Neural Control Of Breathing Flashcards
What happens if the pressure gradient between aveoli and capillary is too low
If this gradient is too low, gas exchange does not occur efficiently.
Why is level of ventilation regulated
Breathing is done to ventilate the alveoli and the level of ventilation is regulated to meet varying
oxygen demand or carbon dioxide production. Ventilation is regulated by changing tidal volume and
breathing rate.
Give examples of when ventilation is increased
Examples of when ventilation is increased is during exercise, emotional stimulus,
infections (sepsis that increases acid production by the body) and trauma.
When do respiratory muscle contraction
There are different respiratory muscles that contract during breathing. They are initiated when
breathing is initiated.
What types of muscles are respiratory muscles
Respiratory muscles are skeletal and require a neural input to contract.
What diseases and injuries can effect breathing
Spinal cord injury (no signal initiating contraction), motor neuron disease (no signal initiating contraction) and muscular dystrophy (muscle not strong enough to perform function) can all affect the act of breathing.
What happens during quiet breathing
During quiet breathing,
contraction and relaxation of the diaphragm provides enough force to move the thoracic cavity
(elastic recoil aids exhalation). During increased or forced ventilation, there are different respiratory
and accessory muscles involved in inspiration and expiration.
What muscles are used in forced inspiration
External intercostals are respiratory
muscles involved in forced inspiration whilst pectorals, sternomastoid and scalene muscles are
accessory muscles involved in forced inspiration.
What are respiratory mediators In forced expiration
Elastic recoil as well as internal intercostal muscles
are respiratory mediators of forced expiration whilst the abdominals are accessory muscles involved
in forced expiration.
What do accessory muscles actually do
Accessory muscles do not have a primary role in breathing but help facilitate
forced breathing.
How are different muscles initiated
The different muscles involved in breathing are initiated to contract and relax by different neural
signals. These signals originate from the brain and travel down via the spinal cord to neurons that
lead to the different target muscles. These signals are initiated at the brainstem of the brain.
Describe the brainstem
In the
brainstem is a series of complex neural networks that function in tandem to interpret various inputs
and signals from around the body and initiate signals to the respiratory system that determines
breathing rate and depth of breathing in order to meet the metabolic demands of the body.
How are signals sent in the brainstem and what is the name
These
signals are sent in a regular pattern to the different respiratory muscles controlling when they breath
in and out. This network in the brainstem that produces a breathing pattern is known as the central
pattern generator.
What is the pattern generator dependant on - factors that effect it
This generator is based on information from central and peripheral
chemoreceptors
What do chemoreceptors use to function- and where found
that give oxygen, carbon dioxide and hydrogen ion concentrations, receptors in
muscles and joints
What receptors do lungs contain and function
stretch receptors in the lungs that indicate how inflated the lungs are as well as
irritant receptors in the lungs that detect different chemical irritants.
What can the central pattern generator also receive
The central pattern generator
also receives signals from higher centres in the brain that influence breathing pattern through
emotional stimuli and other receptors that report back to the hypothalamus (e.g. response to stress
and pain), and voluntary control over breathing through the cerebral cortex.
The central pattern generator
also receives signals from higher centres in the brain that influence breathing pattern through
emotional stimuli and other receptors that report back to the hypothalamus (e.g. response to stress
and pain), and voluntary control over breathing through the cerebral cortex.
The central pattern
generator uses the different inputs to check pH of the cerebral spinal fluid (usually measured through
carbon dioxide partial pressure), how much oxygen, carbon dioxide and hydrogen ions are in arterial
blood, lung volume and how stretched it is, and coordinates stimulation from higher emotional
centres of the brain and the ANS into the breathing pattern.
What is the most important regulatory systems
One of the most important regulatory systems that regulate ventilation are the central and
peripheral chemoreceptors.
What is the most prodominent chemoreceptors
Central respiratory chemoreceptors (CRC) are the more predominant of
the two types of chemoreceptors and they contribute to around 70% of the chemoreceptor influence
on breathing patterns.
Where are CRCS present
CRCs are present in the medulla, a structure present in the brainstem, and
indirectly monitor changes to arterial carbon dioxide levels by responding to changes in hydrogen ion
concentration within cerebrospinal fluid.
Why do CRCS not actually react with h+ ions
This is because hydrogen ions cannot pass through the blood brain barrier as they are charged. The CRCs rather monitor the number of hydrogen ions that have been produced from carbon dioxide diffusing out from the blood into cerebrospinal fluid (can pass through the blood brain barrier as it is uncharged and a small gas) where it is then converted into carbonic acid and then dissociates into hydrogen ions.
What mechanism do central chemoreceptors use
Central
chemoreceptors work by negative feedback in that they are only activated when the number of
hydrogen ions in cerebrospinal fluid is too high.
What is the main aim for CRC
They initiate respiratory control centres in the
brainstem to increase ventilation rate to remove excess carbon dioxide.
