7 - HOMEOSTASIS & ENERGY & EATING Flashcards
information:
the fact that cells need specific conditions to survive and function suggests that multicellular organisms evolved from single cells, living and moving in a salt water environment
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cells in a multicellular organism…
- cannot move to a suitable environment (they are stationary - except red blood cells and microglia) so cannot escape environmental changes
- cut off from ‘natural’ environment as on the inside of the body
- cells must work together and cooperate to create and maintain a suitable environment (suitable for all cell types, some might have different requirements - all needs need to be met)
optimum
cells require a stable environment
- survive only small deviations from ‘working conditions’
- large deviations = disrupted cell function and can lead to cell death (eg too hot)
internally generated environmental conditions that cause constant change
- nutrients being used up
- waste products accumulating (due to metabolism etc)
- growth and reproduction
externally generated environmental conditions that cause constant change
- temperature, humidity etc
- light and dark
- availability of nutrients (changes seasonally etc)
what is homeostasis?
actively keeping an organisms (multi or single celled) internal states within a critical range - to allow cells to survive
what are homeostatic systems?
- negative feedback loops
- oscillating behaviour around the set point (optimum)
- eg like a temperature control (central heating)
- eg 1c above and below = critical range
- buffer around the set point
- never actually on set point
- when too hot, turns off, when too cold, turns on etc
statement:
thirst is a part of homeostatic fluid control
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eating is a homeostatic process
why do we need to eat?
nutrition (4 types)
- nutrition builds and maintains the body
- essential amino acids
- essential fatty acids
- minerals
- vitamins
essential amino acids
- 9 cannot be synthesised by the human body (need to get from diet)
- 20 amino acids in total
- they are the building blocks of proteins (need them to be produced by the human body)
essential fatty acids
- building blocks of fat (eg cell membranes and myelin sheath of neurons)
minerals
- elements like iron, sodium, calcium
- parts of all body structures
- eg iron in red blood cells, calcium in bones etc
vitamins
- no common chemical structure
- organic nutrients needed in small amounts
- eg chemical partners for enzymes etc
what is used for energy generation?
3 things
- carbohydrates
- fats
- proteins (to a lesser extent)
short term control of eating (nutrient and energy regulation)
- when to start a meal
- when to end a meal
long term control of eating (nutrient and energy regulation)
- food not constantly available
- evolution of mechanisms to store energy
- release stored energy
- anticipate the need for energy and nutrient
how short term and long term control of eating interact (nutrient and energy regulation)
- meal size and frequency determines long term body weight
- start meals frequently and don’t end for long time = increase body weight
- start meals infrequently and end meals early = decrease body weight
short term eating control
how are meal sizes and frequency controlled?
- usually start eating before we feel hungry
- usually stop eating before the brain can receive satiety signals
- control of eating is related to ‘feeling hungry’ but that’s not the whole story
- homeostatic factors and non homeostatic factors involved
homeostatic factors involved in short term eating controls
- biochemical signals indicating state of energy stores (corresponds to what you keep in a critical range)
- systems or structures to detect and interpret these signals
non-homeostatic factors involved in short term eating control
- learning: adapting the system to its specific environment
- mood as a non-adaptive factor
why do we eat?
to build up energy
energy is needed by all chemical processes to make the body survive
energy generation model
1 - eat fats, carbohydrates and proteins
2 - digest
3 - fatty acids, glucose and amino acids in blood stream
4 - further breakdown
5 - acetyl-CoA
6 - mitochondria of cells = citric acid cycle
7 - mitochondria of cells = oxidative phosphorylation
8 - ATP
ATP
- ATP = natures universal rechargeable battery!
- found in every cell
- ATP stores energy
- it has 3 phosphate groups which are linked together by compressed spring like structure
- if one phosphate group is removed = energy released
- store energy by adding phosphate group
- we produce our own weight in ATP each day
what is available energy used for?
- mainly used in basal metabolism (letting cells do what they need to do - eg keeping heart beating, and neurons firing etc)
- next largest consumption is active behaviour
- next is digestion (breaking molecules down)
- then finally the remainder is added as a reserve for storing
- 20% of intake goes to the brain but it’s only 2% of our body mass