Lecture 11 Functional Hierarchy of the Motor System Flashcards
a-motorneurones can be referred to as what? and why>
Final common path
Contraction of muscle occurs through this whether voluntary contraction or involuntary contraction
What motor neuron is involved in LMN
Alpha motor neuron
Gamma motor neuron
What pathway is involved in UMN
Corticospinal tract
Ipsilateral/contralateral
What regulates trunk and limb muscle reflexes
Descending inputs from vestibulospinal and reticulospinal tracts
What 4 systems control movement
- Descending control pathways
- Basal ganglia
- Cerebellum
- Local spinal cord/bran stem circuits
What is the function of the basal ganglia
Gating proper initiation of movement
What is the function of the cerebellum
Sensory motor coordination of ongoing movement
What does the descending system consist of
Motor cortex and Brainstem centres
What is the function of the motor cortex
Planning, initiating and directing voluntary movements
What is the function of the brainstem centres
Basic movements and postural control
Where are proximal shoulder muscles mapped in the motor neurones
Medially
Where are distal finger muscles mapped in the motor neurone
Laterally
How does sensory input enter the spinal cord
In the form of proprioceptors, touch, pain
How does sensory input enter the brain stem
Vestibular system informs about balance
How does sensory inout enter at a cortical level
We make movements in response to visual, olfactory, auditory, emotional and intellectual cues
Where is the stretch reflex found
In all muscles
What information does the stretch reflex use
Information from muscle spindles which monitor length
Describe the stretch reflex
Sharp tap to inelastic tendon
Force is transmitted to the muscle fibres (more elastic and therefore stretch)
Stretch activates the sensory nerves in the muscle spindle which increases the number of AP in afferent nerve–> dorsal horn leading to a monosynaptic reflex
During a stretch reflex why does the antagonist muscle relax in response to the agonist muscle contracting
Spindle afferents connect with and activate inhibitory interneurons which decrease activation of a-motorneurones to antagonist muscles (reciprocal inhibition)
Why is the stretch reflex considered a negative feedback loop
Muscle stretch
Reflex causes muscle contraction and shorten to previous length
What is responsible for the Golgi tendon organ reflex
Muscles contract and shorten which pulls strongly on the tendon and 1b sensory nerves from the GTP increase firing AP
What is the result of the increase AP for 1b sensory nerves
- Activation of inhibitory interneurones to the agonist muscle and a decrease in contraction strength- relaxes rapidly
- Activation of excitatory interneurones to antagonist muscles- contracts
What is the purpose of the GTO reflex
Prevents muscles contracting so hard that the tendon insertion is then away from the bone
What is the clasp-knife reflex
Greatly increasing tension in tendon leads to collapse of resistance to protect muscles from damage
