Reflex Arc

Question 1

Reflex arc overview

Answer 1

• Neural pathway that controls a reflex
• Protective mechanism to allow faster reactions to particular stimuli
• Not a voluntary action / No involvement of the brain
• Monosynaptic reflex as it involves direct connection between sensory neurons and motor neurons with no neurons in between.

Question 2

Reflex arc order

Answer 2

• Sensor
• Sensory neuron
• Control centre
• Motor neuron
• Muscle (effector)

Question 3

Knee jerk reflex - Sensor

Answer 3

• Taps patella tendon (just below patella)
• Patella tendon stretches which is detected by stretch receptors (muscle spindles) in the quadriceps muscles.

Question 4

Knee Jerk reflex - Sensory Neurons

Answer 4

Stimulated by receptors and send impulse to the spinal cord

• Also stimulate inter neurons - Inhibit activity of motor neurons that supply opposing muscle (hamstring)
• Cause contraction of the quadriceps to be unopposed.

Question 5

Knee jerk reflex - Integrating centre

Answer 5

Spinal cord receives sensory signal and activates motor neuron.

Question 6

Knee jerk reflex - Motor neuron

Answer 6

Motor neuron carries signal from spinal cord to the effector (Quadriceps)

Question 7

Knee jerk reflex - Effector

Answer 7

Quadriceps contract