21-5: Control of Respiration Flashcards
respiratory centers
neurons clustered in two regions of the brainstem are critical in respiration
dorsal respiratory group
located dorsally near the root of cranial nerve IX; integrates input from peripheral stretch and chemoreceptors and communicates information to VRG
ventral respiratory group
network of neurons on ventral surface of brainstem, extending from the spinal cord to the pons. Generates the basic respiratory rhythm with two groups of neurons, one firing during inspiration and one firing during expiration
What happens when the inspiratory neurons fire?
impulses sent along the phrenic and intercostal nerves, leading to contraction of the diaphragm and external intercostals
What happens when the expiratory neurons fire?
the output stops and the inspiratory muscles relax, allowing lungs to recoil and expiration to occur passively
eupnea
normal respiratory rate and rhythm, determined by the cyclic on/off activity of the inspiratory and expiratory neurons
What controls the rate and depth of breathing?
main:
inflation reflex (stretch receptors)
chemoreceptors
others: cortical control body temp pain stretch of anal sphincter proprioceptors
inflation reflex
if stretch receptors on the walls of the bronchi/bronchioles are overstretched, they send inhibitory impulses via the vagus nerve that end inspiration (protecting lungs from overinflating)
chemoreceptors
special cells sensitive to changing levels of CO2 and O2 in arterial blood, located in the aortic arch and carotid arteries
What is the most important chemical affecting respiration in a healthy individual?
CO2
If CO2 levels rise slightly (hypercapnia), what is the impact on respiration in a healthy person?
rate and depth of breathing increases to quickly flush CO2 from the blood (hyperventiliation)
People experiencing anxiety may hyperventilate - what effect does this have?
causes PCO2 to drop, cerebral blood vessels to constrict, and make them feel faint and dizzy
(breathing into a paper bag allows them to breathe back the CO2 that they exhaled)
If PO2 levels drop slightly (mild hypoxia), what is the impact on respiration in a healthy person?
none, since there is a huge reservoir of O2 bound to hemoglobin
If PO2 levels drop substantially (acute hypoxia), what is the impact on respiration in a healthy person?
if arterial PO2 drops substantially (from 104 to 60), respiratory rate will increase
In a patient with COPD, what is the key driver of respiration?
PO2 (hypoxic drive) - the body adjusts to chronically high PCO2 so PO2 becomes the key driver
cortical control
we can voluntarily alter our breathing rate by sending impulses from our cerebral cortex to motor neurons that stimulate respiratory muscles, bypassing the respiratory center
Our ability to hold our breath is limited because the respiratory center automatically reinitates breathing when CO2 levesl are too high
What influence does body temp have on respiration?
a rise in body temp causes respiratory rate to increase and decrease in temp causes respiratory rate to decrease
A sudden exposure to cold causes temporary apnea
pain
prolonged pain increases respiratory rate
A sudden sharp pain may cause apnea
Stretch of the anal sphincter results in ___ respiratory rate
increased (can be used to stimulate respiration during emergencies)
proprioceptors
special cells that monitor movement in joints and muscles, sending excitatory impulses to the respiratory center when stretched
accounts of the increase in respiratory rate that occurs as soon as exercise begins, before CO2 levels begin to change
