electrochemical equilibria

Define excitable tissue

A tissue or cell that can generate an action potential. 

What are the 4 main excitable tissues

- Neurones

- Muscle

- Glial cells (very small number) 

- Pancreatic beta cells

Define resting membrane potential (Vm(rest)) and give number

Potential of the cell when not active. 

Usually between -65mV to -85mV. 

What are the 2 pairs of ions that help generate the resting membrane potential

Na+ and K+

K+ and CL-

Ionic Differnce of Na+ in and out of the cell

In= 10mM

Out= 140mM

Ionic Differnce of K+ in and out of the cell

In=140mM

Out=10mM

ionic Differnce of Cl- in and out of the cell

in= 10mM

Out= 140mM

Ionic Differnce of Ca2+ in and out of the cell

In=0.001mM

Out= 2.5mM

Explain this

Ions can move based on their gradient and the attraction from positive to negative

Na+ = both move from out to in:because of the graidient and because inside is negative 

K+ = some move out because of concentration graidient some move in because their attracted  to the negative 

Cl- = some move in because of concentrsation gradient some ove out because its negative so dreamers to the positive outside 

Ca2+ = both move in because of graidient and attraction 

** under physicological contrib the conc graidient is stronger 

How is Vm(rest) maintained

Na+/K+ ATPase (3 Na+ exit cell, 2 K+ enter cell, active transport). 

KCC (K+ Cl- cotransporter, both exit cell, active transport).

Explain sodium potassium ATPase

3 NA+ out against gradient

2K+ in against gradient 

Needs ATP 

It is electrogenic as more as total charge is +1 out

Define electrogenic pump and define electroneutral pump.

Electrogenic - charge entering and leaving cell is not equal

Electroneutral - charge entering and leaving cell is neutral

explain the KCC transporter

K+ and Cl- both move same direction out of the cell

No ATP as going down concentration graidient 

Electroneutral as total charge leaving is 0

What are the electrical voltages of:

1. Action potential

2. Restoring membrane potential

3. Post synaptic potential

1. +100mV

2. -70mV

3. +/- 1 to 40

What ions enter the cell in excitatory postsynaptic potentials?

Na+, Ca2+, K+

What ion enters the cell in inhibitory postsynaptic potentials?

Cl-

Electrochemical potential meaning

The membrane potential when the electrical gradient ( attrcation and repulses because fo charge)  balances the concentration gradient so theres no net movement of the room across the membrane.

You calculate using Nernst equation - to find out what is potential when their equal 

what do all the letters in Nernst equation stand for

Ex or E ion = equilirium poteintial for the ion (mV)

R= gas constant (8.314J/molK)

T= temperature (kelvin)

Z= valance charge of the ion 

F= faradays constant ( the amount go electrical charge per mol of electrons) ( C/mol ) 

(Ion) outside/ (x) 0 = concentration  too of the ion outside the cell (mM)

 ( ion) inside/ (x)i = concentration of the ion inside the cell (mM)

   

What are electroplaques

• specialised cells that produces electricity 

• they are attached to a nerve that has acetylecholine receptors 

• they have Nicotone ACh receptors

• when theres an action potential of nerve releases ACh which is detected opening the sodium ion changes so sodium enters 

• this makes a voltage 

How do electroplaques work on eels

Each cell add a voltage of 0.12

There are 5000 electroplaques piled on op of each other so 0.12x5000=600mv

That’s whats total voltage e