Lecture 7.1: Organisation of the Motor System and Spinal Reflexes Flashcards
(39 cards)
What is the role of the motor system?
Control of our muscles
What muscles does the involuntary motor system work on?
Operates more on axial muscles
What is the role of the involuntary motor system? (4)
- Reflexes
- Balance
- Posture
- Locomotion
What muscles does the voluntary motor system work on?
Operates more on distal muscles
What does the motor system comprise of?
Look at image in notability
What are Signs of Upper Motor Neurone Lesions? (5)
- Weakness/Paralysis
- Increased Tone (Spasticity)
- Increased Tendon Reflexes
- Hyperreflexia
- Extensor Plantars (Babinski)
What are Signs of Lower Motor Neurone Lesions? (5)
- Weakness/Paralysis
- Reduced Tone (Flaccidity)
- Loss of Tendon Reflexes
- Wasting
- Fasciculations
What is a Lower Motor Neurone (LMN)?
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
What is a Motor Unit?
- 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
What does a smaller Motor Unit mean?
Finer control
What are the 2 Types of LMNs?
- α-MN: innervate the muscle itself
- γ-MN: innervate the muscle spindle and keep it
taught
What is the Muscle Spindle?
- 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
What is the role of Muscle Spindles? (3)
- 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
What are the 3 Main Components of a Muscle Spindle?
- Specialised intrafusal muscle fibres (central part is
non-contractile and contains nuclei) - Large diameter myelinated sensory nerve fibres
- Small diameter gamma motor nerve fibres
What is the role of large diameter myelinated sensory nerve fibres in muscle spindle?
They are wrapped around non-contractile part of muscle, ends are sensitive to stretch of intrafusal fibres
What is the role of small diameter gamma motor nerve fibres in muscle spindle?
- They innervate contractile ends of intrafusal muscle
fibres - Stimulation causes ends to contract
- Stretches central part and stimulates sensory fibres
What are Golgi Tendon Organs?
Sensory receptors found at the myotendinous junction between the muscle and tendon
What is the role of Golgi Tendon Organs? (2)
- Monitors degree of muscle contraction in terms of
force contracted - Prevents over contraction of muscles (when
activated inhibits the muscle and activates its
antagonist)
When we are awake LMN continually activate muscle, what is this called?
Resting Motor Tone
LMN are under inhibition from …..?
descending pathways
What is Muscle Tone?
The amount of tension (or resistance to movement) in muscles
Why is Muscle Tone important?
- Allows body posture
- Rapid responses to environment
What are the 3 Types of Movements?
- Reflexes
- Posture
- Voluntary Movement
What type of movement is facilitated by LMNs & Spinal Cord Circuits?
Reflexes
