C11 9-11 Flashcards
Energy
capacity to do work
potential energy
stored energy - a concentration or electrical gradient across the plasma membrane
kinetic energy
energy of motion - movement of ions from great to lesser concentration or movement ions (charged particles) to ions of opposite charge
Ions
charged particles - distribution of charged particles are key to nervous function, opposite charges attract and it takes energy to separate them
Cations
positively charges particles - Na+, K+, Ca2+
Anions
negatively charged particle - Cl-, most proteins, ATP phosphate
Voltage
measure of the amount of difference in electrical charge between two points call the potential difference
Current
flow of electrical charge or movement of charged particles from point to point.
Dependent on voltage and resistance.
Current = voltage/resistance
Apply the concepts of voltage, current and resistance to neurons.
Voltage = the difference between charge potential on the inside and outside of the plasma membrane. Current = generated when either + or - charged ions cross the plasma membrane. Resistance = The plasma membrane offers resistance, and the resistance can be altered by opening and closing ion channels
Pump
- Moves sustances against a concentration gradient. -Requires energy.
- Na+/K+ pump, Ca2+ pump
Channel
-Moves substances down a concentration gradient. -Channel types: Leakage/nongated, chemically gated/Ligand, voltage gated, mechanically gated.
Leakage/nongated channel
Always open, Na+ & K+ channels
Chemically gated (Ligand) channel
Open when the appropriate chemical/neurotransmitter/neuromodulator/molecule binds. K+ Na+ Cl- Ca2+
Voltage-gated channel
Open in response to a change in membrane potential. Usually in one of two states: open or closed. Na+ K+ Ca2+
Why are voltage gated sodium channels unique?
They have two gates - an inactivation gate and an activation gate. Also, they exhibit 3 states: resting, activation, inactivation.
Mechanically gated channel
Open when a membrane receptor is physically deformed; found in sensory neurons and respond to things like light or pressure.
Resting state - voltage gated sodium channel
Inactivation gate open, activation gate closed
Activation state - voltage gated sodium channel
Both inactivation and activation gate open
Inactivation state - voltage gated sodium channel
Activation gate open, inactivation gate temporarily closed.
What type of pumps and channels in the entire plasma membrane of a neuron?
Leak channels: Na+ and K+
Pumps: Na+/K+
What type of pumps and channels in receptive region (dendrites/cell body)?
Chemical (ligand) channels: Cation, K+, Cl-
Some voltage gated channels.
What type of pumps and channels in the initial segment (axon hillock)?
Voltage gated Na+ and K+ channels.
What type of pumps and channels in the conductive segment (length of axon/axon terminals)?
Voltage gated Na+ and K+ channels.
What type of pumps and channels in the transmissive or secretory segment (synaptic knobs)?
Voltage gated Ca2+ channels, Ca2+ pumps.
Electrical gradient
Difference in electrical charge between two areas
Chemical gradient
Unequal distribution of a substance
How is RMP established in a neuron?
RMP is a consequence of differences in K+/Na+ concentrations and plasma membrane permeability to ions.
K+ diffuses out of neuron because of chemical gradient, but stops diffusing out because it is pulled back by the electrical gradient. (A-) (-90mV)
Na+ diffuses in because of the electrical and chemical gradient . (Changes to -70mV)
More K+ leak channels than Na+.
Sod-Pot pump plays a small role in establishing
How is RMP maintained in a neuron?
Maintenance of RMP is done by Na+/K+ ATPase pump. Continually establishes gradients for both Na+ and K+. 3 Na+ out to 2 K+ in
Language of the NS
Graded potentials, Action potentials, Neurotransmitters
What contributes to RMP?
Unequal distribution of charge, membrane permeability
Resting membrane potential
The voltage that exists across the plasma membrane during the resting state of an excitable cell.
What substances are found inside the neuron?
Negative phosphate ions found in ATP
Negatively charged proteins
K+
What substances are found in interstitial fluid?
Na+
Cl- (chloride)
