NEURO- Excitable membrane Flashcards
What is main point for cell specialization and controlling its internal environment?
protein synthesis and role of the membrane, determining the transport elements that are in the membrane that are controlling the cellular environment
What determines if both substrates can enter the cell?
Selective permeability- controlled at the membrane via transport molecules w/in membrane
Factors Permeability, Area/Size (Diffusion= permeability x area), concentration diff
What type of diffusion does not require energy?
Simple- channel on B/L lipid membrane. some float within or ontop of membrane
How does glucose move through membrane?
need a transport molecule to bind to the substance -INsulin to move it across the membrane but if its diffusion, it doesn’t need to expend energy to do it
What is all forces at play in balance and at that point there will be no net diffusion b/c all gradients are balanced out?
Equilibrium. NOT equal concentrations. Movement of substrates will stop. electrostatic repulsion and concentration gradient are in balance
What are other forces that play in membrane equilibrium?
- electric- charge particles will move if no concentration gradient.
- Pressure
- Concentration
what is the electrical charge at which the system will be at equilibrium?
Nernst equation- he applied electrical charge to determine how much charge needed for a given concentration to oppose the diffuse. ONLY UNIVALENT ion, NOT Ca2+
If that membrane does not allow dissolved substances to move but water can, water will move to equilibrate the forces and the pressures
osmotic pressure-MUST have NON diffusible elements. Osmole
What is important for establishing the concentration gradient that we need to use to create that electric voltage we need across the membrane?
Na/Kase pump channel receptor protein. 1. Takes OUT 3 Na, 2. ATP phosphorylates confirmation changes 3. Na is expelled. 4 Pump 2K IN 5. Dephosyohlate structure changes 6. 2 K inside at initial state. So moving 3 Na+ out, and 2 K+ in – net positive charge outside and net negative charge inside
WHat are the active transport mechanism?
ATP to phosphorylate-(meaning of life) keeps substrate inside membrane
WHat is the imbalance of charges?
Potential energy- stagnate until flow. Membrane potential= voltage diff across membrane. NERVE-Neg 60 to Neg 90mV/K resting potential
If I apply a little bit more electrical current to the outside of the membrane, then ions will actually start to move into the cell against their concentration gradient
Reversal potential-electricity to apply to oppose the flux of K ions at a given concentration/ EMF
What considers concentration differences of the ions most responsible for the membrane potential. Considers permeability because ions can only contribute to membrane potential if the membrane allows it/if they can diffuse?
GHK equation
If membrane potential is more +, what is reversal potential?
Sodium, if open channels for NA, then its going to rush into the cell
When meeting threshold or the downstroke what is happening?
Threshold-massive opening of Na channels and the membrane potential is driven towards the reversal potential for Na-Depolarization+. Repolarization/Hyperpolariztion – K reversal potential
As long as these two resources are abundant a muscle can sustain a contraction as long as needed
Ca – inhibits blockade of cross bridges by moving troponin/tropomyosin off binding sites
ATP – binds to head of cross bridges causing “cocking” of cross bridge head.
Cl-inhibitory
In this type of summation, alteration of frequency of stimulation before depolarization results in an additive force to the previous contraction.
Temporal summation
In spatial summation these motor units fire first.
Small motor units – recruited first, easily excite, then larger motor units if small can’t do it alone.
Spatial summation – smooth contraction via off setting contraction of motor units
To sustain muscle contraction until oxidative phosphorylation kicks in, this protein is utilized for the production of ATP.
Creatine – one enzymatic step from ADP to ATP using creatine
Myelination of neuron, also known as this, prevents Na leakage and inhibits resistance of ions to flow.
Saltatory conduction
In voltage-gated ion channels this state in a Na channels happens during high voltage.
Inactivation state – Channel can not be used until it has reset to a closed state.
During this phase of an action potential depolarization can not occur.
Absolute refractory period
Relative refractory period = more depolarization (stimulation) required to elicit AP
A muscle that has a higher number of motor unit will have this.
Fine motor control, dexterity, or fine muscle movements
This term is the minimum voltage that the membrane potential has to reach to cause Na channels to open.
Threshold potential
