AUTONOMIC NERVOUS SYSTEM

• Parasympathetic Nervous System

• Sympathetic Nervous system

• Enteric Nervous System

DEFINITIONS• Somatic nervous system= CNS and PNS

neurons involved in sensory info and voluntary actions, innervate skin and muscles

• Visceral NS = Neurons in CNS and PNS that control of glands and muscles in the autonomic nervous system such as smooth muscle around blood vessels.

• Proceeds without conscious intention but can be influenced by volition.

DEFINITIONS

• Autonomic Nervous System= autonomic nerves and ganglia in the PNS that control internal organs such as heart, kidney (viscera)

• These organs also regulated by the neuroendocrine system located in the brain

FUNCTION OF ANS

• Organs are innervated by both sympathetic and parasympathetic fibers

• generally antagonize each other to maintain homeostasis and respond to sensory and emotional information

FUNCTION SYMPATHETIC NS

innervate all organs, skin and arteries 

always active, under influence of hypothalamus to maintain homeostasis

readies body for action. increases heart rate blood pressure, blood to muscles away from viscera.

FUNCTION PARASYMPATHETIC NS

• innervate all organs except liver, skin and arteries

• always active to maintain homeostasis• causes relaxation and inhibits activity

of innervated end organ  • Except increases digestion and few

other activities• blood pressure & heart rate

decreases, blood flow directed from muscle to viscera

DEFINITIONS

• Preganglionic neurons and fibers synapse on postganglionic autonomic neurons

• Postganglionic neurons and fibers synapse on end organ, gland, smooth muscle

• Sensory neurons ends in a specialized receptor or naked ending located in target

• Motor neurons synapse directly on muscle or glands

Autonomic NS Terms

• autonomic neurons are preganglionic neuron with preganglionic axons that synapse on autonomic postganglionic neurons and then the postganglionic axon synapses on organ, gland, smooth muscle, cardiac muscle cell.

SYMPATHETIC NS

• Fear: neurons in hypothalamus and brain stem activate adrenal glands that secrete adrenalin aka epinephrine

• postganglionic fibers use norepinephrine as neurotransmitter

ANATOMY Of SYMPATHETIC NS::

• short preganglionic fibers and long postganglionic fibers

• ganglia lie close to spinal cord in the paravertebral chain aka sympathetic chain

• some ganglia lie in body cavity such as superior cervical, celiac and mesenteric

SYMPATHETIC NS

• preganglionic neurons are found in lateral horns of thoracic and lumbar spinal cord levels only

• fibers always leave the spinal cord through the white communicating ramus

• Fibers have 3 different directions to travel

FUNCTION PARASYMPATHETIC NS

• innervate all organs except liver, skin and arteries

• always active to maintain homeostasis

• causes relaxation and inhibits activity of innervated end organ  

• Except increases digestion and few other activities

• blood pressure & heart rate decreases, blood flow directed from muscle to viscera

ANATOMY

• preganglionic fibers arise from brain stem and travel in cranial nerves 3 oculomotor, 7 facial, 9 glossopharyngeal, 10 vagus

• Also arise from sacral spinal cord and travel in spinal nerves S2-S4

PARASYMPATHETIC ANATOMY

• preganglionic fibers synapse in ganglia close to or in the innervated organ

• Possess a long preganglionic fiber and a short

postganglionic fiber

PARASYMPATHETIC ANATOMY

• preganglionic fiber travels in spinal nerve

• Do not connect with paraverterbral ganglion chain so do not travel in white or grey communicating rami

• terminate in parasympathetic ganglion located close to target organ

• postganglionic fibers use acetylcholine as neurotransmitter

• Hypothathalums (homeostatic regulatory center) regulates brain stem (pons, medulla) that influence autonomic nervous system

• Hypothalamus connected to the limbic center so emotions influence hypo to influences autonomic NS

AUTONOMIC BRAIN

Enteric NS FUNCTION::• controls digestion and elimination• regulates intestinal peristalsis• regulates blood flow through gut• regulates secretions from intestinal

glands• functions autonomously using

sensory information in a closed loop and is modulated by para and symp input

Enteric NS ANATOMY

• 100 million neurons as many as the spinal cord (50 billion in brain)

• Network of two sets of ganglia and nerves in the gut.– Myenteric plexus with ganglia and

nerves lying in between longitudinal and circular muscle layers

– Submucosal plexus with ganglia and nerves in the submucosa

• Receive input from para, sym and sensory neurons