Flower spray ending of muscles

Reading File

Finding Sources

Reading File

Loading Image

Here is a complete, textbook-based explanation of the flower-spray ending of muscles:

Flower-Spray Ending (Secondary Afferent Ending) of the Muscle Spindle

What is it?

The flower-spray ending is the secondary sensory ending of the muscle spindle - a specialized proprioceptor embedded within skeletal muscle. It gets its name from its characteristic appearance: the nerve terminals spread out like branches on a bush (or a flower spray), in contrast to the tightly wound spiral of the primary ending.

Muscle spindle diagram showing nuclear bag and chain fibers, with Group Ia (annulospiral) and Group II (flower-spray) endings

Guyton & Hall - Figure 55.4: Group II fibers (blue) form the flower-spray endings; Group Ia fibers (teal) form the annulospiral primary endings

Key Properties

Feature	Flower-Spray (Secondary) Ending	Annulospiral (Primary) Ending
Nerve fiber type	Group II (Type II), Aβ fibers	Group Ia, Aα fibers
Fiber diameter	~8 µm average	~17 µm average
Conduction velocity	~30-70 m/sec	~70-120 m/sec
Location on spindle	Striated (polar) portions of bag fibers; nuclear chain fibers	Central (equatorial) region of all intrafusal fibers
Intrafusal fibers innervated	Nuclear chain fibers + static nuclear bag fibers	Both nuclear bag AND nuclear chain fibers
Morphology	Branches spreading like a bush/spray	Tight spiral wrapping (annulospiral)

Where exactly does it sit?

The muscle spindle contains two types of intrafusal fibers:

Nuclear bag fibers (1-3 per spindle) - nuclei clumped in a central "bag"
Nuclear chain fibers (3-9 per spindle) - nuclei in a chain along the central region

The flower-spray (type II) endings sit on either side of the primary ending, over the striated polar portions of the nuclear bag fibers and along the nuclear chain fibers. - Histology: A Text and Atlas, p. 833

Muscle spindle cross-section and schematic showing intrafusal fibers, afferent Ia/II fibers, and efferent gamma fibers

Histology A Text and Atlas - Figure 11.16: Schematic and H&E photomicrograph of the muscle spindle

Functional Response

The flower-spray endings respond only to the static (length) component of stretch:

When the muscle is slowly or steadily stretched, they fire in proportion to the degree of elongation and continue firing as long as the stretch is maintained - this is the static response.
Unlike primary endings, they do NOT respond to the rate of change of stretch (i.e., no dynamic response).
They therefore signal absolute muscle length, not velocity of change.

In contrast, primary (annulospiral) endings respond to BOTH static length AND the rate of stretch (dynamic response). - Guyton and Hall Medical Physiology, p. 678

Summary in one sentence

The flower-spray ending = the secondary afferent ending of the muscle spindle, carried by Group II (Aβ) fibers, located over the striated poles of intrafusal fibers (especially nuclear chain), responding only to static muscle length (not velocity).

This is a shared conversation. Sign in to Orris to start your own chat.