What are the 2 divisions of the autonomic nervous system and what are their general functions?
- sympathetic: fight or flight
- parasympathetic: rest and digest
How many neurons link the CNS to the target for the ANS system? What do ANS neurons innervate?
- 2 neurons: preganglionic (grey matter of lateral horn) and postganglionic (cell body outside CNS in autonomic ganglia)
- Smooth muscle, glands, modified cardiac muscle, SA and AV nodes
Sympathetics: origin, fiber lengths, and targets
Origin: T1-L2
FL: Pre = short and Post = long
Ganglia: para and pre vertebral
Targets: everywhere
Parasympathetics: origin, fiber lengths, and targets
Origin: CN nuclei and S2-S4
FL: Pre = long and Post = short
Ganglia: intramural
Targets: head and organs; NO body wall or limbs
Which ANS system does not target structures in the body wall?
Parasympathetic
Where are the cell bodies of origin (preganglionic) for the sympathetic system located?
- T1-L2/3
- IML (in 3D)
- Lateral horn from T1-L2/3 (in cross section)
Be able to describe the somatotopic organization of the IML (head, upper limb, thoracic cavity viscera)
T1-T6
Be able to describe the somatotopic organization of the IML (trunk body wall)
T1-L1
Be able to describe the somatotopic organization of the IML (lower limb)
T12-L2/3
Be able to describe the somatotopic organization of the IML (abdominopelvic viscera)
T5-L2/3
Where are paravertebral (sympathetic) autonomic ganglia found? Which ganglia are associated with targets in upper limb and body wall?
- on either side of vertebral column
- ONLY sympathetic
- smooth muscle, arteries and glands in body wall
- thoracic cavity viscera
- head
Where are prevertebral (sympathetic) autonomic ganglia found? Which ganglia are associated with targets in upper limb and body wall?
- in front of vertebral column, close to abdominal artery
- ONLY sympathetic
- abdominal and pelvic cavity viscera
Why does the sympathetic trunk exist? What is its function?
- Paired structure lying on either side of the vertebral column
- Composed of paravertebral ganglia
- Distributes postganglionic sympathetic innervation throughout the body
How do white and gray rami communicans differ? What is the function of each ramus communicans? Which vertebral levels do you find each of the ramus communicans?
White: Only for T1-L2/3, exit spinal n close to branching point of ventral and dorsal rami, only route preganglionic sympathetic fibers can take to get to sympathetic trunk
Grey: All 31 spinal levels, extends from paravertebral ganglia to spinal n, only route back out to spinal n from sympathetic trunk
How does sympathetic supply to the body wall differ from sympathetic innervation to the body cavities & head neck? What nerve structures are utilized to deliver sympathetic innervation to these areas from the sympathetic trunk?
- T1-L2/3: synapse at same level they entered
- Inferior to L2/3: descend in sympathetic trunk then synapse
- Superior to T1: ascend in sympathetic trunk then synapse
- Abdomen or pelvis: leave synaptic trunk w/o synapsing (referred to as splanchnic)
Routes that a preganglionic sympathetic fiber can take from the entry point into the sympathetic trunk:
