Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Neuroscience (Yeo) > Motor Control 1 - Spinal Reflexes > Flashcards

Motor Control 1 - Spinal Reflexes Flashcards

1
Q

What stain has been used?

A
  • Myelin

(shows thickness of the white matter tracts)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Which part is the grey matter and which part the white matter?

A
  • White Matter Outside
  • Grey Matter is Butterfly
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What does a thick/large dorsal column indicate?

Why would this be so?

A
  • Lots of Fibres
  • Upper Part of the Cord
  • Most Fibres have either not been given off (motor) or have come in (sensory)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What indications are there that this is a cervical transverse section?

A
  • Large White Matter Area
  • Large Gret Matter Enlargement in Ventral Horn (upper limb - brachial plexus)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Where are motor & sensory neurones found in the spinal cord?

A
  • Motor Neurones –> VENTRAL HORN
  • Sensory Neurones –> DORSAL HORN
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Where are the nuclei found in the spinal cord?

A

Middle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How is the spinal cord divided up? (what is it called)

A
  • Rexed Lamination (grey matter division)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How many laminas are there in the Rexed Laminations?

Where is Lamina 10 found?

A
  • 10
  • Around central canal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What lamina of rexed are the motor neurones in?

A
  • Motor Neurones in Ventral Horn –> NOT LAYERED
  • Therefore not appropriate system for motor function
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How are the Motor Neurones in the Ventral Horn organised? (generally)

A
  • Laterally & Medially –> for AXIAL & DISTAL MUSCLES
  • Close & Far to Central Canal –> for FLEXOR & EXTENSOR
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Regarding motor neurones, how are they organised in terms of lateral & medial placement?

A
  • Close to Midline –> control muscles in TRUNK & NECK (axial muscles) –> e.g. posture & balance muscles
  • Lateral (further out) –> control LIMBS & EXTREMITIES –> e.g. fingers & wrists & toes etc.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the radial aspect of organisation for motor neurones.

A
  • Neurones CLOSEST to CENTRAL CANAL –> control FLEXORS
  • Neurones FURTHER from CENTRAL CANAL –> control EXTENSORS
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are extensors very important for?

A
  • Postural Control
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What makes up a motor unit?

A
  • Single motor neurone + muscle fibres it contracts

(It is the basic unit of motor organisation)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

For a small motor unit, (around) how many muscle fibres would it contract?

Would it have high or low input resistance?

A
  • Around 10-20 muscle fibres
  • Small Motor Neurone –> thus HIGH INPUT RESISTANCE

(e.g. extra-ocular muscles)

Produces weak force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

For a large motor unit, (around) how many muscle fibres would it contract?

Would it have high or low input resistance?

A
  • Contact around 1000 muscle fibres
  • Large Motor Neurone –> thus LOW INPUT RESISTANCE

(quadraceps)

Produces a large force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What type of motor neurone innervates muscles & terminates on a number of muscle fibres?

A
  • Alpha Neurone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How can each motor unit create a force over a range?

A
  • It can vary its FIRING RATE (APs)
  • Note that the number of fibres it contracts are still fixed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What 2 factors influence the level of force?

A
  • Size of Motor Unit (number of muscle fibres)
  • *Firing Rate**
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the 3 components of Ohm’s Law?

What is the equation?

A
  • V = IR
  • Current
  • Voltage
  • Resistance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How does surface area of a neurone impact resistance?

A
  • SA –> determines the amount of membrane –> thus if it is a larger unit –> more SA & memrane –> so more channels (absolute number)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What affects the current a neurone can pass?

A
  • Resistance
  • Thus the amount of current that can pass –> which is related to the number of channels/ions that can flow through

(Small neurone has limited amount of memrane thus few channels compared to large unit)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What happens if you apply the same current to a small & large motor unit?

A
  • Small Motor Unit –> Small Neurone –> thus Small SA –> thus Less Channels –> Higher Resistance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What happens in terms of resistance and current as you increase surface area (i.e. neurone size)?

A
  • More SA –> More Membrane –> More Channels –> Less Resistance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What has high or low resistance between small & large motor units?

A
  • Small Motor Units –> HIGH RESISTANCE (easier to activate)
  • Large Motor Units –> LOW RESISTANCE
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Does high resistance increase or decrease the ease of reaching threshold?

A
  • High Resistance –> EASIER to ACTIVATE NEURONE
  • Because HIGHER RESISTANCE –> in V=IR --> means HIGHER VOLTAGE for a CERTAIN CURRENT –> thus enough VOLTAGE to REACH THRESHOLD
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What 2 factors increase voltage?

A
  • Current Size
  • Resistance

V=IR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

How does neurone resistance help in synaptic drive?

A
  • Approx Equivalent Current Source (not voltage)
  • Therefore depolarisation on the post-synaptic side –> relates to input resistance & current –> which determines voltage
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What 2 reasonable assumptions are made for this model?

A
  • Same Density of Channels across All the Neurones
  • Same Types of Channels
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What occurs in low levels of acitvation to a motoneurone pool?

A
  • Activation of small high resistance motor neurones (small motor units)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is this method of recruitment called?

A
  • Motor units –> recruited according to ‘size principle’ to generate increasing amounts of tension
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What occurs in high levels of activation to a motoneurone pool?

A
  • Activation of larger & lower resistance motor neurones (large motor units) - aswell as small
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is basal contraction? What does it cause?

A
  • Most muscles have low amounts of activity
  • This gives their muscle tone
  • Smallest motor units/neurones –> require very little synaptic drive from background activity from interneurones –> thus small sensory drive can keep them activated all the time
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What occurs in complete muscle denervation?

A

Lose Muscle Tone

Flaccidity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What determines the muscles involved in muscle tone?

A
  • Size Principal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

From where do signals come from for voluntary mvoements?

A
  • Motor Cortex (minority)
  • Interneurones (majority)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What 2 inputs do spinal interneurones get?

A
  • Information from motor cortex
  • Somatosensory information from segmental level (consider muscle reflexes in motor control)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What 2 peices of somatosensory information come into interneurones?

A
  • Muscle Spindles
  • Golgi Tendon Organ
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What do muscle spindles measure?

A
  • Distance

(length over which muscles have changes - stabalise length)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What do golgi tendon organs measure?

A
  • Tension

(resultant force generated from the muscle - i.e. force generated tension)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Why are the 2 somatosensory inputs to the spinal cords important?

A
  • Essential for control & movement
  • Increases movement accuracy (allows for fine control)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What are the 2 afferent neurone fibres to muscle spindles called?

A
  • 1a Afferents
  • Type II (A-beta) afferents/fibres
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What exactly are the 1a afferents responsible for measuring?

A
  • Dynamic Changes (in distance)
  • Dynamic aspects of stretch –> such as acceleration & velocity of stretch

(picks up the early part as soon as muscle starts moving to see how rapid the stretch it)

Fire during the cahnge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

What exactly are the Type II (A-beta) afferents responsible for measuring?

A
  • Static Distance Changes
  • Static Length of Muscle
  • Signals over a Period of Time

(sends constant information - thus if you push down and hold on a tendon –> thus they measure the change when its done)

45
Q

How are muscle spindles arranged?

A
  • Parralel with Extrafusal Fibres

(thus measure length rather than tension - would be series)

(There are a lot more extrafusal fibres compared to spindles)

46
Q

What are the muscle spindles anchored to either side?

A
  • Extrafusal Fibres
47
Q

What must change to cause activation of muscle spindles?

A
  • Change in Muscle Length
48
Q

Which parts of a movement do the 1a afferents & Type II afferents measure?

A
  • 1a afferents –> DYNAMIC/RAPID RECEPTOR
  • Type II afferents –> STATIC RECEPTOR

Thus the INITAL (dynamic) PART is measured by 1a Afferents –> however the ONGOING (static) PART is measured by Type II Afferents

(signals fades after the dynamic change is made for 1a afferents)

49
Q

Describe 1a afferents.

A
  • Largest Diameter Axons in PNS
  • Myelinated
  • Very Fast (50-70ms)
50
Q

Where is the only monosynaptci reflex?

A
  • Bicep Reflex
51
Q

What is a homonymous muscle?

A
  • Where the MOTOR OUTPUT is to the SAME MUSCLE as where the SENSORY SIGNAL came from
52
Q

What are synergistic muscles?

A
  • Muscles that have the same action function
  • Motor neurones can have collaterals to these other muscles (not common though)
53
Q

Describe Type II (A-beta) fibres.

A
  • large diameters (not as large as 1a afferents)
54
Q

Where else does the 1a afferents branch to?

A
  • 1a Inhibitory Interneurones (GABAergic)
  • Projects to antagonist muscle neurone in the joint
  • Inhibits the antagonist muscle (slight relaxation)
  • Therefore there is no co-contraction around the joint
  • Thus lowering the force on the joint
    *
55
Q

What is inhibition of the antagonist muscle when contracting called?

A
  • Reciprical Inhibition
56
Q

What 2 things does recipricol inhibition help with?

A
  1. Reduces Stress on Joint
  2. Reduces Energy Consumption
57
Q

What mediates jerk reflexes (e.g. knee jerk reflex)?

A
  • Muscle Spindles (not golgi tendon organs)
58
Q

What are the stretch reflexes & muscle spindles important for?

A
  • Holding Muscle in a Certain Position
  • Jerk Reflexes
59
Q

What keeps the limb at a maintained position?

A
  • Type II Fibres –> STATIC INFORMATION –> thus ONGOING INFORMATION to KEEP it there

(1a afferents detect dynamic aspects when the load is first dropped onto outstretched arm)

60
Q

How are the spinal reflexes important in the spinal cord?

A
  • Keep you still against gravity
  • Reflexes working all the time
  • Keep things where you want them to be (bring them back to where you want in miniature amounts)
  • Muscle spindles –> key part of motor control
    *
61
Q

Why do the spinal reflexes (muscle spindles) interact with voluntary movement systems?

A
  • Correct movements
  • Allow for central command
62
Q

Describe the muscle spindle activation pathways in passive stretch.

63
Q

How does the muscle spindle still stay ‘alert’ during contraction? Is it not laxed?

A
  • Muscle Fibres (extra-fusal fibres) + Spindles –> CO-CONTRACT

Ensures that they are still able to detect stretch (length change)

NB: Spindle is contractile itself

64
Q

Wha are the 2 parts of the muscle spindles?

A
  • Equator Region –> Middle Sensing Part
  • Polar Region –> Polar Contractile Part (contractile elements here)

These are effectively modified muscle fibres which shorten with the extra-fusal cells

65
Q

How is the signal sent out for contraction to extra-fusal and muscle spindles?

A
  • Extra-fusal Muscles –> get a direct monosynaptic signal from 1a afferents
  • Spindles –> go via interneurone
66
Q

Do the extrafusal & muscle spindles contract to the same length?

A
  • No
  • Muscle Spindles --> get own motor instruction from GAMMA MOTOR NEURONES (very small motor neurones from ventral horne)

These ensure they are approcimately the same length

67
Q

Why do we have precision control in terms of muscle spindles?

A
  • Split Alpha-Gamma Co-Activation System
68
Q

What is active contraction?

69
Q

How does Alpha-Gamma Co-Activation work?

A
  1. Motor Instructions (either from direct or indirect source) –> sends a VERSION of the MOTOR COMMAND –> to the GAMMA NEURONE (aswell as to extrafusal neurones)
  2. Thus they CO-CONTRACT via 2 SERPARATE SYSTEMS
70
Q

What is beta innervation?

A
  • Motor Neurone –> diverges to control both the spindles & extrafusal fibres (thus limited function - not much precision control)

(it has properties of both alpha & gamma neurones)

71
Q

Do humans have beta innervation?

A
  • Yes
  • e.g. hips & shoulders
  • Where fine control is not needed & beta-innervation is sufficient
72
Q

How does the split alpha-gamma system work to increase precision?

A
  • Differential Activation of Gamma & Alpha Neurones (allows for high precision movements)
  • Increase Precision –> by pre-stretching the spindles (via gamma) more than usual –> to get them into a sensitive part of their range

(This however limits travel -> thus cannot get as much force & travel - but helps with things such as threading a needle)

(balance between range & accurate)

73
Q

How are pathologies involved in split system?

A
  • They can differentially effect the alpha-gamma systems
74
Q

How are the gamma neurones activated?

A
  • They are co-activated (not at the exact same time)
  • The contraction caused by alpha neurone –> causes stretch of spindle –> causing reflex to the gamma neurone –> causing it correct its length in line with alpha neurone contraction

(1a responds to motor instruction & gamma responds to contraction)

75
Q

Why cant the muscle spindle (gamma) contract at the exact same time as the alpha (extrafusal fibres) contract?

A
  • Would cause a reflex response –> due to spindle stretch at the wrong length
  • Would propogate itself –> causing positive feedback
76
Q

How does spindle sensitivity work?

77
Q

What does EMG stand for?

A
  • Electrical Muscle Signal
78
Q

Do the 1a afferents activate during voluntary movement?

A
  • Yes
  • They correct the movement & keep it controlled
79
Q

When do you see the primary afferent signal for the gamma (spindle) come in?

A
  • After the EMG (motor signal)
  • Thus it corrects it shortly after

(cannot be the same time)

80
Q

What technique do you use to record individual axons?

A
  • Microneurography
81
Q

How does recipricol inhibitory control work?

A
  • 1a afferent neurone –> gives a collateral which sends an inhibitory neurone to antagonist muscle
82
Q

Why is it important there isn’t complete relaxation of the antagonist muscle?

A
  • All Weight on a flexed knee –> cannot hand loose
  • Needs partial co-contraction to support it before you hit the deck
  • Thus so you can remain standing with a bent knee (hamstring needs to be tense)
    *
83
Q

What occurs when there is co-contraction of muscles across a knee joint?

A
  • Knee Joint is Stiff
  • Both Muscle Contract (shorten)
  • Thus highly resistant to movement on the joint
84
Q

What measures muscle tensions at a joint?

A
  • Golgi Tendon Organ
85
Q

In what arrangement is the golgi tendon organ found?

A
  • Series with Extrafusal Fibres
86
Q

What happens when there is pull on the golgi tendon organ?

A
  • Pull on Spring Balance
  • Muscle pulls on the tendon
  • Neural Spring Balance –> causing 1b afferents sending information back
87
Q

How are the sensory endings of the 1b afferents arranged?

A
  • Weave in-between the collagen fibres
  • Therefore, when tension applied they squeeze –> causing signals sent about tension
88
Q

What are the golgi tendon organs located?

A
  • One End –> EXTRAFUSAL MUSCLE FIBRE
  • Other End –> TENDON
89
Q

How is tension distributed across golgi tendon organs?

A
  • Load Muscle Passively onto Tendon
  • Many Golgi Tendon Organs are in parrallel with each other
  • Therefore, actual force of load is divided among the number of supporting golgi tendon organs

(Therefore they are very sensitive as only a fraction of the weight is being measured by each tendon organ)

90
Q

How do they respond to a range of tensions?

A
  • Contract Some Muscle Fibres –> then only the golgi tendon organs associated with those muscle fibres are activated –> but they would be very sensitive
  • Large relative force applied –> depending on level of force –> will affect number of golgi tendon organs involved –> thus able to report a range of tensions in individual fibres –> depending on number of individual fibres involved (all together) –> giving good indications of overall loadings (not just protective feature) –> they manage forces
91
Q

When do you need the golgi tendon organ and cannot use a spindle receptors?

A
  • Co-contraction
  • There is no length change during co-contraction –> thus spindles not involved
  • Golgi tendon organ –> can measure tension instead
92
Q

Describe the golgi tendon organ pathway.

A
  • 1b afferents pick up tension signal
  • These are dynamic & fast-conducting fibres
  • They synapse onto 1b inhibitory interneurones
93
Q

What occurs when there is high tension?

A
  • Activation of 1b inhibitory interneurones –> slow firing
  • Causes homonymous muscle (self-muscle) to relax
  • This causes the opposite of the stretch reflex (‘inverse myotatic reflex’)
  • This is due to tension change

(Someone holding a knife if you pull someone’s arm away but they cannot resist after a certain point thus suddenly release to stop damage to muscle - protective reflex)

94
Q

What are the 2 functions of the golgi tendon organ?

(generally)

A
  • Protective Mechanism (high loads)
    Sensitivity Receptor
95
Q

Why is convergence important onto 1b interneurones?

A
  • Important for descending control convergence
  • Receive command instructions from a variety of place
96
Q

Name 3 places the 1b interneurone will get inputs from?

A
  1. Golgi Tendon Apparatus
  2. Input from Joints
  3. Input from Cutaneous Receptors
97
Q

Why do you get inputs from joints & cutaneous receptors to the 1b inhibitory interneurones?

A
  • These are high threshold nociceptive inputs (including pain & temperature receptors in the joint)
  • e.g. badly inflamed joint (arthiritis) –> causes excitatory firing to 1b inhibitory interneurone –> causing inhibition of motor neurones –> thus difficult to activate –> therefore cannot contract very much
  • Protective Reflex (stop certain movements –> allow for body repair
98
Q

What are the 2 types of nociceptors?

A
  • C-fibres (slow)
  • A-deltas (fast)
99
Q

Which nociceptor is involved in flexion-withdrawal reflex?

A
  • A-delta nociceptors
  • Fast conducting
100
Q

Briefly describe the flexion-withdrawal reflex.

A
  1. Relaxation of extensor + contraction of flexor
  2. Allows for flexion withdrawal –> to lift foot away from sharp object –> with no counter balance from the limb

Nociceptive Signals can illicit reflex –> causes effect via cross-extension reflex

101
Q

What is walking patterns essentially made up by?

A
  • Extension-Withdrawal Patterns –> REPEATED
102
Q

What is a renshaw cell?

A
  • Further Inhibitory Interneurone found in the spinal cord
103
Q

What is the function of a renshaw cell?

A
  • Gives motor units in the agonist muscle –> a break (time off)
  • This occurs when fibres have been very active (allows other fibres to take over)
104
Q

How is a renshaw cell innervated?

A
  • Alpha Motor Neurone –> sends a collateral to the renshaw cell –> driving inhibition back to the same motor neurone
  • Therefore there is co-activation of the inhibitory neurone onto itself
105
Q

Describe how the renshaw cell works.

A
  • Threshold Strategy
  • Motor neurones fire for a long time –> at some point they weaken –> allowing the inhibitory command to be strong enough to inhibit it –> allowing muscle fibre to rest
  • Allows for switching between fibres in motor pool (distribution of work load)
106
Q

What does the renshaw cell do in relation to antagonist muscle?

A
  • Recipricol Control
  • Controls 1a inhibitory interneurones –> to disinhibit the inhibitory neurones on the antagonist
107
Q

What other fibres makes contact with renshaw cells?

A
  • Descending Pathways
108
Q

What drives the oculo-motor reflex?

A
  • Vestibular Input from Semi-Circular Canals

Neuroscience (Yeo) (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions