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Nervous System > Lecture 7.1: Organisation of the Motor System and Spinal Reflexes > Flashcards

Lecture 7.1: Organisation of the Motor System and Spinal Reflexes Flashcards

1
Q

What is the role of the motor system?

A

Control of our muscles

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2
Q

What muscles does the involuntary motor system work on?

A

Operates more on axial muscles

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3
Q

What is the role of the involuntary motor system? (4)

A
  • Reflexes
  • Balance
  • Posture
  • Locomotion
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4
Q

What muscles does the voluntary motor system work on?

A

Operates more on distal muscles

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5
Q

What does the motor system comprise of?

A

Look at image in notability

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6
Q

What are Signs of Upper Motor Neurone Lesions? (5)

A
  • Weakness/Paralysis
  • Increased Tone (Spasticity)
  • Increased Tendon Reflexes
  • Hyperreflexia
  • Extensor Plantars (Babinski)
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7
Q

What are Signs of Lower Motor Neurone Lesions? (5)

A
  • Weakness/Paralysis
  • Reduced Tone (Flaccidity)
  • Loss of Tendon Reflexes
  • Wasting
  • Fasciculations
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8
Q

What is a Lower Motor Neurone (LMN)?

A

A neurone whose cell body lies in either the ventral horn of the spinal cord or cranial nerve nuclei of brain stem and directly innervates a muscle with its axon

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9
Q

What is a Motor Unit?

A
  • The number of muscle fibres innervated by a single
    axon
  • Combination of an individual α-motor neurone and
    all of the muscle fibres that it innervates
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10
Q

What does a smaller Motor Unit mean?

A

Finer control

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11
Q

What are the 2 Types of LMNs?

A
  • α-MN: innervate the muscle itself
  • γ-MN: innervate the muscle spindle and keep it
    taught
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12
Q

What is the Muscle Spindle?

A
  • Encapsulated sensory organ found within the
    muscle
  • Detects muscle contraction
  • Is responsible for tendon reflex
  • Co-activated with α-motor neurones so tighten as
    muscle contracts
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13
Q

What is the role of Muscle Spindles? (3)

A
  • Allow fine motor control and provide limb positional
    information to the CNS
  • Detects extent of muscle tension (contraction/
    relaxation) and informs the CNS
  • Activate LMNs in response to muscle stretch
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14
Q

What are the 3 Main Components of a Muscle Spindle?

A
  • Specialised intrafusal muscle fibres (central part is
    non-contractile and contains nuclei)
  • Large diameter myelinated sensory nerve fibres
  • Small diameter gamma motor nerve fibres
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15
Q

What is the role of large diameter myelinated sensory nerve fibres in muscle spindle?

A

They are wrapped around non-contractile part of muscle, ends are sensitive to stretch of intrafusal fibres

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16
Q

What is the role of small diameter gamma motor nerve fibres in muscle spindle?

A
  • They innervate contractile ends of intrafusal muscle
    fibres
  • Stimulation causes ends to contract
  • Stretches central part and stimulates sensory fibres
17
Q

What are Golgi Tendon Organs?

A

Sensory receptors found at the myotendinous junction between the muscle and tendon

18
Q

What is the role of Golgi Tendon Organs? (2)

A
  • Monitors degree of muscle contraction in terms of
    force contracted
  • Prevents over contraction of muscles (when
    activated inhibits the muscle and activates its
    antagonist)
19
Q

When we are awake LMN continually activate muscle, what is this called?

A

Resting Motor Tone

20
Q

LMN are under inhibition from …..?

A

descending pathways

21
Q

What is Muscle Tone?

A

The amount of tension (or resistance to movement) in muscles

22
Q

Why is Muscle Tone important?

A
  • Allows body posture
  • Rapid responses to environment
23
Q

What are the 3 Types of Movements?

A
  • Reflexes
  • Posture
  • Voluntary Movement
24
Q

What type of movement is facilitated by LMNs & Spinal Cord Circuits?

A

Reflexes

25
Q

What type of movement is facilitated by the Brain Stem & Spinal Cord?

A

Posture

26
Q

What type of movement is facilitated by the Cortex, Brain Stem & Spinal Cord?

A

Voluntary Movement

27
Q

What are Reflexes?

A
  • Automatic, subconscious responses to changes in
    the external environment
  • Does not require the brain!
28
Q

What are the Roles of Reflexes? (2)

A
  • Reflexes maintain homeostasis (HR, BP, digestion,
    balance, posture)
  • Reflexes are protective
29
Q

What are the 5 components of a Reflex Arc?

A
  • Receptor: detects the stimulus
  • Sensory Neurone: carries the impulse (afferent)
  • Integration Centre: processes impulse from sensory
    to motor neuron
  • Motor Neurone: conducts the output to the
    periphery (efferent)
  • Effector: e.g muscle contraction
30
Q

What is the Integration Centre in a Reflex Arc in a Simple Reflex?

A
  • Some simple reflexes may simply be 2 neurones
    and step 3 is a synapse
  • Or it can be more complex and step 3 is an
    interneuron
31
Q

What are the 2 Types of Reflex Arcs?

A
  • Monosynaptic
  • Polysynaptic
32
Q

What is the Stretch Reflex? Why is it important?

A
  • Resists stretching of muscle and maintains its length
  • Importance for posture, balance, holding heavy
    objects
33
Q

The stretch reflex also …1… synergistic muscles and …2… antagonist muscles

A

1) stimulates
2) inhibits

34
Q

How does the stretch reflex stimulate synergistic muscles?

A

Stimulates LMN supplying synergist

35
Q

How does the stretch reflex inhibit antagonist muscles?

A

Inhibits LMN supplying antagonist

36
Q

What is Reciprocal Innervation?

A

Reciprocal innervation describes skeletal muscles as existing in antagonistic pairs, with contraction of one muscle producing forces opposite to those generated by contraction of the other

37
Q

What can alter reflexes?

A

Altered with UMN and LMN lesions

38
Q

What are some examples of LMN Lesions? (4)

A
  • Carpal Tunnel
  • Cauda Equina
  • Infection (Polio)
  • MND
39
Q

What are some examples of UMN Lesions? (5)

A
  • Stroke
  • MS
  • Spinal Trauma
  • Traumatic Brain Injury
  • CP

Nervous System (18 decks)

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