autonomic nervous system ANS

ANS regulates

organs/viscera

• heart, lungs, stomach, bladder, intestines

ANS system type

involuntary visceral motor system (reflex)

GVE

motor → smooth/cardiac mm/glands ONLY

sympathetic region

thoracolumbar

parasympathetic region

craniosacral

both systems are

antagonistic but normally integrated

receive innervation from both system

PNS + SNS chains

2 neuron chain btw CNS + effector organ

1. preganglionic neuron

2. postganglionic neuron

   
   

pregalnglionic neuron

gives rise to myelinated axon/preganglionic fiber (leaves CNS → PNS to synapse)

synapses w/ 2nd neuron

cell bodies in CNS

postganglionic neuron

gives rise to unmyelinated axon/postganglionic fiber

innervates the effector organ

cell body w/in PNS

similarities btw PNS + SNS systems

2 neuron chains

preganglionic axon myelinated + post demyelinated

differences btw PNS + SNS systems

visceral responses (fight/flight + rest/digest)

axon lengths

location of 1st neuron

location of 2nd neuron

system’s impact on body

NT released from system

PNS + SNS axon length difference

SNS: short pregang + long postgang

PNS: long pregang + short postgang

location of 1st neuron in chain in PNS + SNS difference

PNS: CN 3, 7, 9, 10 + S2-4 (craniosacral outflow)

SNS: T1-L2/3 (thoarcolumbar outflow)

location of 2nd neuron in chain SNS + PNS difference

SNS: postgang in para OR pre vertebral ganglia

PNS: postgang in small un/paired terminal ganglia (near/in effector organ)

paravertebral ganglia

sympathetic chains

2 chains of ganglia that run on both sides of vertebral column from skull-coccyx

pre vertebral ganglia

not paired

lie along abdominal aorta

surround larger arterial branches (supplies viscera)

(same names as arteries)

SNS + PNS goes to differences

SNS: entire body (bc blood vessels)

PNS: limited to viscera

NT released at SNS + PNS differences

SNS

• pregang: ACh

• postgang: norepinephrine (adrenergic)

• postgang that innervate sweat glands: ACh

PNS: use ACh (cholinergic)

SNS overview + contains

larger system

contains sympathetic trunks, prevertebral ganglia, branches/plexuses

wider distribution

SNS innervates all

sweat glands

arrector pili mm

muscular wall of blood vessels

heart

lungs

all other viscera

sympathetic activation (fight/flight)

dilation of pupils

contraction of partiers to visceral/skin

accel of rate/F to heart

decrease peristalsis of gut + constriction of spincters (bladder + rectum)

adrenal medulla secretes adrenalin + noradrenalin into blood

ratio of pregang to postgang in SNS

1:20

SNS sympathetic activation produces

diffuse mass responses

via control of arterial blood flow

SNS distribution

uses 2 sympathetic chains to get to whole body

sympathetic chains

lie along side of spinal column + span skull → coccyx

connected to rami communicantes

white rami: myelinated on ramps

gray rami: unmyelinated off ramps

4 actions of preganglionic axon on sympathetic chain

go up

end at level it entered

pass through at level it entered (no synapse here)

go down

(ALL must synapse w/ postgang neuron)

cervical region chains formed by

ascending preganglionic axons

thoracic + upper lumbar region chains formed by

ascending + descending preganglionic axons

lumbar + sacral region chains formed by

descending preganglionic axons

PNS overview

smaller

myelinated pregang parasympathetic fibers leave CNS by 4 CN + 3 sacral spinal nerves

cranial outflow 4 terminal ganglia in head

ciliary

pterygopalatine

submandibular

otic

what nerve innervates most of the cranial outflow

vagus (CNX)

pelvic splanchnic nerves (sacral outflow)

pregang axons that pass directly to viscera

synapse w/ post gang neurons in terminal ganglia

located w/in visceral walls (not visible)

sacral outflow innervates

all pelvic visceral + hindgut

parasympathetic activation examples

pupil constriction

slow of heart

inc peristalsis of gut

digestive enzyme secretion

sphincter relaxation

sexual arousal

engorgment of erectile tissue

sleep

parasympathetic nerve fibers innervate structures in

head

neck

body cavities

(NO BLOOD VESSELS)

parasympathetic activation produces

discrete localized responses

visceral sensory fibers

carry sensory info from cardiac/smooth mm + glands

travel w/ sym + parasympathetic fibers

cell bodies located in dorsal root ganglia or sensory ganglia of CN

preganglionic + parasympathetic

brain: brain stem nuclei of CN 3, 7, 9, 10

spinal cord: S2, S3, S4

myelinated / ACh

postganglionic + parasympathetic

ganglia: terminal ganglia (walls of viscera)

unmyelinated + ACh

preganglionic + sympathetic

SC: T1-L2 (lateral horn)

myelinated + ACh

sympathetic + postganglionic

ganglia: paravertebral/prevertebral ganglia

unmyelinated + NE

what receptors do sweat glands have at postganglionic sites (EXCEPTION TO RULE)

ACh NOT NE