L17 - Introduction To Nerve Cells & Excitability: Resting Potential Membrane Flashcards
What are the parts of a neuron?
- soma/cell body
- dendrite + branches
- axon hillock + axon (+collateral)
- axon branches + telodendria
- synaptic terminal
What are parts of a nerve fiber?
- (myelin sheath)
- swchann cell
- nucleus
- axon
What is the direction of travel in the neuron?
From the soma to the synaptic terminals
What are the structureal classification of neurons?
- multipolar neuron
- bipolar neuron
- unipolar neuron
- anaxonic neuron
What is the classification of neurons on the basis of function?
- afferent neuron
- efferent neuron
- interneuron
What happens to neurons due to their functional and cellular specialisation?
Have lost the ability to mitotically divide
What is an excitable cell?
The ability of some cells to be elctrically excited resulting in the generation of action potentials
What are the main examples of excitable cells?
- neurons
- muscle cells
- endocrine cells
What are examples of non-excitable cells?
- RBD
- adipocytes
What is the resting membrane potential (RMP)?
An electrical charge across the plasma membrane, with the interior of the cell negative with respect to the exterior
In an excitable cell, what happens in response to stimulation?
RMP can change
(Graded or AP)
What does the RMP range from in excitables and non-excitable cells?
Excitable cells: -50mV to -85mV
Non-excitable cells: -5mV to -10mV
What does the outer plama membrane regulate?
What enters to the cells and what is secreted from the cells
- composed by phospholipids
What crosses through the plasma membrane and what doesn’t?
- lipid soluble molecules cross easily following a conc grad
- charge ions or proteins cannot cross
What is a chemical gradient?
Gradient base on conc (high to low)
What is an electrical gradient?
Gradient base on charge
What is the basic principles of charged ions?
- oppositely charged ions attrach
- reverse applies
- forces increases with amount of charge
What is facilitated diffusion?
- ions diffuse down conc grad
- selectively permeable to dif ion
What do active transporters (pump) do?
- move ions against conc grad
- create conc grad across membrane
What ion channels are involved in RMP?
- membrane spanning proteins (connect cytosol to the cell exterior
- gated and non gated
What is flux of ions like? What is direction determine by?
- passive, selective and rapid
- by conc and charge
How is excitability achieved?
Active exhange via Na-K transporter
- exchanges 2K+ in for 3Na+ out
What is the distribution of charged ions?
Intracellular
- K+: 140mM
- Na+: 10-15mM
Extracelullar
- K+: 4-5mM
- Na+: 145mM
What is the movement of ions restricted by?
Relative permeability of plasma membrane
What is the most important component of RMP?
K+
Leak channels (100:1)
How is the RMP established?
Diffusion of K+ out balances by rate of K+ influx from the Na+/K+ pumps
70mV
What does the Nerst eqn calculate?
Calculates electrical potentials
- eq potential for any ion (Eion)
What is the Nerzt eqn?
Eion = RT/zF x logn[ion]out/[ion]in
F - faraday’s constant
Z - valency of the ion
What can the RMP be calculated with?
Goldman eqn
What is the goldman equation?
https://www.cambridge.org/core/books/abs/essential-equations-for-anaesthesia/goldman-equation/BBDB8FDE426783BE5B0922DACFF1A57E
What is the Pion?
Relative permeability of membrane to ion
What is the distribution of charged ions like in a real neuron?
Intracellular
- K+: 140mM
- Na+: 10-15mM
- Cl-: 4-30mM
Extracelullar
- K+: 4-5mM
- Na+: 145mM
- Cl- 110mM
What is eq potential from the Nernst eqn?
~ 85mV for K+
~ +65mV for Na+
~ 70mV for Cl-
What is the goldman eqn membrane potential?
-75mV
