Lecture 33: Control of Respiration and Chemoreceptors

Question 1

Breathing occurs in what pattern

Answer 1

• Continuous, cyclical pattern
• Inspiratory muscles rhythmically contract
• Activities are accomplished automatically without conscious effort

Question 2

Respiratory muscles require what to bring about contraction

Answer 2

nervous stimulation

Question 3

Respiratory control centers are housed where and are responsible for what

Answer 3

in the brain stem

generating the rhythmic pattern of breathing

Question 4

Three respiratory centers in the brain stem

Answer 4

1. Medullary
2. Apneustic
3. Pneumotaxic

Question 5

What is the primary control center for respiration in the brain

Answer 5

Medullary

Consists of cell bodies

Question 6

Two clusters that the medullary respiratory center are composed of

Answer 6

1. Dorsal
   - inspiratory
2. Ventral respiratory
   - expiratory
   - Also composed of inspiratory neurons
   - Dorsal respiratory group has connections to it

Question 7

Inspiratory center of medullary purpose

Answer 7

-Controls basic rhythm for breathing by setting the frequency of breathing

Question 8

Inspiratory center of medullary receives sensory input from

Answer 8

• Peripheral chemoreceptos via glossopharyngeal (CN IX) and vagus (CN X) nerves
• Mechanoreceptors in the lungs via vagus nerves

Question 9

Inspiratory center sends motor output to…

and as a result…

Answer 9

1. The diaphragm via the phrenic nerve, external intercostal muscles via the intercostal nerves
2. As a result, respiration occurs because these muscles produce an increase in intrathoracic pressure and initiates the flows of air into the lungs

Question 10

What muscles may be used for more vigorous respiration

Answer 10

Those connecting the sternum and the head

Question 11

Ventral respiratory group is composed of inspiratory and expiratory neurons which remain inactive during

Answer 11

normal quiet breathing

Question 12

Air is driven out of the lungs by

Answer 12

the reverse pressure gradient between the lungs and the atmosphere until the system reaches its equilibrium point again

Question 13

Purpose of the ventral respiratory group

Answer 13

• Called into play as an overdrive mechanism when demands for ventilation are increased
• Esp important in active expiration

Question 14

Pneumotaxic and apneustic centers are located

Answer 14

in the pons

Question 15

Pneumotaxic and apneustic purpose

Answer 15

Exerts fine-tuning influences over medullary center to help produce normal, smooth, insp and exp

Question 16

Pneumotaxic

Answer 16

Transmits inhibitory impulses to DRG that help turn off insp neurons, limiting duration of inspiration

Question 17

Apneustic center

Answer 17

-Prevents inspiratory neurons from being switched off, providing extra boost to inspiratory drive

Question 18

Pneumotaxic vs apneustic

Answer 18

Pneumotaxic is dominant over apneustic, helping to bring inspiration to a halt and allowing expiration to occur normally

Question 19

Arterial blood gases are maintained within a normal range by

Answer 19

varying the magnitude of ventilation to match the needs of the body for O2 uptake and CO2 removal

Question 20

Three chemical factors that increase ventilation

Answer 20

1. An decrease in arterial PO2
2. An increase in arterial PCO2
3. An increase in H+ concentration

Question 21

Two types of chemoreceptor that monitors ventilation

Answer 21

1. Peripheral

2. Central

Question 22

Where are peripheral chemoreceptors located

Answer 22

Carotid bodies and aortic bodies

Question 23

What do peripheral chemoreceptors respond to

Answer 23

• Primarily to decreases in blood O2

- Less sensitive to increases in CO2 and decreases in blood pH

Question 24

Peripheral chemoreceptors relay info about

Answer 24

Arterial PO2, PCO2, and H+ to medullary inspiratory center via cranial nerves IX and X

Question 25

Most important responsibility for peripheral chemoreceptors

Answer 25

-Detect changes in arterial O2

Question 26

Arterial PO2 must fall below ___ mm HG before peripheral chemoreceptors are activated

Answer 26

60

Question 27

Central chemoreceptors link

Answer 27

changes in arterial PCO2 to compensatory adjustments in ventilation

Question 28

Do central chemoreceptors monitor CO2 itself

Answer 28

Nope

Question 29

What do central chemoreceptors monitor?

Answer 29

Changes in CO2-induced H+ concentration in the ECF of the brain that bathes them

Question 30

Central chemoreceptors monitor what breathing

Answer 30

minute to minute

Question 31

Central chemoreceptors are very sensitive to what?

Answer 31

Changes in the pH of the brain ECF

Question 32

A decrease in pH of ECF leads to

Answer 32

increased breathing rate (hyperventilation)

Question 33

A increase in pH of ECF leads to

Answer 33

a decrease in the breathing rate (hypoventilation)

Question 34

Diabetes mellitus

Answer 34

-Excess of H+ keto acids in the circulation

Question 35

Four “other” respiratory receptors

Answer 35

1. Lung stretch receptors
2. Joint and muscle receptors
3. Irritant receptors
4. J receptors

Question 36

Lung stretch receptors

Answer 36

• Located in smooth muscle of airways
• When stimulated by lung distension, action potentials travel through afferent fibers to the medullary center and inhibit the inspiratory neurons

Question 37

Hering-Breuer reflex

Answer 37

Negative feedback from highly stretched lungs prevents over-inflation

Question 38

Proprioceptors (muscle and joint receptors)

Answer 38

-Increase breathing rate

Question 39

Where are irritant (nocioreceptors) located

Answer 39

• Between epithelial cells lining airways

- Info travels to medulla and causes reflex constriction of bronchial smooth muscle and increase in breathing rate

Question 40

J receptors are called

Answer 40

Juxtacapillary receptors

Question 41

J receptors are located

Answer 41

In alveolar walls of near the capillaries

Question 42

J receptor purpose

Answer 42

Engorgement of pulmonary capillaries with blood and increases in interstitial fluid volume activates these receptors to produce an increase in rate of breathing

Question 43

Example of J receptor activation

Answer 43

In left-sided heart failure, blood backs up in pulmonary circulation. J receptors mediate change in breathing pattern, including rapid shallow breathing