Spinal reflexes

Question 1

Describe the stretch reflex.

Answer 1

Force is transmitted to muscle fibres - they are more elastic than tendons so are able to stretch.
Stretch activates 1a afferent sensory neurons in muscle spindle.
This increases the number of action potentials in 1a afferents projecting through the dorsal horn into the spinal cord.
Spindle sensory afferents divide to make 3 types of connections. (2 in spinal cord).

Question 2

Describe how contraction of a muscle comes from the stretch reflex.