Chapter 7: Moving and positioning
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Source: Adapted from Lindsay et al. ([61]).
Anatomy and physiology
The nervous system is divided into the central nervous system (CNS), which comprises the brain and spinal cord, and the peripheral nervous system (PNS), which comprises all the nerves outside the brain and spine, including the spinal and cranial nerves. The PNS is further divided into the autonomic nervous system (ANS) and the somatic nervous system (SNS) (Lundy‐Ekman [64]). This is illustrated in Figure 7.19.
Figure 7.19 Divisions of the nervous system. Source: Reproduced from PsychLogic ([103]) with permission of CC.
The central nervous system
The brain consists of four lobes (frontal, temporal, parietal and occipital), the brainstem and the cerebellum. Each area has specific functions, as detailed in Figure 7.20.
Figure 7.20 The lobes of the brain and their functions.
The brain connects to the spinal cord via the brainstem and relays messages between the brain and the body via the PNS. The spinal cord exits the skull through an opening called the foramen magnum and travels down the spinal column through a channel at the back of each spinal bone (vertebrae) called the spinal canal. The vertebrae are numbered according to their location. The cervical spine has 7 vertebrae (C1–C7 from top to bottom), the thoracic spine has 12 vertebrae (T1–T12) and the lumbar spine has 5 vertebrae (L1–L5). The spinal cord (and therefore the CNS) stops at around L1 or L2 and forms the cauda equina, which is part of the PNS (Figure 7.21) (Lundy‐Ekman [65]).
Figure 7.21 The spinal cord and spinal nerves.
The peripheral nervous system
Between each vertebrae, a nerve branches off the spinal cord and exits to the body. These are called the spinal nerves and are numbered accordingly (Figure 7.21).
The PNS is divided into the autonomic nervous system (ANS) and the somatic nervous system (SNS) (Figure 7.19). The SNS controls moving and feeling within the body. Efferent or motor nerves carry messages from the brain to the body to cause movement. Afferent or sensory nerves carry sensory information from the body back to the brain to provide feedback. The ANS regulates structures not under conscious control, such as blood pressure, gut motility, sweating and body temperature (Lundy‐Ekman [65]).
Illness, disease and side‐effects of treatment can affect any or all of these parts of the nervous system, which will have implications for moving, positioning and patient management.
Normal movement
Normal movement is dependent on a neuromuscular system that can receive, integrate and respond appropriately to multiple intrinsic and extrinsic stimuli. Key components include:
- Muscle tone: this is the amount of activity in a muscle. Postural muscle tone is continuous partial contraction of the postural muscles to keep the body upright against gravity (Vander et al. [125], [126]).
- Muscle reflexes: these are involuntary and nearly instantaneous muscle contractions in response to a stimulus (Vander et al. [125], [126]).
- Biomechanical properties of muscle: resting muscle is soft and can be easily stretched. To move a joint, a muscle must contract and shorten (Vander et al. [125], [126]).
- Reciprocal innervation of muscles: when a muscle contracts, its opposite muscle relaxes to an equal extent, allowing smooth movement. For example, when the biceps contracts to bend the elbow, the triceps relaxes (Vander et al. [125], [126]).
- Sensory‐motor feedback and feed‐forward mechanisms: the brain gathers information from the body about movement that has happened and sends messages to the muscles to correct the movement or adjust for changes (Duff et al. [35]).
- Balance reactions: the brain uses the feedback and feed‐forward mechanisms described above to make adjustments to the ankle, hip and trunk muscles to maintain balance and prevent falling (Vander et al. [125], [126]).
When any of these components are altered (e.g. if there is damage to or disease of the CNS or PNS; Box 7.3), abnormal movement patterns will exist, and these will affect the patient's functional ability. Positioning and active movement are key strategies in managing the influence of these changes.
Box 7.3
Possible causes of neurological deficit
- Acquired brain injury, such as cerebral palsy (CP), traumatic brain injury (TBI), infection or stroke
- Brain tumour
- Congenital conditions such as spina bifida
- Progressive neurological disorders such as Parkinson's disease (PD) or multiple sclerosis (MS)
- Peripheral motor or sensory neuropathy, such as diabetic neuropathy
- Neuromuscular diseases such as motor neurone disease (MND)
- Spinal cord injury (SCI) or compression
