1 The muscles that are rapidly stretched with a patellar lig

1. The muscles that are rapidly stretched with a patellar ligament tap (testing the pateller reflex) compose the hamstrings muscle group. (True/False)

2. Identify the type of sensory receptor that is stimulated when eliciting the withdraw and crossed-extensor reflex. (select one)

A. chemoreceptors

B. mechanoreceptors

C.nociceptors

D. photoreceptors

Solution

1. Answer: False

The Hamstring muscle group consist of three muscles the biceps femoris muscle, semitendinosus muscle and semimembranosus muscle. These muscles are primarily responsible for knee joint flexion or bending of the knee and also assist the extension of the thigh.

Patellar reflex or knee jerk reflex is a well known example of stretch reflex. Tapping the patella pulls on the tendon of the quadriceps femoris, it is an extensor muscle that extends the lower leg. When this muscle stretches in response to the pull of the tendon, this information is conveyed by the afferent sensory neurons to the spinal cord and the central nervous system. In the spinal cord the sensory neurons act directly on motor neurons that contract the quadriceps femoris.

2. Answer: C. Nociceptor

A nociceptor is a sensory nerve cell that responds to potentially damaging stimuli by sending signals to the spinal cord and brain. This process is called nociception. When nociceptor is stimulated, the signal travels through the sensory nerve to spinal cord. The nerve synapses with motor neurons work to pull body part away from danger within 0.5 seconds. At the same time, the sensory neuron synapses with the motor neuron stabilizes the uninjured side of the body. At the same time as these two synapses, the sensory neuron also sends signals along the spinal cord to get motor neurons to contract muscles that shift the center of gravity of the body to maintain balance. This type contralateral stimulation of motor neurons to stabilize the body is called the crossed extension reflex, and is a result of the withdrawal reflex.