21-5: Control of Respiration

Question 1

respiratory centers

Answer 1

neurons clustered in two regions of the brainstem are critical in respiration

Question 2

dorsal respiratory group

Answer 2

located dorsally near the root of cranial nerve IX; integrates input from peripheral stretch and chemoreceptors and communicates information to VRG

Question 3

ventral respiratory group

Answer 3

network of neurons on ventral surface of brainstem, extending from the spinal cord to the pons. Generates the basic respiratory rhythm with two groups of neurons, one firing during inspiration and one firing during expiration

Question 4

What happens when the inspiratory neurons fire?

Answer 4

impulses sent along the phrenic and intercostal nerves, leading to contraction of the diaphragm and external intercostals

Question 5

What happens when the expiratory neurons fire?

Answer 5

the output stops and the inspiratory muscles relax, allowing lungs to recoil and expiration to occur passively

Question 6

eupnea

Answer 6

normal respiratory rate and rhythm, determined by the cyclic on/off activity of the inspiratory and expiratory neurons

Question 7

What controls the rate and depth of breathing?

Answer 7

main:
inflation reflex (stretch receptors)
chemoreceptors

others:
cortical control
body temp
pain
stretch of anal sphincter
proprioceptors

Question 8

inflation reflex

Answer 8

if stretch receptors on the walls of the bronchi/bronchioles are overstretched, they send inhibitory impulses via the vagus nerve that end inspiration (protecting lungs from overinflating)

Question 9

chemoreceptors

Answer 9

special cells sensitive to changing levels of CO2 and O2 in arterial blood, located in the aortic arch and carotid arteries

Question 10

What is the most important chemical affecting respiration in a healthy individual?

Answer 10

CO2

Question 11

If CO2 levels rise slightly (hypercapnia), what is the impact on respiration in a healthy person?

Answer 11

rate and depth of breathing increases to quickly flush CO2 from the blood (hyperventiliation)

Question 12

People experiencing anxiety may hyperventilate - what effect does this have?

Answer 12

causes PCO2 to drop, cerebral blood vessels to constrict, and make them feel faint and dizzy

(breathing into a paper bag allows them to breathe back the CO2 that they exhaled)

Question 13

If PO2 levels drop slightly (mild hypoxia), what is the impact on respiration in a healthy person?

Answer 13

none, since there is a huge reservoir of O2 bound to hemoglobin

Question 14

If PO2 levels drop substantially (acute hypoxia), what is the impact on respiration in a healthy person?

Answer 14

if arterial PO2 drops substantially (from 104 to 60), respiratory rate will increase

Question 15

In a patient with COPD, what is the key driver of respiration?

Answer 15

PO2 (hypoxic drive) - the body adjusts to chronically high PCO2 so PO2 becomes the key driver

Question 16

cortical control

Answer 16

we can voluntarily alter our breathing rate by sending impulses from our cerebral cortex to motor neurons that stimulate respiratory muscles, bypassing the respiratory center

Our ability to hold our breath is limited because the respiratory center automatically reinitates breathing when CO2 levesl are too high

Question 17

What influence does body temp have on respiration?

Answer 17

a rise in body temp causes respiratory rate to increase and decrease in temp causes respiratory rate to decrease

A sudden exposure to cold causes temporary apnea

Question 18

pain

Answer 18

prolonged pain increases respiratory rate

A sudden sharp pain may cause apnea

Question 19

Stretch of the anal sphincter results in ___ respiratory rate

Answer 19

increased (can be used to stimulate respiration during emergencies)

Question 20

proprioceptors

Answer 20

special cells that monitor movement in joints and muscles, sending excitatory impulses to the respiratory center when stretched

accounts of the increase in respiratory rate that occurs as soon as exercise begins, before CO2 levels begin to change