pH & Body Fluid Homeostasis Flashcards
Proton (H+) donors are called
Acids
Acids are
Substances containing hydrogen which dissociate in a solution (ie. they dissolved in body fluids and release H+)
Pyruvic acid and lactic acid are important for
Cellular respiration
4 physiologically important acids are:
-carbonic acid (H2CO3)
-phosphoric acid (H3PO4)
-Pyruvic acid (C3H4O3)
-lactic acid (C3H6O3)
Proton (H+) acceptors (ie. take hydrogen) are called
Bases
2 physiologically important bases are
-bicarbonate (HCO3-)
-biphosphate (HPO4 2-)
The acid-base balance is primarily concerned with these two ions:
-hydrogen (H+) = acid
-bicarbonate (HCO3-) = base
Bases are
Molecules capable of accepting a hydrogen ion (OH-)
Pure water always has
Equal numbers of H+ and OH- ions
pH (4)
-“power of hydrogen”
-specifies the acidity of a solution
-logarithmic scale
-inversely expresses hydrogen ion concentration in solution
The smaller the pH number,
The more H+ present = acid
Venous blood is more __ than arterial blood
Acidic
Normal blood pH is
7.35-7.45
Alkalosis is when pH is
> 7.45
pH compatible with life is
6.8-8.0
A pH of <7.35 will result in
Acidosis
A volatile acid is
An acid being produced when CO2 is involved
Carbonic Anhydrase reaction produces
-H+
-bicarbonate
A major source of H+ ions is through
Aerobic respiration
Aerobic respiration formula is
Glucose + oxygen —> carbon dioxide + water + energy (ATP)
3 mechanisms that maintain pH of extracellular fluid are
-chemical buffers in the blood (reacts within seconds)
-respiratory regulation (reacts within minutes)
-renal regulation (reacts within hours)
Breathing is controlled by the
Autonomic nervous system
As breathing increases, (2)
-blood CO2 levels decrease
-blood becomes more basic (increase in pH)
Respiratory Regulation (3)
-reacts to pH levels rapidly (within minutes)
-adjusts speed (respiratory frequency) and depth (tidal volume) of breathing to regulate pH
-chemoreceptors in the medulla of the brain sense pH changes and will vary the rate/depth of breathing
As breathing decreases, (2)
-blood CO2 levels increase
-blood becomes more acidic (pH decreases)
As CO2 increases, the body becomes more
Acidic
Tidal volume (Tv) is
Depth of breathing
Respiratory rate is the
Breathing frequency/speed (Rf)
Renal Regulation (2)
-reacts to pH levels slowly (hours to days)
-kidneys can alter the amount of acid or base excreted, but it takes several days
Excess acid is excreted by the ___ as ___
Kidneys; Ammonia
The kidneys can indirectly reabsorb ___ to combat ___
Bicarbonate (base); Acidosis
As CO2 and H+ increase, pH will
Decrease (become more acidic)(
pH buffers work to
Maintain changes in the pH of a solution by binding free acid or base
H+ is buffered by
Haemoglobin
As CO2 and H+ decrease, the pH will
Increase (become more basic)
Plasma has ___ concentrations of CO2
High
Chloride shift ensures
Electrical neutrality
Bicarbonate reacts with hydrogen ions to form
-CO2
-water
Low CO2 concentration levels are found in the
Pulmonary circulation
Two major disturbances in the acid-base balance are
-acidosis (acidaemia)
-alkalosis (alkalaemia)
pH changes can have dramatic effects on normal cell function, such as (3)
-changes in excitability of nerve and muscle cells
-enzyme activity
-K+ levels
A pH of <7.35 will result in
Acidosis
A decrease in pH (4)
-means an increase in H+ ions
-more acidic
-depresses the CNS
-can lead to lose of consciousness
A pH of >7.45 will result in
Alkalosis
An increase in pH (3)
-more basic
-can cause over-excitability
-tingling sensations, nervousness, muscle twitches
Acidosis/Alkalosis can arise from two ways:
-Respiratory (ie. faulty breathing)
-Metabolic (caused by vomiting, diarrhoea,ineffective bicarbonate buffering, kidney disorders, or ingestion of acid/base)
Parietal cells secrete ___ into the ___
Hydrogen ions; lumen of stomach
In pancreatic cells, the direction of ion movement is reversed, which means
-H+ ions are secreted into the blood
-bicarbonate ions diffuse into pancreatic fluid
Metabolic acidosis (3)
-caused by severe diarrhoea or prolonged deep vomiting (from duodenum)
-bicarbonate is lost from the body rather than reabsorbed, lowering the pH
-less bicarbonate is available for buffering H+
Metabolic Alkalosis (4)
-results from vomiting
-excess loss of H+ through hydrochloric acid (HCl)
-bicarbonate is not neutralized in the plasma
-loss of HCl increases plasma bicarbonate resulting in an increase in blood pH
The body responds to alkalosis to lower the pH by: (2)
-retain CO2 by decreasing the breathing rate
-kidneys increase the retention of H+
Normal pH in the present of an acid-base disorder means
It is a mixed respiratory AND metabolic acid-base disroder
What is used to measure pH
Arterial blood gas sample
Partial pressure of CO2 is
40 mmHg
Bicarbonate levels in the blood should be
24 meq/L
A high PCO2 results in
Respiratory Acidosis
A high bicarbonate measurement results in
Metabolic Alkalosis
A low PCO2 measurement results in
Respiratory Alkalosis
A low bicarbonate measurement results in
Metabolic Acidosis
Respiratory acidosis/alkalosis is determined by
Partial pressure of CO2 (high=acidosis, low=alkalosis)
Metabolic acidosis/alkalosis is determined by
Bicarbonate levels in the blood (low=acidosis, high=alkalosis)
Body compartments are made of (3)
-intracellular fluid (~40%)
-extracellular fluid (~20%)
-water (60%)
Fluid within the cells is called
Intracellular fluid (ICF)
Fluid within vessels is called
Intravascular fluid (plasma)
Extracellular fluid (ECF) is made of two parts
-plasma (5%)
-interstitial fluid (15%)
About __% of the body is water while 40% is ___
60; dry matter
Fluid outside the cells is called
Extracellular fluid (ECF)
40% of body weight is
Intracellular fluid
20% of body weight is
Extracellular fluid (5%=plasma, 15%=interstitial fluid)
In dogs, total blood volume is
80-90mL/kg
In cats, total blood volume is
60-70mL/kg
The lipid bilayer makes up the
Cell membrane
A semipermeable membrane means
Some things can cross freely (water, gasses, urea) while others need assistance via facilitated diffusion or active transport
Water is in ____, which means it can ____ across the membrane
-osmotic equilibrium
-move freely
Ions and most solutes are in ___ which establishes ___
Chemical disequilibrium; resting membrane potential
Colloids are
Large molecules such as proteins and starches
There amount of pressure needed to prevent water from going back through the semipermeable membrane is called
Osmotic Pressure
Osmosis is the
Spontaneous movement of water through the semipermeable membrane
Fluids containing electrolytes and small molecules are called
Crystalloids
Crystalloids (2)
-fluids with electrolytes and small molecules
-can move between all 3 compartments
Fluids with large molecules are called
Colloids
Colloids stay in the ___, generating ___
Intravascular space; colloid osmotic pressure
Pros and Cons of Crystalloids
Pros:
-cheap
-accessible
Cons:
-short half life
-larger volume required
Pros and Cons of Colloids
Pros:
-longer half life
-smaller volume required
Cons:
-expensive
-risk of allergic reaction to the proteins
Homeostasis is
Maintaining a relatively constant internal environment for optimal function
Negative Feedback Pathways (2)
-used to maintain a constant value (ie. “set point”)
-corrective mechanisms to increase/decrease from the set point detected
6 ways water loss occurs daily
-urine
-sweat
-faeces
-milk production
-egg production
-respiration
6 factors that influence the input/output of water
-age
-sex
-obesity
-climate
-habits
-level of physical activity
Osmolality is the
Amount of solutes in the solvent (mass)
Osmolarity is
Per volume of a solution, measured in osmol/L
Antidiuretic hormone (vasopressin) controls
The amount of water the body retains from the kidneys
Active regulation of osmotic pressure in the body is done through
Osmoregulation
Osmolarity is ___ and must be regulated to ___
-volume of solution (osmol/L)
-prevent loss of water from cells
Osmoregulation (3)
-maintains fluid balance and electrolyte concentrations
-kidneys play a large role
-controlled by hypothalamus containing osmoreceptor cells
Osmoreceptor cells (2)
-contained in the Hypothalamus
-detect changes in osmolarity of blood passing through the brain
The hypothalamus controls __ and produces ___
-thirst
-vasopressin (antidiuretic hormone)
A dog that weighs 20kg will have how much intracellular fluid?
8 L
(Intracellular fluid = 40% of body weight. 20kg X 0.4 = 8)
When a cell is immersed in a hypertonic solution, the cell volume___ and the cell ___
Decreases; shrinks
When a solution inside the cell has a higher concentration,
Water enters the cell and bursts it
Hypotonic is when
Solution inside the cell has a higher concentration that outside the cell
When a solution outside the cell has a higher concentration,
Water leaves the cell and the cell shrinks
A hypertonic solution is when
Solution outside the cell has a higher concentration
A hypertonic solution is when
Solution outside the cell has a higher concentration
