energy.docx

Energy is required for body’s processes such as DNA and RNA synthesis Active transport Intracellular signalling. Cellular repair. Also required for maintain homeostasis. Cellular respiration Breaking of glucose bonds releases energy. A lot of the energy from nutrients etc is expelled as heat. Much o...

Energy is required for body’s processes such as DNA and RNA synthesis Active transport Intracellular signalling. Cellular repair. Also required for maintain homeostasis. Cellular respiration Breaking of glucose bonds releases energy. A lot of the energy from nutrients etc is expelled as heat. Much of it is used to maintaining body temperature. To optimise enzyme activity Hypothermia Maintain immunity. Internal temperature is maintained at 37.8C and the sites to measure the temperature from are: Oral Rectal Axillary Temporal Eardrum Basal metabolic rate Measurement of the number of calories needed to perform your body’s most basic functions. How to measure metabolic rate? Indirect calorimetry- measures the amount of oxygen consumed, and how much CO2 was given out. Direct calorimetry- measures heat produced (more accurate) Direct vs indirect Direct Indirect Advantages Extremely accurate Cheaper and easy to use Disadvantages Expensive No as accurate as direct Factors that influence the basal metabolic rate Gender (weight, height, and surface) Age Body size Hormonal levels (T4 and adrenaline) Energy input MUST equal energy output to maintain a neutral energy balance. Chemical messengers are responsible for the body’s nutritional status. Adipose stores Feeding status Food intake is primarily controlled by the hypothalamus. Arcuate nucleus: role in long term control of energy balance and body weight and short-term control of food intake from meal to meal. Neurons present in the arcuate nucleus are divided into 2 subsets. Neuropeptide Y and agouti-related peptide = helps to eat more Melanocortin- supresses appetite. Adipose tissue releases adipokines- important role in energy balance and metabolism. Adipose tissue has endocrine functions due to it releasing hormones into the blood directly. Largest hormones secreting organ in the body. e.g. leptin is released by adipose tissue which is essential for regulating body-weight regulation. Genetically obese people produce less or no leptin hence the leptin never sends the signal telling to stop eating. Insulin also has a important role in control of body weight. Stores energy. Regulating inputs The CNS regulates food intake via the brain-gut access. Hypothalamus takes the long- and short-term feedback. When leptin is released, it binds to agouti-related peptide and inhibits it. This upregulates/stimulates the production of pro-opiomelanocortin. Goes through different post translational modifications to generate different peptides e.g. alpha melanocytes stimulating hormone. Agouti-related peptide and stimulating hormone from pro-opiomelanocortin such as alpha melanocytes stimulating hormone compete for melanocortin receptors in the brain/hypothalamus. Agouti-related peptide is a antagonist so if it binds, it blocks the site for alpha melanocytes and increases peptide Alpha melanocytes is a agonist so it binds to receptors, it activates melanocortin and supresses appetite. Eventually the alpha melanocytes stimulating hormone binds and upregulates signals called anorexigenic signals= decrease food intake. **Mostly know about leptins role in regulating food intake** Within the hypothalamus, there are regions called: Lateral hypothalamic area Paraventricular nucleus Lateral hypothalamic area If eating is involved: Neuropeptide Y will be firing and melanocortin will be inhibited. Paraventricular nucleus If eating needs to stop: Neuropeptide Y will be inhibited and melanocortin will be firing. Eating= Agouti-related peptide and Neuropeptide Y are active. Decrease food intake= melanocortin will be stimulated and Agouti-related peptide and Neuropeptide Y will be inhibited. Short-term eating behaviours Ghrelin= produced by the stomach and potent appetite stimulator. PYY3-36= inhibits from eating, produced by small and large intestine. Supresses Agouti-related peptide and Neuropeptide Y and enhances melanocortin. Satiety centre – primarily located within the hypothalamus A Satiety centre located in the brain stem known as nucleus tractus solitarius (NTS) These signals are important as they make you feel full. Catabolic= degrade fuel and generate ATP e.g. breakdown of polysaccharides into monosaccharides. Anabolic= regenerates metabolites and requires energy Gluconeogenesis= making glucose from amino acids etc. Metabolic efficiency= amount of work achieved for a given amount of energy expended. More efficient individuals waste less energy hence less heat loss. Carbohydrates are first and rapidly mobilised. Fats are the second and slowly mobilise. Proteins are the last ones to be broken down and very slow. Glucose reading of 6mol/l whilst fasting is indicative of prediabetes. Anything above 7mol/l glucose reading whilst fasting is type 2 diabetes. During fasting Glycogen is broken down to glucose, goes to obligatory users first such as the brain. Adipose tissue and muscles are broken down to release glucose when fasting for a longer time. During feeding No adipose sites are broken down for glucose, it comes from the food that’s eaten. Glycogen is not broken down. Cori cycle Lactate produced by anaerobic glycolysis in the muscle moves to the liver and converted into glucose which then returns to the muscle and metabolised back to lactate. Glucose fatty acid cycle (Randle cycle) Body chooses which nutrient it needs to metabolise when it has both free fatty acids and glucose. Glucose is not utilised when fatty acids are in abundance therefore saves glucose for important organs such as brain. Insulin is a key regulator of fuel selection and forms a balance between anabolism and catabolism. Stimulates glucose and protein anabolism but reduces lipid catabolism. Stimulates glycogenesis, lipogenesis, amino acid uptake and conversion to proteins. Inhibits lipolysis, gluconeogenesis, and protein catabolism.