Lecture 3 Flashcards
Impulse Conduction
occurs due to the presence of active and electronic potentials along the conductors.
Excitable Cells
cells that conduct passive currents but will not generate Aps
Cable properties
λ (length constant) measures how quickly a potential difference disappears (decays to zero) as a function of distance
λ increases as diameter _________ (less internal resistance)
increases
λ Increases as membrane resistance _________ (less current leaked out & current is forced down the membrane)
increases
Length constant
is defined with internal resistance, extracellular fluid resistance and membrane resistance
- Extracellular fluid resistance is relatively low and stagnant, it is not included in the equation
Myelination
increasing membrane resistance
- Is the most efficient means of increasing conduction velocity
‘Glial’ cells
are cells that assist the nervous system (required for nutrition and increased membrane resistance)
Node of Ranvier
small gap between adjacent glial cells (unmyelinated axon membrane between 2 Schwann cells)
Saltatory Conduction
When Aps jump from one place to the next (in between, AP is not generated)
Unmyelinated Axons
do not have extensive wrapping around the outside (lots of current leakage and slows down the conductance velocity) & has small axon diameter and low
Synapses
functional association of a neuron with another neuron or effector organs (muscle or gland)
Electrical Synapse
at electrical synapses (gap junctions) adjacent membranes are about 35A apart
Axon terminal
axons end in ‘boutons’ filled with vesicles (which contain neurotransmitters) which are then released into the extracellular fluid
Chemical Synapse
the transmitter is into the extracellular space which exists between adjacent cells
