regulation of respiration Flashcards
what is respiratory center
The respiratory center is composed of several groups of
neurons located bilaterally in the medulla oblongata and
pons of the brain stem,
3 neurons present in the respiratory center
(1) a dorsal respiratory group, located in the dorsal portion of
the medulla, which mainly causes inspiration (2) a ventral
respiratory group, located in the ventrolateral part of the medulla, which mainly causes expiration; and (3) the pneumotaxic center, located dorsally in the superior portion of the pons, which mainly controls rate and depth of breathing.
what group of neurons plays a fundamental role in the respiration
dorsal group of neurons
dorsal group of neurons are present in?
nucleus of tractus solitarius
the NTS Is sensory termination of?
vagal and glossopharyngeal nerves
The NTS is the sensory termination
of both the vagal and the glossopharyngeal nerves, which
transmit sensory signals into the respiratory center from
1) peripheral chemoreceptors, (2) baroreceptors, and
(3) several types of receptors in the lungs.
4) liver pancreases and multiple parts of GIT
INSIPIRATORY neuronal action potentials
these are continuously generated by the dorsal group of neurons which cause the rhythmicity of respiration
ramp signal
nervous signals that is transmitted to the inspiratory muscles like the diaphragm is increased gradually and weakly in a ramp manner goes on for 2 secs and then ceases for 3 secs which allows elastic recoil of lungs and causes expiration
so inspiration happens in ramp signals
pneumotaxic center is located
nucleus parabrachialis of upper pons
function of pneumotaxic center
it controls the switch off button of the inspiratory ramp
it deceases the filling period of lungs that is deceases time of inspiration which in turn deceases time of expiration and increases frequency of respiration
ventral respiratory group of neurons are present
rostrally in nucleus ambiguus and caudally at nucleus retroambiguus
function of ventral respiratory group of neurons
they remain inactive during normal quite breathing and only act when high pulmonary ventilation is required
causes both expiration and inspiration
sends signals to abdominal muscles to cause heavy expiration when needed
located in the
muscular portions of the walls of the bronchi and bronchioles throughout the lungs are
stretch receptors
Hering-Breuer
inflation reflex.
stretch receptors that
transmit signals through the vagi into the dorsal respiratory group of neurons when the lungs become overstretched. These signals affect inspiration in much the
same way as signals from the pneumotaxic center; that is,
when the lungs become overly inflated, the stretch receptors activate an appropriate feedback response that
“switches off” the inspiratory ramp and thus stops further
inspiration. This mechanism is called the Hering-Breuer
inflation reflex
what acts directly on the respiratory signal and what doesn’t
co2 and h2 acts directly o2 doesnt
how o2 levels act of respiratory center
they act through peripheral chemoreceptors present in the carotid and aortic bodies that send signals to respiratory center
The sensor neurons in the chemo sensitive area are especially excited
H ions
why H+ concentration has less effect in stimulating chemo sensitive neurons
because it cannot cross the brain blood barrier
how co2 indirectly stimulates the chemo sensitive neurons
it reacts with water
changes into carbonic acid which dissociates into H+ and HCO3
Why does blood CO2 have a more potent effect in
stimulating the chemosensitive neurons than do blood
hydrogen ions?
because of the brain blood barrier does not allow diffusion of H+ IONS
so when pco2 level increases in blood it automatically increases in cerebospinal fluid and fluid of medulla and dissociates into H+ ions which has a direct effect on the chemosensitive areas of the medulla
what happens to indirect stimulatory effect of co2 on the respiratory system
it has potent acute effect but weak chronic effect because hco3 combines with the H+ ions which brings the H+ ion concentration back to normal
changes of o2 has what effect of respiratory center
it has no direct effect on respiratory center
even if p02 level is decreases adequate amount of 02 in transported to tissues
chemoreceptors detect changes in
O2 levels
not co2 levels
what do chemoreceptors do
send nervous signals to respiratory center to regulate respiratory activity
where are chemoreceptors present and their efferent nerves goes to what and how
carotid body- present at the bifurcation of the carotid artery and its afferent nerves pass though herings nerves to glossopharyngeal nerve to dorsal group of neurons
aortic bodies- present at the aortic arch and efferent nerves pass through vagi to dorsal group of neurons
Basic Mechanism of Stimulation of the Chemoreceptors by O2 Deficiency
these bodies of glomus cells which synapse directly or in directly with the nerve endings
they have o2 sensitive K channels which are inactivated when po2 level is less and depolarizes the cells which causes voltage gated calcium channels to open which releases neurotransmitters send signals to nervous system to stimulate respiration
main neurotransmitters released by glomus cells
dopamine and acytelcholine
main neurotransmitters released by glomus cells during hypoxia
ATP
what causes an increase in alveolar ventilation
low po2 level
lower than 100 mm hg of po2
acclimatization
Mountain climbers have found that when they ascend a mountain slowly, over a period of days rather than a period of hours, they breathe much more deeply and therefore can withstand far lower atmospheric O2 concentrations than when they ascend rapidly. This phenomenon is called acclimatization
what causes intense ventilation during exercise
the neurogenic signals send by brainstem to respiratory center is send simultaneously with the signals send to muscles for contraction
Effect of Irritant Receptors in the Airways.
The epithelium of the trachea, bronchi, and bronchioles is supplied
with sensory nerve endings called pulmonary irritant
receptors that are stimulated by many incidents. These
receptors initiate coughing and sneezing,
function of lung j receptor
nerve endings present in the alveolar walls juxtaposition to the poulmonary cappilaries are when engorged with blood during congestive heart failure they give a feeling of dyspnea
The
activity of the respiratory center may be depressed or even
inactivated by what brain disease and how that dysfunction of brain takes place
due to brain edema which can be due to brain concussion which causes the cerebral arteries to press against the cranial vault
causing the blood supply to stop
respiratory depression resulting from
brain edema can be relieved temporarily by
intravenous
injection of hypertonic solutions such as highly concentrated mannitol solution.
periodic breathing
persons breaths deeply for a short period of time and then breathes less or not for another interval of time and the cycle repeates
disease name for periodic breathing
cheyne strokes breathing
The
basic cause of Cheyne-Stokes breathing is
a person overbreathes, thus blowing off too much CO2 from the pulmonary blood while at the same time increasing blood O2, it takes several seconds before the changed pulmonary blood can be transported to the brain and inhibit the excess ventilation. By this time, the person
has already overventilated for an extra few seconds. Therefore, when the overventilated blood finally reaches
the brain respiratory center, the center becomes depressed to an excessive amount, at which point the opposite
cycle begins—that is, CO2 increases and O2 decreases in the alveoli. Again, it takes a few seconds before the brain can respond to these new changes. When the brain does respond, the person breathes hard once again and the cycle repeats
apnea means
absence of spontenous breathing
why sleep apnea happens
due to an obstruction in the upper airways
or impaired cns respiratory drive
Obstructive Sleep Apnea Is Caused by Blockage of the
Upper Airway
muscles of phyrnx keeps the passage open for air to flow but people with narrow air passage way have the issue of closing of the passage with the muscles of pharynx relax during sleeping
which causes snoring, labored breathing followed by a long period of silence apnea (no breathing)
other disorders causes by sleep apnea
cardiovascular disease
increased sympathetic activity heart rate
pulmonary and systemic hypertension
obstructive sleep apnea usually occurs
people who have fat deposition in the soft tissues of pharynx, enlarged tongues, nasal obstruction, enlarged tonsils or shape of the palate
fixation of sleep apnea
tracheostomy, removing of enlarged tongue, CPAP, removing of adenoids and fat from the back of the throat
central sleep apnea is caused by
damage to central respiratory center or abnormalities of respiratory neuromuscular apparatus
could be due to stroke
