Exam 3: Respiratory Integrated Reponses

Sensors (chemoreceptors, lung and other receptors)

gather information and feed it to the central control
center

Central controller (pons, medulla)

(brain)
coordinates information and
sends impulses to effectors

Effectors

(respiratory muscles)
cause ventilation

Medulla and pons

Contain a central pattern generator that sets/initiates the basic rhythmic pattern of breathing

Negative feedback

to maintain arterial PCO2, PO2, and pH

Sensory feedback relating to mechanical states

Prevent overinflation, respond to irritants, minimize work of breathing

Sensory feedback from joint and muscle receptors

Increase ventilation in response to exercise

Integration with SNS

during fight or flight responses, other stress responses
• Ex: high body temp, low arterial blood pressure

Speech and swallowing

Conscious control of pons and medulla

Inspiratory Center (DRG) and expiratory center (VRG)

Two parts of the medullary respiratory center

Inspiratory Center (DRG)

• Controls the basic rhythm of breathing
• Sets the frequency of inspiration

Expiratory center (VRG)

• Responsible for expiration
• Inactive during quiet breathing; active during exercise

apneustic center

Abnormal breathing pattern with prolonged inspiratory gasps, followed by brief expiratory movement

Pneumotaxic center

• Turns off inspiration
• Limits the size of tidal volume
• Regulates respiratory rate

Central chemoreceptors

Initiate changes in ventilation due to altered blood gases and pH

Ventral surface of the medulla

Central chemoreceptors are located on the

Respond to changes in arterial PCO2

• CO2 diffuses readily across the blood-brain barrier
• CSF pH decreases (CSF is poorly buffered due to low protein content)
• Decreased CSF pH (increased H+) stimulates central chemoreceptors

Changes in blood pH are not sensed by central chemoreceptors

• Blood-brain barrier prevents H+ from accessing the brain
• Arterial PO2 and pH rely on input from peripheral chemoreceptors

Peripheral chemoreceptors

Located in the carotid bodies at the
bifurcation of the common carotid arteries and in the aortic bodies in the aortic arch

Decrease in arterial PO2, Increase in arterial PCO2, Decrease in arterial pH

detected by peripheral
chemoreceptors and produces an increase
in breathing rate

Decrease in arterial PO2

Most important
responsibility of peripheral chemoreceptors

Decrease in arterial PCO2

effect is less
important than their response to decrease in
arterial PO2

Hypoxia due to ascent to high altitude

Which of the following conditions would be expected to stimulate the
arterial chemoreceptors?

Lungs and kidney

work together
to maintain acid-base status of the body

Lung excretes

>10,000 mEq
carbonic acid per day

Kidney excretes

<100 mEq fixed
acids per day

Altering alveolar ventilation (elimination of CO)

gives the body
control over acid-base balance

Do not change much during exercise

Arterial PO2 and PCO2

Must increase during exercise

Venous PCO2

Muscle and joint receptors

Send information to the medullary inspiratory center and participate in coordinated response to exercise

cardiac output

Increases during exercise to meet tissue demand for O2

Pulmonary blood flow

_____ ____ _____increases (pulmonary resistance decreases During exercise

Right shift during exercise

O2-Hgb dissociation curve

Makes it easier to unload O2 in teh excerising muscle tissue

• Increased tissue PCO2
• Decreased tissue pH
• Increased temperature

It decreases

A 22-year-old student is
exercising on a treadmill. As their
exercise intensity increases, what
happens to their PVR?

Hypoxemia

Ascent to high altitude can cause

Hyperventilation

Most significant response to high altitude

Polycythemia

• Increased Hgb concentration increased O2-carrying capacity
• Advantageous for O2 transport to tissues; not so advantageous as far as blood viscosity

Increased synthesis of 2,3 DPG by RBCs

• Causes right shift of O2-dissociation curve
• Associated with increased P50, decreased affinity, increased unloading of O2

Pulmonary vasoconstriction

At high altitude, alveolar gas has low PO2 - direct vasoconstricting effect

Acute altitude sickness

• Headache, fatigue, dizziness, nausea, palpitations, insomnia
• Due to initial hypoxia and respiratory alkalosis

False

If a person were hiking at high altitude and had trouble breathing,
this could be because the lower atmospheric pressure lowers the
PO2, and the diffusion gradient between the blood and atmosphere is
greater

Underwater pressure

as you descend deeper in the water, pressure increases

SCUBA

self-contained underwater breathing apparatus

Equalizing pressure

Air-filled spaces (ears/sinuses) are compressed as the
pressure increases during diving

Breathing gases

As you dive, the pressure and density of the air in the tank
increases with depth

Nitrogen absorption

As you breathe compressed air at depth, you absorb
more oxygen and nitrogen. (Must be careful when ascending)

hyperbaric oxygen therapy

Involves breathing pure oxygen in
a pressurized environment

Decompression sickness when SCUBA diving, serious infections, wounds due to diabetes or radiation injury

Conditions that hyperbaric oxygen therapy treats

increased oxygen delivery to
tissues During hyperbaric oxygen therapy

Air pressure is increased 2-3 times
higher than normal to allow

True

As depth increases during
SCUBA diving, lung
volume decreases and
PO2 increases.