ventilatory control Flashcards
(25 cards)
Describe ventilatory control
-respiratory center in our medulla regulates breathing
- it receives afferent feedback from strategically placed receptors
- sends efferent feedback to out ventilatory muscles to either increase or decreases breathing
- intrinsic rhythmic activity largely under involuntary control (control of somatic motor neurons in medulla)
chemoreceptors
sensory input from two sets of chemoreceptors modify the rhythmicity of the central pattern generator (detects change in CO2, O2, pH)
Peripheral chemoreceptors
carotid and aortic bodies) increase in O2 and pH or increase in PCO2 = increase in ventilation, PO2 not powerful regulator,
Central chemoreceptors
medulla sense change in PCO2 and monitors cerebrospinal fluid, CO2 most important chemical regulator of ventilation , responds to pH change in CSF, elevated arterial PCo2– Co2 crosses blood brain barrier
Ve Control during exercise
Disproportional increase before exercise mostly due to stipulation of Cerebral cortex and rapid change in afferent neural activity
At some time point during increasingly intense submaximal exercise, the increase in VE is not proportional but experiences a disproportionate increase. This is largely due to increases in CO2 production via metabolism
Define anaerobic threshold (including lactate and ventilatory threshold)
VO2at which anaerobic energy production supplements the aerobic energy production needed at some time point during graded exercise to fatigue.
Steady state exercise can not be maintained above AnT
Both Ve and lactate have a double breaking point relationship with intensity
Lactate threshold
Phase during incremental exercise when blood lactate accumulation exhibits an abrupt increase (non linear)
Ventilatory threshold
Phase during incremental exercise when certain ventilatory parameters exhibit a change in a defined way
Ve increases disproportionately in relation to VCO2
This occurs because an increase in chemoreceptor activity, afferent neural activity , temperature, perception of intensity
what cause VT
Increase afferent neural activity from muscles
increase H and CO2 levels
Increases perception of energy demands by respiratory center in brain
Relationship of LT to VT
-Respiratory compensation for metabolic acidosis refers to the overall process of respiratory assistance in buffering anaerobically generated H+ via bicarbonate reaction during
graded exercise. ( LT causes VT and therefore slightly precedes VT during graded exercise. )
-BECAUSE linked through the stimulation of VEby chemoreceptors due to
increased [H+] and from increased CO2 levels through the bicarbonate buffering of
H+that are anaerobically produced during graded exercise.
The cardiovascular system is involved in:
Transport of O2 & CO2
Supply nutrients
Circulation of compounds such as
hormones
Waste removal (e.g. urea)
Regulation of blood flow
Thermoregulation
adaptation to exercise
Increase in Q and SV
Decrease in HR
Intrinsic
The sinoatrial node (SA) in rear of right atrium have “leaky ion” channels (to Na+& Ca2+) causing spontaneous depolarization after repolarization.
The SA impulses leads to depolarization of the AV that slows the impulse to allow blood to empty from atria
Depolarization then spreads down more specialized cells to purkinje fibers that stimulate ventricle muscle fibers to contract
Cardiovascular extrinsic
Located in ventro-lateral medulla.
Influenced by brain (motor cortex) and a number of peripheral receptors, mechanoreceptors, chemoreceptors, baroreceptors, hormonal control.
Sends efferent signals to the autonomic nervous system
Sympathetic
Releases of norepinephrine from sympathetic nerve ending accelerators that SA node depolarization thus increasing HR,SV and Q
Increase HR (chronotropic)
Increase myocardial contractility (inotropic)
Release of epinephrine from the adrenal gland also increase HR
Sympathetic stimulation also has large effect on blood flow throughout the body
parasympathetic
Releases of acetylcholine from nerve ending decreasing HR, SV and Q
Baroreceptors
pressure - sensitive receptors found in the aortic arch and carotid sinus
Acts to inhibit sympathetic stimulation at local level
Respond to stretch in arterial vessels such as during an increase in Q and systolic BP
The need for increase blood flow to body during exercise actually overrides barorecptores
hi
hi
Chemoreceptors (muscles and joints)
Respond primarily to H and PCO2 which can increase sympathetic drive, increase Q which leads to increase blood flow to skeletal muscles
Mechanoreceptors (muscles,joints)
Increase afferent nerve activity from mechanoreceptors lead to increased CNS drive, resulting in increased Q and thus increased blood flow to skeletal muscles
How to increase SV
Increased stretch= increased filling
Increase filling= increase pressure
Increased pressure and volume= increasing preload (preload as the LV wall stress before ejection
ORR
Decrease ESV
This would be achieved via increases contractility (inotropy)
Decrease SV (2 ways)
Decrease EDV
Increase ESV
Wall stress during ejection is known as aferload
Increase preload
Greater filling
Increase EDV and SV
Same ESV
Increase contractility
Greater pressure generated on contraction
Same EDV
Decrease ESV
Increase SV
