SBA Answers and Explanations
Vivian A. Elwell, Jonathan M. Fishman, Rajat Chowdhury in SBAs for the MRCS Part A, 2018
There are 12 pairs of cranial nerves and 31 pairs of spinal nerves. The central nervous system comprises the brain and spinal cord. A peripheral nerve is a mixed nerve containing motor, sensory, and autonomic (parasympathetic, sympathetic) elements. Parasympathetic outflow arises from the ‘craniosacral’ region; that is, from certain cranial nerves and sacral roots S2–4. Cranial nerves III (occulomotor), VII (facial), IX (glossopharyngeal), and X (vagus) carry parasympathetic fibres whose function is primarily secretomotor (e.g., salivary secretions in the case of cranial nerve VII) and ciliary motor (pupillary reflexes and accommodation in the case of cranial nerve III), while cranial nerves IX and X play an integral role in blood pressure regulation. Sympathetic outflow is principally ‘thoracolumbar’ (i.e., from spinal segments T1 through to L2). The sympathetic nervous system serves vasomotor (vascular tone), sudomotor (sweating), and pilomotor functions, in addition to controlling smooth muscle and sphincter tone and playing a key role in cardiovascular homeostasis.
Nervous system
David Sturgeon in Introduction to Anatomy and Physiology for Healthcare Students, 2018
The peripheral nervous system refers to the nerves of the body that are not part of the brain and spinal cord (CNS). For example, 31 pairs of spinal nerves emerge from the spinal cord and relay information to/from a particular region on the left or right side of the body. The first pair of spinal nerves originate above C1 which is why there are eight cervical nerves and only seven cervical vertebrae. The thoracic, lumber and sacral nerves number the same as the corresponding vertebrae (e.g. 12, 5 and 5) and there is one pair of coccygeal nerves. In addition to the spinal nerves, there are also 12 cranial nerves that emerge directly from the brain and brainstem via a series of bony canals and small holes (foramina) in the skull. They are generally named according to their structure or function (Table 12.1) and a number of mnemonics have been devised to help students remember their order, function and whether or not they are motor nerves, sensory nerves or both.
Head, neck and vertebral column
David Heylings, Stephen Carmichael, Samuel Leinster, Janak Saada, Bari M. Logan, Ralph T. Hutchings in McMinn’s Concise Human Anatomy, 2017
Body functions are controlled by or through different parts of the central nervous system. Which statement below is the most accurate?Smooth movement of the limbs is coordinated through cells of the precentral gyrus working with the basal ganglia and cerebellum.Smooth movement of the limbs is coordinated through cells of the postcentral gyrus working closely with the cerebellum and basal ganglia.The respiratory centre is located in the medulla and responds to stimuli carried through the nucleus gracilis.The visual light reflex relies on connections between the optic nerves, internal capsule and the precentral gyrus.If the thalamus was damaged in a stroke, it would have no effect on the appreciation at a conscious level of touch, pain and temperature.
Effects of tandem walk and cognitive and motor dual- tasks on gait speed in individuals with chronic idiopathic neck pain: a preliminary study
Published in Physiotherapy Theory and Practice, 2021
Munlika Sremakaew, Somporn Sungkarat, Julia Treleaven, Sureeporn Uthaikhup
The importance of cervical afferent input to the postural control system is well documented (Bove, Diverio, Pozzo, and Schieppati, 2001; Courtine, Papaxanthis, Laroche, and Pozzo, 2003; Vuillerme and Pinsault, 2009). Sensory information from the cervical spine is relayed into the central nervous system, where it is integrated with other sensory information from visual, vestibular, and somatosensory systems (Kristjansson and Treleaven, 2009; Treleaven, 2008). Altered cervical afferent input to the central nervous system can cause impaired postural orientation and equilibrium. Numerous studies demonstrated that patients with chronic neck pain had increased postural sway during quiet standing in different conditions (Field, Treleaven, and Jull, 2008; Juul-Kristensen et al., 2013; Treleaven, Jull, and Lowchoy, 2005). Additionally, they had difficulty balancing in walking, particularly with challenging conditions such as with head movements and at the maximum speed (Poole, Treleaven, and Jull, 2008; Sjostrom et al., 2003; Uthaikhup et al., 2014). Such changes in postural stability may be associated with an increased risk of falls (Ambrose, Paul, and Hausdorff, 2013).
Is PROTAC technology really a game changer for central nervous system drug discovery?
Published in Expert Opinion on Drug Discovery, 2021
Kayla Farrell, Timothy J. Jarome
The central nervous system (CNS), representing the brain, spinal cord and all associated nerves, exerts executive control over every bodily function. There are more than 600 known diseases that affect the CNS, including a wide variety of neurological, neurodevelopmental and neurodegenerative disorders [19], and it is estimated that nearly 1/6 of the world’s population suffers from a CNS disorder [20]. Unlike the peripheral nervous system (PNS), the CNS poses unique challenges that often hinder drug discovery efforts [21], resulting in clinical failure rates that can reach near 100% for some disorders. Some of this failure can be attributed to a poor understanding of the disease itself, making it difficult to correctly target the major cellular mechanisms that underly it. However, in other cases drug development has been largely unsuccessful even when the underlying pathophysiology is well understood, such as in Huntington’s disease. Furthermore, diseases that result from mutations or malfunctioning of proteins expressed in both the PNS and CNS pose unique challenges in regard to localizing the treatment specifically to the CNS. Consequently, even some of the most promising treatments for various CNS disorders continue to fail and, to date, an overwhelming number of major CNS disorders, such as Alzheimer’s disease, lack an effective treatment option.
Re-conceptualizing postural control assessment in sport-related concussion: Transitioning from the reflex/hierarchical model to the systems model
Published in Physiotherapy Theory and Practice, 2021
Thaer S. Manaseer, Douglas P. Gross, Martin Mrazik, Kathryn Schneider, Jackie L. Whittaker
According to the Reflex/Hierarchical Model, postural control is a simple skill that is controlled by one neurophysiological system (Horak, 2006). The system consists of afferent pathways, the central nervous system, and efferent pathways (Guskiewicz, 2011). Specifically, afferent pathways carry sensory cues from the visual, vestibular, and somatosensory mechanisms to the central nervous system. The central nervous system (i.e. cerebral cortex, cerebellum, basal ganglia, brainstem, and spinal cord) processes and hierarchically integrates the sensory cues. The spinal cord represents the lowest level of the hierarchy and is involved in the initial processing of somatosensory information, and the reflex and voluntary control of posture through the motor neurons (Shumway-Cook and Woollacott, 2007). Feedback based on the processed sensory cues travels along the efferent pathway to different muscles responsible for postural control and directs them to contract appropriately (Guskiewicz, 2011).
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