Transmission Within Neurons Flashcards
What is the ability to relay signals within or between neurones called?
Transmission
Involves electrical signals within neurones and chemical signals between neurones.
What type of current is recorded in dendrites?
Dendrites: current attenuated
Dendrites exhibit attenuation of current due to their structural properties.
What does the length constant (λ) represent?
The distance over which the voltage drops to 37% of its original value
The length constant is a crucial concept in cable theory related to signal transmission.
How can a cable engineer improve transmission efficiency?
By increasing Rm, decreasing Ri, or increasing diameter
These adjustments enhance the signal transmission properties of the cables.
True or False: Attenuation is a significant problem for dendrites.
False
Dendrites do not face significant attenuation issues due to short distances and multiple inputs.
What enables axons to transmit signals without attenuation?
Higher density of sodium channels
Have AP waves = effective action potential propagation.
What is the role of myelination in neuronal transmission?
To decrease current leak and increase conduction velocity
Myelination acts like insulation, improving the efficiency of signal transmission in axons.
What is saltatory conduction?
A wave of action potentials interspersed by segments of rapid cable conduction
This process allows for faster signal transmission along myelinated axons.
Fill in the blank: Intervals of myelination are called _______.
Internodes
Internodes are segments of the axon that are covered by myelin sheath and are about 1mm long
What are the two types of cells that form myelin sheaths?
Oligodendrocytes and Schwann cells
Oligodendrocytes myelinate axons in the central nervous system, while Schwann cells do so in the peripheral nervous system.
How does myelination affect the density of sodium channels in axons?
High density of Na+ channels at nodes of Ranvier
The nodes of Ranvier have a significantly higher concentration of sodium channels compared to the internodes.
What is the maximum speed of action potential conduction in myelinated axons?
Up to 150 m/s
Myelinated axons can conduct action potentials much faster than unmyelinated axons.
What is important in dendritic transmission?
Transmission is passive = does not involve a wave of action potentials
How can conduction velocity be increased in axons?
Increase axonal diameter
A strategy used by primitive animals e.g. squids
What are Nodes of Ranvier?
Have a high density of Na+ channels —> decreases rise time of APs
What speeds up transmission of APs?
- Density of sodium channels
- Decreased capacitance of membrane = transmission through internodes is much faster than AP wave
What is a myelin sheath?
Extension of glial cell cytoplasm = insulator
What is Multiple Sclerosis (MS)?
- Demyelination of CNS neurons
- caused by immune attack on oligodendrocytes that provide myelin sheath insulation
- Symptoms = deficit in vision, paraesthesia (pins & needles), weakness, incoordination, Genito- urinary/bowel, cognitive deficiencies
- may be linked to low vitamin D
