Reflex Arc

Question 0

What is the receptor?

Answer 0

Site of the stimulus

Question 1

What are the 5 components of a reflex arc?

Answer 1

1. Receptor
2. Sensory neuron
3. Integration center
4. Motor neuron
5. Effector

Question 2

What does the sensory neuron do?

Answer 2

Transmits the afferent impulse

Question 3

What does the integration center do?

Answer 3

Either monosynaptic or polysynaptic region within the CNS

Question 4

What does the motor neuron do?

Answer 4

Conducts efferent impulses from the integration center to the effector.

Question 5

What is the effector?

Answer 5

Muscle fiber or gland that responds to the efferent impulse.

Question 6

What are the 2 components the nervous system needs in order for skeletal muscle to perform in a normal coordinated fashion?

Answer 6

1. Length of muscle.

2. Amount if tension in the muscle

Question 7

Length if muscle is provided by what?

Answer 7

Muscle Spindles

Question 8

Amount of tension is provided by what?

Answer 8

Golgi tendon organs.

Question 9

What are muscle spindles composed of?

Answer 9

Muscle fibers called Intrafusal Muscle Fibers that are wrapped in a connective tissue capsule that serves as a receptive surface.

Question 10

Where is the contractile portion of a muscle spindle?

What type of fiber is it innervate by?

Answer 10

The ends are contractile.

Innervated by gamma efferent fibers
*note: contractile skeletal fibers are Innervated by alpha efferent fibers.

Question 11

How does a muscle spindle operate?

Answer 11

Gamma efferent signals from the brain cause the muscle spindles to be more taut (ready for a vertical jump) or less taut, depending on the situation.

Question 12

How does stretching activate a muscle spindle?

Answer 12

It sends an afferent impulse to the spinal cord.

The greater the stretch, the higher the impulse frequency.

Question 13

Tapping the patellar tendon quickly causes what?

Answer 13

Stretching of the quadriceps & starts the reflex action.

Question 14

What are the 2 components of a stretch reflex?

Answer 14

1. Monosynaptic Component

2. Polysynaptic Component

Question 15

What happens during the monosynaptic component?

Answer 15

• There is an afferent impulse sent to the spinal cord.
• it synapses with an alpha motor neuron in the ipsilateral ventral horn.
• causing immediate contraction of the quadriceps = knee extension.

Question 16

What happens during the polysnaptic component?

Answer 16

• there is an afferent signal sent to the spinal cord.
• it synapses with an Inhibitory Interneuron which subsequently synapses with the ventral horn alpha-motor neuron for the antagonist muscle.

Question 17

What is the net result of the monosynaptic & polysnaptic components?

Answer 17

Reciprocal Inhibition

Quads contract & hamstrings relax

Question 18

What is the stretch reflex?

Answer 18

When the brain sends commands to the gamma-motor neurons setting a muscle’s length (or tone).

Ex: knees don’t buckle during a squat.