Endorphin System
The locus ceruleus and the A5 and A7 noradrenergic cell groups of the posterolateral pons are the main source of noradrenergic input to the dorsal horn. These regions send bilateral…
Pain Pathways
The current model of descending pain modulation involves both inhibitory and facilitatory influences on spinal nociceptive transmission. The balance between inhibition and facilitation is dependent on different behavioral, emotional, and…
Somatosensory Afferents and Principal Fiber Tracts
The thalamus is the main relay structure for sensory information destined for the cortex; it is involved in reception, integration, and transfer of nociceptive potentials. WDR neurons project to the…
Clinical Presentation of Autonomic Disorders
Autonomic disorders may be classified as peripheral or central and acute or chronic disorders. ACUTE PERIPHERAL AUTONOMIC DISORDERS Acute/subacute autonomic neuropathies are usually due to toxic, metabolic, autoimmune, or paraneoplastic…
Somatosensory System
C-type fibers (unmyelinated) slowly propagate dull, burning (secondary) pain sensation information. Some C fibers are modality-specific and respond only to thermal, mechanical, or chemical noxious stimuli. However, the majority of…
Abnormal Pupillary Conditions
Although initially the affected pupil is larger than the contralateral pupil, with time it can become smaller. The pupil is very sensitive to acetylcholine (probably due to denervation supersensitivity), with…
Autonomic Testing
SWEAT TESTING The thermoregulatory sweat test consists of the visual detection of skin humidity in response to warm external temperature. A dye that changes color when moist is painted or…
Innervation of Male Reproductive Organs
Sympathetic preganglionic fibers are the axons of intermediolateral column cells located in the lowest two or three thoracic and upper one or two lumbar segments of the spinal cord. They…
Innervation of Female Reproductive Organs
An inferior group of a few small nerves arises from the inferior hypogastric plexus and from the nerve loops around the lower end of the ureter (see page 195). This…
Innervation of Urinary Bladder and Lower Ureter
Most of the nerve fasciculi in the urinary bladder wall contain unmyelinated or finely myelinated fibers. A small proportion of larger myelinated and, presumably, sensory fibers are connected with terminal…
