chapter 35

Learning Outcomes

• Identify key anatomical components of the neurological system

• Discuss the function of the neurological system

• Describe the procedure for completing a history and physical assessment of neurological function

• Correlate relevant diagnostic examinations to neurological function

• Explain nursing considerations for diagnostic studies relevant to neurological function

• Discuss changes in neurological function associated with aging

Concepts

• Caring

• Cognition

• Intracranial Regulation

• Medication

• Safety

• Sensory Perception

Essential Terms

• Adrenergic receptors: Receptors that respond to adrenaline.

• Afferent neurons: Neurons that carry sensory information to the CNS.

• Alpha receptors: A type of adrenergic receptor involved in vasoconstriction.

• Aqueduct of Sylvius: A canal connecting the third and fourth ventricles of the brain.

• Arachnoid membrane: Middle layer of the meninges surrounding the brain and spinal cord.

• Autonomic nervous system (ANS): Controls involuntary bodily functions.

• Axon: The part of a neuron that transmits impulses away from the cell body.

• Babinski sign: A reflex action in which the big toe extends when the sole of the foot is stimulated.

• Basal ganglia: Brain structures involved in movement regulation.

• Beta receptors: Adrenergic receptors that usually mediate relaxation and inhibition.

• Blood–brain barrier (BBB): A selective permeability barrier that protects the brain from harmful substances.

• Brainstem: The posterior part of the brain that controls vital functions such as heart rate and breathing.

• Cell body: The part of a neuron that contains the nucleus.

• Central nervous system (CNS): Comprises the brain and spinal cord.

• Cerebellum: Part of the brain responsible for coordination and balance.

• Cerebrospinal fluid (CSF): Fluid that surrounds and protects the brain and spinal cord.

• Cerebrum: The largest part of the brain, responsible for higher functions.

• Cholinergic fibers: Nerve fibers that release acetylcholine.

• Circle of Willis: A circulatory anastomosis that supplies blood to the brain.

• Corpus callosum: A band of nerve fibers that connects the two hemispheres of the brain.

• Decussation: The crossing of nerve fibers in the CNS.

• Dendrites: Branch-like structures of neurons that receive messages.

• Dermatome: An area of skin that is mainly supplied by a single spinal nerve root.

• Dura mater: The tough outer layer of the meninges.

• Efferent neurons: Neurons that carry signals away from the CNS to effectors.

• Enteric system: Part of the ANS that governs the function of the gastrointestinal tract.

Overview of Anatomy and Physiology

Nerve Cell Types and Functions

• Neurons: Responsible for communication within the nervous system (impulse-conducting).

• Neuroglial Cells: Support and protect neurons. More abundant than neurons.

  • Astrocytes: Provide structural support and help form the BBB.

  • Ependymal Cells: Line ventricles and produce CSF.

  • Microglial Cells: Act as immune cells in the CNS.

  • Oligodendrocytes: Form myelin sheaths around CNS axons.

  • Schwann Cells: Form myelin sheaths around PNS axons.

The Structure of Neurons

• Major Components: Cell body (soma), dendrites, axons, myelin sheath, axon terminal, synaptic knob.

• Myelin Sheath: Insulates axons and speeds up nerve impulse transmission.

Conduction of Nerve Impulses

• Action Potential: Changes in the electrical charge across the membrane occur during transmission.

  • Depolarization: Sodium enters the neuron, making it more positive.

  • Repolarization: Potassium exits the neuron, returning it to a negative state.

  • Hyperpolarization: Inside becomes more negative than resting state.

• Synapse: Connection point between neurons where neurotransmitters facilitate signal transmission.

The Central Nervous System (CNS)

• Comprises the brain and spinal cord; protected by the skull and vertebral column.

• Brain Divisions:

  • Cerebrum: Largest part, responsible for sensory and motor processing; divided into lobes (frontal, parietal, temporal, occipital).

  • Cerebellum: Coordinates voluntary movements and balance.

  • Brainstem: Controls vital functions (medulla oblongata, pons, midbrain).

The Peripheral Nervous System (PNS)

Components of the PNS

• Cranial Nerves: 12 pairs originating from the brain.

• Spinal Nerves: 31 pairs originating from the spinal cord; mixed nerves.

• Autonomic Nervous System: Controls involuntary functions, further divided into sympathetic and parasympathetic systems.

Autonomic Nervous System (ANS)

• Sympathetic Nervous System: Elicit “fight-or-flight” response, using norepinephrine.

  • Adrenaline Effect: Increases heart rate, constricts blood vessels.

• Parasympathetic Nervous System: Elicit “rest-and-digest” response using acetylcholine.

  • Muscarinic Receptors: Found on various tissues, can have excitatory or inhibitory effects.

Assessment of Neurological Function

History and Physical Assessment

• Collect comprehensive medical, family, and social histories along with a thorough neurological examination, including:

  • Cognitive Function: Mini-Mental Status Examination (MMSE).

  • Level of Consciousness (LOC): Use of the Glasgow Coma Scale (GCS).

  • Cranial Nerve Assessment: Evaluates function of all 12 cranial nerves.

Diagnostic Studies

• Techniques include CT scans, MRI, and lumbar punctures for cerebrospinal fluid analysis.

Age-Related Changes

• Various neurological changes occur as people age, including:

  • Slowed movements and reaction time, decreased muscle strength, sensory perception alterations, and cognitive decline interactions.

Psychosocial Considerations

• Neurological conditions impact not only patients but also their families; understanding and support are crucial during recovery and rehabilitation.