autonomic nervous system
Body's automatic pilot
The autonomic nervous system is the part of the nervous system that regulates involuntary bodily functions—heartbeat, digestion, breathing, pupil dilation.
It operates largely below conscious awareness, maintaining homeostasis without deliberate effort.
The system divides into sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) branches, which generally oppose each other to keep the body in balance.
Acute threat reaction
- adrenalineEmergency response hormone
- norepinephrineAlertness and stress hormone
- adrenergicActivated by epinephrine-type compounds
- thoracolumbarMid-to-lower spine region
stress response · arousal · alertness · pupil dilation · bronchodilation · heart rate increase · vasoconstriction · sweating
Calming branch of autonomic system
- vagus nerveMajor parasympathetic cranial pathway
- acetylcholineNeurotransmitter for muscles and memory
- cholinergicAcetylcholine-mediated neural signaling
- craniosacralRelating to skull-spine connection
salivation · bronchoconstriction · peristalsis · digestive enzymes · vasodilation · energy conservation · relaxation response · recovery
Masses of nerve tissue
- reflex arcNerve pathway for involuntary responses
- chemoreceptorsCells detecting molecular stimuli
- hypothalamusSubthalamic regulatory brain region
- brainstemLower neural trunk
spinal cord · nerve fibers · synapses · neurotransmitters · receptors · efferent · afferent · plexus
Steadiness or amount owed
- equilibriumState of balance
- stabilityResistance to displacement
- feedbackReturned response data
- steady stateUnchanging system condition
regulation · adaptation · integration · set point · dynamic equilibrium · self-regulation · compensatory · maintenance
fight-or-flight
Acute threat reaction
- adrenalineEmergency response hormone
- norepinephrineAlertness and stress hormone
- adrenergicActivated by epinephrine-type compounds
thoracolumbar · stress response · arousal · alertness · pupil dilation · bronchodilation · heart rate increase · vasoconstriction · sweating · piloerection
rest and digest
Calming branch of autonomic system
- vagus nerveMajor parasympathetic cranial pathway
- acetylcholineNeurotransmitter for muscles and memory
- cholinergicAcetylcholine-mediated neural signaling
craniosacral · salivation · bronchoconstriction · peristalsis · digestive enzymes · vasodilation · energy conservation · relaxation response · recovery · calming
ganglia
Masses of nerve tissue
- reflex arcNerve pathway for involuntary responses
- chemoreceptorsCells detecting molecular stimuli
- hypothalamusSubthalamic regulatory brain region
brainstem · spinal cord · nerve fibers · synapses · neurotransmitters · receptors · efferent · afferent · plexus · medulla oblongata
balance
Steadiness or amount owed
- equilibriumState of balance
- stabilityResistance to displacement
- feedbackReturned response data
steady state · regulation · adaptation · integration · set point · dynamic equilibrium · self-regulation · compensatory · maintenance · baseline
autonomic nervous systemvoluntary movement
Self-initiated bodily action
nervous, system, nerves, autonomy, nervousness, nervously, unnerve, autonomous, nerved