Week 4: ANS Anatomy

Question 1

what are the 3 main differences of the sympathetic and parasympathetic divisions ?

Answer 1

• parasympathetic releases acetylcholine and sympathetic releases norepinephrine
• origin sites: parasympathetic is found in craniosacral region and sympathetic is found in thoracolumbar region of spinal cord in the lateral gray horn.
• parasympathetic has long preganglionic axons and short postganglionic axons, opposite for the sympathetic.
• parasympathetic ganglion is close to the effector and sympathetic ganglion is close to the cns.

Question 2

parasympathetic division is also called ? what is the cranial and sacral outflow ?

Answer 2

craniosacral divison.
cranial outflow: oculomotor nerve, facial nerves, glossopharyngeal nerves, vagus nerve.
sacral outflow: pelvic splanchnic nerves, inferior hypogastric plexus

Question 3

what is the thoracolumbar division ?

Answer 3

the thoracolumbar division refers to the sympathetic nervous system because the preganglionic sympathetic neurons originate from these regions T1-L2. specifically the lateral gray horn.

Question 4

what are the branches of the spinal nerve ?

Answer 4

3 branches to the spinal nerve.
- posterior/dorsal ramus. carries motor and sensory information to and from the muscles/skin on the back of the body.
- anterior/ventral ramus. carries motor and sensory information to and from the front of the body.
- rami communicantes: connect the spinal nerve to the sympathetic trunk.
white ramus communicans: carries preganglionic axons out of spinal nerve to the ganglion.
gray ramus communicans: carries postganglionic axons from the ganglia back to the spinal nerve.

Question 5

once a preganglionic axon reaches a trunk ganglion, there are 3 possibilities for what happens next.

Answer 5

1. it can synapse with the postganglionic neuron at the same sympathetic trunk.
2. it can synapse at a higher or lower level.
3. passes through the trunk ganglion and instead goes into collateral ganglion where it synapses with the postganglionic neuron.

Question 6

visceral reflex ?

Answer 6

a visceral reflex is an involuntary response of an internal organ to a stimulus, controlled by the autonomic nervous system.
1. receptor: detects the stimulus, stretch receptors in the stomach wall detect fullness.
2. afferent sensory neuron: carries the sensory signal from the receptor to the integration center.
3. integrating center: may be dorsal horn interneuron, preganglionic neuron, may be within the walls of the gi tract.
4. efferent motor neuron: the first neuron originates in the cns and synapses in an autonomic ganglion. the second neuron targets the effector.
5. effector response