18. Respiratory Control

Question 1

What controls the frequency of breathing and the pattern?

Answer 1

The brain

If there is a greater inspiration, pattern will be much steeper and vice versa

Question 2

What is the general set up for respiratory control?

Answer 2

Controller (medullary centers) –> Effector (muscles/diaphragm) –>controlled variable –> Sensor –> back to controller

Question 3

What are the medullary respiratory centers in the central respiratory center?

Answer 3

DRG: dorsal respiratory group
VRG: ventral respiratory group
PRG: Pontine (pons) respiratory group 
Botzinger Complex
Pre-Botzinger complex: V IMPORTANT (area between VRG and Botzinger

Question 4

What does the respiratory control center determine?

Answer 4

timing (f) frequency/length inspiration
determines depth (Vt)
sends to motorneurons AP to phrenic N

Question 5

What is believed to be the site which generates the timing (frequency) of the respiratory rhythm?

Answer 5

Pre-Botzinger complex, not the only though

Question 6

What is it called when the pontine respiratory group is damaged, leading to no switching from inspiration to expiration?

Answer 6

Apneusis:failure to turn inspiration off

So therefore the PRG is also considered part of the network that controls length of inspiration

Question 7

What are the two main groups that determine the depth/pattern of breathing? (Vt)

Answer 7

Dorsal respiratory group and ventral respiratory groups

Question 8

DRG sends 95% of premotor to phrenic N (in spinal cord to tell what to do), receives lots of sensory info which generates a pattern appropriate to the circumstances. What do the rostral and caudal parts of the VRG do?

Answer 8

Rostal: premotor to phrenic and other inspiratory muscle
Caudal: premotor to upper airway, other expiration muscles

Question 9

Pre-botzinger does?

Answer 9

generates core rythym, in medullary

Question 10

PRG do?

Answer 10

modifies inspiratory timing, turns off inspiration, in Pons

Question 11

DRG does?

Answer 11

depth of breathing Vt, in medullary

Question 12

VRG does?

Answer 12

inspiration and expiration/depth in medullary

Question 13

What is the difference between apneusis and apnea?

Answer 13

Apneusis: appears as maintained inspiratory discharge d/t damage to PRG, slight delay then inc CO2, dec O2, death
Apnea: No inspiration d/t medullary/spinal damage, Inc CO2, dec O2, death

Question 14

What is a chemoreceptor?

Answer 14

a neuron that is sensitive to specific chemicals such as CO2, O2, and hydrogen ion

Question 15

What will an increase in CO2, decrease in O2, and increase in H+ do to the firing rate of a chemoreceptor?

Answer 15

It will increase the firing rate of neurons which increases breathing rate, with hope of getting more O2 to body

Question 16

What occurs when there is hypoxia or hypercapnia?

Answer 16

chemoreceptors increase their firing rate of activity, activating respiratory centers and increasing respiration

Question 17

What are the two sets of chemoreceptors and where are they located?

Answer 17

Central chemoreceptors, in brain

peripheral chemoreceptors, in carotid and aorta (to tell brain what arterial blood is)

Question 18

The central chemorecptors are located on the ventral surface of the medulla and are (indirectly) sensitive to CO2 in blood. What does this mean?

Answer 18

CO2 is able to cross the BBB and it then reacts with water and carbonic anhydrase, which forms HCO3 and H+. ***H+ THEN STIMULATES THE CENTRAL and drives you to breath

However H+ in blood does not affect central because cannot cross the BBB only CO2

Question 19

In the peripheral chemoreceptors, the main ones are the carotid body, and the aortic arch is the back up system, they are just swellings. What are they mainly activated by?

Answer 19

DOPAMINE

Question 20

Peripheral also communicate back to central pre-botzinger and DRG. Response to CO2 and Hydrogen ion is stronger, than O2. What do they stimulate?

Answer 20

signal afferents from carotid body/aortic arch to pre-bot and DRG, to influence the rate of the breathing, (increase f and Vt)

Question 21

Slowly adapting pulmonary stretch receptors are located in the airways and are sensitive to stretch of airways- increase in stretch receptors (directly proportional to lung volume) fibers travel to brain via vagus nerve and causes what effect?

Answer 21

Inhibition of inspiration (inspiratory termination) and prolongation of expiration

Question 22

What are the slowly adapting pulmonary stretch receptors important for in adults and children?

Answer 22

Adults: controlling respiration during exercise, not during rest
Children: controlling respiration all the time

Question 23

What are the two sets of receptors that are involved in protecting the gas exchange surfaces, rather than controlling respiration on a breath to breath basis?

Answer 23

Rapidly adapting pulmonary stretch receptors and J (juxtacapillary) receptors

Question 24

Rapidly adapting pulmonary stretch receptors are located in the airways and are sensitive to irritation, foreign bodies in the airway and stretch. What effect occurs?

Answer 24

Fibers travel to brain via Vagus nerve and cause a cough, also elicited by receptors at the larynx

Question 25

The J receptors are located next to blood vessels of alveolis and are sensistive to pulmonary edema and cause what?

Answer 25

Effect is couch/tachypnea (fast breathing) cause by fibers via vagus nerve

Question 26

The RARs and J receptors mediate protective refelxes that…?

Answer 26

OVERRIDE normal respiratory control systems, important for survival

Question 27

Cortical influences do control breathing as well, such as talking and holding your breath. What occurs in these cases?

Answer 27

Cortex appears to be bypassing the medullary centers completely and sending input directly to the muscles of respiration as a fail safe if something goes wrong!