Muscles and Neurons Flashcards
Explain the structure of a nerve cell
a soma (cell body) and two types of processes: dendrites and usually a single axon.
Inputs from other neurons (synaptic inputs) are received on the
dendritic tree and the soma.
What is the difference between an action potential and a synaptic potential?
Synaptic potential goes towards the soma, while action potentials go away from the soma
In communication, what are the two types of signals?
Electrical signals Chemical signals
Where does electrical signalling happen?
dendrites, cell body, axon
Where does chemical signalling happen?
synapses
What is the membrane potential?
voltage across the cell membrane
What is the membrane potential range in mV for a cell?
between –100 and +50 mV
What is the resting membrane potential value?
Its value is usually between –50 and –70 mV (typically -65 mV).
True or false: Almost all cells in the body have a negative resting membrane potential.
True
Only x, y and some z can suddenly respond with a transient change of this potential (ie. with an action potential) in response to a stimulus – so they are excitable !
Only neurons, muscle fibres and some endocrine cells can suddenly respond with a transient change of this potential (ie. with an action potential) in response to a stimulus – so they are excitable !
How are the intracellular potentials measured today ?
The microelectrode recording technique and The patch-clamp technique (additional feature of being able to measure current)
What is the RMP definition?
Electrical potential difference (50 to 70 mV) across the cell membrane which results from separation of charge. There is more negative charges inside the cell in comparison to the extracellular fluid.
The RMP is due to what three factors?
a) Unequal concentrations of Na+ and K+ inside and outside the cell b) Unequal permeability of the cell membrane to these ions [c) Electrogenic action of the Na-K pump – only a small contribution !]
What is the Approximate concentrations of K+ and Na+ ions inside and outside neurons?
OUTSIDE [Na+] 150 mM [K+] 5 mM INSIDE [K+] 100 mM [Na+] 15 mM 
Explain Ca2+ ion’s affect on the RMP:
Ca2+ ions do not affect the RMP as the membrane is not permeable to these ions at rest
Explain Cl2- ion’s affect on the RMP:
Cl- ions also do not contribute to the RMP as their distribution is usually ’passive’ (i.e. in most neurones there are no active Cl- pumps).
How do large ions affect RMP?
There are many negatively charged proteins inside the cell. However, since the cell membrane is not permeable to these large ions, they do not affect the RMP !
State the Na/K pump ratio:
3 Na+ out 2 K+ in
How is unequal permeability of the cell membrane to different ions (including Na+ and K+) explained ?
Two main types of ion channels (ie. channels which have selective permeability to ions) in neurons: a) Non-gated (‘leak’) channels - open at rest b) Gated channels (voltage-gated, ligand-gated*, or mechanically-gated) -usuallyclosed at rest
In cell membrane of neurons, there are many leak __ channels, but very few leak___ channels.
In cell membrane of neurons, there are many leak K+ channels, but very few leak Na+ channels.
At rest: PK+ / PNa+ ≈ where p means membrane permeability
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Explain The concept of the ‘Equilibrium potential’
An intracellular potential at which the net flow of ions is zero, in spite of a concentration gradient and permeability!
The equilibrium potential can be calculated for each ion by the ‘Nernst equation’ What is this equation?
Eion = 61.5 mV x log ([ion]o / [ion]i)










