3 main components of a muscle spindle:
– intrafusal fibres (specialized small muscle fibres)
– sensory neuron endings; groups Ia and II (wrap around the central regions of the intrafusal muscle
– gamma motor neuron endings (activate the polar contractile regions of the intrafusal fibres
2 subtypes of intrafusal muscle fibres:
– nuclear bag signals the static length of an entire muscle and dynamic changes in muscle length
- have many spherical nuclei at their centre and can stretch quickly when lengthened due to
– nuclear chain only signals the static length of an entire muscle
- have a single row of nuclei that stretch more slowly (are less elastic)
Type Ia afferent neurons are best able to respond quickly to stretching and sense the rate of change.
They can be found wrapped around the equatorial region (which is most elastic) of both bag and
chain intrafusal muscle fibres
Which intrafusal muscle fibres do Type II afferents mainly innervate and why are they less sensitive
to dynamic change in muscle length when compared to type Ia afferents?
What is the main difference between alpha and gamma motor neuron function?
The activation of __________ enhances dynamic response of Ia affer