Lecture 17: Control of movement 1 Flashcards
What are the 3 classes of movements
- Voluntary
- Somatic reflexes (eg. stretch reflex)
- Rhythmic motor patterns (eg. breathing, locomotion, chewing)
What are the two motor circuits in the motor system and what do they do
- Cerebral cortex to basal ganglia and thalamus: involved in Planning movements occurring in a short amount of time.
- Brainstem, cerebellum and thalamus: keeps movements smooth
What parts of the motor system are important for the control of the 3 movements
Voluntary movements = Forebrain (cortex loops)
Reflex and rhythmic motor patterns: Spinal cord and brainstem
Where are Motoneurons/ lower motor neurons located?
Mainly located in the anterior horn of the spinal cord as well as in the brainstem where nerve cells form nuclei send axons with cranial nerves to muscles. (all of 12 except 1,2,and 8).
What is 3 segments of brainstem from inferior to superior
medulla oblongata, pons and midbrain
What do alpha motor neurons do
-Alpha innervate extrafusal muscles fibres through the ventral horn to ventral root and are directly responsible for the generation of force by muscles) with different types for different muscle fibres
Who was Sir John C Eccles
He developed a method to impale motor neurons to record membrane potential, synaptic potential and response to activation of some nerve cells
Compare the somatic , sympathetic and parasympathetic target tissue and neurotransmitters used from CNS to PNS to target tissue
Target tissue for somatic is skeletal muscle whereas for ANS its smooth muscle, cardiac muscle and glands.
Somatic only has one neuron to target tissue. ANS has 2 with sympathetic synapsing in the PNS and Parasympathetic synapsing at the target tissue.
Somatic uses ACh and so does first synapse of ANS.
Sympathetic uses NA at target tissue. Parasympathetic uses ACh at target tissue
What do gamma motoneurons do
Gamma motoneurons innervate the intrafusal muscle fibres within the muscle spindle.
They increase the response of muscle spindles to stretch- control the excitability of stretch receptors in the muscle spindle
Define motor unit and its 4 components
Anatomical and functional element of the motor system made of a
- cell body + dendrites of an a-motoneuron,
- its axon,
- all neuromuscular junctions formed by single motorneuron and
- all extrafusal muscle fibres innervated by single motoneuron
How many neurons can innervate a muscle fibre at one endplate vs how many muscle fibres can an a-motoneuron innervate
At one neuromuscular junction only 1 motoneuron is synapsing, but the number of individual muscle fibres 1 motoneuron can synapse with is up to 2000
What are the 2 types of motor units
S type (slow twitch) called Type 1 and FF type (fast twitch, fatigable) called Type 2B. (There is also a rare intermediate type 2A)
Compare the metabolism, and therefore amount of myoglobin, glycogen, mitochondria and capillaries present. How does this affect appearance of type 1 and 2B muscle fibres
Metabolism of type 1 is oxidative whereas for type 2B its glycolytic.
This means that myoglobin, mitochondria and capillaries are high density in type 1 fibres but the there is little glycogen. This means type 1 fibres appear small and red while type 2B appear large and pale
Compare the twitch time for type 1 and 2B and therefore the time of recruitment, tetanic tension and fatigue
Twitch time of Type 1 is long (>50ms) compared to Type 2B (20s). Therefore type 1 is recruited early and type 2B late. The tetanic tension of type 2B is large (powerful_ but the fatigue is rapid whereas type 1 fatigue is little or none but its weak
Compare the number of units, axon diameter and number of terminals of the type 1 and 2B
Type 1 has relatively more units compared to 2B but 2B has larger axon diameter and number of terminals
