Autonomic nervous system (ANS)

homeostasis

the maintenance of a relatively constant internal environment

CNS

brain and sp. cord

PNS

sensory and motor

somatic

skeletal muscles/voluntarily controlled

autonomic (parasympathetic and sympathetic)

involuntarily controlled

autonomic nervous system

functions in total body homeostasis at the unconscious level (routine homeostatic adjustments in physiological systems, to include the cardiovascular, respiratory, digestive, excretory and reproductive systems)

organization of ANS

commands from autonomic centers in the brain/ brainstem are sent to the sp. cord

Organization of ANS

messages are sent out via visceral motor neurons:

preganglionic neurons (1st order)

located in CNS, are myelinated axons, quite divergent

Organization of ANS

messages are sent out via visceral motor neurons:

post ganglionic neurons (2nd order)

located in PNS, are unmyelinated axons, to target tissue Eg.) target tissue= heart, visceral smooth muscle, glands, adipose tissue

subdivisions of ANS:

sympathetic

fight or flight responses

systems are altered in order to deal with emergencies, increased alertness, increased metabolism

for example: increased heart rate

increased perspiration

increased blood flow to skeletal muscles

increased breathing rate

subdivisions of ANS:

parasympathetic

rest and repose or rest and digest responses

systems altered to converse energy, digest, promote sedentary activities

For example: decreased heart rate

increased digestive secretions and movement

increased blood flow to intrstine

increased bladder contractions