NEURO- Excitable membrane

Question 1

What is main point for cell specialization and controlling its internal environment?

Answer 1

protein synthesis and role of the membrane, determining the transport elements that are in the membrane that are controlling the cellular environment

Question 2

What determines if both substrates can enter the cell?

Answer 2

Selective permeability- controlled at the membrane via transport molecules w/in membrane
Factors Permeability, Area/Size (Diffusion= permeability x area), concentration diff

Question 3

What type of diffusion does not require energy?

Answer 3

Simple- channel on B/L lipid membrane. some float within or ontop of membrane

Question 4

How does glucose move through membrane?

Answer 4

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

Question 5

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?

Answer 5

Equilibrium. NOT equal concentrations. Movement of substrates will stop. electrostatic repulsion and concentration gradient are in balance

Question 6

What are other forces that play in membrane equilibrium?

Answer 6

1. electric- charge particles will move if no concentration gradient.
2. Pressure
3. Concentration

Question 7

what is the electrical charge at which the system will be at equilibrium?

Answer 7

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+

Question 8

If that membrane does not allow dissolved substances to move but water can, water will move to equilibrate the forces and the pressures

Answer 8

osmotic pressure-MUST have NON diffusible elements. Osmole

Question 9

What is important for establishing the concentration gradient that we need to use to create that electric voltage we need across the membrane?

Answer 9

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

Question 10

WHat are the active transport mechanism?

Answer 10

ATP to phosphorylate-(meaning of life) keeps substrate inside membrane

Question 11

WHat is the imbalance of charges?

Answer 11

Potential energy- stagnate until flow. Membrane potential= voltage diff across membrane. NERVE-Neg 60 to Neg 90mV/K resting potential

Question 12

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

Answer 12

Reversal potential-electricity to apply to oppose the flux of K ions at a given concentration/ EMF

Question 13

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?

Answer 13

GHK equation

Question 14

If membrane potential is more +, what is reversal potential?

Answer 14

Sodium, if open channels for NA, then its going to rush into the cell

Question 15

When meeting threshold or the downstroke what is happening?

Answer 15

Threshold-massive opening of Na channels and the membrane potential is driven towards the reversal potential for Na-Depolarization+. Repolarization/Hyperpolariztion – K reversal potential

Question 16

As long as these two resources are abundant a muscle can sustain a contraction as long as needed

Answer 16

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

Question 17

In this type of summation, alteration of frequency of stimulation before depolarization results in an additive force to the previous contraction.

Answer 17

Temporal summation

Question 18

In spatial summation these motor units fire first.

Answer 18

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

Question 19

To sustain muscle contraction until oxidative phosphorylation kicks in, this protein is utilized for the production of ATP.

Answer 19

Creatine – one enzymatic step from ADP to ATP using creatine

Question 20

Myelination of neuron, also known as this, prevents Na leakage and inhibits resistance of ions to flow.

Answer 20

Saltatory conduction

Question 21

In voltage-gated ion channels this state in a Na channels happens during high voltage.

Answer 21

Inactivation state – Channel can not be used until it has reset to a closed state.

Question 22

During this phase of an action potential depolarization can not occur.

Answer 22

Absolute refractory period

Relative refractory period = more depolarization (stimulation) required to elicit AP

Question 23

A muscle that has a higher number of motor unit will have this.

Answer 23

Fine motor control, dexterity, or fine muscle movements

Question 24

This term is the minimum voltage that the membrane potential has to reach to cause Na channels to open.

Answer 24

Threshold potential

Question 25

This force can move charged particle across a permeable membrane regardless of the concentration gradient.

Answer 25

Electrostatic forces

Question 26

Then Nernst and subsequent GHK equation only works with these types of ions.

Answer 26

Univalent –
Multivalent like Ca and Mg don’t work
p.s. Nernst is for one single ion while GHK works with multiple.

Question 27

This is the main transmembrane protein used to create the reversal potential across nerve cell membranes. IMPACTS the membrane potential

Answer 27

Na/K ATPase pump – primary active transport

Also responsible for the osmotic balance (turgor) of the cell

Question 28

In the Goldman-Hodgkin-Katz (GHK) equation this key factor leads to the membrane potential being almost that of K reversible potential.

Answer 28

Membrane Leak of K

Question 29

What occurs when membrane potential is permeable to a certain ion?

Answer 29

takes that membrane potential, the EMF, toward its own reversal potential.

Question 30

What does the resting low potential of normal membrane tell us?

Answer 30

Reversal potential is K equilibrium, slow leak f K

Question 31

Opening of sodium channels means?

Answer 31

Trying to reach reversal potential of Na at rest

Question 32

In a nerve what cause a opening of to release NT?

Answer 32

Ca reversal potential via Na trigger/excite a AP

Question 33

What prevents an AP?

Answer 33

Chloride