Structure of the Autonomic NS Flashcards
Describe the path of information from the brain to visceral effectors in the Autonomic NS.
Visceral motor nuclei in hypothalamus
–> neurons (pre-ganglionic) descending into spinal chord or brain stem
–> In autonomic ganglion, synapse with other neurons (post-ganglionic)
–> Post-ganglionic neuron synapses with visceral effectors
Where do pre-ganglionic fibers originate from ? Post-ganglionic fibers ?
Pre-ganglionic fibers: from the CNS
Post-ganglionic fibers: from autonomic ganglia
Where specifically do the pre-ganglionic fibers of the SNS originate from ? of the PSNS ?
SNS: Thoracolumbar
PSNS: Craniosacral
Where specifically do the post-ganglionic fibers of the SNS originate from ? of the PSNS ?
SNS: Paravertebral Chain Prevertebral Ganglia
PSNS: In or Near Target Organ
Which of SNS or PSNS is long pre-ganglionic and which is long post-ganglionic fibers ?
SNS: Short pre-ganglionic neuron and long post-ganglionic neuron
PSNS: Long pre-ganglionic neuron and short post-ganglionic neuron
Does the vagus nerve serve the SNS or PSNS ? What structures does it innervate ?
PSNS
Viscera of trunk
Which organs are innervated by SNS and which by the PSNS ?
Broadly the same organs (pupils, salivary glands, heart, lungs, small intestine)
BUT SNS also innervates adrenal glands, kidneys, liver, sweat glands, blood vessels and structures of body walls.
What is a sympathetic trunk ? Where do they originate from and where do they extent to ? How do these trunks fuse with each other ?
Paired bundle of nerve fibers
Run from the atlas to the coccyx.
Fuse with each other in impar ganglion opposite coccyx.
What structure does the inferior cervical ganglion fuse with ? Where exactly does this occur ?
T1 ganglion to form the Stellate Ganglion
Lies on the neck of the 1st rib
What is the sympathetic supply to organs in the head ?
Internal carotid plexus
What are the four possible routes for a pre-ganglionic nerve leaving the CNS ?
- Enters sympathetic ganglion higher up (SYNAPSES) then ascends (has effectors in head and neck).
- Enters sympathetic ganglion at same level (SYNAPSES), and passes back into spinal nerve into periphery (sweat glands, smooth muscle) OR Enters sympathetic ganglion at same level, (SYNAPSES) and leaves into its own little nerve to influence viscera at that same level.
- Enters sympathetic chain (WITHOUT SYNAPSING) then descend into sympathetic ganglion (SYNAPSES ) (e.g. in sacral region) then passes back into a spinal nerve and then head off down to lower limbs.
- Enters sympathetic chain (WITHOUT SYNAPSING) passes out the front of sympathetic chain (still as pre-ganglionic neuron) then head to pre-vertebral ganglia (through splachnic nerve) in the abdomen. (SYNAPSES) then heads out to influence the gut.
Describe the general path of an autonomic motor reflex. What is the point of autonomic reflex arcs ?
- Stimulus in an organ (e.g. distended blood vessel)
- Sensory afferent neuron synapses at interneuron at CNS
- Pre-ganglionic fiber synapses at autonomic ganglion (may be SNS or PSNS depending on response required)
- Post-ganglionic fiber affects organ
POINT IS: VISCERAL CONTROL
What is a visceral pain response ?
Response to some distension, spasm, chemical irritation, ischiaemia.
What is referred pain ? Why does it occur ?
Pain from an organ, but felt as somatic pain (e.g. heart stroke, feeling in jaw and shoulder).
Because afferent neuron from injured organ to CNS synapses at same place as neuron from somatic region where the referred pain is actually felt.
Which of SNS or PSNS is fight or flight and which is rest and digest ?
SNS: fight or flight
PSNS: rest and digest
What is the effect of the SNS and PSNS on the heart ?
PSNS: Decreased heart rate
SNS: Increased heart rate + Increase rate of contraction
What is the effect of the SNS and PSNS on the digestive tract ?
PSNS: Increased motility and secretion
SNS: Decreased motility and secretion
What is the effect of the SNS and PSNS on the lungs ?
PSNS: Bronchoconstriction
SNS: Bronchodilation
What is the effect of the SNS and PSNS on the urinary bladder ?
PSNS: Release of urine
SNS: Urinary retention
What is the effect of the SNS and PSNS on the pupil of the eye ?
PSNS: Constrict
SNS: Dilate
What is the effect of the SNS and PSNS on the male sexual organs ?
PSNS: Erection
SNS: Ejaculation
What is the effect of the SNS and PSNS on the blood vessels ?
PSNS: Mainly no effect
SNS: Vasoconstriction (mostly)
What is the effect of the SNS and PSNS on salivary glands ?
PSNS: Increase secretion
SNS: Increase secretion
What is the effect of the SNS and PSNS on sweat glands ?
PSNS: No effect
SNS: Increased secretions
What is the effect of the SNS and PSNS on liver ?
PSNS: No effect
SNS: Glycogenolysis and gluconogenesis