– Delta (δ) cells = somatostatin• Not sure
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Pancreatic islets = islets of Langerhans
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Regulation of insulin and glucagon secretion
•• Effects of glucose and amino acidsEffects of glucose and amino acids– rise in plasma glucose
• stimulation of β cells• inhibits α cells
– fall in plasma glucose• decreased insulin• increased glucagon
– meals high in protein• stimulates insulin
– meals high in protein and low in carbohydrate• stimulates glucagon• result: increase in blood glucose and increased incorporation of
amino acids into tissues
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Regulation of insulin and glucagon secretion
•• Effects of autonomic nerves and GIPEffects of autonomic nerves and GIP– parasympathetic
• increased insulin– sympathetic
• increased glucagon, inhibits insulin• stress hyperglycemia = glucagon + epinephrine
– GIP: stimulates release of insulin before it appears in blood (presence of glucose in intestines)
– Goal: Keep blood glucose between 50mg/100ml and 170mg/100ml
• higher = glycosilation; lower = brain damage
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Absorptive state• High insulin and low glucagon• Insulin
– cellular uptake of glucose– uptake & incorporation of amino acids– conversion of glucose to glycogen– additional glucose to fat– incorporation of glucose into adipose
tissue– suppression of liver glycogen hydrolysis
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Postabsorptive state
• Low insulin, high glucagon– low insulin encourages movement of amino acids
out of the muscles• cortisol -- stimulates production of enzymes to
convert pyruvic acid to glucose• glucagon
– stimulates glycogenolysis– stimulates gluconeogenesis– stimulates lipolysis– stimulates ketogenesis
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Diabetes mellitus
• IDDM: insulin deficiency– autoimmune, ketosis (can lead to ketoacidosis)– increased blood glucagon secretions– 3 p’s = polydypsia, polyuria, polyphagia
• NIDDM: insulin resistance and deficiency– slow to develop– hereditary component– overweight– usually no ketoacidosis, but serious sequelae
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Hyper and hypoglycemia
• Hyperglycemia = chronic high blood glucose– insufficient secretion of insulin from β cells– inability of insulin to stimulate glucose uptake
• Hypoglycemia – overdose of insulin– reactive hypoglycemia = excessive increase in insulin
after carbo meal– symptoms: tremor, hunger, weakness, blurred vision,
impaired mental ability
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Metabolic regulation by adrenal hormones
•• Metabolic effects of epinephrineMetabolic effects of epinephrine– similar to glucagon– conditions for secretion
• fight or flight• low blood glucose• fasting
•• Metabolic effects of Metabolic effects of glucocorticoidsglucocorticoids– prolonged fasting or exercise = stress– Effects
• lipolysis & ketogenesis, stimulates hepatic enzyme synthesis for gluconeogenesis, promotes release of amino acids from muscle
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Metabolic regulation by thyroxin
• Function– cellular respiration, growth & development in
early childhood• Cellular respiration
– calorigenic effect = increases BMR– sets BMR
• Growth and development– RNA and protein synthesis– cretinism
• Hypothyroidism and hyperthyroidism
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Metabolic regulation by growth hormone
• Regulation of secretion– GHRH– increase aa in plasma– decrease glucose in plasma
• insulin-like growth factors– Mediates action of growth hormone
• Effects on metabolism– protein synthesis– catabolism
• Effects on body growth– hypersecretion & hyposecretion in children and adults
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Regulation of calcium and phosphate balance
• PTH, active vitamin D, calcitonin• bone remodeling• plasma concentration• role of Ca++ in body
– bone formation– muscle contraction– second messenger– membrane permeability
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Parathyroid hormone
• Stimulus: decrease in plasma Ca++
• Action:– stimulates osteoclasts– stimulates Ca++ reabsorption by kidneys– inhibits reabsorption of PO4
-3
– promotes formation of active vitamin D3
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1,25-dihydroxyvitamin D3
• Action: raises plasma Ca++/PO4-3 by:
– intestinal absorption– resorption– renal reabsorption
• Absence/inadequate secretion
7- dehydro-cholesterol
Vitamin D3
25-hydroxy-vitamin D3
1,25 dihydroxyvitamin D3
sun
liver
kidney
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Calcitonin
• Calcium lowering hormone• Stimulus• Action:
– inhibition of osteoclasts– inhibition of reabsorption of Ca++ and
PO4-3 in the kidneys