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Terms in this set (40)

Upper motor neuron lesions prevent signals from traveling from your brain and spinal cord to your muscles. Your muscles can't move without these signals and become stiff and weak. Damage to upper motor neurons leads to a group of symptoms called upper motor neuron syndrome:
In lower motor neuron lesions (damage to the nucleus or nerve), the upper and lower facial muscles on the same side as the lesion are paralysed. Inability to close the eyelids may lead to corneal ulceration, especially if reflex lacrimation is also lost.
Knee jerk: In a knee jerk reflex, the patellar tendon is tapped using a hammer. This stimulates the stretch receptors AKA muscle spindles in the quadriceps, which elicits an extension of the leg. This is done by stimulating the afferent receptor then the afferent nerve. Information is processed in the CNS where there is a synapse between the sensory and motor nerves and the signal is transferred to the efferent nerve which extends the knee. The lower motor neuron ability is tested with the knee jerk reflex test. With an upper motor neuron lesion the response would still happen but with a lower motor neuron lesion, there wouldn't be a response.
Achilles: distal attachment site is the calcaneus. The muscle group activated is the gastrocnemius which is innervated by the tibial nerve. The level of the spinal cord that innervates this muscle is the S1 which eventually elicits a response from the tibialis anterior. The tibialis anterior then causes dorsiflexion of the foot. A lower motor neuron lesion would prevent this reflex from occurring.