Terms: aortic, bicarbonate, blood, carbon dioxide, carbonic acid , carotid, cent

Question

Terms: aortic, bicarbonate, blood, carbon dioxide, carbonic acid, carotid, central, CSF, hydrogen, inversely,medulla, oxygen, peripheral, pH, pons, proportional

The body must be able to change the rate and depth of breathing appropriately to meet the constantly changing needs for oxygen delivery to and carbon dioxide removal from the metabolically active tissues of the body. The respiratory control center, located (in alphabetical order) in the _______ and _________ regions of the brainstem, is responsible for making these changes in the rate and/or depth of breathing, depending upon the input it receives from specialized sensors that respond to changes in the chemical composition of the blood. These sensors are referred to as _____________ chemoreceptors if they lie outside of the central nervous system, or as _____________ chemoreceptors if they are present within the central nervous system. The sensory cells in these special chemoreceptors respond to changes in 3 main chemical constituents in body fluids, including: 1) decreases in the ________ content, and/or 2) increases in the _________ ion content, and/or 3) increases in the [waste] _________ content.

The peripheral chemoreceptors consist of multiple clusters of specialized neuronal cell bodies. These clusters of neuronal cells are termed, alphabetically, the _____ and the _______ bodies because of their locations in the aortic arch and the carotid blood vessels, respectively. These sensory cells are sensitive to changes [decreases] in the oxygen content and [increases] in the H+ content in the ____________. Remember - the H+ content is ___________ to the acidity of a body fluid - that is - as the H+ content of the fluid goes up - so does the acidity of the fluid; however, H+ and _______ (a measure of acidity) are ___________ related - so as the H+ content of a fluid increases, the fluid's pH decreases - or goes toward the zero end of the pH scale.  The peripheral chemoreceptors are relatively insensitive to changes in the carbon dioxide content of the blood.

Central chemoreceptors consist of specialized chemically sensitive sensory cells that lie within the CNS. These neuronal cells are separated from the blood itself by the blood-brain barrier - so they cannot respond to changes in the chemical composition of the blood per se. Rather, they are bathed in and sensitive to changes [increases] in the CO2 and H+ contents of the cerebrospinal fluid [a.k.a. ________]. However, if the content of CO2 in blood increases, the CO2 molecules are small readily diffuse through the blood brain barrier causing a secondary, concomitant increase in the CO2 of the cerebrospinal fluid. The CO2 in CSF combines with H2O in the CSF to form __________ which then dissociates rapidly into H+ and HCO3- (a.k.a. _____________ ion). The central chemoreceptors are highly sensitive to increases in CSF CO2 content and H+. Unlike the peripheral chemoreceptors, the central chemoreceptors are relatively insensitive to decreases in O2 content of body fluids.

Of all the factors that influence rate and depth of respiration, changes in CO2 content of the blood cause the most dramatic changes in respiration.

Explanation / Answer

The body must be able to change the rate and depth of breathing appropriately to meet the constantly changing needs for oxygen delivery to and carbon dioxide removal from the metabolically active tissues of the body. The respiratory control center, located (in alphabetical order) in the medulla and pons regions of the brainstem, is responsible for making these changes in the rate and/or depth of breathing, depending upon the input it receives from specialized sensors that respond to changes in the chemical composition of the blood. These sensors are referred to as peripheral chemoreceptors if they lie outside of the central nervous system, or as central chemoreceptors if they are present within the central nervous system. The sensory cells in these special chemoreceptors respond to changes in 3 main chemical constituents in body fluids, including: 1) decreases in the oxygen content, and/or 2) increases in the hydrogen ion content, and/or 3) increases in the [waste] carbon dioxide content.

The peripheral chemoreceptors consist of multiple clusters of specialized neuronal cell bodies. These clusters of neuronal cells are termed, alphabetically, the aortic and the carotid bodies because of their locations in the aortic arch and the carotid blood vessels, respectively. These sensory cells are sensitive to changes [decreases] in the oxygen content and [increases] in the H+ content in the blood. Remember - the H+ content is proportional to the acidity of a body fluid - that is - as the H+ content of the fluid goes up - so does the acidity of the fluid; however, H+ and pH (a measure of acidity) are inversely related - so as the H+ content of a fluid increases, the fluid's pH decreases - or goes toward the zero end of the pH scale.  The peripheral chemoreceptors are relatively insensitive to changes in the carbon dioxide content of the blood.

Central chemoreceptors consist of specialized chemically sensitive sensory cells that lie within the CNS. These neuronal cells are separated from the blood itself by the blood-brain barrier - so they cannot respond to changes in the chemical composition of the blood per se. Rather, they are bathed in and sensitive to changes [increases] in the CO2 and H+ contents of the cerebrospinal fluid [a.k.a. CSF]. However, if the content of CO2 in blood increases, the CO2 molecules are small readily diffuse through the blood brain barrier causing a secondary, concomitant increase in the CO2 of the cerebrospinal fluid. The CO2 in CSF combines with H2O in the CSF to form carbonic acid which then dissociates rapidly into H+ and HCO3- (a.k.a. bicarbonate ion). The central chemoreceptors are highly sensitive to increases in CSF CO2 content and H+. Unlike the peripheral chemoreceptors, the central chemoreceptors are relatively insensitive to decreases in O2 content of body fluids.

Of all the factors that influence rate and depth of respiration, changes in CO2 content of the blood cause the most dramatic changes in respiration.

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