Principles of Physiology II 8.16 Flashcards
Metabolic Clearance Rate
- Substances (like hormones) are “cleared” (metabolized) from the blood.
– Rate at which this occurs is called the metabolic clearance rate (MCR).
– The higher the MCR, the faster the material is removed from the blood.
Half Life
Half-life (t1/2) is the time it takes for half of a substance to disappear from the plasma.
Relationship between MCR and half-life
High MCR = short half-life
Factors that influence half-life
- Chemical class.
- Size
- Plasma protein binding
- Renal handling
Simple Diffusion
(Passive - downstream): Rate of movement proportional to concentration difference and permeability.
Facilitated Diffusion
(Passive - downstream): Rate of movement proportional to concentration difference and permeability.
Active Transport
“Pumps” can move substances “upstream” against a concentration gradient.
Ion Channels
Ions are molecules or atoms that are positively or negatively charged. Ion channels create tiny openings in the membrane. They only allow specific ions to pass through (selectivity).
Sodium ATP-ase
Pump that pushes 3 Na into its high gradient (extracellular), and pushes 2 K+ into its high gradient (cellular)
Osmolarity
Total (osmotically active) solute concentration (Osm/Liter of liquid)
Osmolality
Total (osmotically active) solute concentration (Osm/Kg of water). Used in clinical context.
Oncotic Pressure
Form of osmotic pressure exerted by proteins, notably albumin, in a blood vessel’s plasma (blood/liquid) that usually tends to pull water into the circulatory system.
Osmosis
a process by which molecules of a solvent (typically water) tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one, thus equalizing the concentrations on each side of the membrane.
Hematocrit
Ration of RBCs over total blood volume
Cardinal rule of free molecules (oxygen) in plasma
It is the “free” oxygen that can diffuse into the tissues and exert a biological effect in the cells. O2 must dissociate from Hb in the tissues.
IT IS THE FREE (biologically-active) OXYGEN THAT IS HIGHLY REGULATED BY HOMEOSTASIS. (The Hb concentration is also regulated but much more slowly.)
Compliance
Compliance is the total volume that can be stored in a container for each unit of pressure.
• Change in volume divided by a change in pressure.
• Gives an idea of the “stiffness” or “distensibility” of a compartment
High compliance is “floppy”
Low compliance is “stiff”
Compliance in veins vs arteries
Veins - high
Arteries - low
Surface Tension
The intermolecular attraction at the surface of a liquid in contact with air…..tending to pull the molecules of the liquid inward from the surface
Role of surfactant in lungs
– Lowers surface tension of air water interface
overall (like a detergent)
– Other unique properties that stabilize alveolar volume that you will learn later in the course.
Surfactant in premature infants
Babies born prematurely have inadequate surfactant in their lungs.
– Their lung surface tension is very high.
– The lungs easily collapse as a result and take
an enormous amount of energy to fill with air.
Series vs. Parallel vessels
Series increases resistance
Parallel decreases resistance
(hence decrease in BP in pregnancy, parallel vessels from placenta)
Gluconeogenesis
Generation of glucose from non- carbohydrate carbon substrates such as lactate, glycerol, and glucogenic amino acids. Liver major site.
Glycogenolysis
is the breakdown of stored glycogen (n) to glucose-6-phosphate and glycogen (n-1).
Lypolysis
the breakdown of fats and other lipids by hydrolysis to release fatty acids
