Reflexes

Question 1

Stretch reflex

Answer 1

Monosynaptic reflex. Excited by a sharp tap to the inelastic tendons which transfer the force to muscle fibres which stretch and stimulate the spindles. This activates the alpha motoneurones and the agonist muscle contracts.
The antagonist muscle will relax as the spindle afferents activate inhibitory interneurones which decrease alpha motorneurone transmission to the antagonist.

Question 2

Reflex mediated by Golgi tendon organ

Answer 2

Inverse stretch reflex/clasp-knife reflex.
It is protective as it prevents over contraction causing tears in the tendons. It is polysynaptic.
As the muscle contracts it pulls on the tendons amd the golgi tendon bodies increase their discharge of APs. This activates inhibitory interneurones to the agonist muscle and decreases the contraction strength while also activating excitatory interneurones to the antagonist. Can be overcome.

Question 3

Interneurones

Answer 3

Create neural circuits in the CNS enabling communication between sensory and motor neurones.

Question 4

Ispislateral reflex

Answer 4

A reflex action on the same side of the body to where the stimulus was perceived. Monosynaptic.

Question 5

Contralateral reflex

Answer 5

The reflex occurs on the opposite side of the body from the stimulus.

Question 6

Flexor-withdrawal reflex

Answer 6

Polysynaptic. Information comes from nociceptors in skin, muscle and joints. It withdraws the affected part of the body away from stimulus towards the body.
The sensory stimulus causes excitatory interneurones to increase activity in the flexor and inhibitory interneurones work in the antagonist.

Question 7

Higher centres in reflexes

Answer 7

Higher centres control subconscious maintenance of the body’s posture (postural reflexes). When movement and position is altered they ensure that the body remains upright and balanced.