Chap 7 - notes PDF

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Fluids - Substances composed of freely moving molecules - Have the ability to conform to the shape of the container that holds them - There are different types of fluids in our bodies - Two-thirds of the body’s fluid is intracellular fluid - The remaining one-third is extracellular fluid - Intracellular fluid composes about 2/3rds of the body fluid. It is held within the walls of cells. If cells lose water, they shrink and die. Conversely if they take up too much water they can swell up and burst this is why appropriate fluid balance is important. - The remaining 1/3 of body water: - Extracellular fluids include - Tissue fluid found between the cells within tissues and organs of the body - Cerebrospinal fluid, mucus, synovial fluid - Intravascular fluid – found within blood and lymphatic vessels. - Plasma, the fluid portion of blood that carries the blood cells - The remaining 1/3rd of the body water is outside of the cells and is called extracellular fluid. - Two types of extracellular fluid: - tissue fluid – also called interstitial fluid. Flows between the cells that make up a particular tissue or organ. Cerebrospinal fluid, mucus, and synovial fluid are also considered tissue fluid. - Intravascular fluid – found within blood and lymphatic vessels. Plasma is the fluid portion of blood that transports red blood cells through blood vessels. -

The body fluid composition of tissue varies by Tissue type—lean tissues have higher fluid content than fat tissues Gender—males have more lean tissue and therefore more body fluid Age—lean tissue is lost with age and body fluid is lost with it Muscle is about 70% fluid by weight fat is about 10-20% water

Electrolytes - In intracellular fluid, potassium (K+) and phosphorus (HPO42–) are the predominant electrolytes - In extracellular fluid, sodium (Na+) and chloride (Cl–) predominate - There is a slight electrical charge difference on either side of the cell membrane - Within body fluids are a variety of solutes (dissolved substances) critical to life. The 4 major minerals are sodium, potassium, chloride, and phosphorus. These are called electrolytes. - Electrolyte – when dissolved in water 2 component minerals separate and form charged particles called ions which carry an electrical current. The charge is a spark that stimulates nerves and causes muscles to contract, making electrolytes critical to body functioning. - Na and K are positive charges, CL and HPO4 (phosphorus) are negatively charged.

Function of fluids - Fluids dissolve and transport substances - Water is an excellent solvent because it can dissolve many different substances - The dissolved materials, or solutes, include ions, carbohydrates, amino acids, vitamins, and minerals - Fats and fat-soluble vitamins do not dissolve in water so they either attach to or are surrounded by water-soluble proteins that then can transport them to cells in the blood. - Fluids account for blood volume - Blood volume is the amount of fluid in the blood - Increased blood volume can cause blood pressure to rise (hypertension) - Decreased blood volume can cause low blood pressure - Maintaining appropriate fluid levels are essential to maintaining a healthful blood volume. - Fluids help maintain body temperature - Because water has a high heat capacity, the temperature of our body fluids remains quite stable - Sweating releases heat as the evaporation of water from the skin cools the skin and blood - When core body temp rises, blood is shunted to the skin which transports heat out of the body core and to the periphery where it can be released through the skin. Sweat glands secrete more sweat from the skin. As sweat evaporates heat is released and the skin and underlying blood are cooled. The cooler blood flows back to the core and reduces internal body core. -

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Fluids protect and lubricate body tissues - Cerebrospinal fluid protects the brain and spinal column - Amniotic fluid protects the fetus - Synovial fluid is a lubricant around joints - Digestive secretions allow for easy passage of material - Pleural fluid covering the lungs allows friction-free expansion and retraction Electrolytes help regulate fluid balance - Water follows the movement of electrolytes, moving by osmosis to areas where the concentration of electrolytes is high - This allows for the controlled movement of fluids into and out of cells - Some illnesses that lead to protracted vomiting and diarrhea can alter this balance

Functions of electrolytes; osmosis - Osmosis – pure water will flow through the permeable filter toward the high concentration of electrolytes (NaCl in this case). Water flows to areas where solutes are higher in concentration. - Osmosis – is a mechanism for controlling the movement of fluid into and out of cells.

Fluids and electrolyte balance - If concentrations of electrolytes are higher inside a cell, water will flow into the cells in such large amounts the cells can burst. (b) - If electrolyte concentration is much higher outside of the cell (extracellular fluid) water will flow out of the cell and they can dry up. (c) - Homeostasis – process to keep internal environment stable. Electrolytes help nerves respond to stimuli - Electrolytes help nerves respond to stimuli - Movement of Na+ and K+ across the membranes of nerve cells changes the electrical charge across the membrane - This change in electrical charge carries the nerve impulse along the nerve cell Role of electrolytes in nerve function - Nerve stimuli prompt changes in membranes that allow an influx of Na in the nerve cell, causing the cell to become slightly less negatively charged, this is depolarization. When enough Na sodium enters the cell, an electrical impulse is generated along the membrane. After the impulse has been transmitted, the cell membrane returns to it’s normal state through the release of K to the outside of the cell. This is Repolarization. Functions of electrolytes - Electrolytes signal our muscles to contract - The movement of calcium (Ca2+) into a muscle cell stimulates the muscle to contract - The Ca2+ is pumped back out of the cell after the muscle contraction - When a muscle fiber is stimulated by an electrical signal, changes occur in the cell membrane that lead to an increased flow of calcium into the muscle from the extracellular space. The calcium provides the stimulus for muscle contraction. When the electrical signal is complete, the muscle relaxes as calcium is pumped out of the muscle cell.

Maintaining fluid balance - Fluid balance is maintained by different mechanisms prompting us to drink and retain fluid - The thirst mechanism occurs from a cluster of nerve cells that stimulate our desire to drink - However, the thirst mechanism is not always sufficient; the amount of fluids people drink may not be enough to achieve fluid balance - The hypothalamus triggers thirst (as well as hunger) and is triggered by: 1.) an increased concentration of salt in our blood, - 2.)a reduction in blood volume and blood pressure – due to profuse sweating, blood loss, vomiting, or diarrhea, or when fluid intake is just too low. - 3.) dryness of the mouth and throat. - When the hypothalamus detects change, it stimulates a release of a hormone that signals the kidneys to reduce urine flow and return more water to the blood stream. - Water lost from the body must be replaced - Water is lost through urine, sweat, exhalation, and feces - Water is gained through beverages, food, and metabolic reactions - Metabolic water contributes about 10-14% of the water the body needs Loss of water - Most water is lost through urine - The kidneys control how much water is reabsorbed; excess water is processed by the kidneys and excreted as urine - Insensible water is lost through the skin or through the lungs during exhalation - Lose < 1 L/day in normal conditions - Diuretics increase fluid loss via the urine - We can lose up to 2 L per hour when exercising at high intensity in hot and humid conditions just from insensible - Other ways we lose water: illness, traumatic injury (blood loss), exercise, dry environments (desert or plane), pregnancy, breastfeeding, diuretics

Water -

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Functions of water Essential for life Required for fluid and electrolyte balance and many metabolic reactions Recommended intake Varies with environment and activity level Intake and output - Amount and sources of water intake and output for a woman expending 2,500 kcal/day. Surface water comes from lakes, rivers, and reservoirs Groundwater comes from underground rock formations called aquifers “Hard water” is relatively high in calcium The U.S. Environmental Protection Agency (EPA) sets and monitors standards for public water systems and is responsible for regulation of bottled water What if you drink too much water? - Becoming overhydrated is rare - Can result in a dilution of sodium (hyponatremia) Not enough water - Dehydration - Infants and the elderly are especially vulnerable

Sodium - Fluid and electrolyte balance - Associated with blood pressure and pH balance in the body - Required for nerve impulse transmission - Assists in the transport of certain nutrients (e.g., glucose) into body cells - Recommended intake - 1.5 g/day is required - Less than 2.3 g/day is recommended - Sources of sodium - Salt, 1 tsp = ~2,300 mg Na - Processed foods are generally high in sodium - What if blood sodium levels become too high? - Hypernatremia: abnormally high blood sodium concentration - Can occur in patients with congestive heart failure or kidney disease - Results in high blood volume, edema, and high blood pressure - What if blood sodium levels become too low? - Hyponatremia: an abnormally low blood sodium level - Can result from prolonged vomiting, diarrhea, or sweating - Has been seen in marathon athletes who consume too much water and fail to

replace sodium Potassium - Functions of potassium - Fluid and electrolyte balance - Very important in muscle contractions and transmission of nerve impulses - High potassium intake helps to maintain a lower blood pressure - But not too high - Recommended intake - 4.7 g/day - Sources of potassium - Processed foods are usually low in potassium - Fresh fruit and vegetables and whole grains are good sources of potassium - A diet high in processed foods will increase your Na intake and decrease your K intake - What if blood potassium levels get too high? - Hyperkalemia: a high blood potassium level - Can occur in patients with kidney disease - Can alter normal heart rhythm, resulting in a heart attack - It’s role in cardiac muscle contraction, severe hyperkalemia can alter normal heart rhythm and can result in a heart attack and death - What if blood potassium levels are too low? - Hypokalemia: low blood potassium levels - Can be seen in patients with kidney disease or diabetic acidosis - Can occur when taking certain diuretic medications - Extreme dehydration, vomiting, diarrhea can all cause hypokalemia. - Alcoholics and those who abuse laxatives are also at risk. - Symptoms: confusion, loss of appetite, muscle weakness. - Some diuretics are K sparing. - Extreme cases result in fatal changes in the heart rate. - Alcoholics – reason is usually because of poor nutrition

Chloride

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Functions of chloride - Assists with maintaining fluid balance - Assists the immune system – helps kill bacteria - Component of HCl in the stomach Recommended intake - Minimum recommendation is 2.3 g/day Component of hydrochloric acid in the stomach which aids in digestion. Works with white blood cells during immune responses to help kill bacteria and assist in transmission of nerve impulses. What if you blood chloride levels are too high? - May lead to hypertension in salt-sensitive patients - No Dietary Reference Intake (DRI) has been set for chloride What if blood chloride levels are too low? - This is rare but can occur in people with eating disorders Our primary dietary source of chloride is salt.

Phosphorus - Functions of phosphorus - Most commonly found as phosphate (P042-) - The major intracellular negatively charged electrolyte - Required for fluid balance - Critical role in bone formation (85% of body’s phosphorus is found in bone) - Regulates biochemical pathways by activating or deactivating enzymes - Found in ATP, DNA, RNA - Adenosine triphosphate – phosphorus plays a key role in creating energy. - Recommended intake - Recommended Dietary Allowance (RDA) for phosphorus is 700 mg/day - Sources of phosphorus - Found widespread in many foods - Found in high amounts in foods that contain protein (e.g., meat, milk, eggs) - The average adult consumes twice the RDA. Phosphorus from animal sources is better absorbed than that from plant sources. - In beans, cereals, and nuts – phosphorus is in the form of phytic acid a plant storage form. We don’t produce enzymes that can break down phytic acid but we still absorb about 50% of phosphorus found in plant foods because of other food and the bacteria in our large intestine can break it down. - What if blood phosphorus levels are too high? - High blood levels of phosphorus can occur with kidney disease or when taking too many vitamin D supplements - Causes muscle spasms, convulsions -

What if blood phosphorus levels are too low? - Deficiencies of phosphorus are rare Fluid imbalance

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Serious health problems that can occur when fluid excretion exceeds intake include Dehydration Heat illnesses

Dehydration - Dehydration occurs when water loss exceeds water intake - Commonly due to heavy exercise or high environmental temperatures - Infants and the elderly are more at risk - Other common causes of dehydration include - Diarrhea Vomiting - Fever - Burns Poorly managed diabetes Abuse of diuretics or laxatives - Dehydration is classified in terms of percentage of weight loss that is exclusively due to the loss of fluids

Heat illness - Three common types of heat illnesses closely linked to dehydration are - ■ Heat cramps - ■ Heat exhaustion - ■ Heatstroke Heat cramps - Painful muscle cramps, usually in the abdomen, arms, or legs - Develop during vigorous activity sessions in the heat - Spasms can last seconds or minutes - Important to stop activity immediately, cool down, and rest; cramps may signal a more serious problem Heat exhaustion - Typically occurs from vigorous activity in heat - May develop after several days in high heat when fluids are inadequate - Symptoms include cramps, weakness, vomiting, dizziness, and elevated blood pressure and pulse - Must be treated promptly and aggressively to prevent heatstroke from developing

Heat stroke

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Heatstroke occurs if the body’s temperature regulation mechanisms fail Occurs in hot, humid environments Symptoms include rapid pulse, hot and dry skin, high body temperature, and weakness Has been fatal for athletes during exercise in extreme heat If it occurs, provide immediate cooling and rest, and contact emergency medical help quickly...