Open full size image Autonomic Nervous System 16.1 General Organization of the Autonomic Nervous System See next page. The autonomic nervous system is a two-neuron chain connecting preganglionic neurons through ganglia to visceral target tissues (cardiac muscle, smooth muscle, secretory glands, metabolic cells, cells of the immune system). The sympathetic division (sympathetic nervous system; SNS) is a thoracolumbar (T1-L2) system arising from the intermediolateral cell column…

Open full size image Lower Motor Neurons 15.1 Alpha and Gamma Lower Motor Neurons All lower motor neuron (LMN) groups except the facial nerve nucleus that supplies the muscles of facial expression consist of both alpha LMNs that supply the skeletal muscle fibers (extrafusal fibers) and gamma LMNs that supply the small contractile elements in the muscle spindles (intrafusal fibers). The muscles of facial expression do…

Open full size image Somatosensory Systems 14.1 Somatosensory Afferents to the Spinal Cord Unmyelinated (UNM) and small myelinated (M) axons that convey nociception and temperature sensation terminate in laminae I and V (origin of the spinothalamic tract). Other UNM axons terminate in the dorsal horn, from which neurons for polysynaptic reflexes and for the spinoreticular system originate. M axons for touch and pressure terminate in the…

Open full size image 13.1A Axial (Horizontal) Sections Through the Forebrain: Level 1—Mid Pons These axial (horizontal) sections compare anatomical sections and high-resolution magnetic resonance (MR) images. They are cut in the true horizontal (axial) plane, not in the older 25-degree tilt. The most important anatomical relationships in these sections center on the internal capsule (IC). The head of the caudate nucleus is medial to the…

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Open full size image Brainstem Cross-Sectional Anatomy 11.1 Brainstem Cross-Sectional Anatomy: Section 1 Illustrations of brainstem cross sections (Figs. 11.1–11.4) are arranged from caudal to rostral, from the spinal-medullary junction to the rostral mesencephalon-diencephalon junction; T1-weighted magnetic resonance images of the brainstem and surrounding tissue are provided for each level. Corresponding histology cross sections, stained with a fiber stain, are provided of each level. CN, cranial…

Open full size image 10.1 Cytoarchitecture of the Spinal Cord Gray Matter The spinal cord gray matter is located centrally in the interior of the spinal cord in a butterfly pattern. The gray matter is subdivided into three horns: (1) the dorsal horn, a site of major sensory processing; (2) the intermediate gray with a lateral horn, a site where preganglionic sympathetic (thoracolumbar) and parasympathetic (sacral)…

Open full size image Introduction and Basic Organization 9.1 Schematic of the Spinal Cord with Sensory, Motor, and Autonomic Components of Peripheral Nerves Peripheral nerves consist of axons from primary sensory neurons, lower motor neurons (LMNs), and preganglionic and postganglionic autonomic neurons. The primary sensory axons have sensory receptors (transducing elements) at their peripheral (distal) ends, contiguous with the initial segment of the axon. The proximal…

Open full size image 8.1 Formation of the Neural Plate, Neural Tube, and Neural Crest The neural plate, neural tube, and neural crest form at the 18-day stage of embryonic development. The underlying notochord induces the neural plate, and a midline neural groove forms. The elevated lateral margins become the neural folds, tissue destined to become the neural crest with future contributions to many components of…

Open full size image Arterial System 7.1 Meningeal Arteries: Relationship to Skull and Dura Meningeal arteries are found in the outer portion of the dura; they supply it with blood. They also help to supply blood to adjacent skull and have some anastomoses with cerebral arteries. The skull has grooves, or sulci, for the meningeal vessels. This relationship reflects an important functional consequence of skull fractures.…

Open full size image 6.1 Ventricular Anatomy The lateral ventricles are C-shaped, reflecting their association with the developing telencephalon as it sweeps upward, back, and then down and forward as the temporal lobe. The position of the lateral ventricles in relation to the head and body of the caudate nucleus is an important radiological landmark in a variety of conditions, such as hydrocephalus, caudate atrophy in…

Open full size image 5.1 Spinal Column: Bony Anatomy Anterior, lateral, and posterior views of the bony spinal column show the relationships of the intervertebral discs with the vertebral bodies. The discs’ proximity to the intervertebral foramina provides an anatomical substrate for understanding the possible impingement of a herniated nucleus pulposus on spinal roots. Such impingement can cause excruciating, radiating pain if dorsal roots are involved…

Open full size image 4.1 Brainstem Surface Anatomy: Posterolateral View The entire telencephalon, most of the diencephalon, and the cerebellum are removed to reveal the dorsal surface of the brainstem. The three cerebellar peduncles (superior, middle, and inferior) are sectioned and the cerebellum removed. The dorsal roots provide input into the spinal cord, and the cranial nerves provide input into and receive output from the brainstem.…

Open full size image 3.1 Surface Anatomy of the Forebrain: Lateral View The convolutions of the cerebral cortex permit a large expanse of cortex to be compactly folded into a small volume, an adaptation particularly prominent in primates. Major dependable landmarks separate the forebrain into lobes; the lateral (sylvian) fissure separates the temporal lobe below from the parietal and frontal lobes above, and the central sulcus…

Open full size image 2.1 Interior View of the Base of the Adult Skull The anterior, middle, and posterior cranial fossae house the anterior frontal lobe, temporal lobe, and cerebellum and brainstem, respectively. The fossae are separated from each other by bony structures and dural membranes. A swelling of the brain or the presence of mass lesions can selectively exert pressure within an individual fossa. The…

Open full size image Anatomical and Molecular Properties 1.1 Neuronal Structure Neuronal structure reflects the functional characteristics of the individual neuron. Incoming information is projected to a neuron mainly through axonal terminations on the cell body and dendrites. These synapses are isolated and are protected by astrocytic processes. The dendrites usually make up the greatest surface area of the neuron. Some protrusions from dendritic branches (dendritic…