Physiology Flashcards
Homeostasis
The state of physiological equilibrium and the processes involved maintain it
It involves control pathways that integrate sensory (input) and effector (output) information in order to respond to a challenge or to remain in a physiological steady state
Physiological steady state
A steady internal, physical, and chemical balance within the different cellular components of the body
Thermoregulation
The homeostatic process by which our body regulates its core temperature
Negative feedback
When some variable triggers a counteracting response in order to come back to some set point (to achieve homeostasis)
Positive feedback
When instead of getting a counteracting response to some variable you instead intensify the variable
Osmosis
The process by which water flows across a semi-permeable membrane down its concentration gradient
Hypertonic
A solution with a higher concentration of solutes than the cell it is being compared to; causes water to flow out of the cell and the cell shrinks
E.g. saltwater
Hypotonic
A solution with a lower concentration of solutes than the cell. It is being compared to; causes water to move into the cell which swells and possibly bursts
E.g. distilled water
Isotonic Solution
When the solution has the same concentration of solutes as the cells it is being compared to; results in no net movement of water across the cell membrane
E.g. normal saline
Water Potential ψ
The measurement of potential energy and water, considering both solute potential and pressure potential
Water Potential formula
Ψ = Ψp + Ψs
Water potential = pressure potential (lowering pressure lowers pressure potential) + solute potential (adding solute lowers solution potential)
Water travels to the lower water potential
Tonicity
The effective osmolarity and is equal to the sum of the concentrations of the solutes which have the capacity to exert an osmotic force across the membrane (i.e. it depends on the concentration of impermeant solutes)
Total body water
The total amount of fluid or water within one body; correlates inversely with body fat
60% for men on average
55% for women on average (usually due to a higher percentage of adipose tissue)
Extracellular fluid volume
Fluid outside of cells which comprises about 1/3 of the body’s total body fluid
Intracellular fluid volume
Fluid found inside cells which comprises about 2/3 of the body’s total body fluid
Plasma volume
Fluid in circulation which comprises about 20% of the ECF volume
Interstitial fluid volume
The fluid between cells which comprises about 80% of the total ECF volume
Concentrations of the main electrolytes within extracellular spaces
Sodium 145 mmol/L (main ECF cation) Potassium 4 mmol/L Calcium 2.5 mmol/L Chloride 115 mmol/L (main ECF anion) Bicarbonate 28 mmol/L
Sodium potassium pumps
Transports three sodium molecules out of the intracellular space and in exchange, moves to potassium molecules into the intracellular space
Requires ATP
Main electrolyte concentrations within intracellular fluid
Sodium 12 mmol/L Potassium 155 mmol/L (main ICF cation) Calcium <0.5 mmol/L Chloride 4 mmol/L Phosphorus 105 mmol/L (main ICF anion)
Electrolyte concentration comparison between ECF and ICF
ECF/ICF (mmol/L)
Na+ 145/12
K+ 4/155
Ca²+ 2.5/<0.5
Cl- 115/4
Interstitial space
The fluid that bathes the outside of the cells, and through which substances pass when traveling from plasma to intracellular spaces and vice versa
Hypovolemic hypernatremia
Decreased plasma volume and increased plasma sodium concentration which is caused by fluid loss
Ouabain
A drug that blocks the NA+/K+ ATPase pump.
This causes cells to swell due to the larger hydration shell for sodium (6-8 water molecules/Na molecules than for potassium (3-5)