BIOSCI 107 ET: Neurons Flashcards
What is the Nervous System Comprised of?
CNS and PNS.
What are Neurons (Nerve Cells)?
The principal building blocks and instruments of communication in the brain.
What 2 Communication Types are used by Neurons?
Electrical signals, chemical signals.
Where are Electrical Signals Used?
Dendrites, cell body, axon.
Where are Chemical Signals Used?
Synapses.
What is the Resting Membrane Potential?
Electrical potential difference (50 to 70 mV) across the cell membrane which results from separation of charge.
What is the Typical Resting Membrane Potential of Cells?
Almost all cells have a negative resting membrane potential.
Which 3 Areas are Excitable?
Neurons, muscle fibres, some endocrine cells.
What does Excitable Mean?
Ability to suddenly respond with a transient change of the resting membrane potential in response to a stimulus.
Which 2 Techniques are used to Measure Intracellular Potentials Today?
Microelectrode recording technique, patch-clamp technique.
What is an Important Convention to Remember about RMP?
The potential outside the cell is defined as zero.
Which 3 Factors Cause the RMP?
Unequal concentrations of Na and K inside/outside the cell, unequal permeability of cell membrane to these ions, electrogenic action of Na/K pump (minor).
What are the Approximate Concentrations of K and Na Outside the Cell?
K: 5 mM
Na: 150 mM
What are the Approximate Concentrations of K and Na Inside the Cell?
K: 100 mM
Na: 15 mM
How are the Concentration Gradients for K and Na Maintained?
By the Na/K pump.
What are the 2 Main Types of Ion Channel in Ions?
Non-gated channels, gated channels.
What are Non-Gated Channels in Neurons?
‘Leak’ channels open at rest.
What are Gated Channels in Neurons?
Voltage/ligand (chemical)/mechanically gated - closed at rest.
How do the Numbers of K Channels compare to those of Na?
At rest: Pk / PNa = 40 / 1.
P = membrane permeability.
How can we Calculate Equilibrium Potential for Each Ion?
Using the Nernst Equation.
What is an Equilibrium Potential?
An intracellular potential at which the net flow of ions is zero, in spite of a concentration gradient and permeability.
What is Unique about Glia Cells?
They only have leak channels for K.
What is an Important Rule about Cell Membranes and Permeability?
Higher the permeability of the cell membrane to an ion, the more this ion can shift RMP towards its equilibrium potential.
What is the Goldman Equation?
Calculates value of RMP, including both concentration gradients and relative permeability to K and Na ions.
When does Neuron Potential Change?
When membrane permeability or ion concentrations change.
What is Hyperpolarisation?
When potential becomes more negative.
What is Depolarisation?
When potential becomes less negative.
What is the Action Potential?
A brief fluctuation in membrane potential.
What causes the Action Potential?
A transient opening of voltage-gated ion channels, which spreads like a wave, along axon.
When do Action Potentials Occur?
After the membrane potential reaches certain voltage - threshold (55 mV).
Why are Action Potentials Important?
Information coded in their frequency - language, also a key element of signal transmission along axons.
What are the 3 Stages of Action Potentials?
Fast depolarisation, repolarisation, after-hyperpolarisation.