55 - Nutrition – main principles in defining physiological standards: muscle mass and energy needs. Physiological mechanisms of starvation and satiety

sections

main principles in defining physiological standards

muscle mass

energy needs

physiological mechanism for starvation and satiety (fullness)

main principles in defining physiological standards

• A balanced diet is one which provides the body with all the essential nutrients it needs to function properly with approximately 80 essential nutrients that are necessary for health however they cannot be synthesised by the body in adequate amounts and must be obtained from diet

• Water is an essential nutrient, lost in urine, respiration and by the skin. Water intake is essential

• Mineral elements- a lot are lost through urine, faeces and other secretions. Large supply is needed but only small amounts needed in the body

• Vitamins

  • Water soluble- in the large intestine lead to rapid excretion of urine

  • Fat soluble vitamins- large intake leads to build up in adipose tissue which can have toxic effects

  • cofactors for various reactions that help to release energy

muscle mass

• Muscle growth is known as hypertrophy.

• This is the growth in muscle density, mass, it refers to the shape and function of the muscles.

• regulate muscle growth : growth hormone, testosterone, cortisol, IGF-1, beta endorphin and parathyroid hormone.

• Muscle growth occurs due to an increase in water, number of myofibrils and connective tissue.

• An increase in age is associated with a loss in muscle mass.- This is known as sarcopenia -because decrease in total number of fibres, muscle fibre size, imperial contractile mechanisms and a decrease in motor unit recruitment

energy needs

• based upon estimations in energy expenditure plus additional energy needs for growth, pregnancy and location. Humans need energy for:

• basal metabolism for cellular function and replacement.

• Cellular formation includes the secretion of enzymes and hormones, transport of substances and maintenance of body temperature.

• Metabolic response to food requires energy.

• Energy from Ingestion of foods digestion,, transport, absorption etc. energy is needed for physical activities.

• During pregnancy extra energy is needed for growth of the foetus, placenta etc

physiological mechanism for starvation and satiety (fullness)

• Mechanisms of starvation and satiety are controlled by the hypothalamus.

• During a stage of satiety

• leptin is secreted by adipose cells and acts in the hypothalamus to decrease food intake ,inhibits neuropeptide Y which stimulates a s6ppetite.

• Satiety signals are… which decrease appetite by causing feelings of hunger and sets the time before hunger returns.

• During starvation breakdown of glycogen to glucose. eventually

• Fats in adipose tissue are broken down into fatty acids and glycerol.

• liver produces ketone bodies as source of fuel