Anna Ayres, Holly Munsterman, Jessica Gile 19.4 | Control of Breathing Anna Ayres, Holly Munsterman, Jessica Gile

Normal breathing is rhythmic, involuntary, and continues when a person is unconscious. Try it! By taking a deep breath or fast shallow breaths, the respiratory muscles can be controlled voluntarily.

Respiratory Areas | Vocabulary Respiratory Areas: groups of neurons in the brainstem that control breathing Medullary Respiratory Center: includes two bilateral groups of neurons that extend throughout the length of the medulla oblongata - these groups are the called the ventral respiratory group and the dorsal respiratory group

Respiratory Areas impulses travel on cranial and spinal nerves arrive at breathing muscles inspiration and expiration Respiratory areas also adjust the rate and depth of breathing to meet cellular requirements for supply of oxygen and removal of carbon dioxide.

The Medulla Oblongata & Breathing (and Pons, too) The ventral respiratory group is believed to be responsible for the basic rhythm of breathing. The dorsal respiratory group stimulates the inspiratory muscles, primarily the diaphragm. It also helps process sensory information related to the respiratory system. The pontine respiratory group may also contribute to the rhythm of breathing by limiting inspiration.

a- means “not, without” -pnea means “to breathe” Sleep apnea in adults is generally obstructive and caused by an airway blockage. This type of sleep apnea is generally associated with snoring. Sleep apnea is diagnosed in a sleep in a sleep lab, where breathing is monitored. One treatment for sleep apnea is a CPAP, or a nasal continuous positive airway pressure, which covers the nose and helps maintain air flow into the the respiratory system. Rx Sleep Apnea a- means “not, without” -pnea means “to breathe”

“Back to Sleep” Sudden infant death syndrome, or SIDS, is sometimes caused by sleep apnea. Infant sleep apnea is usually caused by a problem with the respiratory control centers. Infants who struggle with breathing are sent home with monitoring devices. These alert parents when the infant is in need of resuscitation. A campaign for infant safety known as “Back to Sleep” aims to decrease the risk of sleep apnea, as sleeping on the back or side is the safest during the first year of life.

Partial Pressure -in a mixture of gases such as air, each gas accounts for a portion of the total pressure the mixture produces -the amount of pressure each gas contributes is called the partial pressure of that gas and is proportional to the its concentration Ex: because air is 21% oxygen, oxygen then accounts for 21% of the atmospheric pressure (21% of 760 Hg), or 160 mm Hg (.21 x 760 = 160)

Partial Pressure -gas molecules from the air may enter, or dissolve, in liquid Ex: Carbon dioxide being added to a carbonated beverage Inspired gases dissolve in the blood in the alveolar capillaries -partial pressure of a gas dissolved in a liquid = partial pressure of that gas in the air

Factors Affecting Breathing Factors that influence breathing depth & rate: - Po2 & Pco2 in body fluids -degree to which lung tissues are stretched -emotional state -level of physical activity Receptors involved: -mechanoreceptors that sense stretch -central & peripheral chemoreceptors

Factors Affecting Breathing -Po2 has an unimportant role which is surprising considering how important oxygen is for sustaining life -blood oxygen is carried bound to hemoglobin molecules in red blood cells - “oxygen poor” systemic venous blood still has 75% of its original amount of oxygen -excess oxygen “frees up” respiratory control from responding to blood oxygen levels -predominantly responds to blood Pco2 & H+ concentration

Factors Affecting Breathing -blood Pco2 and hydrogen ion concentration are important in maintaining the pH of the internal environment, especially in the brain -Receptors that respond to Po2 and Pco2 are the central and peripheral chemoreceptors

Central Chemoreceptors -low blood Po2 has little effect on central chemoreceptors -located in ventral portion of medulla oblongata where they mainly monitor the pH of the brain -central chemoreceptors also respond to changes in blood pH, indirectly, because hydrogen ions are unable to pass through the blood-brain barrier very easily making it so they don’t have access to this area - CO2 can cross this barrier making it so the CO2 in the brain is equal to the CO2 in the blood

Central Chemoreceptors -if plasma Pco2 rises, CO2 easily diffuses into the brian and combines with water and cerebrospinal fluid to form carbonic acid (H2CO3) CO2 + H2O → H2CO3 -carbonic acid then quickly ionizes and releases hydrogen ions and bicarbonate ions H2CO3 → H+ + HCO-3

Central Chemoreceptors -central chemoreceptors only respond to the hydrogen ions that have been released, not the carbon dioxide -breathing rate and tidal volume increase when we inhale CO2 rich air or when our body cells produce extra CO2 -changes increase alveolar ventilation, exhaling more CO2 and the blood Pco2 and hydrogen ion concentration return to normal

-adding CO2 to air can stimulate the rate and depth of breathing -ordinary air is about 0.04% CO2 -if a person inhales air containing 4% CO2 , breathing rate usually doubles Fun Fact

Peripheral Chemoreceptors Sense changes in the blood Po2, in specialized structures called the carotid bodies and aortic bodies (in the walls of the carotid sinuses and aortic arch) the chemoreceptors are positioned to monitor O2 that will reach the brain and rest of the body

Decreased Po2 This mechanism does not have a major effect until Po2 decreases to around 50% of normal (oxygen has a minor influence on the control of normal respiration) Stimulates peripheral receptors Send impulses to the respiratory center Breathing rate and tidal volume rise ( alveolar ventilation)

‘s in blood pH Stimulate the peripheral chemoreceptors of the carotid and aortic bodies These chemoreceptors become important when the pH of the blood changes and CO2 does not Example: - Under conditions of strenuous exercise, lactic acid production may threaten to lower pH. If this occurs, the peripheral chemoreceptors signal the respiratory centers to increase alveolar ventilation. Hydrogen ions and CO2’s impact on blood pH can be considered equal. By stimulating the respiratory centers to exhale more CO2, the peripheral chemoreceptors effectively stabilize blood pH in the presence of excess lactic acid. Gradually the kidneys eliminate the extra hydrogen ions, and blood CO2 returns to normal.

COPD (chronic obstructive pulmonary disease) - a chronic lung disease that makes breathing difficult Patients who have COPD gradually adapt to high levels of CO2 Low oxygen levels may serve as a necessary respiratory stimulus If patient was placed on 100% oxygen, the low arterial Po2 may be corrected enough to remove the stimulus. Resulting in suppressed breathing, or possibly stopping breathing completely.

Inflation Reflex (Hering-Breuer Reflex) Helps regulate the depth of breathing Occurs when stretch receptors in the visceral pleura, bronchioles, and alveoli are stimulated as lung tissues are stretched Prevents over-inflation of the lungs during forceful breathing

Emotions that may cause gasping or rapid breathing: Emotional upset or strong sensory stimulation alters the normal breathing pattern Emotions that may cause gasping or rapid breathing: Fear Anger Excitement Surprise We can alter our breathing pattern consciously, because control of the respiratory muscles is voluntary Example: During childbirth, concentration on controlling breathing can distract the mother from her pain

Hyperventilation - breathing rapidly and deeply Breathing that lowers the blood CO2 concentration below normal Can increase breath-holding time It takes longer than usual for the carbon dioxide concentration to reach the level needed to override the conscious effort of breath holding Hampered oxygen supply to the brain causes fainting