L22: Respiratory System III Flashcards
CO2 is ___ soluble in body fluids than O2
more
in what ways is CO2 transported in the blood?
1) dissolved in the blood (7%)
2) as a bicarbonate ion (70%)
3) binds to hemoglobin - HbCO2 (23%)
the rapid conversion of CO2 into bicarbonate ion depends on the presence of __
carbonic anhydrase (CA)
carbonic anhydrase (CA) is found in __
in red blood cells
effects of O2 affinity changes upon __
Hb loading and unloading
conversion of CO2 to H+ and HCO3- continues until
equilibrium is reached
to keep the reaction going, the products __
must be removed from the cytoplasm
what are the ways of removing free H+ and HCO3- from RBCs?
1) an antiport protein exchanges HCO3- for Cl- in a process known as chloride shift
2) Deoxyhemoglobin within the RBC acts as a buffer and binds H+ in the reaction:
H+ + Hb -> HbH
how does CO2 bind to hemoglobin?
when O2 leaves its binding sites on the Hb molecule, CO2 binds with free Hb at exposed amino groups
what is formed when CO2 binds to Hb?
HbCO2 carbaminohemoglobin
most of the HCO3- __
moves out of the erythrocytes into the plasma in exchange for chloride ions
as venous blood flows through lung capillaries, __
blood P(CO2) decreases because of the diffusion of CO2 out of the blood into the alveoli, and the reactions are reversed
most of H+ generated in the erythrocytes from carbonic acid
binds to deoxyhemoglobin because deoxyhemoglobin formed as oxygen unloads from oxyhemoglobin, has a higher affinity for H+
as the blood flows through the lung capillaries
H+ bound to deoxyhemoglobin is released and combines with HCO3- to yield carbon dioxide and water
diaphragm and intercostal muscles are
skeletal muscles
skeletal muscles do not contract without
stimulation by motor neurons
breathing depends entirely upon
cyclical respiratory muscle excitation by the motor nerves
inhibition or destruction of motor nerves results from
paralysis of the respiratory muscles and death unless artificial respiration is instituted
when action potentials cease
the inspiratory muscles relax, and expiration occurs as the elastic lungs recoil
inspiration is initiated by
a burst of action potentials in the spinal motor nerves to inspiratory muscles like the diaphragm
in active expiration,
both inspiration and expiration are facilitated by a burst of action potentials
the integrating center for the control of breathing is located in
the medulla oblongata
the medullary respiratory center is located in
reticular formation
the components of medullary respiration center
a small group of pacemaker cells in the pre-Botzinger complex located on either side of the medulla
these neurons fire ___
rhythmically and produce rhythmic discharges in phrenic motor neurons
what regulates contraction of inspiratory and expiratory muscles?
complex interactions within the medulla oblongata
inspiratory and expiratory neurons in the medulla show
reciprocal inhibition
during increases in breathing, the inspiratory and expiratory motor nerves and muscles are
not activated at the same time, rather alternate in function
__ fine tunes the transition between inspiration and expiration
the Pontine respiratory group (PKG) of the Pons
the actions of the pons and medualla are modulated by
the cortex (voluntary control) and sensory input
__ provide regulatory input to the medullary inspiratory neurons
peripheral (arterial) and central chemoreceptors
peripheral chemoreceptors location
close to the baroreceptors involved in reflex control of blood pressure
peripheral chemoreceptors functions
P(O2), pH, P(CO2)
peripheral chemoreceptors types
carotid bodies and aortic bodies
carotid bodies monitor
O2 supply, predominant
central chemoreceptors location
medulla oblongata
central chemoreceptors provide __
excitatory synaptic input to the medullary inspiratory neurons
central chemoreceptors are stimulated by
an increase in the H+ concentration of the brain ECF
why does H+ concentration in the brain’s ECF change?
changes in blood P(CO2)
___ in the carotid and aortic bodies are activated by ___
specialized glomus cells, a decrease in P(O2) or pH or an increase in P(CO2)
glomus cells trigger __
a reflex increase in ventilation
oxygen is ___ factor in regulating ventilation
not usually an important
to what level P(O2) should fall to trigger the ventilation reflex?
to less than 60 mm Hg
when is O2 important in glomus cells reflex?
extreme conditions, high altitude, pathologies, chronic obstructive pulmonary disease (COPD)
any condition __ will activate carotid and aortic glomus cells and increase ventilation
that reduces plasm pH or increases P(CO2)
central chemoreceptors set __
the respiratory pace by providing continuous input into the control network
the central chemoreceptors are located on
the ventral surface of the medulla
the central chemoreceptors respond to
pH changes in the CSF, they are not directly responsive to CO2
