Nutrition 12 ch10
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What percentage of total body weight is water?
60% - 70%
There is fluid inside and outside of cells in the body, what portion of water is inside cells and what portion is outside cells?
- 2/3 water is intracellular - inside the cells
- 1/3 water is extracellular - outside the cells
What is a solution?
A mixture of two or more different substances, often liquid and a non-liquid.
The solvent would be the liquid portion.
The solute would be the non-liquid portion.
In salt water solution - water is the solvent and salt is the solvent.
What are some functions of water in the body?
- Acts as a solvent to form various solutions in your body.
- Lubricator for tissues, joints, eyes.
- Transports nutrients, oxygen and other things through your blood and other body fluids. Water transports waste filtered through your kidneys out of the body in urine.
- Regulates temperature ( human temperature is about 98.6 F ) - water inside your body helps retain heat and on the surface of your body as sweat helps cool you down.
- Regulates pH ( pH for most body fluids in a human should be 7.4 - much lower or higher could be deadly ).
What is osmosis, how does it help regulate the movement of water in the body.
Osmosis is the movement of water across a semi-permeable membrane. A semi-permeable membrane is a membrane that some stuff, like water, can pass through but other stuff, like large proteins, cannot.
It works through a concentration gradient. If a blood cell has a higher concentration of water inside of it than there is in the fluid outside of it, then water will leave the cell. If the fluid outside the cell has a higher concentration of water in it than inside the cell, then water will move into the cell.
What is water balance?
We need to keep about the same amount of water in our body at all times. But some of it leaves our body through sweat, urine, even poop.
To replenish this we drink more water. We tend to drink the same amount of water that we lose.
How does thirst work?
You can think of blood as water and stuff, solvent and solute. As you sweat and pee water leaves your body and the water / solvent part of blood is lowered.
Since blood is mostly water ( 90% water ) this decreases the amount of blood in your system.
The decrease in blood volume triggers the thirst center in the hypothalmus in your brain which sends signals to your body making you feel thirsty. The decrease in water also makes your mouth dry since there is less water in your body to make saliva which also makes you want to drink water.
What is ADH, what does it do?
ADH stands for antidiuretic hormone.
It is a hormone secreted by the pituitary gland which tells the kidneys to reasbsorb more water and send less out through urine.
What are the DRIs for water intake?
- 3.7 liters / day for men
- 2.7 liters / day for women
What are some things that can affect water need?
Activity ( exercise ), diet, temperature of your environment. Pregnancy and lactation increase water need.
What are some effects of water deficiency / dehydration?
You can live without food for a few weeks but you can live without water for only a few days.
Blood is mostly water. You lose water through sweat, urination, evaporation. If you lose enough water the amount of blood in your system decreases. You need blood to carry oxygen and nutrients to different parts of your body.
- Symptoms of dehydration are:
- Headache, fatigue, loss of appetite, dry eyes and mouth.
More severe dehydration can cause nausea, difficulty concentrating, confusion.
Water toxicity, overhydration...
Your body needs a proper balance of water as a solvent and other substances as solutes to function properly. If you drink too much plain water ( with no electrolytes like salt ) then you could upset the balance.
Symptoms are similar for dehydration.
What is hyponatremia?
Low blood sodium concentration. Too much water ( solvent ), not enough sodium ( solute ) in blood.
Since water moves from high concentration to low concentration via osmosis, and since the concentration of water in blood is very high during hyponatremia, water leaves the blood and enters surrounding tissues, causing swelling.
What is an electrolyte?
A substance that when dissolved in water dissociates ( breaks into ) positively and negatively charged mollecules called ions which can conduct electricity.
What are some functions of electrolytes?
Regulates fluid balance - water moves from higher concentration of water to lower concentrations of water. Similarly, it moves from low concentrations of electrolytes to high concentrations of electrolytes.
Nerve function - electrolytes can conduct electricity which allow nerve cells to transmit signals.
Muscle contractions - Muscles need electrical impulses to allow them to work. Electrolytes allow these nerve impulses to be transmitted.
Sodium and potassium are both electrolytes. What kinds of foods have more of these different electrolytes?
There is more sodium in processed food, it is used as both a flavor enhancer and preservative.
There is more potassium in fresh foods.
Which electrolyte regulates extracellular fluid / fluid outside of a cell?
Sodium regulates ECF / extracellular fluid.
When there is more sodium in the body, more water is consumed to maintain the sodium-fluid balance in blood, this increases the blood volume. When there is more blood in the system, blood pressure increases.
Which electrolyte regulates intracellular fluid / fluid inside the cell?
Potassium regulates ICF / intracellular fluid.
How does the body react to low blood pressure?
Low blood pressure causes the kidneys to release renin.
Renin causes angiotensin in the body to convert to angiotensin 1, which is then converted to angiotensin 2.
Causes the constriction of blood vessels ( blood vessels get smaller / narrower ) which increases blood pressure.
Angiotensin 2 also...
Causes the adrenal glands to release aldosterone which causes kidneys to reabsorb more salt. There is then more salt in the system and more water is consumed to maintain the salt-fluid balance in the body, which increases the amount of blood in the system, which increases blood pressure.
After blood pressure is brought back up to normal level the release of renin is reduced.
Sodium is an electrolyte and is lost in sweat. Vomiting and diarrhea can cause the loss of electrolytes. Urinating too much can flush needed electrolytes out of your system.
Loss of electrolytes can lead to poor appetite, muscle cramps, confusion, constipation, irregular heartbeat, confusion. It can affect a lot of systems that rely on electrolytes to carry electrical impulses.
It's not very common.
Excess potassium intake from suppliments can lead to irregular heart beat.
For people with salt sensitivity, the mechanisms for regulating blood pressure when salt is consumed don't work very well and blood pressure increases.
Understanding blood pressure readings...
Blood pressure is measured as a set of two numbers, a larger number over a smaller number - 120/80.
The larger number is systolic blood pressure - the maximum pressure in the artery, measured when the heart beats / contracts.
The smaller number is diastolic blood pressure - the minimum pressure in the artery, measured between beats.
Blood pressure might be read as 120/80 mm Hg. The mm is milimeters, the Hg is chemical symbol for mercury. Blood pressure used to be shown as a column of mercury in a tube, kind of like a thermometer. So it was read as mm Hg, millimeters of mercury.
What is optimal systolic blood pressure?
Remember this is just the larger number on top.
Optimal systolic blood pressure is 90 - 120 mm Hg
What is hypertension?
High blood pressure.
Specifically blood pressure that is 140/90 mm Hg or higher.
What causes hypertension?
Usually some kind of disorder that affects the way the body controls electrolyte and fluid balance. Kidneys release renin to increase blood pressure when needed, if this system doesn't work well then blood pressure could be too high.
What are some risk factors for hypertension?
- Genetics - family history of hypertension
- Age - Arteries aren't as elastic / able to stretch and expand as a person gets older. If the amount of blood in the system increases but the arteries don't expand to accomodate then blood pressure will go up.
- Existing conditions / diseases - Kidneys release renin to regulate blood pressure. If a person has kidney disease and renin isn't released properly or too much is released then blood pressure could increase more than it should.
- Lifestyle - Lack of exercise, too much alcohol consumption, smoking, and stress can all cause hypertension.
Can increased sodium intake increase blood pressure?
It can, but it occurs more often in people who are at higher risk for hypertension.
What are some minerals that reduce the risk of hypertension?
What is the DASH diet?
It stands for Dietary Approaches to Stop Hypertension.
It's mostly just a diet that high in fruits and vegetables and low in fat, like you should be eating anyway.
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