Respiratory system 3: control of respiration Flashcards
what is the function of medullary rhythmicity area
to control the basic rhythm of respiration
Dorsal respiratory group (Inspiratory area) has an intrinsic excitability of auto rhythmic neurons that sets the basic rhythm of respiration
Ventral respiratory group (Expiratory area) neurons remain inactive during most quiet respiration but are probably activated during high levels of ventilation to cause contraction of muscles used in forced expiration.
Respiratory center
- Medullary rhythmicity (medulla oblongata)
- pneumotaxic area (pons)
- apneustic centers (pons)
During normal quiet breathing what activates what
Dorsal respiratory group activate Diaphragm, external intercostals actively contract (2 seconds) = normal quiet inhalation
For exhalation DRG is inactive. Diaphragm, external intercostals relax, followed by elastic recoil of chest wall and lungs
During forceful breathing what activates what
DRG activate diaphragm and external intercostal muscles contracts for forceful inhalation
DRG also activates VRG to activate accessory muscle of inhalation (SCM, scalene, pec minor) to contract to inhale
For exhalation, VRG activates accessory muscles of exhalation (internal intercostal, external oblique, internal oblique, transversus abdominis and rectus abdominis muscle) to contract
Pneumotaxic area
Pontine respiratory group in the upper pons helps coordinate the transition between inspiration and expiration
Ventral respiratory group is also known as
Pre Botzinger complex
Apneustic area
The apneustic area sends impulses to the inspiratory area that activate it and prolong inspiration, inhibiting expiration
Regulation of respiratory center
Cortical influences
Voluntarily alter breathing patterns
Cortical influences allows
conscious control of respiration that may be needed to avoid inhaling noxious gasses or water
Voluntary breath holding is limited by
the overriding stimuli of increase H+ and CO2
Chemoreceptor regulation of respiration is stimulated when….
Increase of PCO2 (and thus H+) will stimulate…
1. Central chemoreceptors (hypercapnia) in Medulla oblongata in the central nervous system
Then O2 decreases…
2. is activated and hyperventilation, rapid and deep breathing occur.
When the chemoreceptors are not stimulated
Hypocapnia. Arterial PCO2 is lower than 40 mmHg.
Severe deficiency of O2 will…
depress activity of the central chemoreceptors and respiratory center.
Peripheral chemoreceptors (2 bodies)
respond to changes in H+, PO2 or PCO2
- aortic body in the wall of aorta.
- in walls of common carotid arteries.
Where does aortic body of chemoreceptors join?
nerves join vagus
Where does carotid bodies of chemoreceptors join?
nerves join glossopharyngeal nerve
Negative feedback regulation of breathing
- Increase in arterial pCO2
- Stimulates receptors
- respiratory center receives input
- Muscles of respiration contract more frequently and forcefully
- PCO2 decrease
What will activate the inspiratory center to increase ventilation prior to exercise induced oxygen need.
Proprioceptors of joints and muscles
what detects lung expansion with stretch receptors and limits it depending on ventilatory need and prevention of damage
Inflation (Hering-Breuer) reflex
Stretch receptors = baroreceptors
where does stretch receptors located
in the walls of bronchi and bronchioles, also called as baroreceptors
what makes ventilation rate and depth increase (8)
- Voluntary hyperventilation controlled by cerebral cortex
- Anticipation of activity via stimulation of the limbic system
- Increase in arterial blood H+ level or pCO2 above 40mm Hg and decrease in arterial blood pO2
from 100 to 50 mmHg. Detected by central and peripheral chemoreceptors - Increase in sensory impulses from proprioceptors in muscles and joints and increase in motor impulses from the motor cortex.
- Decrease in blood pressure detected by baroreceptors
- Increase in body temperature
- Prolonged (somatic) pain
- stretching anal sphincter
what makes ventilation rate and depth decrease with
- Voluntary hypoventilation controlled by cerebral cortex (limited by buildup of CO2 and H+)
- Decrease in arterial blood H+ level or pCO2 below 40mm Hg and decrease in arterial blood pO2 below 50 mm Hg, detected by central and peripheral chemoreceptors
- Decrease in sensory impulses from proprioceptors in muscles and joints and decrease in motor impulses from the motor cortex
- Increase in blood pressure detected by baroreceptors
- Decrease in body temperature (sudden cold stimulus causes apnea)
- severe pain causes apnea
- Irritation of pharynx or larynx by touch or chemicals causes apnea followed by coughing or sneezing
4 different type of hypoxia
- Hypoxic hypoxia - low pO2 in arterial blood (high altitude, airway obstruction, fluid in lungs)
- Anemic hypoxia - to little functioning hemoglobin in the blood (hemorrhage, anemia, carbon monoxide poisoning)
- Stagnant/Ischemic hypoxia - results from the inability of blood to carry oxygen to tissues fast enough to sustain their needs (heart failure, circulatory shock)
- In histotoxic hypoxia, the blood delivers adequate oxygen to the tissues, but the tissues are unable to use it properly (cyanide poisoning)
how exercises will increase the respiration
- blood flow increases with lower O2 and higher CO2 content
- is matched by increased ventilation and oxygen diffusion capacity as more pulmonary capillaries open
- ventilatory modifications can increase 30 times above resting levels initially neural influences and then gradually due to chemical stimulation from changes in cell metabolism
why smokers have difficulty breathing
- nicotine constricts terminal bronchioles
- carbon monoxide in smoke binds to hemoglobin
- irritants in smoke cause excess mucus secretion
- irritants inhibit movements of cilia
- in time destroys elastic fibers in lungs and leads to emphysema (trapping of air in alveoli and reduced gas exchange)
when fetus develops lungs with sufficient surfactant for survival
26 - 28 weeks
Aging of respiratory system (6)
- Respiratory tissue and chest wall become more rigid
- vital capacity decreases to 35% by age 70
- Decreases in macrophage activity
- Diminished ciliary action
- Decrease in blood levels of O2
- Result is an age-related susceptibility to pneumonia or bronchitis
