Intro to Physiology Review Flashcards
What is physiology?
study of the function of body parts
- how all the body parts work and carry out their life-sustinaining activities
Biological membranes are made up of…
a. lipids (phospholipids, cholesterol, and glycolipids)
b. proteins
Cell Membrane Structure
lipids of cell membrane form a phospholipid bilayer with the hydrophobic (water insoluble) ends of each lipid molecule face the interior of the membrane and the hydrophilic (water soluble) ends face outwards
Integral membrane Proteins
they are embedded in the phospholipid bilayer of cell membrane and cannot be removed without disrupting it. They include channels, pumps, carriers and receptors
Peripheral Proteins
they bind to the hydrophilic polar heads of the lipids or the integral proteins
Passive Transport
ions being able to fuse across the membrane without any energy expenditure of the cell (ATP use)
1. Diffusion (simple or facilitated)
2. Osmosis
Active Transport
ions have to be transported with the help of channels that require ATP expenditure to work
1. Primary Active Transport
2. Secondary Active Transport
Vesicular Traffic & Plasma Membrane
travel of things in and out of the cell through membrane bound things
1. endocytosis
2. exocytosis
Simple Diffusion
net movement of molecules (or ions) from a region of their high concentration to a region of their lower concentration
- occurs through the cell membrane by two pathways:
a. interstices of the lipid bilayer
b. through protein channels
- no interactions with carrier proteins
ex: O2, CO2
“Gating of Channels”
protein channels can be gated and these are regulated by:
a. electrical signals (voltage-gated)
b. chemicals (ligand-gated)
Factors Affecting Rate of Simple Diffusion
- concentration gradient across membrane
- surface area of membrane
- solubility in the membrane or permeability (the more soluble the substance, the faster it will diffuse)
- thickness of membrane (thicker membrane = slower rate of diffusion)
- molecular weight of ion (not directly clinically important)
Facilitated/Carrier Diffusion
movement of substances in combination with carrier protein without utilization of energy
- diffusion approches a maximum which is dependent on the saturation of the carrier proteins
- ex: transport of glucose and most amino acids
Osmosis
diffusion of water across a semipermeable membrane or selectively permeable membrane
- water will diffuse from a region of higher water concentration to a. region of lower water concentration
Isotonic Medium
no movement of fluid from ICF or ECF
Hypertonic Solution
higher concentration of things outside cell and lower concentration of water so water moves out of cell into solution to balance it and therefore shrinking the cell
Hypotonic Solution
lower concentration of things outside the cell than inside and higher concentration of water outside so fluid moves from ECF to ICF, expanding the cell and in some instances, bursting it
Active Transport
net movement against a concentration gradient and requires energy to do so (ATP)
Primary Active Transport
ATP is consumed directly by the transporting protein
- ex: Na/K-ATPase pump, calcium pump
Secondary Active Transport
depends directly on ATP as a source of energy
- in co-transport, molecules move in the same direction
- for ex, movement of Na+ and glucose in renal tubules and gut
- in counter transport, molecules move in opposite direction for example, Na+ and Ca2+ in heart and muscle
Characteristics of All Protein-Mediated Transport
a. Rate of Transport: transport faster than it would be by diffusion
b. Saturation Kinetics: transport rate increases directly with the rise of concentration, but once the transporters become saturated, transport rate is maximal
c. Chemical Specificity: substance must have a certain chemical structure that matches with the transporter
d. Competition for Carrier: substance of similar chemical structure may compete for the same transporter
Endocytosis
the movement of macromolecules from outside the cell to inside the cell by active invagination of plasma membrane
Phagocytosis
process by which solid bits of material are engulfed by cells (type of endocytosis)
Pinocytosis
uptake of molecules in the solution
Exocytosis
process by which macromolecules are packed in secretory vesicles and extruded from the cell
- requires both calcium and energy
Constitutive Secretion
vesicles are not coated with clathrin and are continuously fusing with the cell membrane and being released
ex: release of proteins such as albumin
Regulated Exocytosis
vesicles are coated with clathrin, and a signal is required before the vesicle will fuse with the membrane
Intracellular Fluid (ICF)
fluid inside cells
- takes up approx 2/3 of total body water
Extracellular Fluid (ECF)
fluid outside/around cells
- takes up approx 1/3 of total body water
Interstitial Fluid (ISF)
outside cell and in between cells specifically
- approx 2/3 of ECF
Vascular Fluid (VF)
type of ECF and is a mix of plasma + RBC, flows through veins, capillaries, etc.
- approx 1/3 of ECF
ICF Components
- K+
- Mg
- PO4
- Protein
ECF Components
- Na+
- Ca2+
- Cl2-
- HCO3-
- O2, CO2, glucose, fatty acids, amino acids
What happens in the case of loss of isotonic fluid?
the volume of the ECF and VF is reduced but the osmolarity does NOT change as isotonic fluid was lost and so osmolarity is NOT affected
- since ECF osmolarity is unchanged, there is no change to ICF volume
What happens in the case of a loss of Hypotonic fluid (sweating, hypotonic urine)?
Loss of hypotonic fluid from ECF makes ECF hypertonic so ICF fluid will move to ECF to balance it out, shrinking the cells
What happens if you ingest salt tablets?
Salt tablets make ECF hypertonic so fluid goes from ICF to ECF
Isotonic Fluid gain will cause:
Increase in ECF volume but no change in osmolarity and no effect on ICF osmolarity or volume
Hypotonic fluid gain will cause:
Increase in ICF osmolarity as ECF becomes hypotonic, so then fluid flows into the ICF, increasing the osmolarity
Action Potential
a short lasting, reversible change in electrical potential occurring on the surface of an excitable cell, especially of a nerve or a muscle cell, that occurs when it is stimulated, resulting in the transmission of an electrical impulse
Resting Membrane Potential
-90 mv (in some cells) but USUALLY (-70mv)
Depolarization
+30mv
Threshold Potential
USUALLY -55mv
Voltage Changes During Action Potential
1st step: Depolarization: voltage gated Na channels open and there is influx of Na ions causing the resting membrane (-70mv usually) potential to become more positive
2nd step: Repolarization: voltage gated K channels open and there is efflux of K ions causing the membrane potential to return back to its resting state
- all through cell there are Na+K+ pumps which keep pumping in K and Na out of the cell at a ratio of 2:3
Ungated Potassium Channels
these channels are always open, and unless the membrane potential reaches the potassium equilibrium potential
- a potassium equilibrium is maintained through these Channels
Voltage-Gated Sodium Channel
these channels are closed under resting conditions. membrane stimulus/signal causes these channels to quickly open and close and cause the depolarization phase. once they close, they will not respond to a second stimulus until the cell almost completely repolarizes
Voltage-Gated Potassium Channels
these channels are closed under resting conditions. they require a stimulis/signal to open and are responsible for…slide cuts off
Absolute Refractory Period
the period during which no matter how strong the stimulus, it cannot induce a second action potential
- this period is due to voltage inactivation of sodium channels
Relative Refractory Period
that period during which a greater than normal stimulus is required to induce a second action potential
Cell Diameter
the greater the cell diameter, the greater the conduction velocity
