1.4 - Motor Systems

Question 1

simple system approach

Answer 1

to make task of relating neurons to behaviour easier, we focus on simpler situations

Question 2

stretch reflex

Answer 2

stretching a muscle in body causes the same muscle to contract die to an increase in tension

Question 3

role of stretch reflex

Answer 3

help keep limbs in position when external forces change

Question 4

circuit for monosynaptic stretch reflex (2)

Answer 4

1. stretching muscle activates stretch receptors -> via sensory-motor synapse in spinal cord cause same muscle to contract
2. involves simple monosynaptic excitatory synaptic connection between sensory and motor neuron

Question 5

secondary reflex

Answer 5

reflex circuit also involves inhibitory pathways

Question 6

inhibitory pathways of reflex circuitry (2)

Answer 6

1. stretching muscle not only excites stretched muscle but inhibits antagonistic muscle
2. inhibition of antagonistic muscle involves special type of inhibitory interneuron in spinal cord

Question 7

fixed action patterns

Answer 7

complex behavioural sequences

Question 8

why is the sea slug (Tritonia) often used to analyse fixed action patterns (2)

Answer 8

1. simple and accessible nervous systems
2. can get detailed analysis of underlying neuronal mechanisms
   (simple system approach)

Question 9

where are fixed action patterns often found

Answer 9

invertebrates

Question 10

Tritonia simple systems approach (3)

Answer 10

1. Tritonia brain made up of balls of neurons (ganglia)
2. each neuron has large cell body (can be recorded with micro-electrodes)
3. each neuron has specific intrinsic firing properties, arranged into circuits with precise connectivity
   (circuits are same from animal to animal)

Question 11

Trisonia swim circuit

Answer 11

can see properties of the fixed action pattern in activity of individual neurons

Question 12

escape behaviour in locusts (2)

Answer 12

1. dedicated neuron responds to looming visual stimuli
2. visual information bypasses brain and targets motor areas

Question 13

example of how escape reflexes can be flexible (Drosophila) (2)

Answer 13

1. take off direction depends on stimulus direction
2. before jumping, they adjust posture to move centre of mass relative to middle legs

Question 14

example of conserved features of visual pathways across vertebrates

Answer 14

evasive responses to visual patterns via the SC/OT
(same pathway that drives blindsight

Question 15

parallel circuits for different visual behaviours

Answer 15

visual reflexes can drive attraction as well as avoidance

Question 16

example of parallel circuits for different visual behaviours

Answer 16

attraction to small objects can drive hunting of paramecium in larval zebrafish

Question 17

central pattern generators

Answer 17

network of neurons capable of generating patterned (rhythmic) activity in absence of sensory input to drive timing of outputs

Question 18

examples of behaviours driven by central pattern generators (5)

Answer 18

1. walking
2. swimming
3. flying
4. breathing
5. chewing

Question 19

different neuron excitation types (3)

Answer 19

1. endogenous bursting
2. plateau potentials
3. post-inhibitory rebound

Question 20

endogenous bursting

Answer 20

pacemaker like activity

Question 21

plateau potentials

Answer 21

persistent depolarised state once triggered cell can fire action potentials without continuous excitation

Question 22

post-inhibitory rebound

Answer 22

increased neuronal excitatory after period of inhibition

Question 23

categories of factors effecting neuron activity (3)

Answer 23

1. intrinsic/endogenous properties of neurons
2. synaptic properties
3. patterns of connection

Question 24

intrinsic/endogenous properties of neurons (poo poo smells fucking eggy) (5)

Answer 24

1. post-inhibitory rebound
2. plateau potentials
3. spike frequency adaptation
4. firing threshold
5. endogenous bursting

Question 25

synaptic properties of neurons (the shit made sam faint) (5)

Answer 25

1. time course 2. sign (inhibitory/excitatory) 3. mode of transmission (chemical/electrotonic) 4. strength 5. facilitation/depression etc

Question 26

patterns of connection in neurons (my poo reeks) (3)

Answer 26

1. mutual excitation 2. parallel excitation and inhibition 3. reciprocal inhibition

Question 27

radula

Answer 27

tongue like organ with teeth (rhythmic control involved in lymnaea feeding)

Question 28

names of 3 CPG neurons involved in Lymnaea feeding (3)

Answer 28

1. N1 2. N2 3. N3

Question 29

role of N1 in lymnaea feeding (3)

Answer 29

1. starts plateau potential 2. weakly excites N2 3. inhibits N3

Question 30

role of N2 in lymnaea feeding (2)

Answer 30

1. reaches threshold and fires plateau potential (high threshold) 2. inhibits N1 and N3

Question 31

role of N3 in lymnaea feeding (3)

Answer 31

1. has post-inhibitory rebound 2. fires when N2 stops inhibiting it 3. inhibits N1

Question 32

behavioural switching

Answer 32

same CPG circuit can be involved in generating different behaviours operating in different ways (allows CPGs to be flexible)

Question 33

learn about lobter stomatogastric system?

Answer 33

go!

Question 34

lobster stomatogastric system

Answer 34

different CPGs for different compartments (pyloric CPG best understood)

Question 35

how can neuromodulators reconfigure the pyloric rhythm (lobster stomatogastric system)

Answer 35

dopamine leads to increased secondary sieving of food in pylorus

Question 36

how can dopamine effect neurons (2)

Answer 36

1. strength of connections between neurons 2. endogenous properties of individual cells

Question 37

learn about multifunctionality of pyloric suppressor in lobster stomatogastric system

Answer 37

go!