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biology > B&B Invertebrate motor control > Flashcards

B&B Invertebrate motor control Flashcards

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1
Q

How many neurons do the following have:
1mm3 mouse cortex
Entire nervous system of fly Musca
Entire nervous system of bee Apis

A

100,000
350,000
850,000

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2
Q

Describe how the nervous system of an insect is organised

A

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

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3
Q

Describe how the ganglia of an insect are organised

A 
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)
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4
Q

Vertebrate motor neurones use WHAT

Vertebrate sensory neurones use WHAT

A

acetyl choline

glutamate

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5
Q

Invertebrate motor neurones use WHAT

Invertebrate sensory neurones use WHAT

A

glutamate

acetyl choline

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6
Q

In vertebrates, dendrites emerge from the cell body. Where do they emerge from in invertebrates?

A

A process comes off the cell body and they emerge from this - sometimes called a neurite

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7
Q

What is a motor pool? vertebrates

A

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)

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8
Q

What is a motor unit? vertebrates

A

Each motor neurone contacts many muscle fibres

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9
Q

True or false vertebrates

Large motor neurons contact many muscle fibres while small motor neurons contact only a few

A

True

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10
Q

Each muscle fibre is innervated by how many motorneurones? vertebrates

A

1

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11
Q

Because vertebrate muscle fibres respond with AP when they are stimulated, we call their contractions what?

A

All or nothing

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12
Q

What is the size principle of muscle activation?

A

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

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13
Q

Invertebrate motor neurons can be described as fast or slow. What does this mean in terms of transmitter?

A

Fast neurons release a lot of transmitter with each AP and small neurons release little transmitter

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14
Q

In invertebrates, each motor neurone supplies most of the muscle fibres within the muscle.
True or false?

A

True

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15
Q

In invertebrates, when glutamate is released, they don’t generate an AP in the muscle membrane but a what?

A

excitatory post synaptic potential (epsp)
This allows summation between epsps and other potentials
Fast excitatory motor neurons induce large epsps

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16
Q

If epsps come close together what happens?

A

They will summate to become larger

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17
Q

Describe inhibitory motor neurons in invertebrates

A

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

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18
Q

The extensor tibia muscle lies within the femur and does what?

A

extends the tibia during walking and jumping

Fast extensor tibia, slow extensor tibia and common inhibitor

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19
Q

what is an epsp and an ipsp

A 
epsp = excitatory post synaptic potential
ipsp = inhibitory post synaptic potential
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20
Q

DUM neurones are modulatory motor neurones. They send axons to many muscles on both sides of the body. What does DUM stand for?

A

Dorsal unpaired median neurones

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21
Q

What neurotransmitter do DUM neurones contain?

A

Octopamine
Not found in vertebrates
Structurally related to noradrenaline and dopamine

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22
Q

DUM neurons do not generate epsps or ipsps. What does this mean?

A

This means they do not cause contraction

Instead, octopamine acts on the cellular components within the muscles and on the motor neurone axons

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23
Q

Describe what happens when octopamine is released.

A

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

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24
Q

Vertebrate muscles require hundreds or thousands of motor neurones to allow precise control of the force generated
The locust extensor tibiae muscle requires how many motorneurones?

A 
4
SETi
FETi
CI
DUMETi
25
Q

Describe SETi

A

The slow extensor
Used mainly for walking
Increasing spike frequency gradually increases the force generated in many muscle fibres

26
Q

Describe FETi

A

The fast extensor
Used in kicking or jumping
Activates all muscle fibres

27
Q

Describe CI

A

The common inhibitor

Ensures that each contraction ends quickly

28
Q

Describe DUMETi

A

The modulator

Increases the effect of the excitors and optimises energy availability

29
Q

True or false

Insect motor neurones can act as interneurones

A

True
Some excitatory insect motor neurones make output synapses from their dendrites
not true of inhibitory or dum

30
Q

What are the 2 types of local interneurones?

A

Spiking localinterneurones

Non-spiking local interneurones (don’t fire AP)

31
Q

What are intersegmental interneurones?

A

Projecting

Their dendrites are in one ganglion and their axon runs to one or more other ganglia

32
Q

What are some sensory structures on an insect’s body?

A

Touch sensitive and chemosensory hairs

Cuticular strain detectors

33
Q

What is a chordotonal organ?

A

Monitor joint angle and speed of movement
Lie in parallel to muscles
Have their own tendon
Which stretches the dendrites of the sensory cells as the joint moves

34
Q

What is the sensory neuropile rich in?

A

The ends of the axons of sensory neurones

35
Q

The inflow of sensory information can be controlled by what?

A

Inhibitory synapses
Contain neurotransmitter GABA
Blocks glutamate release from the sensory axons

36
Q

What is presynaptic inhibition?

A

The inflow of sensory info being controlled by inhibitory synapses
Found on all vertebrate and invertebrate sensory axons

37
Q

Sensory neurones synapse onto what (whose branches are entirely contained within one ganglion)

A

Spiking local interneurones
These have 2 fields of branches
One in the sensory neuropile and one in the motor neuropile linked by a short axon

38
Q

How are extracellular recordings made?

A

Using 2 hook electrodes on a nerve
APs go above and below the line as they move past first one electrode then the other
1st positive then negative

39
Q

How are intracellular recordings made?

A

Put electrode (hollow glass capillary) inside neurone
In the cell body
Close to dendrites so large psps, far from axon so small spikes
Small upwards and downwards peaks are excitatory and inhibitory synapse potentials
APs (spikes) are very sharp upward deflections

40
Q

True or false

Excitation is direct and inhibition is indirect

A

False - other way around

Inhibition (inhibitory interneurone between the sensory neurone and the spiking local interneurone)

41
Q

Choose correct word
Spiking local interneurons
The dendrites receive direct/indirect excitatory input synapses from sensory neurones
The dendrites also receive direct/indirect inhibitory inputs from sensory neurones
They are therefore primarily sensory/motor interneurones
The dendrites also make input/output synapses which is almost never seen in the vertebrate CNA

A

Direct
Indirect
Sensory
Output

42
Q

What is graded transmitter release?

A

As the membrane potential changes, so does the amount of transmitter released
So cannot be said to have a true resting potential

43
Q

If the neurons contain an excitatory transmitter, the postsynaptic neurones are what as the non spiking neurones are what?

A

Excited

Depolarised but also may be inhibited as the non spiking neurones are hyperpolarised

44
Q

If the non spiking neurons contain an inhibitory transmitter, their postsynaptic neurones are what as the non spiking neurones are what?

A

Inhibited

Depolarised but also may be excited as the non spiking neurones are depolarised

45
Q

Non spiking interneurones contain groups of motor neurones. They are therefore what?

A

Premotor interneurones

46
Q

True or false
Depolarising one non spiking neuron that drives flexor muscles can lead to the inhibition of another non spiking neuron that drives extensor muscles

A

True

47
Q

What does the cuticular spring do?

A

Stores energy

48
Q

A locusts jump is not just powered by direct muscle action but also by energy stored where?

A

Cuticular spring

Adds power and speed

49
Q

In vertebrates, body energy is not stored in the cuticular spring but where?

A

Tendons

50
Q

What are descending contralateral movement detectors? DCMD

A

Detects movement across visual field

51
Q

What do DCMDs activate and what does it do?

A

Activated the cocking neurone

Initiates jump motor sequence

52
Q

What does the cocking neurone activate?

A

Via the mesothoracic ganglion it activates the fast extensor tibae mn and the flexor mn

53
Q

The fast extensor MN has a synapse directly onto the flexor mn. why?

A

Coactivate muscles to disort the cuticular spring

54
Q

Sat on the surface of the cuticle are campaniform sensillae. What do they do?

A

Buckle when the cuticle is put under strain
Dendrites beneath which will send info to ganglia
Go directly to fast extensor mn and flexor mn

55
Q

What neurone inhibits the flexor neurone, thus triggering the jump?

A

M neurone

56
Q

What does the common inhibitor mn do?

A

Inhibits flexor muscle directly

57
Q

Strong connections between the DCMD and the what often trigger an AP?

A

M neurone

58
Q

How does a mantis shrimp use its claw?

A

Same principle as locust jump

The extensor and flexor muscle contract together to deform the cuticle of the saddle which is part of the exoskeleton

59
Q

In the mantis shrimp, the co-contraction of the flexor and extensor muscles disorts the saddle and especially the what?

A

The merus bar

To store energy for the strike

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