Phys Chapter 9: Sensory Systems

what are the 3 types of proprioceptors

1. muscle spindles

2. tendon organs

3. joint kinesthetic receptors

what are proprioceptors

receptors that detect position of body in respect to the environment

where are muscle spindles

within skeletal muscle

what do muscle spindles respond to 

muscle length

what does stretching a muscle cause spindles to do

stretch

what does the muscle spindle capsule do

prevents the muscle from overstretching

what are the 2 connective fibers that muscle spindles are composed of

• intrafusal fibers

• extrafusal fibers

what are the 2 types of intrafusal fibers

• nuclear chain fibers

• nuclear bag fibers

what are nuclear bag fibers

nuclei that are randomly bunched together

what are nuclear chain fibers

nuclei that are arranged in a chain/row

what are the 2 types of sensory cells that wrap around the intrafusal fibers

• primary (annulospiral) - spiral around muscle cell

• secondary (flower-spary) - look like flower

What are extrafusal fibers

fibers outside

what are the 2 motor neurons that stimulate fibers

• alpha

• gamma

what do the alpha motor neurons innervate

innervate extrafusal (contracting) muscle

what do teh gamma motor neurons innervate

innervate intrafusal (active stretch) muscle fibers

• always slightly contracted to increase sensitivity to stretch/stimulate sensory receptors more

what do tendon organs do

protect tendons and associated muscles from excessive tension/ prevents damage from increased tension

where do joint kinesthetic receptors present

within and around capsules of joints

what responds to pressure

Free nerve endings and Ruffini corpuscles

what responds to joint rotation

Ruffini corpuscles

What responds to acceleration and decelerattion of joints during movement

Pacinian corpuscles