Physiology of Respiration

Question 1

Eupnea definition

Answer 1

normal breathing, normal respiratory rate and rhythm

Question 2

apneustic breathing

Answer 2

gasping

indicative of end of life

Question 3

apnea

Answer 3

stoppage of breathing

Question 4

hyperpnea

Answer 4

increased ventilation

• occurs normally with exercise
• increased rate, rhythm, depth of breathing

Question 5

brainstem respiratory center

• primary groups of neurons
• location of each

Answer 5

dorsal respiratory group (DRG)
-medulla
pneumotaxis center (PRG)
-pons (pontine respiratory group)
ventral respiratory group (VRG)
-medulla

Question 6

DRG

• function
• neurons lie in…

Answer 6

control of inspiration

neurons line in nucleus of the tractus solitarius

Question 7

DRG

-receive sensory information from _____ nerves, including signals from…

Answer 7

vagal and glossopharyngeal nerves
signals from
-peripheral chemoreceptors
-baroreceptors
-types of receptors in the lungs

Question 8

basic rhythm or respiration

• primarily set in…
• how does it occur?

Answer 8

primarily set in dorsal respiratory group
APs from the dorsal respiratory group “ramp up” and signal the inspiratory muscles (primarily the diaphragm) to contract
-signals travel along the reticulospinal tracts in the spinal cord to the phrenic nerve and intercostal nerves
signals stop suddenly for about 3 seconds which stops stimulating the diaphragm to contract - time for passive recoil

Question 9

basic rhythm of respiration

-why is the “ramp up” good rather than all APs being sent at once?

Answer 9

allows for gradual inspiration

Question 10

inspiratory ramp

• what are the 2 points of control of the ramp
• how can these points be manipulated

Answer 10

rate of increase of the ramp signal
-ramp can occur quickly when needed for rapid breathing
end of ramping
-provides limit to time of inspiration - usual method for controlling rate or respiration

Question 11

pneuotaxic center

-function

Answer 11

signals DRG

-determines the “turn off” point of the inspiratory ramp; limits inspiration

Question 12

strong pneumotaxic signal =

Answer 12

short lung filling time

Question 13

limiting the ramp time _____ the inspiratory time and _____ the expiratory time
-this leads to

Answer 13

shortens inspiratory, shortens expiratory

overall increase rate of breathing

Question 14

VRG

-when is it active

Answer 14

normally inactive during quiet breathing
with increased need for ventilation, ventral neuron group contributes to inspiration and expiration
-diaphragm
-abs

Question 15

how can respiratory muscle fibers be recruited

Answer 15

increase signals from DRG to VRG

Question 16

what is the Hering-Breuer Reflex

-when is it active?

Answer 16

stretch receptors in the walls of bronchi and bronchioles send signals to DRG when overstretched
-turns off ramp
this increases the respiratory rate, similar to the response of the pneumotixic center
appears to function with tidal volume > 15500 mL
-protective response

Question 17

what molecules are we primarily concerned with when it comes to regulating ventilation

Answer 17

CO2
O2
H+

Question 18

acute effect of increased CO2 and H+

• what area is primarily affected
• -what is the primary stimulus
• -what happens as a result?

Answer 18

chemosensitive area

• in the medulla
• strongly affected by changes in blood PCO2 or [H+]
• -[H+] primary stimulus but presents across the blood brain barrier as a direct effect of [CO2]
• stimulates other parts of the respiratory

Question 19

how does H+ get into the medulla?

Answer 19

CO2 + H2O –> H2CO3- –> H+ + CO3-

Question 20

long-term control of excitation by [CO2]

Answer 20

effect of increased [CO2] decreases over subsequent 1-2 days

• renal adjustment
• -released bicarbonate

Question 21

bottom line for regulation of [CO2]

Answer 21

change in blood [CO2] has strong acute effect on controlling respiratory drive but weak chronic effect after a few days’ adaptation

Question 22

role of oxygen in respiratory control

Answer 22

no direct effect on respiratory center
oxygen-hemoglobin buffer system ensures adequate O2 delivery through wide range of PO2
there are mechanisms to assure O2 delivery when blood O2 falls too low

Question 23

peripheral chemoreceptor system

• primarily respond to…
• transmit signals to…
• rapid response to…

Answer 23

primarily respond to changes in blood O2
transmit nervous signals to the respiratory center (DRG)
vagus takes signal from aortic bodies
glossopharyngeal takes signal from carotid bodies
rapid response to low arterial PO2
-especially if PO2 falls between 30-60 mmHg

Question 24

[CO2] and [H+] peripheral receptor response

• how strong?
• how fast?
• -why might this be important

Answer 24

much less powerful than their direct effects on the respiratory center
peripheral effects of CO2 occur 5x fast than central effects
-might offer important role at onset of exercise

Question 25

regarding respiration, how do we adapt to high altitude

Answer 25

respiratory center in brainstem loses 4/5 of sensitivity to changes in PCO2 and H+ over 2-3 days excess ventilation reducing CO2 that would then inhibit an increase in respiration fails low O2 can drive system to high level of alveolar ventilation

Question 26

brain's response to exercise in regards to ventilation

Answer 26

may initially stimulate respiratory center in brainstem when sending motor impulses to the working muscles -termed "anticipatory stimulation" after 30-40 seconds, CO2 released from active muscle cells approximately matches ventilation rate to keep values "normal" brain can have a learned response so you can accommodate quicker

Question 27

other influences on ventilation

Answer 27

``` pain -hypothalamic control pulmonary irritant receptors -trachea, bronchi, bronchioles -lung receptors proprioceptors -motion of limbs brain edema anesthesia ANP (atrial natriuretic peptide) -increases ventilation ```

Question 28

hyperventilation - what is it - low blood CO2 causes... - quick treatment

Answer 28

``` increase in rate and depth of breathing -exceepds need to remove CO2 low blood CO2 (hypocapnia) causes cerebral vasoconstriction Tx -breathe into bag ```

Question 29

pulmonary disease - what con happen to [CO2} - example

Answer 29

``` retention of CO2 can occur Emphysema -PCO2 chronically elevated --chemoreceptors adapt --therefore, reduced PO2 acts on peripheral chemoreceptors and provides main stimulus for respiration = hypoxic drive ```

Question 30

why not give someone with COPD supplemental oxygen

Answer 30

they have elevated CO2 levels, so the main drive of their respiration is low O2 levels giving them supplemental O2 means they stop breathing, which increases CO2 even more