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Hello student, here the question has given, the question is about these stretch reflex, so we know this is also known as the knee jerk reflex, knee jerk reflex or it is also termed as this myo -thertic reflex, so it is a kind of a simple rapid and involuntary response, involuntary response to a sudden increase in its length, so this is the sudden response of muscles, we can say this is the involuntary response to of the muscles to this sudden increase in this due to the stretch or this increase in length due to this stretch, so this is mainly a reflex reaction and the important part is this muscle, body is going over all the control and this in the coordinated manner, so here the some step which are involved in this case, so first one this stretching of the muscles, so this stretching of muscles is reflex is initiated of this stretching of muscles whenever this reflex is initiated, reflex is initiated when muscles is going to be stretched, so in that case the patellar tendon, so in that this patellar tendon and this is the just below the kneecap, the kneecap is tapped, so if it is going to tap with the hammer, so due to this with the reflex ham, the cause of this quadriceps muscles, the muscles which is going to be stretched in the thigh, so in that particular case this muscle spindle activation taking place, spindle activation and we know this is a specialized sensory receptors which is called as this muscle spindle, so these muscle spindle are a stretch receptor and they are sensitive to changes in their muscle length, so when the muscle is a stretch then it is going to be activated, so here if you look into this, so the blue one is the sensory neuron and the red one is the motor neuron and these green one is represented as a interneuron, so in the case of when this knee is going to be, this reflexes with this hammer then this sensory stretch receptors which is this muscle spindle is going to be activated and by the activation of this, this sensory neurons are the going to send the signal to this spinal cord and from the sensory neurons in the dorsal root ganglions and come into this spinal cord wherein this is the gray matter which is represented, so from here it is going to be interplay from these synapse which is the acting as a interneurons, so here these are the synapse, so in that case this one is the acting as a motor neuron, so here this motor neuron is going to send back this signal to the quadriceps and these quadriceps muscles are going to be this in the response of this they are going to be flexor, so this one is going to be extended toward the upward side, so this is the knee jerk reflex action and this one is the interneuron which is going to be send this, this one is the inhibitory motor neuron and this going to send the signal to this flexor muscle and these flexor muscles are going to be relaxed in that condition because this one is going to be inhibitory in the nature while this one is going to be excitatory and this one is going to be inhibitory in that particular case, so if we are talking about this muscle spindle activation which is a sensory receptor, so this one is the sensory receptor, so this is activated as we can see and after that it is send the signal from this sensory neuron which is also called as this afferent sensory neuron or afferent neuron and this send signal to the spinal cord and from this spinal cord they are the we know these are neurons are the part of the peripheral nervous system and this is spinal cord processing mainly this going to be transmitted to the motor neuron, so from this it is going to be transmitted to this motor neuron and this sensory neuron synapses is present in the case of with interneurons, so the motor neuron within the spinal cord which is present within this gray matter and these motor neuron activation will be taking place and these motor neuron receiving the sensory input from the synapse with this motor unit and we know this is the group of muscles fiber and here the single motor neuron controlled by this single motor neuron of the same muscle which is going to be stretched, so in case of this knee jerk reflex the motor neuron innervate this quadriceps muscles, so this quadriceps muscle is going to be extensure and the muscle contraction will be taking place, so these motor neuron stimulate this motor unit to contract the muscles and in this contraction of these quadriceps muscles causes legs to extend and resulting in this knee jerk response, so this is a kind of monosynaptic reflexes because there is a single synapse between these knee jerk reflexes, so this is a kind of monosynaptic reflex because here the single synapse involved...