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Anatomy Unit III > ANS of Thorax > Flashcards

ANS of Thorax Flashcards

1
Q

What is the heart’s inherent contractility?

A

Due to pacemaker properties of the SA and AV nodes

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2
Q

Although the heart has inherent contractility, what innervates it and modifies the heart rate and strength of its contractility?

A

ANS - parasymp and symp

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3
Q

What is cardiac output?

A

Strength of the heart’s contractility plus heart rate

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4
Q

What augments the heart’s rate and contractility?

A

Sympathetic (SS)

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5
Q

What diminishes the heart’s rate and contractility?

A

Parasympathetic (PS)

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6
Q

What does PS and SS innervation of the smooth m;uscle in the bronchial tree alter?

A

It increases or decreases the lumen patency of the airways, and innervates mucus and blood vessels that provide moisture and warmth of these airways.

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7
Q

What is the affect of PS innervation to the lungs?

A

Increased mucus secretion and vasoconstriction

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8
Q

What is the affect of SS innervation to the lungs?

A

Decreased mucus secretion and vasodilation

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9
Q

Describe the ANS reflexes that control respiration and blood pressure:

A

Visceral sensory (afferent) fibers from stretch receptors which sense distention in the wall of airways and major vessels (lung, aortic arch, carotid sinus) and from chemoreceptors which sense O2/CO2 blood levels) in the carotid body are part of the ANS reflexes

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10
Q

Describe the pathway of the Right vagus nerve:

A

Crosses the right subclavian a –> descends next to the trachea and reaches the root of the lung –> contributes to the right pulmonary plexus –> PS fibers join the esophageal plexus –> in the distal most part of the esophagus, many of these fibers form the POSTERIOR vagal trunk –> passes thru the esophageal hiatus –> enters abdomen

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11
Q

Describe the pathway of the LEFT vagus nerve:

A

Enters thorax between left carotid and subclavian aa –> crosses the arch of the aorta –> passes between ascending aorta and left pulmonary a –> reaches root of lung –> contributes to left pulmonary plexus –> from this plexus PS fibers join the esophageal plexus with many of these fibers –> form the ANTERIOR vagal trunk –> passes into abdomen thru the esophageal hiatus (below diaphragm)

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12
Q

The right vagus n contributes to the _______ vagal trunk.

A

POSTERIOR

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13
Q

The left vagus n. contributes to the _______ vagal trunk.

A

ANTERIOR

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14
Q

Where do SS preganglionic cell bodies lie? For thoracic innervation

A

In the interomediolateral cell column at T1-5 spinal nerves

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15
Q

Describe the SS innervation of thoracic viscera (the pathway):

A

SS pregang cell bodies in intermediolateral cell column at T1-T5 spinal levels –> SS pregang fibers enter SS chain ganglia with WCR of spinal nerves T1-5 –> axons may ascend in the SCG and terminate in the 3 cervical (superior, middle, inferior/stellate) ganglia and the upper 4 or 5 thoracic ganglia –> SS postgang

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16
Q

Cont: SS postganglionic fibers:

A

leave the above ganglia s the cardiac, pulmonary, esophageal, or aortic SS nerves –> pass thru the ANS thoracic plexuses –> reach their visceral targets

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17
Q

The arch of the aorta is _____ to the trachea and _______ to its bifurcation into the right and left bronchi.

A

Anterior; superior

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18
Q

The esophagus descends in the thorax ______ to the descending aorta.

A

Anterior

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19
Q

What are the autonomic plexuses? (5)

A
  1. Superior cardiac plexus - anterior surface of arch of aorta
  2. Deep cardiac plexus - at bifurcation of trachea
  3. Pulmonary plexus
  4. Esophageal plexus
  5. Aortic plexus
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20
Q

** What innervates heart and lungs?

A
  1. POSTGANGLIONIC sympathetic fibers
  2. PREGANGLIONIC parasympathetic fibers
  3. Visceral sensory (afferent) fibers
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21
Q

What is the cardiac plexus?

A
  1. PS (only pregang) fibers from R and L vagus, 2. SS (mostly postgang) fibers from 3 cervical and upper 4 or 5 thoracic ganglia and
  2. Visceral sensory (VA) fibers overlap in an elaborate plexus around the wall of the great vessels (aorta, pulmonary aa) at the base of the heart and at the bifurcation of the trachea.
22
Q

The cardiac plexus is subdivided into (based on location):

A
  1. Superficial (over the arch of the aorta)
  2. Deep (between bifurcation of trachea and aortic arch)
  3. R and L atrial (over right and left atria)
  4. R and L coronary (over R and L coronary aa and their branches)

In addition, esophageal and aortic plexuses occur around the walls of the esophagus and thoracic aorta

23
Q

Where are the PS pregang cell bodies located? For thoracic

A

In the dorsal motor nucleus of the vagus n. at the medulla level

24
Q

Describe PS innervation of the heart:

A

PS pregang cell bodies in dorsal motor nucleus of vagus n. at medulla level –> PS pregang fibers separate from vagus nn at the neck and thoracic levels –> join the cardiac plexus –> pierce the epicardium –> terminate in PS terminal ganglia under the epicardium –> short PS postgang fibers (originating under the epicardium) innervate specialized cardiac muscle in SA and AV nodes, as well as Purkinje conduction system

25
Q

Function of PS innervation of the heart:

A
  • Decreases the heart rate (bradycardia)
  • Reduces the force of myocardial contractility and
  • Decreases coronary a. blood flow (because of lessened metabolic demand of O2 to the heart)
26
Q

Describe SS innervation of the heart:

A

SS pregang cell bodies in the interomediolateral cell column at T1-4 spinal levels –> SS pregang fibers enter SCG –> synapse with postgang neurons in the 3 cervical ganglia and the uppermost 3 or 4 thoracic ganglia –> SS postgang fibers follow SS cardiac nn to the cardiac plexus (innervated SA, AV, and conduction system) –> piggy back with coronary aa and their branches –> to reach the ventricular myocardium and smooth muscles of coronary aa.

(SS innervation of the heart is more extensive than PS)

27
Q

What is the function of SS innervation of the heart?

A

SS activation causes:

  • Increased heart rate (tachycardia)
  • Increased force of ventricular contractility
  • Induces coronary aa vasodilation
28
Q

How is the force of ventricular contractility increased?

A

Via the beta-1 adrenergic receptors

29
Q

Visceral afferent (sensory) pain fibers follow:

A

Symphathetics

30
Q

For sensory innervation (VA) of the heart, what two types of VA fibers innervate it?

A

Reflex (for regulation of cardiac output) and

Pain (for detection of pain from the heart - angina pectoris

31
Q

Explain the Reflex, or regulation of cardiac output:

A

These fibers join vagus nerves (cell bodies in NODOSE ganglia) and course upstream to medullae where they modify cardiovascular and respiratory centers.

32
Q

Explain pain innervation, for detection of pain from the heart (angina pectoris):

A

These fibers join cardiac SS branches –> to SCG –> thru T1-4 WCR back into the spinal cord (cell bodies in dorsal root ganglia) –> synapse with 2nd order sensory neurons that also receive SA information from T1-4 somatic dermatomes (soma wall is more richly innervated than the viscera). The brain interprets heart pain (referred) as originating from the left anterior chest wall and axillary region

33
Q

ANS innervation of the lung: PS

A

PS cell bodies in the dorsal motor nucleus of vagus (medulla level) –> PS pregang fibers descend with R and L vagus nn –> join pulmonary plexuses –> pass into the bronchial tree –> terminated in PS terminal ganglia within the wall of the tree (seen only at histological level) –> PS postgang fibers innervate smooth muscle within the wall of bronchioles

34
Q

Function of PS innervation of the lung:

A

Activation of PS produces contraction of bronchiolar smooth muscle (bronchoconstriction, Ach mediated) and increased mucus secretion from glands in lung

35
Q

ANS innervation of lung - describe SS:

A

SS pregang cell bodies in intermediolateral cell column at T1-5 spinal levels –> SS pregang fibers pass into SCG and terminate on postgang neurons in the 3 cervical and first 4 or 5 thoracic ganglia –> SS postgang fibers join SS pulmonary nerves –> course thru pulmonary plexus and then into bronchial tree where they –> innervate smooth muscle (bronchiolar and vascular) as well as mucus glands

36
Q

Function of SS innervation of the lungs:

A

Activation of SS causes bronchodilation which enhances airflow, reduction of mucus secretion and vasoconstriction. This response is seen during the stress syndrome (fight or flight) when the body needs to increase oxygenation of all tissues

37
Q

Bronchodilation is activated via:

A

Beta-2 adrenergic receptor

38
Q

Reduction of mucus secretion and vasoconstriction is activated via:

A

Alpha adrenergic receptor

39
Q

Beta-2 just affects the _______.

A

Lungs, not heart

40
Q

What else controls respiration and blood pressure? (In addition to ANS)

A

VA (sensory) fibers and autoregulatory reflexes

41
Q

What are the stretch receptors in the lung?

A

Activated during inspiration (when lungs are expanded due to air intake). Fibers go upstream with the vagus to the medulla where they terminate in respiratory centers. Part of the HERING-BREUER REFLEX to trigger transition from inspiration to expiration (air outflow)

42
Q

Describe what happens with the aortic arch and carotid sinus baroreceptors ?

A

They sense stretch distention of the wall of arch or sinus. It is activated by increase in blood pressure. Impulses from the aortic arch travel with the vagus and those from the carotid sinus travel with the glossopharyngeal n.

43
Q

Impulses from the aortic arch travel with:

A

Vagus n.

44
Q

Impulses from the carotid sinus travel with:

A

Glossopharyngeal n.

45
Q

What does increased BP cause?

A

Causes greater firing of baroreceptors in aortic arch and carotid sinus which results in DECREASED heart rate and peripheral vasodilation (decreased resistance of blood flow). These 2 actions automatically lower the BP

46
Q

What is the role of the carotid body chemoreceptors?

A

Glomus cells (at the carotid bifurcation) are innervated by glossopharyngeal (IX) n. Cells become active after a pO2 (oxygen tension) reduction of 15% or more. Activation causes increased respiratory and heart rates –> both actions resulting in increased oxygenation of tissues.

47
Q

Two diseases of the lung/respiratory system:

A

Chronic Obstructive Pulmonary Disease (COPD) and Asthma

48
Q

What is COPD?

A

A chronic inflammatory disease which can bring about severe bronchoconstriction and restriction of airflow in the respiratory pathways. COPD is due mostly to smoking, there is emphysema (or breakdown of lung tissue) coupled with broncospasm (sustained bronchoconstriction).

49
Q

What is asthma?

A

Bronchitis without lung breakdown, is a condition triggered by allergies/irritants in individuals with certain genetic predisposition. Severe bronchoconstriction/bronchospasm causes wheezing, coughing, shortness of breath and sometimes death

50
Q

What are 2 common drugs used for COPD and asthma? HOw do they work?

A

Advair and Symbicort are commonly used. These drugs contain combinations of corticosteroids (Symbicort contains BUDESONIDE which blunts the inflammatory response) with long-acting beta adrenergic agonists (Symbicort contains FORMETOROL which relaxes bronchiolar smooth muscle)

Anatomy Unit III (13 decks)

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