Chapter 6 Interactive Brief Anatomical Study Guide

1. Motor and sensory pathways are somatotopically organized, with the cortical representations for the face located _______ to the hand and with the leg represented most medially (see Figure 6.2).

2. The spinal cord has _______ sensory roots, ventral motor roots, central gray matter, and surrounding white matter columns (see Figure 6.3). The appearance of the spinal cord varies at different levels and is thickest at the cervical enlargement and lumbosacral enlargement, where nerves for the arms and legs, respectively, arise (see Figure 6.4).

3. Blood supply for the spinal cord derives from the ________ artery and posterior spinal arteries (see Figure 6.5).

4. The lateral corticospinal tract is the most clinically important pathway in the nervous system, and knowledge of its anatomy is sufficient to localize many neurological disorders (see Figure 6.8 and Figure 6.11A). The lateral corticospinal tract originates mainly in the primary motor cortex of the precentral gyrus, descends through the ________ of the internal capsule (see Figure 6.10), down through the cerebral peduncle in the midbrain, and passes through the ventral pons to form fiber bundles along the ventral medulla called the pyramids (see Figure 6.11A and Figure 2.22A).

5. The lateral corticospinal tract crosses to the opposite side at the _______ located at the junction between the medulla and spinal cord—an essential piece of information for localizing lesions (see Figure 6.8, Figure 6.11A, and Figure 6.14). It then continues in the lateral spinal cord white matter to synapse onto motor neurons in the spinal cord anterior (ventral) horn.

6. Motor neurons projecting from the motor cortex to the spinal cord are called _______; those projecting from the spinal cord to the muscles are called lower motor neurons (see Figure 6.8). Upper motor neuron versus lower motor neuron signs (see Table 6.4) often have important implications for determining whether patients are suffering from lesions of the central nervous system versus peripheral nerves.

7. Patterns of weakness can also be very useful for localizing lesions (see Figure 6.14).

8. Although the lateral corticospinal tract is clinically the most important, there are several additional descending motor pathways. Descending motor pathways are organized into _______, such as the lateral corticospinal tract involved in limb control, and medial motor systems, which are involved in controlling proximal trunk muscles (see Table 6.3; see also Figure 6.6 and Figure 6.11).

9. The autonomic nervous system generally controls homeostatic body functions that are not under voluntary control and has two main divisions (see Figure 6.12 and Figure 6.13).

10. The _______ division is involved in "fight-or-flight" functions such as increased heart rate and blood pressure and uses norepinephrine as its neurotransmitter on end organs.

11. The _______ division subserves "rest and digest" functions such as increased salivation and peristalsis, using acetylcholine as its peripheral neurotransmitter.

12. Sympathetic (thoracolumbar) efferents arise from the _______ of the thoracic and upper lumbar spinal cord and synapse in paravertebral and prevertebral ganglia en route to their targets. Parasympathetic (craniosacral) efferents arise from brainstem and sacral spinal nuclei, synapsing in ganglia located in or near their end organs.

Back to top