B&B Invertebrate motor control Flashcards
How many neurons do the following have:
1mm3 mouse cortex
Entire nervous system of fly Musca
Entire nervous system of bee Apis
100,000
350,000
850,000
Describe how the nervous system of an insect is organised
Composed of a system of ganglia
Segmental NS
Each ganglion control one segment
Each ganglion linked to the other by connectors
Carry the axons of long interneurons
Large structures eg brain are created by the fusion ganglia
Describe how the ganglia of an insect are organised
Have tracts (ascending and descending axons). Connectives running between them. Axons are not myelinated (so do not look like white matter but have the same role) Cell bodies of motor and interneurons are on the outside of the ganglia (mainly ventral and lateral surface) The synaptic regions (neuropile) lie in the centre (equivalent of grey matter in vertebrates)
Vertebrate motor neurones use WHAT
Vertebrate sensory neurones use WHAT
acetyl choline
glutamate
Invertebrate motor neurones use WHAT
Invertebrate sensory neurones use WHAT
glutamate
acetyl choline
In vertebrates, dendrites emerge from the cell body. Where do they emerge from in invertebrates?
A process comes off the cell body and they emerge from this - sometimes called a neurite
What is a motor pool? vertebrates
Each muscle is supplied by hundreds or thousands of motor neurones - this is a motor pool (the group of hundreds of motor neurons that control a single muscle)
What is a motor unit? vertebrates
Each motor neurone contacts many muscle fibres
True or false vertebrates
Large motor neurons contact many muscle fibres while small motor neurons contact only a few
True
Each muscle fibre is innervated by how many motorneurones? vertebrates
1
Because vertebrate muscle fibres respond with AP when they are stimulated, we call their contractions what?
All or nothing
What is the size principle of muscle activation?
Movements that use small forces - small motor neurones are recruited
Movements that use large forces - large motor neurones recruited
Contraction reaches maximum - largest motor units recruited
Invertebrate motor neurons can be described as fast or slow. What does this mean in terms of transmitter?
Fast neurons release a lot of transmitter with each AP and small neurons release little transmitter
In invertebrates, each motor neurone supplies most of the muscle fibres within the muscle.
True or false?
True
In invertebrates, when glutamate is released, they don’t generate an AP in the muscle membrane but a what?
excitatory post synaptic potential (epsp)
This allows summation between epsps and other potentials
Fast excitatory motor neurons induce large epsps
If epsps come close together what happens?
They will summate to become larger
Describe inhibitory motor neurons in invertebrates
Neurotransmitter is GABA
Produces an inhibitory post synaptic potential in muscle fibres
Each inhibitory neurone has an axon that branches axons into several nerves and contacts many muscles
Their main role is to end the contraction rapidly to prevent overlap with the contraction of antagonist muscles
The extensor tibia muscle lies within the femur and does what?
extends the tibia during walking and jumping
Fast extensor tibia, slow extensor tibia and common inhibitor
what is an epsp and an ipsp
epsp = excitatory post synaptic potential ipsp = inhibitory post synaptic potential
DUM neurones are modulatory motor neurones. They send axons to many muscles on both sides of the body. What does DUM stand for?
Dorsal unpaired median neurones
What neurotransmitter do DUM neurones contain?
Octopamine
Not found in vertebrates
Structurally related to noradrenaline and dopamine
DUM neurons do not generate epsps or ipsps. What does this mean?
This means they do not cause contraction
Instead, octopamine acts on the cellular components within the muscles and on the motor neurone axons
Describe what happens when octopamine is released.
Released from DUM neurones
Increases the amount of glutamate released at the synapse
This increases muscle twitch by 5%
It increases how fast the muscle is relaxed
This is important in rhythmic activity eg locomotion
Increases muscle ATP production from carbohydrates
Mobilises lipid for energy production