Poster Conference for Lampreys Flashcards
The focus on neuroscience has been to
understand the nervous system’s ability to perform motor tasks, such as locomotion
Locomotion is
moving from one place to another
How does a lamprey swim?
A lamprey swims by alternately the activity of motor neurons on the left and right sides of each of its spinal cord segments
Fictive locomotion
Measures different locomotor modes in lampreys by dissecting their spinal cord and put in a bath of solution to keep tissues in a viable state and electrodes placed in ventral roots to measure motor neuron output
It is difficult to understand the lamprey motor system as a whole
despite a lot of more empirical evidence beyond the fictive locomotion
The conceputal models
single cell and network model ahs been developed to understand lamprey motor system as a whole
The conceputal model has
experimentally established parameters
Single cell model which has
compartments of the soma (cell body) and dendrities which has ion channels
Lamprey spinal cord network (3)
- Reticuospinal neurones (RS) in brainstem excite interneurons and motor neurons
- This excitation descends onto this neurons which causes EINs on one side of the segment to excite MN (contract muscles) and CCINs which inhibit neurons on contralateral side (opposite)
- One side becomes active and other side is inactive
Neural mechanisms which stops one side from being active is
spike-frequency adapation (sAPH)
sAPH (3)
long-lasting afterhyperpolarisations that follow EIN’s spike of AP are added
makes EINs first spike interval (gap between spikes) bigger then the following ones.
Over time the gaps becomes larger allowing the neurons on contralateral side to fire loads of APs allowing to inhbit the previously active side
The sAPH is due to
calcium ions flowing into the cell with each AP which activates this calcium-dependent potassium channel
Simulation of kainate receptor (type of excitatory amino acid) via bath application showed
regular rhythmic activity alternating between two sides of network.
Role of AHP summation (causes sAPH)
Size of long-lasting AHPs in the model was reduced by lowering the conductance of KCa channels by 15,20, and 25%. Figure 4 at 30% shows that alternating burst activity progressively slowed down as KCa channel conductance decreased. Thus sAPH plays a role in burst-termination
Role of LINs in burst termination:
Inhibit CCINs mid-cycle allowing contralateral neurons to be active