Respiratory Control

Question 1

Basic elements of the control system

Answer 1

Chemoreceptors (central and peripheal) and vagal bronchopulmonary receptors (stretch, irritant, J)…input to pontine and medullary centers…output to motor neurons of respiratory muscel

Question 2

Respiratory centers

Answer 2

Specific groups o neruons i nthe pontine and medullary regions

Responsible for generation and maintennace of resp rhythm and reg of breathing pattern

Question 3

Pontine center primary function and different centers

Answer 3

Regulate breathing pattern but NOT essential for maintaining respiration

Pneumotaxic - upper 1/3 …electrical stimulation causes rapid breathing

Apneustic cnter - lower 1/3 of pons…electrical stimulation causes apneusis (sustained contraction of inspiratory muscles)

Question 4

Medullary centers (DRG)

Answer 4

Essential for maintaing resp rhythm

Located in dorsomedial medulla - in vicinity of NTS

Affarent inputs from vagal BP receptors and peripheral chemoreceptors

Source of rhythmic phrenic motor drive to diaphragm

Question 5

VRG

Answer 5

Ventrolateral region of medulla

Rhythmic motor drive to internal and external intercostals, accessary muscles, and laryngeal msucles

Question 6

Thoeries of resp rhythm genesis

Suprapontine structures

Answer 6

Pacemaker neurons

Neuronal network interaction…circuit so interuption of the circuit leads to the breathing pattern

Mid-brain, cerebral cortex ,and other higher

Question 7

Rett syndrome

Cheyne-stokes

Answer 7

Mutation of MeCP2 gene

Oscillation between apnea and hyperpnea in .5-2 min cycles

Question 8

Asphyxia
Apnea
Hyperpnea
Hyperventilation vs. tachypnea

Answer 8

Extreme decrease in oxygen and increase in CO2 in the body due to stop breathing

Long delay of inspiration

Increase in tidal volume

Tachyp is rapid rate but hyperventilation is increase in minute ventilation**

Question 9

Chemoreceptors (central)

Answer 9

Detect changes in chemical compositions in arterial blood

Cental - near surface of ventrolateral medullla

Central stimulated by low pH in CSF…or high PCO2 (or low arterial pH), but NOT low arterial PO2

Question 10

Peripheral chemoreceptors

Answer 10

Carotid bodies (main one) - on carotid artery

Aortic bodies - scattered near aortic arch

Stimulated by LOW arterial PO2**, high arterial PCO2 or low pH…ONLY sensors in the body that can detect hypoxia

Question 11

BP sensory receptors

Answer 11

Play role in regulating breathing pattern and airway functions

Protect against inhaled irritants

Affarent nural activity in vagus nerves to the NTS in the medulla

Question 12

BP stretch receptors

Answer 12

Slowly adapting

Volume expansio in the lung is stimulus (even within tidal volume range)…activated during inspiraiton…stops the inspiration

Slowly adapting play important role in regulaiton of breathing pattern

Question 13

BP irritant receotrs

Answer 13

Rapidly adapting

Stimulated by decreased compliance or lung atelectasis and certain inhaled irritants

Reflex responses - sigh and cough

Question 14

BP C fibers

Answer 14

Juxtacapillary receptors

75% of vagal sensory nerves in the lung

Stimulated by certain endogenous inflammatory mediators, inhaled chemical irritants

Reflex response - reflex bronchoconstriction, cough, increase in mucous secretion, dyspneic sensation

Question 15

Cough reflex

Answer 15

Can be generated by inhaled irritants or aspiration, or airway inflammation/infection in patients

Question 16

Cough in dz and defense function

Answer 16

Chronic cough as an airway dz

Def - protective against inhaled irritants or aspiration and expel excessive ariway secretion (or inhalaed irritants or allergens)

Larynx closes and will activate compression of the diaphragm…this causes an increase in pressure which creates high velocity flow

Question 17

Cough sensors

Answer 17

Inhaled irritants

Endogenous inflammatory mediators

Very superficial

Question 18

Ventilatory response to hypoxia

Answer 18

Not very sensitive to change in O2 in normal range of PO2…no significant change in ventilation until arterial PO2 falls below 60 mmHG

Response potentiated by hypercapnea

Reflex response elicited ONLY by stimulation or peripheral chemoreceptors

Question 19

Response to hypercapnea

Answer 19

Very sensitive to change in CO2 in normal range of PCO2

Response potentied by hypoxia

Most of response is elicited by stimulation of central chemoreceptors

Question 20

Difference between hypoventilation and other causes of hypoxia/hypercapnea

Answer 20

hypoventilation is MUCH more likely to cause hypercapnea than the other three

The other three will cause much more hypoxemia

Question 21

Anesthesia effect

Answer 21

Drugs that act on CNS will decrease the minute ventilation and can therefore increase the PaCO2 by inducing hypoventilation

Question 22

Dyspnea in healthy, pts with lung dz, and pts with heart dz

Answer 22

During exercise and exertion or in high altitude

Common in boht obstructive and restrictive dz

Congestive heart failure, acute cardiac ischemia…orthopnea (harder when lying down)

Question 23

Receptors in generating dyspnea

Answer 23

Peripheral - hypoxia and acidosis

Vagal sensory innervating the lung and airways (C fibers or juxtacap receptors)…airway diseases

Mechanoreceptors in resp muscles

Also central motor commands and behavioral factors can be involved