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Anatomy Unit 3 > ANS Thorax > Flashcards

Flashcards in ANS Thorax Deck (28):
1

What is the ANS function with respect to the heart?

Heart can beat normally without any autonomic input, but SANS + PANS modify the rate and strength of cardiac contractility (cardiac output)

2

What is the ANS function with respect to the lungs?

Innervates smooth muscles of the bronchial tree to increase / decrease the lumen patency of airways, also innervates mucus glands + blood vessels

3

What are the visceral sensory (VA) fibers of the thorax?

Sense stretch (volume) from distention of wall of airways and major vessels, + chemoreceptors, and will function as part of ANS reflexes

4

What is the PANS course of the right vagus nerve?

1. Cross subclavian artery with vagus
2. Contribute to pulmonary plexus
3. Some fibers continue to esophageal plexus
4. Distal esophageal plexus form posterior vagal trunk through esophageal hiatus

5

What is the PANS course of the left vagus nerve?

1. Cross arch of aorta with vagus
2. Contribute to pulmonary plexus
3. Some fibers continue to esophageal plexus
4. Distal esophageal plexus forms anterior vagal trunk through esophageal hiatus

6

How does SANS innervate the thoracic viscera?

1. Preganglionic cell bodies in ILC of T1-T5
2. Preganglionic fibers enter SCG through WCR, the same axons will descend or ascend SCG
3. Preganglionic fibers terminate in 3 cervical or upper 4-5 thoracic ganglia
4. Postganglionic fibers leave as cardiac, pulmonary, esophageal, or aortic SANS nerves, and pass through ANS plexuses to reach their visceral targets

7

What are the three components of a thoracic plexus?

1. Preganglionic PANS (VE)
2. Postganglionic SANS (VE)
3. Visceral afferent fibers (sensory - VA)

8

What are the four subdivisions of the cardiac plexus and where do they occur?

1. Superficial - over arch of aorta
2. Deep - between bifurcation of trachea and aortic arch
3. Right / Left Atrial - over right + left atria, under epicardium of heart
4. Right / Left Coronary - Over the right and left coronary artery + branches

9

Where is the pulmonary plexus?

The walls of bronchi

10

Where is the esophagus (enteric) plexus?

In the walls of the GI tract. Esophageal plexus is just the proximal portion of the larger enteric plexus

11

Where is the aortic plexus?

In the thoracic aorta

12

What is the PANS course to modify the heart?

1. Ambiguus nucleus and dorsal motor nucleus of vagus nerve in medulla
2. Preganglionic fibers run with vagus and separate to join the cardiac plexus, pierce epicardium
3. Terminate in Terminal ganglia under the epicardium
4. Postganglionic fibers innervate SA (mostly left vagus), AV (mostly right), as well as purkinje system

13

What is the function of PANS to the heart? What are the receptors?

Decreases heart rate (bradycardia), reduces force of myocardial contractility, and increases smooth muscle tone of coronary arteries to decrease blood flow (less metabolic demand)

Ach released at muscarinic cholinergic receptors

14

What is the SANS course to modify the heart?

More extensive than PANS
1. ILC from T1-T4
2. SANS preganglionic enter SCG
3. Synapse in 3 cervical + T1-T4 thoracic ganglia
4. SANS postganglionic follow SANS cardiac nerve to cardiac plexus to innervate conduction system
5. SANS postganglionic also follow coronary arteries + branches to reach ventricular myocardium + smooth muscles of coronary arteries

15

What is the stellate ganglion?

ANS ganglion of brachial plexus. It is the fused inferior cervical ganglion + T1 thoracic ganglion

16

What is the function of SANS to the heart? What receptors does it use

Activation causes increased heart rate, increased force of ventricular contractility, and increased coronary artery vasodilation (relaxes smooth muscle)

Receptor - beta-1 adrenergic

17

What are the two types of VA fibers to the heart? What is a common response vasodilator

1. Reflex fibers - Regulate cardiac output from baro- and volume receptors.
2. Pain fibers - Detect pain from the heart, leading to angina pectoris. Generally as a result of decreased oxygen which the brain interprets as heart pain from lateral anterior chest wall + axillary region
-> Nitroglycerin commonly used to relax vasomotor tone during angina pectoris

18

What are the courses of the two types of VA fibers? Why is this relevant in terms of pain VA fibers?

Reflex - Join vagus nerves and synapse in Nodose ganglion (inferior X ganglion) before entering medulla

Pain - Join cardiac SANS branches to SCG and through T1-T4 WCR BACK into the spinal cord, with cell bodies in the dorsal root ganglion. They synapse there with 2nd order sensory neurons (same place as somatic dermatomes of T1-T4) -> origin of referred pain

19

What is the PANS course to modify the lungs?

1. Cell body in dorsal motor nucleus of X in medulla
2. Preganglionic fibers descent right and left vagus to pulmonary plexus
3. Synapse in terminal ganglia within the wall of bronchial tree
4. Innervate smooth muscle + glands in wall of bronchioles

20

What is the PANS function for the lungs? What type of receptor is it?

Contraction of bronchiolar smooth muscle (bronchoconstriction)
Increased mucus secretion from glands of lung

Muscle - muscarinic cholinergic receptor

21

What is the SANS course to modify the lungs?

1. Cell body in ILC of T1-T5
2. Preganglionic fibers in SCG
3. Synapse in 3 cervical, and first 4-5 thoracic ganglia
4. Postganglionic fibers travel with pulmonary nerves, course through pulmonary plexus and into bronchial tree to innervate smooth muscle (vascular, bronchiolar) as well as mucus glands

22

What is the SANS function for the lungs? What type of receptors?

Bronchodilation via bronchiolar smooth muscle to incrase air flow
Reduction of vasoconstriction via alpha adrenergic to increase blood flow
Reduction of mucus secretion in glands

Receptor type - beta-2 adrenergic receptor for bronchiolar smooth muscle

23

What is beta-1 vs beta-2 important?

beta-1 = heart
beta-2 = lungs

These are adrenergic receptors that can be specifically targeted by pharmaceuticals to change heart / lung function.

24

What are COPD and asthma?

COPD - chronic inflammatory disease with lung breakdown (emphysema) and bronchospasm (bronchoconstriction). Usually in smokers

Asthma - Chronic inflammatory disease without lung breakdown. Bronchospasm persists due to allergic conditions / irritants

25

What drugs are used to treat COPD / asthma?

Advair or Symbicort. They are combinations of corticosteroids (decrease inflammation) and beta-2 adrenergic agonists (relax bronchiolar smooth muscle to open airways)

26

How do stretch receptors in lung work?

They are activated during inspiration, VA fibers go upstream with vagus to medullary respiratory sensors. As part of Hering-Breuer reflex, they trigger transition from inspiration to expiration

27

How do aortic / carotid baroreceptors work?

Sense distention in wall of aorta or carotid sinus due to increased blood pressure

Aortic - VA travel with CNX
Carotid sinus - VA travel with CNIX

Leads to decreased heart rate and peripheral vasodilation to decrease blood pressure

28

How do carotid body chemoreceptors work?

Glomus cells at carotid bifurcation sense pO2 reduction of 15% or more, as well as increases in CO2.
VA fibers travel with glossopharyngeal nerve (IX) sinus nerve.

Activation causes increased respiratory and heart rates, increasing oxygenation of tissues