exam 2 lecture 22 Flashcards
The goal of respiration: maintain sufficient ____ with minimal energy
ventilation
central processor controls ___
•Pattern generator of breathing depth / amplitude
Rhythm generator for breathing rate (periodicity
three types of sensors to control ventilation
chemoreceptors
baroreceptors
stretch receptors
where is the central controller?
pon
most in the medulla
what innervates accessory respiratory muscles?
ventral respiratory group
what innervates the diaphragm and external intercostal muscles?
dorsal respiratory group
by the phrenic nerve
respiratory control is a ___ feedback system
neagtive
what is the hering breuer reflex and what disproves this theory?
taking a breathe triggers a stretch receptor in smooth muscle that triggers another breathe
lung transplant patients disproves this
•Inspiratory impulses are ___ and are dynamic
dominate
neurons needed to inhale
during sleep, central drive is ____ so peripheral chemoreceptors stimulate based on O2 and CO2 levels
reduced
why are expiratory neurons not as important
exhale is passive
neurons only needed for forced exhale
what happens when you cut below the DRG?
breathing stops
phrenic nerve comes off the DRG - no dorsal respiratory group= no breathing
what happens if you cut off the pons?
breathing with very sharp amplitude
what happens if you cut off the PRG but keep the apneustic center?
breathing more normal
still high amplitude and slightly slower but more steady
if you cut above the PRG what happens to breathing?
normal breathing
locked in syndrome
what is the most important principal initiator of breathing?
dorsal respiratory group
what part of the DRG receives afferent fibers?
nucleus tractus solaris
•Nucleus tractus solaris is where afferent fibers of the glossopharyngeal and vagus nerves project, carrying information received about PO2, PCO2, and pH from the carotid and aortic arterial chemoreceptors
•Nucleus tractus solaris is where ___ fibers of the glossopharyngeal and vagus nerves project, carrying information received about ___ from the carotid and aortic arterial chemoreceptors.
afferent
PO2, PCO2, and pH
the DRG has outputs via the ___ to the diaphragm, therefor controlling the most important respiratory muscle
phrenic nerve
what is the most important respiratory group and why?
the dorsal respiratory group (DRG) is responsible for
1) driving the diaphragm
2) receiving/ integrating input from peripheral chemoreceptors.
Therefor it is the MOST IMPORTANT RESPIRATORY GROUP
what does the ventral respiratory group do?
- Connected primarily to vagus nerve
- “patency of airway”
- Expiratory neurons
the VRG contains what two specialized groups
- Botzinger complex: inhibit inspiratory cells in the DRG
- Pre-Botzinger complex: hypothesized (but not proven) to be the precise location of the respiratory rhythm generator
•Botzinger complex:
•Botzinger complex: inhibit inspiratory cells in the DRG
found in the ventral respiratory group
•Pre-Botzinger complex
•Pre-Botzinger complex: hypothesized (but not proven) to be the precise location of the respiratory rhythm generator
found in the ventral respiratory group
what are the two groups found in the pons that control breathing
apneustic center
pontine respiratory group
apneustic center
- Apneustic center - nucleus of the pons
- Coordinates speed of inhalation and exhalation
- Sends stimulatory impulses to the inspiratory area – activates and prolongs inhalation (long, deep breaths)
- Site of the “inspiratory cutoff switch”
Site of the “inspiratory cutoff switch”
apneustic center in the pons
___ coordinates speed of inhalation and exhalation
apneustic center of the pons
this is why when you cut this area off, very sharp very long breaths
___ sends stimulatory impulses to the inspiratory area – activates and prolongs inhalation (long, deep breaths)
apneustic center of the pons
Pontine respiratory group
- Formerly known as the pneumotaxic center
- Coordinate speed of inhalation and exhalation
- Sends inhibitory impulses to the inspiratory area•Involved in fine tuning respiration rate
___ Coordinate speed of inhalation and exhalation
pontine respiratory group in the pons
___ sends inhibitory impulses to the inspiratory area of the DRG
pontine respiratory group of the pons
___ involved in fine tuning respiration rate
pontine respiratory group of the pons
•Cheyne-Stokes respiration
- Alternating episodes of apnea and crescendo-decrescendo hypernea
- Caused by damage to respiratory centers in the brainstem, hypoxia
___ •Alternating episodes of apnea and crescendo-decrescendo hypernea
•Cheyne-Stokes respiration
•Apneustic breathing
- Prolonged inspiration due to interruption of the pneumotaxic center (pontine respiratory group of the pons)
- i.e. “dying gasps”- most likely in the pons
•Biot’s breathing
- Normal breathing interrupted by sudden apnea
- Damage to the pons
- Normal breathing interrupted by sudden apnea
- Damage to the pons
biot’s breathing
•Kussmaul’s breathing
- Hyperventilation with hypocapnia caused by acidosis (diabetic)
- Brain is normal, caused entirely by chemoreceptors
- Hyperventilation with hypocapnia caused by acidosis (diabetic)
- Brain is normal, caused entirely by chemoreceptors
•Kussmaul’s breathing
•Respiratory center is in the brainstem (medulla ___)
oblongata
what are two regions of the brain that affect respiration
•Cortex•Conscious control of breath•E.g., holding your breath
•Limbic system and hypothalamus•Emotional states•Panic attack
how does the body measure changes in CO2
CO2 can diffuse across blood brain barrier combines with H20 and forms H and HCO3-
this will decrease the pH of the CSF (make more acidic)
this change in pH can be detected by H+ receptors
•Protons (H+) pass poorly through the ___ but CO2 passes easily
blood brain barrier
•Blood pH is therefor transmitted via CO2 to CSF
adapt to elevated CO2 levels (reduced pH) by transfer of ___ into CSF (slow). this will stimulate ___
HCO3- or Cl-
•Stimulation of this system causes the urge to breath (increase ventilation, get rid of that CO2)
•Recent studies suggest additional chemoreceptors throughout the brainstem:NTS, ___
locus coeruleus
where is all O2 sensing done to control breathing
carotid and aortic bodies (peripheral chemosensors)
•Afferent nerves (glossopharyngeal for carotid body, vagus for aortic body) run back to the ___ in the medulla to then change the breathing patterns
respiratory center (DRG)
true or false
aortic bodies exert greater influence than carotid bodies
false
•Carotid bodies exert greater influence than do aortic bodies
___ receptors are more important in short-term, transient responses than in normal ventilatory control
carotid body and aortic bodies
peripheral chemosensors
how do O2 sensors work
•Glomus cells (type I cells)
- K channel with O2 sensor
- O2 opens channel and hyperpolarizes cell
- Drop in O2 causes reduction in K current and depolarization
- Resulting Ca2+ influx triggers dopamine release
- Dopamine initiates action potential in sensory nerve to send the signal back up to the medula•
Glomus cells are derived from the neural crest•
Glomus cells may also be the primary CO2 / pH chemosensor, but isn’t certain
Supported by type II cells (sustentacular cells)
how does low O2 effect glomus cells
causes K channels to close, which causes depolarization and dopamine to be released causing an action potential
what enzyme helps glomus cells to detect oxygen
CSE (cystathione gamma-lyase )
•hypoxia decreases CO production•Less CO means less inhibition of CSE•More active CSE means more H2S•More H2S depolarizes cells causing neurotransmitter release
what do cigarette help at high altitude
- PO2 must drop to 60 mm Hg (~10,000 ft elevation) before this triggers a change in the glomus cells
- At these high elevations, PCO2 is also lower, so fails to increase respiratory drive (stimulates person to breathe)
___ are much less important than arterial chemoreceptors for ventilation
arterial baroreceptors
•Bronchiolar smooth muscle is enriched in __ adrenergic receptors
β2
•____ (sympathetic) lead to bronchodilation
Catecholamines
•Parasympathetic stimulation of the muscarinic M3 receptors (via ___) causes bronchoconstriction
acetylcholine
catecholamines cause ___ and acetylcholine causes ___
•bronchodilation (sympathetic innervation)
bronchoconstriction (parasympathetic innervation)
what is triggered in an asthma attack to cause bronchoconstriction?
muscarinic M3 receptors (via acetylcholine- parasympathetic innervation)
•J-receptors
- Sense interstitial fluid changes (pulmonary edema)
- Cause sense of breathlessness
- Located in capillary walls
breathlessness
what is the dominant respiratory driver?
CO2
