Respiration Control and Reflexes

Bohr effect

As more CO₂ enters the bloodstream (lower pH), oxygen dissociates from hemoglobin at a higher rate

Biphosphoglycerate (BPG)

Byproduct of glycolysis that is found in erythrocytes; greater concentration leads to higher oxygen dissociation from Hb

Carbonic anhydrase (CA)

Enzyme that causes carbon dioxide and water to form carbonic acid

Chloride shift

At high levels of bicarbonate within erythrocytes, some will diffuse into plasma in exchange for chloride ions entering the cell

Carbaminohemoglobin

Carbon dioxide that is bound to the amino acid sections on the globin portions of Hb for transportation to the lungs

Haldane effect

Hb that is heavily saturated with oxygen does not readily bind carbon dioxide; Hb that is undersaturated will readily bind to carbon dioxide

Hypoxic pulmonary vasoconstriction

In pulmonary capillaries, a rising PCO₂ causes vasoconstriction to redirect blood to alveoli with more oxygen

Dorsal respiratory group (DRG)

Primarily inspiratory group in quiet and forced breathing; inhibition allows for passive exhalation

Ventral respiratory group (VRG)

Primarily expiratory group that stimulates accessory respiratory muscles during forced breathing

Respiratory rhythmicity centers

Pacemaker cells in the medulla that generate the coordinated contraction and relaxation of the diaphragm

Apneustic center

Cluster of neuronal cell bodies in the pons that stimulates the DRG and controls the depth of breathing

Pneumotaxic center

Network of neurons in the pons that inhibits the apneustic center, therefore inhibiting the DRG; increased stimulation shortens the duration of inhalations (faster rate of breathing)

Systemic stimuli

Dose-response where the greater the stimuli, the greater the response

Central chemoreceptor

Specialized receptor in the brain and brainstem that monitors carbon dioxide levels and pH in the CSF

Peripheral chemoreceptor

Specialized receptors located in the carotid arteries and aortic arch that monitor carbon dioxide levels and pH in the blood, as well as large oxygen concentration changes

Hypercapnia

Increased arterial carbon dioxide levels; causes an increase in respiratory rate

Hypocapnia

Abnormally low arterial carbon dioxide levels; causes a decrease in respiratory rate

Hering-Breuer Reflexes

Baroreceptors in the lungs responding to changes in lung volume by sending feedback to the apneustic centers and VRG; not involved in quiet breathing

Inflation reflex

Receptors in bronchioles prevent the overexpansion of the lungs via the vagus nerve to the respiratory rhythmicity centers

Deflation reflex

Receptors in alveolar walls that gradually inhibit expiratory centers and stimulate inspiratory centers during lung deflation

Laryngeal spasm

Reflex that temporarily closes the airway o prevent foreign objects, chemical irritants, or fluids from entering the lungs

Apnea

Period of prolonged suspended respiration usually followed by a forceful exhalation of air to remove an irritating stimulus