Ch. 14 - Sympathetic Division

Sympathetic division

"Fight-or-flight" response; activated during times of stress, emergency, excitement, or exercise; it's energy consuming

Preganglionic neuron of sympathetic division:

Body is in the lateral horn of thoracic or lumbar region off the spinal cord; axon extends to postganglionic neuron

Postganglionic neuron of sympathetic division:

Body is in ganglion of sympathetic chain and synapse in either sympathetic chain ganglia or collateral ganglia

What is sympathetic ganglia's location in regardance to the spinal cord?

In general, they are located close to the spinal cord

All preganglionic neurons enter the sympathetic chain and then there are possibilities of 1 of 3 things happening:

Preganglionic axon enters chain and synapses at that same level, preganglionic axon enters chain, but then travels up or down to synapse at a higher or lower level, or preganglionic axon passes through chain without synapsing; synapse will occur at collateral ganglion

Divergence of fibers in ganglion:

In the SNS, a preganglionic axon can branch to synapse with many postganglionic neurons located at different levels in te sympathetic chain

Results of divergence in the sympathetic chain:

Allows impulses from 1 preganglionic fiber to affect many postganglionic fibers, and contributes to "mass action" of the sympathetic division; sympathetic division is activated as a whole

Neurotransmitters released - preganglionic neuron:

Acetycholine

Neurotransmitters released - postganglionic neuron:

norepinephrine (noradrendaline)

Note about norepinephrine:

Norepinephrine has a longer-lasting effect than the ACh released to effectors by the parasympathetic division

Adrenal medulla

(Central portion of adrenal gland) is innervated by preganglionic sympathetic neurons, It secretes epinephrine and norepinephrine when the sympathetic division is activated.

What is the adrenal medulla an extension of?

It is really an extension of the sympathetic division so the sympathetic division plus the adrenal medulla is termed the "sympathoadrenal system"

Effects of sympathetic division on cardiovascular system:

Causes heart rate to beat faster and stronger, dilates blood vessels supplying blood to heart and skeletal muscles, constricts blood vessels supplying blood to the digestive system and kidneys

Effects of sympathetic division on respiratory system:

Dilates bronchioles to allow more air flow

Effects of sympathetic division on digestive system:

Decreases activity of glands and smooth muscle in walls and causes liver to reduce glucose into the blood

Other effects of sympathetic division:

sweating, pupil dilation, contraction of arrector pili muscles, metabolic rate increase, mental alertness increase, hinders urine formation & voiding