lecture 20: regulation of respiration Flashcards
true or false: Rate of alveolar ventilation (VA) is adjusted almost
exactly to demands of the body such that PO2 and
PCO2 in arterial blood are hardly ever altered
true
Rate of alveolar ventilation (VA) is adjusted to what
almost
exactly to demands of the body such that PO2 and
PCO2 in arterial blood are hardly ever altered
are the PO2 and PCO2 in arterial blood usually alterned
no , usually rate of alverolar ventilationn is adjusted to almost exactly demands of the body
what are the 3 elements involved in regulation of respiration
- Basic control of respiration
- Chemical control of respiration
- Peripheral chemoreceptor control of respiration
what are the functions of sensors in terms of regulation of respiration snf give examples
– Gather information
– Stretch receptors, peripheral chemoreceptors, baroreceptors, etc
WHAT IS THE FFUNCTIONN OF central controllers in terms of regulation of respiration and give examples
– Integrate signals
– Respiratory center (dorsal, ventral, pneumotaxic groups)
what is an example of effectots of regulation of resrpiration
respiratory muscles (ex: diaphragm, intercostals)
basic Control of basic rhythm of respiration is generated by what
– Generated by the respiratory center (central controller)
where is the respiratory center
Mainly in dorsal respiratory group of neurons
true or false; Neurons emits repetitive bursts of inspiratory neuronal action
potentials (cause is unknown)
true
explain ramp signal
begins weakly (low frequency of impulses)
impulse frequency increases gradually in a ramp manner for 2 seconds, which results in gradual expansion of lungs and chest
excitation then suddenly ceases for next 3 seconds, so that elastic recoil of lung occurs for expiration
the neurons part of the respirtory center induce whatt types of discharges and whatt does that mean
Induces rhythmical inspiratory discharges (diaphragmatic
contraction)
inhibtion of the excitory signal from the respiratory center does what
promotes expiratiton
what are the 2 ways to control inspiratory ramp
1) Control of rate of increase of ramp signal
2) Control of limiting point at which ramp
signal suddenly ceases
increased ramp slope promotes what
faster fillimng of air Vt in lungs
Early ramp signal cessation shortens or increases duration of inspiration
shortens
early ramp signal cessation shortens what
shortens duration of inspiration as well as duration of expiration (reason is unclear)
=increased rate (frequency) of breathing
The inherent activity of inspiratory neurons with cell
bodies located in the medulla governs the normal
respiratory cycle how
by activating the diaphragm and
intercostal muscles to cause the lungs to inflate
why do the inspirtaory neursons cease firing
The inspiratory neurons cease firing because of selflimitations
and inhibitory influence of expiratory
neurons also located in the medulla
as expiration proceeds/elongations, what happens to the inspiratory cetner
As expiration proceeds, the inspiratory center becomes
progressively less inhibited and once again becomes
active
the neurons of the respiratory centers are located where and form what
in the medully oblongata
from the rhymicity center
what does the rhytmicitt center control
automatic breathing
what are the 2 types of neurons in the respiratory center
Consists of interacting neurons that fire either during inspiration (I neurons) or
expiration (E neurons)
activation of E neurons inhibit or active the I neurons
inhibit
what are the 3 major collections of neurons in the respiratory center
1) dorsal respiratory group
2) pneumotaxic center
3) ventral respiratory center
the dorsal respiratory group neurons cause what (inspiration or expirmation)
innspiration
where is the dorsal respiratory group of neurons located and what is their sensation
Located in dorsal portion of medulla, with sensory termination of vagal and glossopharyngeal sensory nerves, which transmit signals from peripheral chemoreceptors, baroreceptors, and lung receptors
where is the pneumotaxic center neuronns location
in the sup portion of the pons
what do the neurons of the pnemotaxic center control and how
control breathinng pattern by limitinng duration of filling phase
where are the neuronns of the ventral respiratory group lcated
in the ventrtolateral part of the medulla
what is the main function of the neurons in the ventral respiratory group
Inactive during normal quiet breathing,
but contributes extra respiratory drive
(especially expiration) when needed
invovled in forced expriationn and innspirtationn
chemical control of respirationn is achieved via what two chemicals
co2 and h+
true or false: Excess CO2 or H+ in blood acts indirectly on respiratory center itself
false
Excess CO2 or H+ in blood can act directly on respiratory center itself
Excess CO2 or H+ in blood greatly increases or decrases the strength of both inspiratory and expiratory signals to
respiratory muscles
increases
Co2 and H+ Greatly increases the strength of (both inspiratory and expiratory) or just expiratory signals to respiratory muscles
both
at rest, what provudes the most imporatant respiratory stimulus
At rest, carbon dioxide pressure in arterial plasma provides the most
important respiratory stimulus
ex: small inncreases in Po2 in inspired air trigger large increases in minute ventilation
why do Small increases in PCO2 in inspired air trigger large increases in minute
ventilation
because there is a very narror range for PCO2
does plasma acidity have an affect over minute ventilation?
yes
Plasma acidity, which varies with the blood’s carbon dioxide content,
exerts command over minute ventilation
a fall in ph signals and reflects what
A fall in blood pH signals acidosis and reflects carbon dioxide retention
and carbonic acid formation
what happens to inspiratory activtiy as arterial pH declines and hydrogen ions accumulate
As arterial pH declines and hydrogen ions accumulate, inspiratory activity
increases to eliminate carbon dioxide and reduce arterial levels of carbonic
acid
which out of these 3 have a direct effect on respiratory center (o2, co2 or h+)
co2 and h+
which out of these 3 do not have significant direct effect on respiratory center (co2, o2 or H+)
o2
trtue or false and explain: 02 has a direct effect on respiratory center
false: INDIRECT
• Rather acts almost entirely on peripheral chemoreceptors
located in carotid and aortic bodies à these in turn transmit
nervous signals to respiratory center for control of respiration
explain how o2 has an indirect effect on the thee respiratory centr
• Rather acts almost entirely on peripheral chemoreceptors
located in carotid and aortic bodies à these in turn transmit
nervous signals to respiratory center for control of respiration
co2 and H+ directly stimulate what neuronal area
chemosensoitive ara located beneath ventral surface of medualla
what area is highly sensorite to changes in blood co2 and h+
neuronal area called chemosensitive area
what does stimulation of the chemosensitve area (area sensitive to co2 and h+) cause and result in
Stimulation of this area causes excitation of other portions of respiratory center
• Results in increased rate and depth of breathing
sensory neurons in the chemosensotive neuronal area are mosttly stimulated by what
h+ ions (versus co2)
true or false; H+ ions have difficulty
permeating blood-brain barrier (BBB) and
blood-cerebrospinal fluid (CSF) barrier
true
explain the reason that altho the chemoreceptive area is more sensotive to H+ ions, blood pco2 actually has a bigger effect
becais eH+ ions have difficulty
permeating blood-brain barrier (BBB) and
blood-cerebrospinal fluid (CSF) barrier
which has a larger effect in stimulated chemosensotive area: change in blood H+ or change in blood PCo2 and why
blood pco2 becuase H+ has a hard time going thru BBB
CO2 has less direct effect in stimulating chemosensitive
area or more direct effect than H+ ions
less
CO2 has less direct effect in stimulating chemosensitive
area than H+ ions , so why does it have a larger effectt in stimulated the chemosensotive area
because but easily crosses blood-brain barrier
and blood-cerebrospinal fluid barrier
explain the effect of carbon dioxide on chemosensotive area
When blood PCO2 increases, PCO2 in interstitial fluid of
medulla and cerebrospinal fluid increases.
CO2 molecules in these fluids bind with H2O to form carbonic acid (H2CO3)
H2CO3 dissociates into H+ and bicarbonate ion (HCO3-)
H+ ions (those dissociating from H2CO3, not the freely
circulating H+ ions outside the BBB) stimulate the sensory
neurons in chemosensitive area.
what happens when the lungs become overinflated
When lungs become over-inflated, sensory stretch
receptors located in bronchi and bronchioles are activated
=Afferent sensory signals from stretch receptors feed back
to dorsal respiratory group through vagus nerve à
“switch off” inspiratory ramp signal à inspiration ceases
=hering-breur inflation reflex
the hering breur inflation reflex is activated when and what does that prtect you from
Hering-Breuer reflex is activated when inflation or tidal
volume (VT) exceeds 1.5 L, i.e. protects lungs from overinflation
what are 2 locations of peripheral chemorecpros
1) carotid bodies
2) aortic bodies
where are the carotid bpdoes located
Located bilaterally at
bifurcation of carotid arteries
explain the passageway of afferent nerves in the carotid bodies
Afferent nerve fibers pass
through Hering’s nerves
=to glossopharyngeal nerve
=to dorsal respiratory center.
where are aortic bodies located
located along the arch of aorta
where do the nerves pass in the aortic boddies
Afferent nerve fibers pass
through vagus nerve
= to dorsal respiratory center.
true or false: changes in
PCO2 have a tremendous
effect on alveolar ventilation
true
increases in blood PCO2 within the normal range (35-75) cause what incrase inn alveolar ventilation
1 to 8 fold increase
does changes in PCO2 or changes in blood pH s there a larger effect on alveolar ventilation
PCO@
sensitive to reduced oxygen pressures resides where
in peripheral chemorecptors
The carotid bodies monitors the state of arterial blood where/when
just
before it perfuses the brain
Decreased arterial PO2 increases
alveolar ventilation through what
aortic
and carotid chemoreceptor stimulation
decreased arterial PO2 through aortic amnd carotid chemorecptors causes what
increase in alveolar ventilation
what protects us from reduced oxygen pressure in inspired air
the carotid bodies n
Peripheral chemoreceptors also stimulate ventilation in
exercise because of what
increases in temperature, acidity, and
carbon dioxide and potassium concentrations
ADD SLIDES 21 AND 22
….
true or false; Increase of CO2 and H+ also excites chemoreceptors and
causes indirect effect on respiratory center
true
The indirect effect of CO2 and H+ through chemoreceptors has
the 2 following characteristics compared to their direct effect:
1) It is much less powerful (7 times less) than their direct effect on
the respiratory center in the brain. Therefore, their indirect effect is
often neglected.
2) It is much faster (5 times) than the direct effect, so it might play an
important role in increasing the response time to CO2 at the onset
of exercise
alveolar ventilation can increase collectively by what 3 factors
– Increased CO2 or PCO2 – Decreased O2 or PO2 – Decreased pH or increased blood H+ concentration
add slide 25/26
.
after holding your breath for how long does the urge for inspiration come
40 s
where does the stimulus to breath com from after holding breath
The stimulus to breathe comes primarily from increased arterial
PCO2 and H+ concentration
– The breakpoint for breath holding = 50 mm Hg PCO2
what does hyperventilating before breath holding do tto PCO2
Hyperventilating before breath holding causes alveolar
PCO2 to decrease to 15 mm Hg
explain why Hyperventilating before breath holding causes alveolar
PCO2 to decrease to 15 mm Hg
– A larger-than-normal quantity of carbon dioxide leaves the blood
and arterial PCO2 decreases
– Extends breath-holding duration until arterial PCO2 and/or H+
concentration cause the urge to breathe
