The dorsal, or posterior, horns of the gray matter are mainly devoted to sensory functions whereas the ventral, or anterior, and lateral horns are associated with motor functions. E All of the answers are correct. Forceful trauma to the trunk may cause ribs or vertebrae to fracture, and debris can crush or section through part of the spinal cord. The patient is asked to stand straight with feet together. Another issue of sensory discrimination is not distinguishing between different submodalities, but rather location. B output to visceral organs would be blocked. B injured one of her ascending nerve tracts.
Within the spinal cord, the two systems are segregated. As a result, which of the following would you expect? Why is the distance between the caliper points closer on the fingertips as opposed to the palm of the hand? A loss of sensation in his torso B inability to breathe C problems with moving his arms D uncontrollable sweating of his feet E problems moving his legs 61 Mary is in an automobile accident and suffers a spinal cord injury. Sensory discrimination can pinpoint the level of damage in the spinal cord. The plantar reflex is commonly tested in newborn infants to establish the presence of neuromuscular function. Identify and describe the anatomical features of the spinal cord and spinal nerves 2. The trauma would be at the level just before sensory discrimination returns to normal, helping to pinpoint the trauma.
The sensory results are more complicated. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Other superficial reflexes are not commonly tested, though a series of abdominal reflexes can target function in the lower thoracic spinal segments. The examiner will ask the patient to lift the arm, for example, while the examiner is pushing down on it. C It can provide sensory and motor anesthesia, depending on the anesthetic selected. The descending input of the corticospinal tract modifies the response of the plantar reflex, meaning that a negative Babinski sign is the expected response in testing the reflex.
For the arm, the common reflexes to test are of the biceps, brachioradialis, triceps, and flexors for the digits. This test can indicate deficits in dorsal column pathway proprioception, as well as problems with proprioceptive projections to the cerebellum through the spinocerebellar tract. Testing of the senses begins with examining the regions known as dermatomes that connect to the cortical region where somatosensation is perceived in the postcentral gyrus. C the spinal cord would not be able to process information at that level. Testing these stimuli provides information about whether these two major ascending pathways are functioning properly.
The likelihood of trauma to the spinal cord resulting in a hemisection that affects one anterior column, but not the other, is very unlikely. Whereas the brain develops into a complex series of nuclei and fiber tracts, the spinal cord remains relatively simple in its configuration. Somatic senses are incorporated mostly into the skin, muscles, or tendons, whereas the visceral senses come from nervous tissue incorporated into the majority of organs such as the heart or stomach. The full section of a spinal cord would result in paraplegia, or loss of voluntary motor control of the lower body, as well as loss of sensations from that point down. C the spinal cord would not be able to process information at that level. If none of the other subtests suggest particular deficits with the pathways, the deficit is likely to be in the cortex where conscious perception is based. The Publishers assumes no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information herein.
C Some reflex responses are hereditary. Her knee-jerk reflex is normal and she exhibits a plantar reflex negative Babinski reflex. E All of the answers are correct. For the leg, the knee-jerk reflex of the quadriceps is common, as is the ankle reflex for the gastrocnemius and soleus. D the brain would not be able to communicate with that level of the spinal cord. The reason for this is that the dorsal column pathway ascends ipsilateral to the sensation, so it would be damaged the same way as the lateral corticospinal tract.
She has lost feeling in her lower body. Muscle Strength and Voluntary Movement The skeletomotor system is largely based on the simple, two-cell projection from the precentral gyrus of the frontal lobe to the skeletal muscles. External Website Watch this to see a quick demonstration of two-point discrimination. The arm is moved at the elbow and wrist, and the leg is moved at the knee and ankle. Pairing the light touch and pain subtests together makes it possible to compare the two submodalities at the same time, and therefore the two major ascending tracts at the same time. Mistaking painful stimuli for light touch, or vice versa, may point to errors in ascending projections, such as in a hemisection of the spinal cord that might come from a motor vehicle accident.
If one side is not perceived, this may indicate damage to the contralateral posterior parietal lobe. If a muscle is stretched, it reflexively contracts to return the muscle to compensate for the change in length. In the white matter, the dorsal column relays sensory information to the brain, and the anterior column is almost exclusively relaying motor commands to the ventral horn motor neurons. The two-point discrimination subtest highlights the density of sensory endings, and therefore receptive fields in the skin. The motor system can indicate the loss of input to the ventral horn in the lumbar enlargement where motor neurons to the leg are found, but motor function in the trunk is less clear. D a spinal injury in the cervical region.