Lecture 2-4 Flashcards
Define kinetic energy
Energy a body possesses by being in motion
Define thermal energy
Energy that comes. From heat. Faster particles move= the more heat generated
How are thermal and kinetic energy related to molecular movement.
Diffusion means random molecular movement; therefore, the energy that causes diffusion is kinetic energy. Whenever something needs energy to go from low to high [ ], additional energy must be applied and can be in the form of thermal energy (active transport) p.46
Define diffusion
Movement of particles from high to low [ ]
Define osmosis
Movement of a solvent -water- from region of low [ ] to high [ ]across a semipermeable membrane.
How does diffusion and osmosis r/t semipermeable membrane?
Cell membrane is semipermeable membrane and it is what maintains the [ ] of either side of it. Therefore for there to be a [ ] gradient for which the process of diffusion or osmosis is to occur would really depend on the semipermeable membrane
How is osmotic pressure generated?
Water is continually trying to balance [ ] on either side of membrane. Ex; the L side compartment can never completely remove all water from r side. As pressure is building from the water moving from R to L side the water will begin to slow movement from R to L. Until max is reached then there will be some water pushed back to the R side d/t osmotic pressure
Difference between diffusion and facilitated diffusion:
Diffusion is simple movement from high to low [ ] w/o energy or transporter.
Facilitated is movement from high to low [ ] as well w/o energy but it does require a transporter.
Define active transport
A transporter w/ assistance of ATP input will be able to move particles against gradient (low to high [ ])
Difference btw primary and secondary active transport
Primary uses ATP /GTP and readily Req’s ATPases
Secondary energy is derived secondarily from [ ] differences of molecular/ionic substances created originally by primary active transport
Uniporters
Facilitated- down electrochemical gradient, uses stereospecificity, competitive, one substance at a time
Multiporters
Includes symporters and antiporters. Moves 2 or more particle simultaneously in one or both directions through membrane.
Uniporters /Multiporters r/t movement across membrane
Uniporters /Multiporters are transmembrane proteins that take part in electrochemical gradient by distributing these substances crating [ ]. Gradients on either side of membrane
Brush border [fig 4-15]
Transport of sodium ions through epithelial sheet. The brush border on luminal side of cell is permeable to sodium and water diffusing readily from lumen to interior of cell. However, the basal surface of the cell Req’s active transport into ECF of surrounding connective tissues and blood vessels. Creates high [ ] of Sodium ions in membrane at the Basolateral sides of the epithelial cells result in transport not only of sodium but water too.
How can body compartments be altered?
Diffusion: simple facilitated, and by active transport
DEfine excitable cell
Cells in which an AP can be induced. Ex: neuron, skeletal, cardiac, smooth muscle
What part of the neuron is capable of developing an AP?
DEndrites and axon conduct local potentials. Voltage-gated ion channels can generate an AP.
Characterize cell membrane w/o ion channels
Biphospholipid layer is generally only permeble to lipid soluble (hydrophobic-nonpolar substances). Hydrophilic substances are prohibited from passing the membrane.
Permeability of membranes to ions at rest:
Sodium and Ca++: low permeability at rest
Potassium: high at rest
Chloride: moderate at rest
Major types of ion channels present on cell membranes:
Voltage, ligand, and Modality- gated channels
Voltage-gated channels
Changes in voltage/charges
Ligand-gated channels
Binding of specific molecules to receptor
Modality-gated channels
Mechanical changes-differences in pressure
Nernst potential
Ion difference on either side of membrane that exactly opposes the net diffusion of a particular ion through membrane
E = 2.3 RT/F log Co / Ci
Assumptions of the Nernst equation:
1- can only be used for one ion at at time.
2- membrane must be completely permeable to the ion.
Diffusion potential
Ion [ ] difference on either side of a membrane
Equilibrium potential
Determined by [ ] and electrical forces. Where the electrical force driving Cl-ions L to R is = force pushing R to L
Electrical neutrality principle
The sum of the [ ] of cations w/in any compartment must be = the sum of the [ ] of anions—sol’n is electrically neutral
Donnan equilibrium
Specifies condition that must be met if 2 ions that can cross a membrane are simultaneously to be at equilibrium, electrical potential across the membrane must exactly balance the [ ].
3 characters of an AP
“All-or-none”, self-propagating, and non-decremental
All or none
It will either occur or not
Self-propagating
Each region of depolarization serves to generate AP’s on either side
Non-decremental
It does not decrease in strength
Types of ions channels
Slow leak and gated channels
When are Slow leak channels open?
Always open
Gated channels
Only open when certain conditions are met
2 types gated channels
Ligand: Req’s attachment of a chemical messenger
Voltage: Req’ a change in membrane potential
Sodium channels
Consists of 4 domains in cylindrical configuration w/ 6 hydrophobic transmembrane segments. S4 segment w/ in each domain has high + charge. Inactivation gate is asso. W/ hydrophilic linkage btw domains 3 and 4.
There are 2 gates. When both open=rapid depolarization
Potassium channels
Diameters are too small for hydrated K+ or Na+. There’s selectivity filter in channel by way of carbonyl groups. Slower kinetics than Na+ channels. This is primary mechanism for repolarization
Voltages asso. W/ propagation of AP
Resting: -90 mV (Na activation closed-inactivation open)[K channel closed]
Depolarization: -90 - +35 (sodium gates are open. Approx. -60)
Repolarization: +35 - 90 (sodium inactivation gate closes but activation is still open—–K channels slowly open
Hyperpolarization:
2 ways an axon can increase speed of conduction of AP
1-increasing diameter of axon:larger area for internal flow of current
2-increasing membrane resistance of the axon: insulation[myelin]-capacitor effect…essential b/c it is insulated there can be more charge d/t more area for the plate of the capacitor[ICF&ECF]
Define absolute refractory period
Period that 2nd AP CANNOT be elicited no matter how strong the stimulus
Define relative refractory period
A stronger than normal stimulus can cause an AP
Effect of changes in sodium/potassium ion [ ] in ECF on membrane potentials
Shows how significant balance of Extracellular ions is. Ex in class: Ca++ depleted cattle slowly infuse Ca++to correct value or it would die.
