733 Autonomic Nervous System

effectors of the somatic nervous system

skeletal muscle (voluntary)

effectors of autonomic nervous system

smooth muscle, cardiac muscle, glands

neuron chain in the somatic nervous system

single motor neuron to effector

neuron chain in the autonomic nervous system

two neuron chain: preganglionic—> postganglionic

myelination of the somatic nervous system

heavily myelinated (A, B)

myelination of the autonomic nervous system

Pre: lightly myelinated (B)

Post: unmyelinated (C)

primary neurotransmitter of the somatic nervous system

Ach at neuromuscular junction (nicotinic)

primary neurotransmitter of the autonomic nervous system

Ach (preganglionic both)

NE or Ach (postganglionic)

speed of somatic nervous system

fast, discrete

speed of autonomic nervous system

slower, diffuse, sustained

nicotinic (Nn) receptor location

all autonomic ganglia

nicotinic (Nn) ligand

ACh

Nicotinic (Nn) key effect

excitatory; ganglionic transmission

Nicotinic (Nm) location

neuromuscular junction

Nicotinic (Nm) ligand

ACh

Nicotnic (Nm) key effect

skeletal muscle contraction

Muscarinic (M1) location

CNS, gastric parietal cells

Muscarinic (M1) ligand

ACh

Muscarinic (M1) key effect

CNS excitation, increase gastric acid

Muscarinic (M2) location

heart- SA and AV nodes

Muscarinic (M2) ligand

ACh

Muscarinic (M2) key effect

decrease heart rate and decrease heart conduction velocity

Muscarinic (M3) location

smooth muscle, glands

Muscarinic (M3) ligand

ACh

Muscarinic (M3) key effect

contraction (gastrointestinal bladder), secretion

α1 adrenergic location

vascular smooth muscle, urethral sphincter

α1 adrenergic ligand

more norepinephrine than epinephrine

α1 adrenergic key effect

vasoconstriction, sphincter contraction

α2 adrenergic location

presynaptic terminals, platelets

α2 adrenergic ligand

more norepinephrine than epinephrine

α2 adrenergic key effect

decreased neurotransmitter release

β1 adrenergic location

heart, kidney

β1 adrenergic ligand

same amounts of norepinephrine and epinephrine

β1 adrenergic key effect

increase heart rate, increase heart contractility, increase renin

β2 adrenergic location

bronchi, skeletal muscle vessels, uterus

β2 adrenergic ligand

more epinephrine than norepinephrine

β2 adrenergic key effect

bronchodilation, vasodilation

β3 adrenergic location

adipose, bladder detrusor

β3 adrenergic ligand

same amounts of norepinephrine and epinephrine

β3 adrenergic key effect

lipolysis, bladder relaxation

how do beta blockers work

blunt the heart rate and contractility response to exercise

how do alpha-1 blockers work

they relax the urethral sphincter and predispose to orthostatic hypotension

how to muscarinic antagonists work

cause urinary retention, dry mouth, constipation, and in older adults, confusion

thoracolumbar outflow

sympathetic preganglionic neurons arise from the interomedial cell column, present only from T1 through L2

white ramus communicans

axons leave through the ventral root, join the spinal nerve briefly, then peel off through these pathways to reach the sympathetic chain (only present in T1-L2 and myelinated)

sympathetic chain synapse

synapse at it’s own level

how many pairs of ganglia in the sympathetic chain

22-25 pairs

superior cervical ganglion (C2-C3)

largest; supplies the head and neck. Damage anywhere along the pathway produces Horner Syndrome

Middle cervical ganglion (~C6)

smallest; contributes to cardiac and thyroid innervation

inferior cervical ganglion

fuses with T1 to form the stellate ganglion supplying the heart, lungs, and upper limb vasculature

thoracic ganglia

supply the cardiac plexus (T1-T5) and gives rise to the splanchnic nerves

gray rami communicantes

postganglionic fibers to the body wall exit through this pathway and is how sympathetic innervation reaches territory well outside T1-L2

prevertebral (collateral) ganglia

lies anterior to the vertebral column around the origins of the abdominal aorta’s major branches, receiving fibers via the splanchnic nerves

celiac ganglion/plexus location

T12-L1, celiac trunk

celiac ganglion/plexus splanchnic input

Greater (T5-T9)

celiac ganglion/plexus target organs

stomach, liver, gallbladder, spleen, pancreas, small intestine, ascending/transverse colon

superior mesenteric ganglion location

L1, superior to mesenteric artery origin

superior mesenteric ganglion splanchnic input

Lesser (T10-T11)

superior mesenteric ganglion target organs

small intestine, ascending/transverse colon

inferior mesenteric ganglion location

L3, inferior mesenteric artery origin

inferior mesenteric ganglion splanchnic input

Lumbar (L1-L2)

inferior mesenteric ganglion target organs

descneding/sigmoid colon, rectum, bladder, internal urethral sphincter, vas deferens

aorticorenal ganglion location

L1-L2 renal artery

aorticorenal ganglion splanchnic input

Least (T12)

aorticorenal ganglion target organs

kidneys, adrenal glands, proximal ureter

lumbar splanchnics

arise from lumbar chain ganglia and carry postganglionic fibers to the superior hypogastric plexus, promoting storage

sacral splanchnics

add sympathetic fibers to the inferior hypogastric plexus

adrenal medulla

modified sympathetic ganglion whose postganglionic neurons lost their axons and became secretory cells

heart sympathetic effect

increase heart rate, increase contractility, increase conduction velocity

heart sympathetic nervous system receptor

B1

lungs sympathetic effect

bronchodilation, decrease secretion

lungs sympathetic nervous system receptor

B2

systemic vessels sympathetic effect

vasoconstriction leading to increased blood pressure

systemic vessels sympathetic nervous system receptor

a1

skeletal muscle vessels sympathetic effect

vasodilation leading to increased muscle perfusion

skeletal muscle vessels sympathetic nervous system receptor

B2 (epi)

GI tract sympathetic effect

decreased motility, sphincter contraction

GI tract sympathetic nervous system receptor

a1, B2

bladder sympathetic effect

detrusor relaxation, internal sphincter contraction (storage)

bladder sympathetic nervous system receptor

B3, a1

eyes sympathetic effect

mydriasis (dilation), far focus

eyes sympathetic nervous system receptor

a1

skin sympathetic effect

piloerection (goosebumps); sweating

skin sympathetic nervous system receptor

a1, M3

liver sympathetic effect

glycogenolysis (breakdown of glucogen into glucose) and gluconeogenesis (increase glucose)

liver sympathetic nervous system receptor

B2

adrenal medulla sympathetic effect

epinephrine and norepinephrine release into blood

adrenal medulla sympathetic nervous system receptor

Nn

fat sympathetic effect

lipolysis (fats break down into glycerol and used for energy)

fat sympathetic nervous system receptor

B3

Horner Syndrome symptoms

ptosis, miosis, and anhidrosis

parasympathetic nervous system

conserves and restores; rest and digest

parasympathetic fibers

long preganglionic fibers inside the target organ

short postganglionic fibers

parasympathetic divison cranial outflow cranial component

travels in cranial nerves (CN) III, VII, IX, and X

parasympathetic divison sacral outflow

leaves the spinal cord at S2-S4

where do sympathetic fibers not travel

in the spinal nerves of the body wall

heart parasympathetic effect

decrease heart rate and conduction velocity

heart parasympathetic nervous system receptor

M2

heart parasympathetic nerve/ganglion

CN X

lungs parasympahtetic effect

bronchoconstriction and increase mucus