Chapter 11 Efferent Division

targets if efferent divison of autonomic

smooth muscle, cardiac muscle, glands, and adipose tissue

divisions of autonomic nervous system

sympathetic, parasympathetic, and enteric

sympathetic function

fight or flight

sympathetic effects

increase heart rate

sypathetic origin 

primarily exits spinal cord from thoracic and lumbar region 

sympathetic ganglia

clustered in chain

sympathetic preganglionic

short fibers

sympathetic postganglionic

long fibers

sympathetic neurotransmitter 

norepinephrine 

parasympathetic function

rest and digest

parasympathetic effects

decrease heart rate

parasympathetic origin

arises from brain stem and sacral region of spinal cord

parasympathetic ganglia 

located near/on effector organ 

parasympathetic preganglionic

long fiber

parasympathetic postganglionic

short fiber

enteric function

controls digestive tract independently

target of somatic system 

skeletal muscle

function of somatic division

voluntary movement causes contraction

autonomic reflexes and homeostasis is controlled by

hypothalamus, pons, and medullar

autonomic reflexes and homeostasis regulate

blood pressure, temperature, and water balance using antagonistic control

preganglionic neurotransmitter 

ACh 

preganglionic receptor

Nicotinic (nAChR)

postganglionic sympathetic neurotransmitter

norepinephrine

postganglionic parasympathetic neurotransmitter 

ACh 

postganglionic receptors

adrenergic or muscarinic

the adrenal medulla is a modified

sympathetic ganglion

chromaffin cells are in 

adrenal medulla 

chromaffin cells act as

postganglionic neurons without axons

adrenal medulla chromaffin cells release

epinephrine directly into blood

neuroeffector junction 

synapse between autonomic neuron and target cell 

neuroeffector junction (what happens)

neurotransmitters released from varicosities along the axon

varicosities

swelling

norepinephrine is released from

sympathetic postganglionic neurons

norepinephrine pathway 

action potential → Ca2+ channels open → exocytosis of NE → binds adrenergic receptors 

norepinephrine is removed via

diffusion, reuptake, or degradation by monoamine oxidase

types of adrenergic receptors

alpha and beta

Alpha 1 location 

most sympathetic target tissues 

alpha 1 function

vasoconstriction, smooth muscle contraction

alpha 1 affinity

high NE

Alpha 2 location 

GI tract and pancreas 

alpha 2 function

inhibits secretion and smooth muscle relaxation

alpha 2 affinity

high for NE

Beta 1 location 

heart and kidney 

beta 1 function

increase heart ate and renin release

beta 1 affinity

equal NE and E

Beta 2 location 

blood vessels and bronchi 

beta 2 function

vasodilation and bronchodilation

beta 2 affinity

high for E

beta 3 location 

adipose tissue 

beta 3 function

lipolysis

beta 3 affinity

equal NE and E

adrenergic receptors 

GPCRs responding to NE/E (sympathetic) 

muscarinic receptors

GPCRs responding to ACh(parasympathetic)

nicotinic receptor type

ligan gated ion channel

nicotinic location 

postganglionic neurons and neuromuscular junction

nicotinic mechanism

fast depolarization

muscarinic receptor type

GPCR

muscarinic location

parasympathetic target tissues 

muscarinic mechanism

slow and modulatory effects

somatic pathway

single neuron

somatic neurotransmitter 

ACh only 

somatic target

skeletal muscle

somatic control

voluntary

somatic effect 

always excitatory 

autonomic pathway

two neuron chain

autonomic neurotransmitter

ACh or NE

autonomic target 

smooth, cardiac muscle. and glands 

autonomic control

involuntary

autonomic effect

excitatory or inhibitory

synaptic transmission at neuromuscular junction 

1. motor neuron releases ACh 

2. ACh diffuses across synaptic cleft and binds nAChRs on muscle 

3. opens cation channels

4. depolarization → muscle contraction

5. ACh broken down by acetylcholinesterase