By I. Kaelin. West Virginia University Parkersburg.
The word means “bridge” and refers to the thick bundle of myelinated axons that form a bulge on its ventral surface generic floxin 200mg line bacteria model. Those fibers are axons that project from the gray matter of the pons into the contralateral cerebellar cortex generic 400 mg floxin antibiotics for uti and pneumonia. It includes a copy of the motor commands sent from the precentral gyrus through the corticospinal tract, arising from collateral branches that synapse in the gray matter of the pons, along with input from other regions such as the visual cortex. These connections describe a circuit that compares motor commands and sensory feedback to generate a new output. The cerebellum is divided into regions that are based on the particular functions and connections involved. The midline regions of the cerebellum, the vermis and flocculonodular lobe, are involved in comparing visual information, equilibrium, and proprioceptive feedback to maintain balance and coordinate movements such as walking, or gait, through the descending output of the red nucleus (Figure 16. The lateral hemispheres are primarily concerned with planning motor functions through frontal lobe inputs that are returned through the thalamic projections back to the premotor and motor cortices. Processing in the midline regions targets movements of the axial musculature, whereas the lateral regions target movements of the appendicular musculature. The vermis is referred to as the spinocerebellum because it primarily receives input from the dorsal columns and spinocerebellar pathways. The flocculonodular lobe is referred to as the vestibulocerebellum because of the vestibular projection into that region. Finally, the lateral cerebellum is referred to as the cerebrocerebellum, reflecting the significant input from the cerebral cortex through the cortico-ponto-cerebellar pathway. The midline is composed of the vermis and the flocculonodular lobe, and the hemispheres are the lateral regions. Coordination and Alternating Movement Testing for cerebellar function is the basis of the coordination exam. The subtests target appendicular musculature, controlling the limbs, and axial musculature for posture and gait. The assessment of cerebellar function will depend on the normal functioning of other systems addressed in previous sections of the neurological exam. Motor control from the cerebrum, as well as sensory input from somatic, visual, and vestibular senses, are important to cerebellar function. The subtests that address appendicular musculature, and therefore the lateral regions of the cerebellum, begin with a check for tremor. The examiner watches for the presence of tremors that would not be present if the muscles are relaxed. By pushing down on the arms in this position, the examiner can check for the rebound response, which is when the arms are automatically brought back to the extended position. The extension of the arms is an ongoing motor process, and the tap or push on the arms presents a change in the proprioceptive feedback. The cerebellum compares the cerebral motor command with the proprioceptive feedback and adjusts the descending input to correct. The check reflex depends on cerebellar input to keep increased contraction from continuing after the removal of resistance. When the examiner releases the arm, the patient should be able to stop the increased contraction and keep the arm from moving.
In cases of “whiplash” in which the head is suddenly moved backward and then forward generic floxin 200 mg on line antimicrobial resistance in developing countries, a patient may experience both hyperextension and hyperflexion of the cervical region order floxin 400 mg with mastercard best antibiotic for sinus infection cipro. Abduction and Adduction Abduction and adduction motions occur within the coronal plane and involve medial-lateral motions of the limbs, fingers, toes, or thumb. Abduction moves the limb laterally away from the midline of the body, while adduction is the opposing movement that brings the limb toward the body or across the midline. For example, abduction is raising the arm at the shoulder joint, moving it laterally away from the body, while adduction brings the arm down to the side of the body. Similarly, abduction and adduction at the wrist moves the hand away from or toward the midline of the body. Spreading the fingers or toes apart is also abduction, while bringing the fingers or toes together is adduction. For the thumb, abduction is the anterior movement that brings the thumb to a 90° perpendicular position, pointing straight out from the palm. Abduction and adduction movements are seen at condyloid, saddle, and ball-and-socket joints (see Figure 9. Circumduction Circumduction is the movement of a body region in a circular manner, in which one end of the body region being moved stays relatively stationary while the other end describes a circle. This type of motion is found at biaxial condyloid and saddle joints, and at multiaxial ball-and-sockets joints (see Figure 9. Rotation Rotation can occur within the vertebral column, at a pivot joint, or at a ball-and-socket joint. Rotation of the neck or body is the twisting movement produced by the summation of the small rotational movements available between adjacent vertebrae. For example, at the atlantoaxial joint, the first cervical (C1) vertebra (atlas) rotates around the dens, the upward projection from the second cervical (C2) vertebra (axis). This joint allows for the radius to rotate along its length during pronation and supination movements of the forearm. Here, the humerus and femur rotate around their long axis, which moves the anterior surface of the arm or thigh either toward or away from the midline of the body. Movement that brings the anterior surface of the limb toward the midline of the body is called medial (internal) rotation. Conversely, rotation of the limb so that the anterior surface moves away from the midline is lateral (external) rotation (see Figure 9. Be sure to distinguish medial and lateral rotation, which can only occur at the multiaxial shoulder and hip joints, from circumduction, which can occur at either biaxial or multiaxial joints. When the palm of the hand faces backward, the forearm is in the pronated position, and the radius and ulna form an X-shape. Pronation is the motion that moves the forearm from the supinated (anatomical) position to the pronated (palm backward) position. This motion is produced by rotation of the radius at the proximal radioulnar joint, accompanied by movement of the radius at the distal radioulnar joint. Because of the slight curvature of the shaft of the radius, this rotation causes the distal end of the radius to cross over the distal ulna at This OpenStax book is available for free at http://cnx. Supination is the opposite motion, in which rotation of the radius returns the bones to their parallel positions and moves the palm to the anterior facing (supinated) position. It helps to remember that supination is the motion you use when scooping up soup with a spoon (see Figure 9. Dorsiflexion and Plantar Flexion Dorsiflexion and plantar flexion are movements at the ankle joint, which is a hinge joint. Lifting the front of the foot, so that the top of the foot moves toward the anterior leg is dorsiflexion, while lifting the heel of the foot from the ground or pointing the toes downward is plantar flexion. Inversion and Eversion Inversion and eversion are complex movements that involve the multiple plane joints among the tarsal bones of the posterior foot (intertarsal joints) and thus are not motions that take place at the ankle joint.