Chapter 27 Flashcards
Body fluid
Consists of water and dissolved solute constitutes between 55 and 60% of total body mass
What are the parts of extra cellular fluid?
80% is interstitial fluid and 20% is blood plasma
What are the two general barriers that separate intracellular fluid, interstitial fluid and blood plasma?
Plasma membrane and blood vessel walls
Thirst center
Found in the hypothalamus governs the urge to drink
What’s the main factor that determines body fluid volume?
Urinary salt (NaCl) loss
What’s the main factor that determines body fluid osmolarity?
The extent of urinary water loss
What is antidiuretic hormone also known as?
Vasopressin
What are the two most important hormones that regulate the extent of renal sodium reabsorption and thus how much is lost in the urine?
Aldosterone and atrial natriuretic peptide
Aldosterone
Increases sodium reabsorption in the late distal tubules and collecting ducts of the kidneys which relieves the sodium deficiency in the plasma
Occurs after a decrease in blood pressure
Atrial natriuretic peptide
Occurs with an increase in blood volume
Stretching of the atria of the heart promotes the release
Promotes natriuesis; elevated excretion of sodium into the urine
What can increase the osmolarity of extra cellular fluid?
A salty meal
A decrease in the osmolarity of extra cellular fluid can occur from what?
Drinking a large volume of water
Water intoxication
A state in which excessive body water causes cells to swell dangerously
What are the four general functions in the body when electrolytes dissolve and dissociate?
- Because they are largely confined to particular fluid compartments then non-electrolytes certain ions help control the osmosis of water between fluid compartments
- Ions help maintain the acid base balance required for normal cellular activities
- Ions carry electrical current which allows production of action potentials and graded potential’s
- Several ions serve as co-factors needed for optimal activity of enzymes
Sodium
Most abundant ion in extracellular fluid
Accounts for half of the osmolarity an extra cellular fluid
Necessary for generation and conduction of action potentials in neurons and muscle fibres
Kidneys excrete and conserve sodium as necessary
Sodium is controlled in the blood by aldosterone, antidiuretic hormone, and atrial natriuretic peptide
Chloride
Most prevailant anion in extra cellular fluid
Moves easily between extra cellular fluid and intracellular fluid because most plasma membranes contain many chloride leakage channels and Antiporters
Helps balance the level of an ions in different fluid compartments
ADH helps regulate chloride balance through the urinary system
Processes that increase or decrease renal absorption of sodium ions also affects direction of chloride ions
Potassium
Most abundant cation in intracellular fluid
Key role in establishing the resting membrane potential and then repolarization phase of action potentials in neurons and muscle fibres
When potassium moves into or out of cells it is often exchange for hydrogen and thereby helps regulate the pH of body fluids
Increase potassium causes more aldosterone secreted into the blood which stimulates principal cells of the renal collecting duct to secrete more potassium through the urine
Needed in repolarization phase of action potentials
Bicarbonate
Second most prevailant extra cellular anions
Concentration increases when blood flows through systemic capillaries because carbon dioxide released by metabolically active cells combines with water to form carbonic acid
When it flows through pulmonary capillaries concentration’s decrease because carbon dioxide is exhaled
Calcium
Stored in bone and is the most abundant mineral in the body
Please important rules in blood clotting, neurotransmitter release, maintenance of muscle tone, and excitability of nervous and muscle tissue
Main regulators are parathyroid hormone and calcitonin
Phosphate
85% of phosphate in adult his present is calcium phosphate salts which is structural components of bones and teeth
Governed by parathyroid hormone and calcitriol
Magnesium
54% of the total body magnesium is part of bone matrix is magnesium salt the remaining 46% occurs is magnesium ions in ICF
The removal of hydrogen from body fluids and it subsequent elimination from the body depends on what three major mechanisms?
- Buffer systems
- exhalation of carbon dioxide
- kidney excretion of hydrogen
Buffer systems
Consist of a weak acid and the salt of that I said which functions as a weak base and prevent rapid drastic changes in pH of body fluids by converting strong acids and bases into weak acids and bases
Protein buffer system
Most abundant buffer in intracellular fluid and blood plasma
Proteins are composed of amino acids organic molecules that contain at least one carboxyl group and at least one amino group which function as components of the protein buffer system
Carbonic acid bicarbonate buffer system
Bicarbonate ion acts as a weak base and carbonic acid acts as weak acid
Doesn’t protect against respiratory problems
Phosphate buffer system
Is it important regulator of pH in the cytosol
can also buffer acids in urine
One way that the kidneys excrete hydrogen to control blood pH
Volatile acid
Because H2CO3 can be eliminated by exhaling CO2 it is a volatile acid
Nonvolatile acids
Metabolic reactions that produce acid such as sulphuric acid and is excreted through the urine
Acidosis
Condition in which blood pH below 7.35
Causes depression of the central nervous system through depression of the synaptic transmission
Can cause individuals to become disoriented, comatose, and die
Alkalosis
Condition in which blood pH is higher than 7.45
Causes overexcitability in both the central nervous system and peripheral nerves
Neurons conduct impulses repetitively even when not stimulated resulting in nervousness, muscle spasms, convulsions, and death
Respiratory compensation
Occurs within minutes and reaches its maximum within hours
Renal compensation
Begins in minutes but it can take days to reach maximum effectiveness
Respiratory acidosis
Abnormally high PCO2 In systemic arterial blood
In adequate exhalation of CO2 causes the blood pH to drop
Conditions such as emphysema, pulmonary edema, injury to respiratory centre of the medulla, airway obstruction, or disorders of muscles involved and breathing
Reversed by exhalation of CO2
Respiratory alkalosis
Systemic arterial blood PCO to falls below 35 mmHg
Cause of drop in PCO to and resulting increase in pH is hyperventilation
Conditions like oxygen deficiency due to high altitude or pulmonary disease, cerebrovascular accident, or severe anxiety
Can be treated by breathing through a paper bag
Metabolic acidosis
The systemic arterial blood HCO3 levels drop below 22mEQ per litre
Caused by loss of bicarbonate like in diarrhea or renal disfunction
accumulation of an acid other than carbonic acid such as with ketosis
failure of the kidneys to excrete hydrogen from the metabolism of dietary proteins
Metabolic alkalosis
Systemic arterial blood bicarbonate concentration is above 26mEq per litre
A non respiratory loss of acid or excessive intake of alkaline drugs causes a blood pH to increase above 7.45
