Physiology π« Flashcards
what is the importance and the definition of ATP?
- It is used as an energy source for almost all cellular functions or its similar nucleotide guanosine triphosphate (GTP) .
what is the energy currency of the body?
ATP (adenosine triphosphate)
what are the sources of ATP generation?
- Combustion of carbohydrates mainly glucose
(but also small amount of other sugars as fructose), which occurring by the process of glycolysis and by the krebs cycle. - Combustion of proteins: hydrolysis to amino acids then its degradation to intermediate compounds of citric acid cycle.
- Combustion of fatty acids in the mitochondria by beta oxidation .
what is the definition of phosphocreatine?
- Accessory storage depot for energy .
- It is the most abundant store of high energy phosphate bond in the cells.
what happens when ATP begins to be used up?
the energy in phosphocreatine is transferred rapidly back to ATP.
what is the significance of phosphocreatine?
- It thus keeps the concentration of ATP nearly constant .
- The concentration of ATP must be maintained constant because the rate of chemical reactions in the body depends on this constancy.
what are the uses of ATP?
- Energizes the synthesis of cellular components:
- Formation of peptide linkages amino acids during synthesis of proteins.
- Synthesis of glucose from lactic acid
- Synthesis of fatty acids from acetyl co enzyme A .
- Synthesis of phospholipids, cholesterol and hormones.
- Synthesis of urea from ammonia. - ATP energizes muscle contraction.
- ATP energize active transport across cell membrane.
- ATP energizes nerve conduction.
- Digestion ,absorption and processing of food.
- Maintenance of body temperature.
what is considered as a major controlling factor of energy releasing reactions in the cell?
ADP concentration as amajor controlling foctor of the energy releasing reactions in the cell:
- When the cell become active, ATP is converted to ADP , when its concentration increases ,it enhances the rate of all energy releasing reactions in the cell.
- In abscence of cellular activity ,all these reactions stops because all ADP is converted toATP.
what is the definition of metabolism and metabolic rate?
Metabolism: all chemical reactions in all body cells.
Metabolic rate: rate of heat liberation during the
chemical reactions .
what is the end product of almost all the energy released in the body?
Heat
what is the percentage of energy that becomes heat during ATP formation?
50% becomes heat during ATP Formation.
what are the forms in which the energy is lost as heat during ATP formation & Synthesis?
- 50% becomes heat during ATP Formation.
- Heat is released as energy is transferred from ATP to functional systems of cells.
- No more than 27% of all energy from food is finally used by functional systems ,this also becomes heat during
what is the amount of energy that is finally used by functional system?
- No more than 27% of all energy from food is finally used by functional systems ,this also becomes heat during
how does the 27% of energy used in functional system become heat?
- During protein degradation :part of energy stored in peptide linkages is released as heat.
- Overcoming the viscosity of muscles and other tissues during muscle contraction and body movements.
- Friction between the different layers of blood as blood flows through blood vessels.
- The only significance exception is when the muscles uses this energy to perform work.
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what is the amount of calories consumed by an average man waiting 70 kg and lies in bed all day?
1650 calories
what is the amount of calories consumed by an average man waiting 70 kg and eating a resoanable diet?
1850 cals per day
what is the amount of calories consumed by an average man waiting 70 kg and sits in a chair all day?
2000 -2250 calories per day.
what does the amount of energy used to perform a physical activity vary according to?
- Type of physical activity
- Amount of physical activity
what is the amount of total energy expenditure used during normal daily activities?
25%
give an example for variation in energy expenditure according to activity:
- A person performing heavy labour can achieve a maximal rate of energy utilization as graet as 6000 to 7000 calories.
- Even in sedentary individuals significant energy is spent to maintain muscle tone and body position and other non exercise activities.
what is the definition of heat value of food?
Amount of heat released by oxidation of 1 gm food.
what are the units of heat?
Calorie (C) (= 1000 small calorie, c)
what are the physiological and physical heat values of macronutrients?
why is a physical and physiological heat value of carbohydrates and fats equal in vitro & in vivo?
because they are completely oxidized to CO2 + H2O in & out the body.
Why is physical and physiological heat value of proteins different?
Proteins contain 16% N2
- Outside the body : β completely oxidized
- Inside the body: β not completely oxidized otherwise N2 is oxidized into nitric acid β fatal decrease in pH). This N2 is transformed to urea by liverβ excreted in urine (causing loss of part of energy of protein).
what is the definition of (Specific Dynamic Action (SDA) or Postprandial Thermogenesis)?
Power of food to stimulate metabolic rate & heat production.
when does SDA start?
1 hour after ingestion of food.
when does SDA reach maximum rise?
a maximal rise after 3 hours.
when does SDA decrease to normal?
Decrease to normal in 10 β 12 hours.
what are the factors affecting SDA?
what are the causes of SDA?
- Increased sympathetic activity after feeding
- Metabolic reactions through which food is metabolized
- CHO: Metabolic processes that occur in liver e.g. glycogenesis
- Fat: Direct stimulating effect of fatty acids on the metabolic processes in the tissues
- Protein: Metabolic processes that occur to amino acids in liver as deamination and urea formation, A direct stimulating effect of amino acids on metabolic processes in tissues
what is the significance of SDA?
It is a waste heat liberated after food ingestion
- During exposure to cold β proteins ingestion keep body temperature constant.
- Guard against development of obesity.
regulation of food intake
Short term control system:
- Make the person eat much smaller quantities at each eating session to make digestion and absorption work at optimal rates.
- Prevent persons from eating amounts at each meal that would be too much for metabolic storage system .
Long term control system:
- It help maintain constant stores of nutrients in the tissues thus preventing them from becoming too low or too high .
what are the hypothalamic feeding centers (Appestat)?
1. The lateral nuclei: Feeding centre ( hunger centre).
2. The ventromedial nuclei: Satiety centre.
3. The paraventricular nuclei: satiety centre.
4. Dorsomedial nuclei: feeding centre.
5. The arcuate nuclei: are the sites where multiple hormones released from the gastrointestinal tract and adipose tissues converge to regulate food intake and energy expenditure.
6. Amygdala and prefrontal cortex: control appetite.
what is the definition of hunger and what is it associated with?
- organic sensation that indicates the need for food
- It is associated with hunger pains due to rhythmic contraction of the stomach
what is the definition of appetite?
- Organic sensation that indicates that desire for a particular type of food
what is the definition of satiety?
sense of satisfaction as regard feeding
what do the hypothalamic centers receive? (Concerning food appetite and satiety)
- Neural signals from the gastrointestinal tract that provide sensory information about stomach filling.
- Chemical signals from nutrients in the blood (glucose ,amino acids and fatty acids) that signify satiety.
- Signals from GIT, Adipose tissue & cerebral cortex that influence feeding behavior (smell ,sight taste).
what are the neurotransmitters and hormones that influence feeding and satiety centers in the hypothalamus?
1. Orexigenic (increase feeding):
- Neuropeptide y
- Ghrelin
- Galanin
- Cortisol
- Orexin A & B
- Endorphins
2. Anorexigenic(decrease feeding):
- Leptin
- Insulin
- Corticotropin releasing hormone
- Glucagon like peptide.
- Peptide yy
- Cholecyctokinin
what are other neural centers that influence feeding?
- Appetite center
- Centers that regulate the mechanics of feeding as salivating chewing & swallowing
what is the site of appetite Center?
Amygdala
what happens if there is a lesion in the appetite Center?
loss of appetite control (type & quality of food).
what is the site of the centers that control the mechanics of feeding?
brain stem.
what are the types of nerve fibers in the arcuate nucleus?
- Proopiomelanocortin ( POMC)
- Agouti related peptide
what is Pro-opio-melano-cortin (POMC)? And what does its activation lead to?
- A type of neurone in the arcuate nucleus of the hypothalamus that produce alpha melanocyte stimulating hormone( alpha MNS) which act on MCR4 receptor.
- decrease food intake and increase energy expenditure
what is agouti related peptide?
A neuron in the acruate nucleus which has opposite effect to POMC
what are the importance of short term of control of food intake?
Regulate the size of each meal.
what are the factors that affect short term control of food intake?
- Rapid neuroendocrine interaction that suppress feeding
- Gastrointestinal filling
- Mouth receptors
- Others
what are examples of Neuro endocrine interactions that suppress feeding?
how does GIT filling inhibit feeding?
Distension of stomach & duodenum by food β sends inhibitory impulses through vagi β inhibits feeding center β decreases desire for food.
how do mouth receptors inhibit feeding?
- As food enters the mouth β certain oral receptors stimulated by certain factors related to feeding such as chewing ,salivations ,swallowing and tasting register (measure) the amount of food ingested β sends satiety signals to stimulate satiety center.
- Degree of hunger decreases after reasonable amount of food.