Assessment of Neurologic Function Chapter 60

Neuron Structure and Function

• Dendrites are branch-like structures that receive messages from other neurons and allow the transmission of messages to the cell body.
• The nucleus is the structure in the neuron that contains the chromosomes.
• Axon is a tube-like structure that carries electrical impulses from the cell body to the axon terminals that pass the impulse to another neuron.
• Synapse is a chemical junction between the terminal of one neuron and the dendrites of another neuron.
• Cell body is composed of a nucleus, golgi body, endoplasmic reticulum, mitochondria, etc.

Node of Ranvier and Myelin Sheath

• Node of Ranvier are gaps formed between the myelin sheath where the axons are left uncovered.
• The myelin sheath is largely composed of an insulating fatty substance, allowing the generation of a fast electrical impulse along the axon.

Musculoskeletal System Functions

• Protection of vital organs
• Framework to support body structures
• Mobility and movement
• Production of heat and maintenance of body temperature
• Facilitation of the return of blood to the heart
• Reservoir for immature blood cells
• Reservoir for vital minerals

Nervous System Structure and Function

• The nervous system consists of the central nervous system (CNS) and the peripheral nervous system.
• CNS includes the brain and spinal cord.
• Peripheral nervous system includes cranial and spinal nerves, and autonomic and somatic systems.
• The basic functional unit is the neuron, which controls all motor, sensory, autonomic, cognitive, and behavioral activities.

Neurotransmitters

• Communicate messages from one neuron to another or to a specific target tissue.
• Can potentiate, terminate, or modulate a specific action or can excite or inhibit a target cell.
• Many neurologic disorders are caused by an imbalance in neurotransmitters.

Autonomic Nervous System

• Functions to regulate activities of internal organs and to maintain and restore internal homeostasis.
• Sympathetic nervous system: "fight-or-flight" responses, main neurotransmitter is norepinephrine.
• Parasympathetic nervous system: controls mostly visceral functions, regulated by centers in the spinal cord, brainstem, and hypothalamus.

Neurologic Assessment

• Health history: pain, seizures, dizziness, visual disturbances, weakness, abnormal sensations.
• Consciousness and cognition: mental status, intellectual function, thought content, emotional status, language ability, impact on lifestyle.
• Cranial nerves: 12 pairs of cranial nerves that emerge from the lower surface of the brain.
• Motor system: muscle size, muscle tone and strength, coordination and balance, Romberg test.
• Sensory system: tactile sensation, superficial pain, temperature, vibration and position sense (proprioception).
• Reflexes: DTRs, biceps, triceps, brachioradialis, patellar, Achilles, superficial, pathologic, plantar (Babinski).

Gerontologic Considerations

• Important to distinguish normal aging changes from abnormal changes.
• Structural and physiologic changes, motor and sensory alterations, temperature regulation, and pain perception.
• Determine previous mental status for comparison.

Diagnostic Tests

• Computed tomography (CT): combines a series of X-ray images taken from different angles around the body and a computer to recreate cross-sectional views.
• Positron emission tomography (PET): uses a radioactive substance called a tracer to look for diseases in the body.
• Single-photon emission computed tomography (SPECT): imaging test that uses a radioactive substance and a special camera to create 3D pictures.
• Magnetic resonance imaging (MRI): uses a magnetic field and computer-generated radio waves to create detailed images of the organs and tissues in the body.
• Cerebral angiography: uses a special contrast plus X-ray to visualize the blood flow in the brain.
• Myelography: uses a contrast plus X-rays or CT scans to look for problems in the spinal canal.
• Noninvasive carotid flow studies: noninvasive and painless procedure that uses sound waves to examine the blood flow through the carotid arteries.
• Transcranial Doppler: painless test that uses sound waves to detect blood flow in the brain and for any visualized problems.
• Electroencephalography (EEG): records the electrical activity of the brain.
• Electromyography (EMG): records the electrical activity of muscles.
• Nerve conduction studies: measures the speed and strength of nerve signals.
• Evoked potential studies: measures the electrical activity of the brain in response to specific stimuli.
• Lumbar puncture: procedure in which a sample of cerebrospinal fluid is collected from the spinal canal.
• Queckenstedt test: measures the pressure of cerebrospinal fluid in the spinal canal.
• Analysis of cerebrospinal fluid: examines the components of cerebrospinal fluid to diagnose conditions affecting the brain and spinal cord.