Reflexes and Central Pattern Generator Circuits

Question 1

What is a reflex?

Answer 1

involuntary response to a stimulus

• Organized at the level of the spinal cord or the brainstem
• Doesn’t need to be learned

Question 2

What is not required for the reflexes to occur?

Answer 2

Brain

Question 3

Reflexes are modified by what?

Answer 3

(facilitated or inhibited) by the brain and brainstem and by spinal interneurons

Requires at least 2 neurons and 1 synapse

Question 4

What is a monosynaptic?

Answer 4

Only naturally occurring reflex that does not involve interneurons.

-Deep tendon reflex

Question 5

An Exaggerated reflex response with injury to descending inhibitory motor tracts

Increased reflex output

Answer 5

Hyperreflexia

Question 6

What is decreased or abolished reflex response to the first order Ia afferent neuron or the Alpha motor neuron?

Decreased reflex output

Answer 6

Hyporeflexia

Question 7

What is a reciprocal inhibition?

Answer 7

Inhibits activation of the antagonist muscle to allow unopposed contraction of agonist.

Involves an inhibitory interneuron.

Question 8

What does reciprocal inhibition occur as?

Answer 8

a Reflex

Reflex activated by a quick lengthening of an agonist muscle.

Question 9

Reciprocal inhibition comes from where for motor control?

Answer 9

It comes from the brain or brainstem

Question 10

Higher center control involves simultaneous excitation of both the agonist Alpha motor neuron and an inhibitory interneuron to the antagonist Alpha motor neuron which means?

Answer 10

Excitation of the agonist Alpha motor neuron and simultaneous inhibition of antagonist Alpha motor neuron.

Question 11

What does a Tendon Organ Reflex - Autogenic inhibition do?

Answer 11

Prevents a contraction so strong that it would damage the tendon.

Question 12

What does a withdrawal/nocifensive reflex do?

Answer 12

Protective response

When a bad stimulus is near the body the body withdraws that body part away.

Question 13

The withdrawal/nocifensive reflex the afferents and/or interneurons travel where?

Answer 13

Up and down the spinal cord to reach the appropriate levels to activate muscles for withdrawal from the stimulus.

Question 14

What is the crossed-extension reflex?

Answer 14

Occurs at the same time as the withdrawal reflex

-Allows for weight bearing support when a limb is suddenly lifted off the ground or the trunk quickly shifts position.

Question 15

What is a Babinski Reflex

Answer 15

Simulation to the sole of the foot

Normal response is flexion of the toes

Question 16

What is a positive Babinski?

Answer 16

Abnormal response - Extension of the great toe which may be accompanied by fanning of the lesser toes

-A positive Babinski is a sign of a upper motor neuron injury.

Question 17

Central Pattern Generators are circuits of neurons connected inside the gray matter of the spinal cord by interneurons allowing for?

Answer 17

Repetitive rhythmic behaviors without involvement of the cortex

Question 18

Central pattern generators allow for?

Answer 18

Stereotyped behaviors without control of higher centers.

• Walking (called stepping pattern generators)
• Chewing
• Feeding (hand to mouth)