Sympathetic Nervous system - Lecture 21

what is the somatic nervous system

• Part of the peripheral nervous system

• controls voluntary skeletal muscles

• afferent & efferent neurons

  • GSA & GSE - ONE NEURON FROM CNS TO PNS to target muscle

Autonomic nervous system

• involuntary or visceral 

• heart muscle, smooth muscle, and glands 

• GVE - REQUIRE 2 EFFERENT NEURONS to innervate target organ 

  • 1: preganglionic 2: postganglionic neurons

Where are preganglionic nucleus on sympathetic neurons located?

In the thoracolumbar region: T3-L3

What is GVE

General Visceral Efferent: responsible for control of involuntary or visceral body functions

• both in parasympathetic and sympathetic

• plays key role in the body’s response to stress (PRODUCTION)

  • cardiovascular, respiratory, digestive, urinary, reproductive functions

Sympathetic GVE responses

+ cardiovascular

+ respiratory 

- digestive

- urinary

- reproductive functions

“fight or flight”

What are the parts of the sympathetic nervous system? Like how is it organized?

• Sympathetic trunk: chain of ganglia

• Visceral ganglia: connected with the sympathetic trunk by nerves; chain of ganglia close to viscera

Describe the neurotransmitters of the sympathetic nervous system

1st projection neuron/preganglionic neuron releases ACh (synapses) at sympathetic ganglion

2nd projection neuron/postganglionic neuron releases norepinephrine (synapses) onto target tissue

What nerve horn, roots and branches are used by an efferent sympathetic fiber?

lateral horn, ventral root, spinal nerve, communicating branch TO the sympathetic trunk…..varies after that depending what the target is 

How many pathways are in target 1 of sympathetic?

two: Axial and Limbs

• Neck (axial) and thoracic limb

• Thorax (axial) and pelvic limbs

Describe what makes target 1 - neck and thoracic limbs pathway, what makes it differnt?

lateral horn → ventral root → spinal nerve → communicating branch → cervicothoracic ganglion of sympathetic trunk → SYNAPSES → vertebral n. → target tissue (thoracic limbs and neck)

Describe what makes target 1 - trunk and pelvic limbs pathway, what makes it different?

lateral horn → ventral root → spinal nerve → communicating branch → sympathetic trunk → SYNAPSES → back up communicating branch to → sympathetic trunk → dorsal or ventral branch to target tissue

Describe what makes target 2 - heart, smooth mm, glands of thoracic organs pathway, what makes it different?

a) lateral horn → ventral root → spinal nerve → communicating branch → cervicothoracic ganglion of sympathetic trunk → ansa subclavian (communicating branch) → Middle cervical ganglion → SYNAPSES → cervical n → target tissue = heart or lungs 

b) lateral horn → ventral root → spinal nerve → communicating branch → cervicothoracic ganglion of sympathetic trunk → target tissue = smooth mm & glands of thoracic organs  

Describe what makes target 2 - smooth mm, glands of abdominal organs pathway, what makes it different?

lateral horn → ventral root → spinal nerve → communicating branch to → sympathetic trunk → take Splanchnic nn. → to visceral ganglion → SYNAPSES → post-gang neuron → smooth mm. & glands of pelvic limbs 

Describe what makes target 2 - smooth mm, glands of pelvic organs pathway, what makes it different?

a) lateral horn → ventral root → spinal nerve → communicating branch to → sympathetic trunk → take Splanchnic nn. → to visceral sympathetic ganglia → SYNAPSES → take POST SNYAPTIC hypogastric nn. to → Pelvic Plexus → target tissue 

b) lateral horn → vetral root → spinal nerve → communicating branch → sympathetic ganglion → Splanchnic nn. to → visceral sympathetic ganglia → take PRE_SYNAPTIC hypogastric nn. to → Pelvic plexus → SYNAPSES → post-synaptic branch → target tissue

Describe what makes target 3 - smooth mm. & glands of the HEAD pathway, what makes it different?

lateral horn → ventral root → spinal nerve → communicating branch → cervicothoracic ganglion of sympathetic trunk → Ansa subclavian (communicating branch) to → Middle cervical ganglion → uses preganglionic fibers of vasosympathetic trunk → to cranial cervical ganglion → SYNAPSES→ postganglionic sympathetic fibers → target 

what are hypogastric nerves?

pre & post synaptic sympathetic nerves that go toward the pelvic plexus

• runs parallel to aorta and internal iliac aa.