Unit
- Autonomic nervous system (ANS): The ANS regulates involuntary bodily functions including heart rate, blood pressure, digestion, and temperature. It operates largely outside conscious control and maintains internal homeostasis through constant feedback from sensory receptors.
- Sympathetic division: Often called the fight-or-flight system, it prepares the body for stress by increasing heart rate, dilating airways, and redirecting blood flow to skeletal muscles. This division uses norepinephrine as its primary neurotransmitter at target organs.
- Parasympathetic division: Known as the rest-and-digest system, it promotes relaxation, slows heart rate, and stimulates digestive processes. Acetylcholine is the main neurotransmitter, and the vagus nerve is a key pathway.
- Enteric nervous system: Sometimes called the second brain, this network of neurons in the gut wall controls gastrointestinal motility, secretion, and blood flow. It can function independently but communicates with the central nervous system via the ANS.
- Autonomic reflexes: These are rapid, involuntary responses that help maintain stability. The baroreflex adjusts blood pressure in response to changes in body position, while the pupillary light reflex controls eye pupil diameter.
- Central integration: The hypothalamus and brainstem nuclei integrate sensory input and coordinate autonomic output. For example, the medulla oblongata contains centers for cardiac, vasomotor, and respiratory control.
- Neurotransmitter systems: Cholinergic fibers release acetylcholine at all preganglionic synapses and at parasympathetic postganglionic terminals. Adrenergic fibers release norepinephrine at most sympathetic postganglionic terminals, except sweat glands and some blood vessels.
- Receptor subtypes: Alpha-1, alpha-2, beta-1, and beta-2 adrenergic receptors mediate different effects. For instance, beta-1 receptors increase heart rate and contractility, while beta-2 receptors dilate bronchioles. Understanding these helps predict drug side effects.
- Autonomic dysfunction syndromes: Orthostatic hypotension involves a sustained drop in blood pressure upon standing, often due to impaired vasoconstriction. Postural orthostatic tachycardia syndrome (POTS) features excessive heart rate increase without hypotension. Both require monitoring and non-pharmacologic interventions like increased fluid and salt intake.
- Clinical assessment tools: The COMPASS 31 and autonomic symptom profile questionnaires quantify symptom burden. Tilt-table testing measures blood pressure and heart rate responses to postural change, while the Valsalva maneuver evaluates baroreflex function. These assessments help identify dysautonomia patterns and guide management.
- Non-pharmacologic management: Lifestyle modifications are first-line for many autonomic disorders. These include increased fluid and sodium intake, compression garments, head-of-bed elevation, and counter-pressure maneuvers. Patient education on avoiding heat or prolonged standing is also essential for symptom control.
Scope of Practice
Role: Autonomic Disorder Support Coordinator
Within scope:
- Explaining basic ANS anatomy to patients and families using approved materials.
- Identifying signs of autonomic dysfunction (dizziness, palpitations) and reporting to clinicians.
- Documenting patient-reported symptoms using standardized questionnaires.
- Coordinating referral to autonomic testing laboratories.
- Participating in care plan development within a multidisciplinary team.
Outside scope:
- Interpreting autonomic test results or making diagnoses.
- Prescribing or adjusting medications for autonomic disorders.
- Providing medical advice without direct supervision from a licensed provider.
- Performing autonomic function tests such as tilt-table or sweat testing.
- Recommending specific treatments without a physician order.
Quick Revision
- The ANS has three divisions: sympathetic, parasympathetic, and enteric. Each plays a distinct role in maintaining homeostasis.
- Sympathetic activation prepares the body for stress; parasympathetic activation promotes rest and digestion.
- Central control centers in the hypothalamus and brainstem integrate autonomic output.
- Support coordinators educate patients on ANS basics but do not interpret tests or prescribe treatments.