Neurons Intro: Resting Membrane Potential Flashcards
Equation for the nervous system
Nervous system = CNS + PNS
What is the challenge for neuroscience
To prevent and treat neurological and psychiatric disorders
4 examples of neurological and psychiatric disorders
- Alzheimer’s
- Motoneuron
- Parkinson’s
- Autism
What are neurons (nerve cells)
The principal building blocks and instruments of communication in the brain
Structure and communication are important parts of…
Neurons
What are glia cells
Supporting cells
What are the 2 methods of communication
- Electrical signals (dendrites, cell body, axon)
- Chemical signals (synapses)
What direction do synaptic potentials flow
Towards the cell body
What direction do action potentials flow
Away from the cell body
4 features of neurons and their functions
- Dendrites: receive electrical input
- Cell body: passively conducts electrical input
- Axon: propagate action potentials
- Axon terminal: release chemical signals
What do electrodes measure
Electrodes measure difference between them with reference electrode as reference
What does every cell have
Resting membrane potential (mostly all have -ve resting membrane potential)
In neurons and their _____, the cytosol has a potential that is __ to __mV lower (more __) than the potential of the _____ fluid
In neurons and their PROCESSES, the cytosol has a potential that is 50 to 70mV lower (more -ve) than the potential of the EXTRACELLULAR fluid
Why are only neurons and muscle fibres considered ‘excitable tissues’?
They can suddenly respond with a transient change of this potential (ie: action potential) in response to stimulus
How are intracellular potentials measured today?
- Microelectrode recording technique
- Patch-clamp technique
What technique to measure intracellular potentials “compare to ground/reference electrode”
Microelectrode recording technique
What technique to measure intracellular potentials “membrane ruptures so intracellular fluid is continuous with the pipette”
Patch-clamp technique
By convention the potential _____ the cell is defined as ‘___’. Therefore the _____ potential is normally _____ zero (eg: -65mV)
By convention the potential OUTSIDE the cell is defined as ‘ZERO’. Therefore the INTRACELLULAR potential is normally BELOW zero (eg: -65mV)
What 2 things can potential outside cell ‘zero’ and intracellular potential below -65mV be caused by?
- Unequal concentrations of Na+ and K+ inside and outside the cell resulting in the electrochemical gradients driving the movement of these ions
- Unequal permeability (P) of the cell membrane to these ions
What generates the resting membrane potential (RMP)?
Electrical potential difference (50-70mV) across cell membrane. Results from separation of charge so there is more -ve charge inside the cell vs. extracellular fluid
What ion has a conc. higher inside the neurons and lower outside the neurons
K+ ions
What ion has a conc. lower inside the neurons and higher outside the neurons
Na+
How are concentration gradients for K+ and Na+ maintained?
Na+/K+ pump
How does the Na+/K+ pump work to give ratio
Use 1ATP, pump out 3 Na+ ions and take in 2 K+ ions
Are the ion channels in neurons selectively permeable or fully permeable to ions
Selectively permeable to ions
What are the 2 types of channels of ion channels in neurons
- Non-gated (‘leak’) channels
- Gated channels
What type of channel “open at rest (‘on-off’ state), allow for diffusion of ions”
Non-gated (‘leak’) channels
Type of channel these “voltage-gated, ligand-gated, mechanically gated” are categorised as
Gated channels
True or false gated channels are closed at rest
TRUE
In cell membranes of neurons, there are ___ leak K+ channels, but _____ leak Na+ channels
In cell membranes of neurons, there are MANY leak K+ channels, but FEW leak Na+ channels
Eq for the (P) membrane permeability at rest
PK+/PNa+ = 40/1
K+ greater diffusion and lower Na+ diffusion
The concept of the ‘equilibrium potential’ for one ion type is…
An intracellular potential at which the new flow of ions is 0 according to its electrochemical gradient
What equation is used to calculate equilibrium potential for each ion
Nernst Equation
What is the approx. value for equilibrium potentials of Na+ in mammalian neurons
ENa = +60mV
True or false; glia cells have leak channels for both K+ and Na+
FALSE; glia cells have leak channels ONLY for K+
What is the RMP in glia cells
RMP = EK -80mV
Neurons have leak channels for ___, ____ and ____ which will affect RMP
Neurons have leak channels for BOTH K+ and Na+ which will affect RMP
The higher the permeability of the cell membrane to an ion the….
More this ion shifts the RMP towards its own equilibrium potential
At ___ in neurons, the membrane permeability is much ____ to K+ than to Na+, therefore the RMP is ____ to the equilibrium potential for___ (EK) than the equilibrium potential for ___ (ENa)
At REST in neurons, the membrane permeability is much HIGHER to K+ than to Na+, therefore the RMP is CLOSER to the equilibrium potential for K+ (EK) than the equilibrium potential for Na+ (ENa)
Compared to glial cells, neurons RMP less negative than EK (-65mV)
Due to small contribution of leak Na+ channels
What is needed to be considered for calculating RMP
BOTH concentration gradients and relative permeability of resting cell membrane to K+ and Na+ ions
PK =
40
PNa =
1
What type of K+ and Na+ channels are responsible for RMP
Non-gated (leak) channels
