Spinal reflexes

Question 1

Muscle spindle

Answer 1

Stretch receptor

• senses change in muscle length
• arranged in parallel with extrafusal muscle fibers

Question 2

Gamma MNs

Answer 2

innervate intrafusal muscle fibers

• small diameter
• no force generation
• affect stiffness
• shortens the intrafusal muscle

Question 3

Intrafusal muscle fibers

Answer 3

Ia receptors and tyep II receptors

Question 4

Type Ia receptors

Answer 4

Dynamic- intense firing during stretch

bag fibers

Question 5

Type II receptors

Answer 5

Static- steady firing
increase with increasing stretch
chain fibers

Question 6

GTO type Ib

Answer 6

in series with extrafusal fibers

• active muscle contraction- causes firing of GTO
• Passive doesn’t fire GTO

Question 7

GTO reflex

Answer 7

fires Ib inhibitory interneurons

• inhibits homonymous muscle
• excites disynaptic pathway- excite antagonist muscle

Question 8

interneurons

Answer 8

amplify/distribute excitatory signal

change polarity of signal