Neural Regulation: Setting the Basic Rhythm Flashcards
What regulates the activity of the respiratory muscles and where are the neural centers located?
The respiratory muscles (diaphragm and external intercostals) are regulated by nerve impulses from the brain via the phrenic nerves (for the diaphragm) and intercostal nerves (for external intercostals).
Neural centers controlling respiratory rhythm and depth are located mainly in the medulla oblongata and pons.
Much is still unknown about the detailed mechanisms of neural regulation of breathing.
What are the roles of the medulla oblongata and pons in regulating breathing?
Medulla Oblongata contains two respiratory centers:
Ventral Respiratory Group (VRG):
Contains inspiratory and expiratory neurons.
Inspiratory neurons stimulate the diaphragm and external intercostal muscles via the phrenic and intercostal nerves during quiet breathing (eupnea, 12-15 breaths/min).
Expiratory neurons stop stimulation of these muscles, allowing passive exhalation.
Dorsal Respiratory Group (DRG):
Integrates sensory information from chemoreceptors and stretch receptors.
Communicates with the VRG to adjust breathing rhythms.
Pons Respiratory Centers:
Modify the timing of inhalation and exhalation, smoothing transitions during activities like singing, sleeping, or exercising.
Communicate with the VRG to adjust breathing patterns.
How do stretch receptors in the bronchioles and alveoli protect the lungs from overinflation?
Stretch receptors in the bronchioles and alveoli detect extreme overinflation, which could damage the lungs.
When overinflation occurs, these receptors send impulses via the vagus nerves to the medulla oblongata.
This triggers a protective reflex, causing inspiration to stop and expiration to begin.
This is an example of DRG integration in regulating respiratory control to prevent lung damage.
What happens to breathing during exercise and how does expiration change after strenuous activity?
Hyperpnea (increased breathing depth and rate) occurs during exercise because brain centers send more impulses to the respiratory muscles.
After strenuous exercise, expiration becomes active, and muscles such as the abdominal muscles and other muscles that can depress the ribs assist in forceful expiration.
What happens if the medullary centers are suppressed, and what is the result?
If the medullary centers are completely suppressed (e.g., due to an overdose of sleeping pills, morphine, or alcohol), respiration stops completely.
Without intervention, death will occur due to the cessation of breathing.
What physical factors can modify the rate and depth of breathing?
Medulla oblongata sets the basic rhythm, but physical factors can modify it, including:
Talking, coughing, and exercising.
Increased body temperature raises the rate of breathing.
These factors are part of nonrespiratory air movements that influence breathing patterns.
How does conscious control affect breathing, and what limits it?
We can consciously control our breathing during activities like singing, swallowing, or holding our breath (e.g., swimming underwater).
However, voluntary control is limited: if oxygen levels drop or blood pH falls, the respiratory centers will override conscious control.
Involuntary controls take over, ensuring normal respiration resumes (e.g., after intense exercise or if a toddler holds their breath).
Proof: It’s impossible to talk normally or hold your breath after running at high speeds.
How do emotional factors modify breathing patterns?
Emotional stimuli (e.g., fear, excitement) can affect the rate and depth of breathing.
Examples include:
Holding breath during a horror movie or panting due to fear.
Gasping after touching something cold and clammy.
These responses are reflexes initiated by the hypothalamus in response to emotional triggers.
What are the chemical factors that influence the rate and depth of breathing?
The most important chemical factors affecting breathing are the levels of carbon dioxide (CO₂) and oxygen in the blood.
Increased CO₂ and decreased blood pH are key stimuli that increase the rate and depth of breathing.
High CO₂ levels lead to more carbonic acid, which lowers blood pH.
Low blood pH can also result from metabolic activities independent of breathing.
Changes in CO₂ concentration or ion concentration (affecting pH) in the brain’s tissue influence the respiratory centers in the medulla oblongata, affecting local tissue pH.
How are changes in oxygen and carbon dioxide levels detected in the body, and which is the most important stimulus for breathing?
Oxygen concentration in the blood is detected by peripheral chemoreceptors in the aortic body (aortic arch) and the carotid body (at the fork of the common carotid artery).
When blood oxygen levels drop, these chemoreceptors send impulses to the medulla oblongata.
These chemoreceptors can also detect high carbon dioxide levels when oxygen levels are low.
The most important stimulus for breathing is the body’s need to eliminate carbon dioxide, not the need for oxygen.
Oxygen level becomes a significant stimulus only when it drops to dangerously low levels.
Why do people with chronic lung diseases, such as emphysema or chronic bronchitis, receive low levels of oxygen?
In individuals with chronic lung diseases (e.g., emphysema, chronic bronchitis), the brain no longer recognizes high carbon dioxide (CO₂) levels as an important stimulus for breathing due to CO₂ retention.
In these cases, a dropping oxygen level becomes the primary respiratory stimulus.
These patients are given low levels of oxygen to maintain the low oxygen level as the stimulus for breathing, as higher oxygen could suppress their breathing drive.
What happens during hyperventilation, and how does it affect blood pH?
Hyperventilation is an increase in rate and depth of breathing that exceeds the body’s need to remove carbon dioxide.
During hyperventilation, more carbon dioxide is exhaled than necessary, leading to an elevated blood pH.
This occurs because less carbonic acid forms in the blood, resulting in a higher pH (alkalosis).
The body normally breathes more deeply and rapidly to restore pH when carbon dioxide or other acids accumulate.
What happens when blood becomes slightly alkaline, and how does breathing adjust?
When blood becomes slightly alkaline (basic), breathing slows and becomes shallow.
Slower breathing allows carbon dioxide to accumulate in the blood, which helps to lower blood pH and bring it back into the normal range.
This is part of the body’s mechanism to maintain pH homeostasis.
How does breathing control pH during rest, and what happens during hypoventilation and hyperventilation?
During rest, breathing control primarily regulates the hydrogen ion concentration in the brain to maintain normal pH.
Hypoventilation (slow or shallow breathing) causes carbonic acid to increase dramatically in the blood, leading to acidosis.
Hyperventilation (rapid or deep breathing) causes carbonic acid to decrease substantially, leading to alkalosis.
In both cases, the blood’s buffering ability may be overwhelmed, resulting in acidosis or alkalosis.
What happens during hyperventilation, and how can it be managed during an anxiety attack?
Hyperventilation often caused by anxiety leads to brief apnea (cessation of breathing) until carbon dioxide levels build up again.
Cyanosis (bluish skin) can occur if breathing stops for too long due to insufficient oxygen.
Dizziness and fainting may occur because alkalosis constricts cerebral blood vessels.
To manage hyperventilation, have the person breathe into a paper bag:
Exhaled air has more carbon dioxide than the atmosphere, which disrupts the diffusion gradient.
This causes CO₂ levels and carbonic acid to rise, ending alkalosis and returning blood pH to normal.
What makes the respiratory system vulnerable to infections, and what are some disabling respiratory disorders?
The respiratory system is vulnerable to infections because it is open to airborne pathogens.
Some disabling respiratory disorders include:
Chronic Obstructive Pulmonary Disease (COPD)
Lung cancer
These diseases are strongly linked to cigarette smoking, which is devastating to the lungs.
Cigarette smoking not only promotes cardiovascular disease but is also highly effective at destroying the lungs.
What are the key features of Chronic Obstructive Pulmonary Disease (COPD)?
COPD includes diseases like chronic bronchitis and emphysema, and is a major cause of death and disability.
Common features of COPD:
History of smoking in nearly all patients.
Dyspnea (difficult or labored breathing) that progressively worsens.
Coughing and frequent pulmonary infections.
Hypoxia, carbon dioxide retention, and respiratory acidosis are common, leading to respiratory failure.
What happens in chronic bronchitis, and why are patients sometimes called “blue bloaters”?
In chronic bronchitis, the mucosa of the lower respiratory passages becomes severely inflamed, producing excessive mucus.
The pooled mucus impairs ventilation and gas exchange, increasing the risk of lung infections, including pneumonias.
Patients with chronic bronchitis are sometimes called “blue bloaters” because:
Hypoxia (low oxygen) and carbon dioxide retention occur early.
Cyanosis (bluish skin) is common due to low oxygen levels in the blood.
What are the causes, types, and treatments for lung cancer?
Lung cancer is the leading cause of cancer death in both men and women in North America, with 90% of cases linked to smoking.
Causes: Smoking overwhelms the lungs’ natural defenses (nasal hairs, mucus, cilia), leading to:
Increased mucus production and impaired cilia function.
Depressed lung macrophages and frequent pulmonary infections.
Toxic chemicals in tobacco smoke cause lung cancer.
Types of lung cancer:
Adenocarcinoma (40%): Develops from bronchial glands and alveolar cells in peripheral lung areas.
Squamous cell carcinoma (25–30%): Arises in the epithelium of larger bronchi, forms masses that hollow out and bleed.
Small cell carcinoma (20%): Lymphocyte-like cells originating in the main bronchi, grows rapidly and metastasizes.
Treatment:
Complete removal of lung lobes is most effective but only possible before metastasis.
If metastasis has occurred, radiation and chemotherapy are common, though less effective.
New therapies under development include:
Antibodies targeting tumor molecules.
Cancer vaccines to stimulate the immune system.
Gene therapy to replace defective genes in tumor cells.
Prevention: Quitting smoking is the most effective way to prevent lung cancer.
