Control of Muscle Length Flashcards
What are the three types of movement?
1 - Involuntary / reflex (simplest).
2 - Voluntary (most complex).
3 - Rhythmic (a combination of reflex and voluntary).
Describe the pathway of output from the brain to motoneurones.
1 - Initiation of motor act.
2 - Association cortex.
3 - Basal ganglia and cerebellum.
4 - Thalamus.
5 - Primary motor cortex.
6 - Brainstem.
7 - Spinal neurones.
8 - Motoneurones.
List 4 sources of sensory feedback for motor movements.
1 - Visual system.
2 - Vestibular system.
3 - Skin receptors.
4 - Proprioceptors.
Which of the sources of sensory feedback for motor movements are responsible for somatic sensation?
Skin receptors and proprioceptors.
Which of the sources of sensory feedback for motor movements are responsible for the vestibulo-ocular reflex and optokinetic reflex?
The visual and vestibular systems.
Which proprioceptors are found in series with / parallel to muscle fibres?
1 - Muscle spindle (in parallel with fibres, composed of intrafusal muscle fibres).
2 - Golgi tendon organs (NOT in the muscle but in tendons, in series with fibres).
What do proprioceptors in the muscle help control?
Relex of muscle length and tension.
What regions of the muscle spindle are there?
- Central and polar regions.
- Central regions have primary and secondary sensory afferent endings.
- Polar regions adjust the sensitivity of spindle.
What are the polar regions of muscle spindle innervated by?
Gamma motoneurones.
What are the functions of the regions of the muscle spindle?
Describe the innervation of these regions.
- Central regions are innervated by primary and secondary sensory afferents:
Primary afferents respond to velocity of lengthening.
Secondary afferents respond to static length.
- Polar regions adjust the sensitivity of the spindle.
- Polar regions are innervated by gamma motoneurones.
How are the primary and secondary afferents of the spindle distributed?
Primary afferents innervate the whole central region whereas secondary afferents innervate the ends of the central region.
Where does integration of tonic muscle contraction occur?
In the spinal cord.
What is the difference between intrafusal and extrafusal muscle fibres?
Intrafusal muscle fibres are sensory organs, whereas extrafusal muscle fibres contract.
List the stages of the stretch reflex.
1 - Muscle stretches.
2 - Increased afferent signals generated by gamma motoneurones of intrafusal fibres.
3 - Afferent signals travel to the spinal cord where integration occurs.
4 - Alpha motor neurones carry efferent signals to the extrafusal muscle fibre.
5 - Muscle contracts.
Explain the role of gamma efferents in reflexes.
- Passive stretch activates gamma efferents, which can initiate corrective reflexes.
- If an alpha motor neurone is activated without firing of gamma efferents, the spindle loses activity when the muscle contracts, so no corrective reflexes can occur.
