ANS anatomy Flashcards
the autonomic nervous system is separated how?
- sympathetic
- parasympathetic - vagus nerve
Vasovagal response does what?
involves parasympathetic
- reduces heart rate and blood pressure etc -
Where do the sympathetic nerves come from?
T1-L2
Where do the parasympathetics come from?
brainstem and 4 cranial nerve
as well as the S2-S4 of the sacral part of spinal cord - supply parasympathetic in pelvis
Parasympathetic uses what nueroreceptor?
acetylcholine nicotinic at pre-ganglionic
acetylcholine muscarinic at post-ganglionic
Grey matter = what?
cell bodies
What exits from the lateral horn?
sympathetics - go alonng the anterior root to the spinal nerve -
sympathetic chain allows what?
it is the highway for sympathetic activity beyond its short origins at the cranial segments
the pre-ganglionic fibers are myelinated or unmyelinated?
myelinated like most
postganglionic sympathetic fibers are myelinated or unmylinated?
unmyelinated - pretty much the only unmyelinated region you’ll come across is the postganglionic sympathetic fibers which is why they are called “grey”
do preganglionic fibers run up or down the sympathetic chain before synapsing?
they can run either up or down
*the postganglionic fibers may run up or down the chain before exiting*
can preganglionic fibers leave the sympathetic chain without synapsing?
Absolutely!
ex) fibers can come from T5-T9 , don’t synapse and continue on as the splanchnic nerves and going to the ganglia before aortic trunk- then moves to bowels? What I’m getting here is that they can be entirely random
the thoracic sympathetic trunk is enclosed by what?
the parietal pleura
Describe the path of the thoracic sympathetic trunk
continuation of the cervical trunk - crosses the neck of 1st rib, heads of ribs 2-10, bodies of 11th and 12th rib - moves more medially as it moves inferiorly
where does the vagus nerve begin?
tries to stay posterior and medial all the way down - (on the left side though the aorta is in the way) - runs behind the hilum of lung and tries to run on the
What is the name of the vagus nerves in the thorax?
enter as vagus nerves
then makes the esophageal plexus?
exit as vagal trunks - (main contributor = right vagus nerve) anterior and (main contributor = left vagus nerve) posterior trunks
what plexuses are contributed to by the autonomic system?
- cardiac plexus - in thorax
- coeliac - in abdomen
- hypogastric - in pelvis
where do the sympathetic fibers of the cardiac plexus run to?
SA and AV nodes- coronary vessels and cardiac muscle
where are the preganglionic fibers of the parasympathetic?
brainstem - make vagus nerve - relay to heart wall
*only synapses with the post-ganglionic fibers in the actual wall of the heart *
What is the main function of the cardiac plexus?
regulate heart rate
force of each contraction
cardiac output
divide the cardiac plexus functions into sympathetic and parasympathetic
Sympathetic
- increase heart rate
- increase force of contraction
- dilate coronary arteries
parasympathetic
- decrease heart rate
- reduce force of contraction
- constrict coronary arteries
How does the brain interpret cardiac pain?
brain has a hard time interpreting visceral pain - so in the case of an MI when cardiac cells actually die- the visceral pain fibers travel along with the sympathetic fibers- they are co-stimulated- and therefore the level of the spinal cord that those sympathetics return to are effected ( T1-T4)
- these pain signals then enter the T1-T4 segments of the spinal cord which is the dermatome level of the left medial arm
- the phrenic nerve is also irritated in this process at (C3,4,5) which are the dermatomes to the neck - therefore you could feel it along the jaw
*cardiac pain can be variable/atypical because your body is trying to distinguish visceral feelings -
what is the ‘typical ‘ cardiac pain?
crushing restrosternal pain
radiating to the neck, jaw, left arm
What is an atypical presentation of an MI?
mild epigastric discomfort and severe nausea
