Respiratory System: Control of respiration, hypoxia, and applying physiological principles to athletic performance

Question 1

Rhythmical breathing is controlled by which skeletal muscles?

Answer 1

diaphragm and intercostal muscles

Question 2

___ requires action potentials in ___ neurons and ___ is due to cessation of motor neuron activity and lung ___.

Answer 2

Inspiration; motor; expiration; recoil

Question 3

What type of neurons control rhythmic contraction?

Answer 3

pacemaker neurons

Question 4

The ___ stretch receptors are another ___ signal for inspiration and are activated by a large lung ___.

Answer 4

pulmonary; cutoff; inflation

Question 5

T/F. Action potentials from the afferent nerve fibers from stretch receptors travel to the brain and inhibit the activity of the medullary inspiratory neurons. This is called the Hering-Breuer reflex.

Answer 5

True, feedback from the lungs helps to terminate inspiration by inhibiting inspiratory nerves in the DRG.

Question 6

___ inspiratory neurons are quite sensitive to inhibition by drugs, such as ___ and ___. Death from overdose of these drugs is often due directly to a cessation of ___.

Answer 6

Medullary; barbiturates; ;morphine; breathing

Question 7

T/F. Inspiratory motor neurons are driven primarily by the VRG while expiratory motor neurons (active mostly during forced expiration and strenuous exercise) are driven primarily by the DRG.

Answer 7

False, Inspiratory motor neurons are driven primarily by the DRG while expiratory motor neurons (active mostly during forced expiration and strenuous exercise) are driven primarily by the VRG.

Question 8

Peripheral chemoreceptors include what two bodies? What is the role of these receptors?

Answer 8

1. carotid
2. aortic

to respond to changes in the arterial blood.

Question 9

How are peripheral chemoreceptors stimulated?

Answer 9

1. significantly decreased PO2 (hypoxia)
2. increased H+ concentration (metabolic acidosis)
3. Increased PCO2 (respiratory acidosis)

These changes will cause in ↑ in ventilation rate

Question 10

Central chemoreceptors are located in the ___ ___ and respond to ___ in the H+ concentration of the ___ extracellular fluid.

Answer 10

medulla oblongata; increases; brain

Question 11

T/F. Little increase in ventilation is observed until the oxygen concentration of the inspired air is reduced enough to lower arterial PO2 to 45mmHg.

Answer 11

False, Little increase in ventilation is observed until the oxygen concentration of the inspired air is reduced enough to lower arterial PO2 to 60 mmHg.

Question 12

At PO2 = ___ mmHg, ___ is 90% saturated, so ventilation rate begins to ___ before blood is depleted of O2.

Answer 12

60; hemoglobin; increased

Question 13

Complete with the correct arrow (↑↓):

1. ↓ inspired PO2
2. ___ alveolar PO2
3. ___ arterial PO2
4. Peripheral chemoreceptors ____ firing
5. Respiratory muscles ___ contractions
6. ___ ventilation
7. Return of alveolar and arterial PO2 toward normal.

Answer 13

2. ↓
3. ↓
4. ↑
5. ↑
6. ↑

Question 14

T/F. Ventilation rate is more sensitive to PCO2 than to PO2.

Answer 14

True.

Question 15

What value to PCO2 causes the rate to increase?

Answer 15

40 mmHg

Question 16

Increased ___ increases the brain extracellular ___ concentration, which stimulates ___ chemoreceptors to stimulate the ___ inspiratory neurons to increase ventilation.

Answer 16

PCO2; H+ (decrease in brain pH); central; medullary

Question 17

T/F. Increases in arterial PCO2 cause both peripheral and central chemoreceptors to be stimulated.

Answer 17

True.

Question 18

T/F. Peripheral chemoreceptors are stimulated by an increase in H+ concentration AND a decrease in PO2.

Answer 18

True.

Question 19

T/F. Ventilation rate can be modified by non-respiratory sources of H+.

Answer 19

True, by metabolic acidosis and alkalosis

Question 20

With metabolic acidosis the H+ concentration is ___ and with metabolic alkalosis it is ___.

Answer 20

increased; decreased

Question 21

In the case of metabolic ___ due to excess lactic acid, the excess ___ is detected by ___ chemoreceptors, which eliminate additional ___, but the lactic acid stays.

Answer 21

acidosis; H+; peripheral; CO2

Question 22

In the case of metabolic ___ due to severe vomiting, ___ is removed from the body and the vomit acid must be replaced. Therefore, it is pulled from the ___ causing alkalosis. The body will increase ___ to increase the acid in the blood because it can’t correct the loss of ___.

Answer 22

alkalosis; H+; blood; CO2; H+

Question 23

Why does anemia not change ventilation?

Answer 23

The Hb content is reduced but the PO2 is normal.

The total O2 is ↓ but the partial pressure of dissolved PO2 is unchanged. Chemoreceptors only detect the levels of dissolved PO2 not the amount of Hb.

Question 24

Why does carbon monoxide poisoning not change ventilation?

Answer 24

HbO2 is reduced but PO2 is normal.

CO ↑ affinity and displaces O2 but PO2 is normal. Chemoreceptors only detect the levels of dissolved PO2 not the amount of Hb.

Question 25

During ventilation, alveolar ventilation can increase by ___ fold.

Answer 25

20

Question 26

Arterial ___ remains unchanged until exercise becomes ___. Then venous PCO2 increases but no change in arterial values. Why is there no change?

Answer 26

PCO2; strenuous

Chemoreceptors (peripheral) only detect PCO2 in the blood

Question 27

Ventilation increases in exact proportion to venous ___ production and with severe exercise. Arterial PCO2 decreases due to ___.

Answer 27

PCO2; hyperventilation

Question 28

If there is decreased PO2 during exercise, how does this control ventilation?

Answer 28

as with CO2, venous O2 decreases, but not arterial

increase in ventilation is proportional to O2 use

Question 29

T/F. During exercise, increased H+ requires intense exercise due to lactic acid accumulation.

Answer 29

True.

Question 30

Multiple factors provide input to the respiratory center and contribute to increasing ventilation during exercise. What are they and what do they do?

Answer 30

1. temperature - trigger body to cool off
2. proprioceptors - signal tells lungs to ↑ ventilation rate to supply more O2 b/c muscles are working
3. ↑ epinephrine and ↑ K+ - Epi acts on respiratory neuron and K+ from exercising muscles depolarize so muscles are slightly more sensitive to contraction
4. conditioned responses - ↑ output of motor neurons in muscle and stimulates respiratory center to ↑ ventilation

Question 31

___ = a deficiency of O2 at the level of the tissues.

Answer 31

Hypoxia

Question 32

Match the following

1. Hypoxic hypoxia or hypoxemia
2. Anemic hypoxia
3. Ischemic hypoxia
4. Histotoxic hypoxia

A. normal arterial PO2; decreased Hb and O2 content of blood
B. blood flow to tissues is low
C. cells unable to utilize O2
D. decreased arterial PO2

Answer 32

1 - D
2 - A
3 - B
4 - C

Question 33

Cyanide poisoning is an example of ___ hypoxia. It competes with O2 for the ___ ___ ___ preventing O2 from becoming the final electron acceptor. This causes a ↓ in ___.

Answer 33

histotoxic; electron transport chain; ATP

Question 34

What conditions can cause hypoxia?

Answer 34

1. hypoventilation - increases in arterial PCO2 (also causes hypercapnia - excess PCO2)
2. diffusion impairment (within lung) - thickened alveoli-blood interface or fluid in lung. This ↓ the rate of O2 diffusion from air alveoli
3. vascular shunt - blood bypasses alveoli and there is mixing of blood from the right to the left side of the heart (blood ↓ O2) or unventilated alveoli due to bronchiole blockage.
4. ventilation-perfusion inequality - can occur as a consequence of COPD (can also cause hypercapnia). Air in lungs has ↓ O2 or lungs cant expand to make use of O2

Question 35

Because Patm decreases as altitude ___, PO2 ___ (even though O2 is still ___%).

Answer 35

increases; decrease; 21

Question 36

Sea Level
Patm = ___ mmHg
Alveolar PO2 = ___ mmHg

Mt. Everest
Patm = ___ mmHg
Alveolar PO2 = ___ mmHg

Answer 36

Sea Level
Patm = 760 mmHg
Alveolar PO2 = 105 mmHg

Mt. Everest
Patm = 253 mmHg
Alveolar PO2 = 43 mmHg

Question 37

What are the immediate responses to high altitude?

Answer 37

1. stimulate ventilation - ↓ PO2 in arterial stimulate peripheral chemoreceptors causing hyperventilation
2. increased dependence on anaerobic glycolysis - ↓ ATP and ↑ lactic acid

Question 38

T/F. Acclimatization to high altitude depends on delayed responses that take 1 - 2 days.

Answer 38

False, Acclimatization to high altitude depends on delayed responses that take DAYS TO WEEKS.

Question 39

At high altitudes, increased ___ which results in ___, stimulated by ___, a hormone from the kidneys

Answer 39

erythropoiesis; polycytothemia; EPO

Question 40

At high altitudes, ___ increase , ___ synthesis which will shift the Hb-O2 curve to the ___.

Answer 40

RBCs; 2,3 DPG; right

This unloads O2 at higher PO2 and more O2 is available to the tissues. But Hb does not pick up O2 as readily in the lung b/c ↑ PO2 at which Hb is saturated.

Question 41

At high altitudes, there is increased synthesis of other components of O2 delivery and consumption. What are these delayed responses that take place at a cellular level?

Answer 41

1. ↑ capillary density - ↑delivery of blood to tissues
2. ↑ mitochondria - ↑ ATP production
3. ↑ myoglobin - respiratory pigment with heme group found in skeletal muscles is a nonvascular source of O2.

Question 42

How can acclimatization to high altitude be accomplished at sea level?

Answer 42

by sleeping in a hypobaric atmosphere. This trains the body at low/ normal altitude and conditions the body to utilize increased O2 availability

One can also train at high altitude to stimulate EPO production in response to low arterial PO2

Question 43

What is the old school vs the modern way to get EPO for blood doping?

Answer 43

old - RBC packing or use recombinant human EPO

new - gene therapy to increase endogenous EPO

Question 44

What are the dangerous side effects of EPO use when blood doping?

Answer 44

increased blood viscosity
increased risk of stroke due to clot formation
high BP
autoimmune anemia