FACULTY OF SCIENCE & AGRICULTURE
DEPARTMENT OF BIOKINETICS & SPORTS SCIENCE
SHMD 339 – Exercise Physiology
TEST 3 – 11 September 2013
DURATION: 1 hour
MARKS: 65
Lecturer
Internal Moderator
Ms. K Frames
Ms. V. Khumalo
INSTRUCTION TO CANDIDATES
1. Please ascertain that this paper has five (5) pages, including the cover.
2. Answer all questions in the answer book provided.
3. Number the questions correctly.
4. Answer each question on a new page.
5. Please do not use tipex.
6. Write neatly.
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Question One
[10]
Write down which letter corresponds with the correct answer to the following questions:
1. Red blood cells are also called:
a. Erythropoeitin.
b. Erythrocytes.
c. Hemoglobin.
d. Bicarbonate.
2. Partial pressure is:
a. The pressure that any one gas would exert on the walls of a container if it were the
only gas present.
b. The pressure that any one gas would exert on the walls of a container if there were
multiple gases present.
c. The pressure that a mixture of gases would exert on the walls of a container.
d. The pressure that any one gas would exert on other gases in a container if there
were multiple gas present.
3. In the lungs where the alveoli and capillaries exchanges gases, PO2 is:
a. Average, between 40mmHg and 60mmHg.
b. Low, below 40mmHg.
c. High, above 60mmHg.
d. Non-existent, at 0mmHg.
4. Myoglobin is found in:
a. Skeletal muscle fibers only.
b. Smooth and cardiac muscle fibers.
c. Skeletal and smooth muscle fibers.
d. Skeletal and cardiac muscle fibers.
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5. At the onset of constant load, submaximal exercise:
a. Ventilation increases slowly and then slowly rises to steady state.
b. Ventilation increases rapidly and then rapidly rises to steady state.
c. Ventilation increases rapidly and then exponentially rises.
d. Ventilation increases rapidly and then slowly rises to steady state.
6. During prolonged submaximal exercise:
a. Ventilation drifts upwards and there is little change in PCO2.
b. Ventilation drifts downwards and there is little change in PCO2.
c. Ventilation drifts upwards and there is a significant change in PCO2.
d. Ventilation drifts downwards and there is a significant change in PCO2.
7. Involuntary heat production includes:
a. Exercise.
b. Shivering and non – shivering thermogenesis.
c. Only the action of catecholamies.
d. The action of catecholamines and thyroxine.
8. The rate of evaporation from the skin is dependent on:
a. Temperature, relative humidity, radiation.
b. Relative humidity, dehydration, amount of skin surface exposed.
c. Radiation, convection currents, relative humidity, dehydration.
d. Temperature, relative humidity, convection currents, amount of skin surface
exposed.
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9. The heat index can be determined as:
a. Relative humidity subtracted from air temperature.
b. Air temperature minus sweat rate.
c. Relative humidity added to air temperature.
d. Air temperature minus core temperature.
10. Adequate rehydration after exercise in a hot and humid environment consists of:
a. 1.5kg body weight = 1L fluid replacement.
b. 2kg body weight = 1L fluid replacement.
c. 5kh body weight = 1L fluid replacement.
d. 1kg body weight = 1.5L fluid replacement.
Question Two
[25]
2.1 Discuss the use of the oxyheamoglobin dissociation curve in regards to:
why it is used, what the significance of the flat portion is and, what the
significance of the steep portion is.
(12)
Shows the percentage of O2 that is bound to hemoglobin at each O2 pressure.
The flat portion of the curve shows that the PO2 can fall from 100 to 60 mmHg and the
hemoglobin will still be 90% saturated with O2.
This means the O2 content does not change much (even with large changes in the partial
pressure of oxygen).
E.g. PO2 can fluctuate between 90 – 100mmHg without a large drop in the percentage of
hemoglobin that is saturated with O2.
This is important because there is a drop in PO2 with aging and with climbing high altitudes.
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b. Significance of the steep portion
PO2 reductions below 40 mm Hg produce a rapid decrease in the amount of O2 bound to
hemoglobin.
When the PO2 falls below 40 mm Hg, the quantity of O2 delivered to the tissue cells may be
significantly reduced.
As PO2decrease in this steep area of the curve, the O2 is unloaded to peripheral tissue as
hemoglobin’s affinity for O2 diminishes.
Therefore, small changes in PO2 will release large amounts of O2 from hemoglobin.
This is critical during exercise when O2 consumption is high.
2.2 What are the factors that affect the oxyheamoglobin dissociation curve?
(3)
pH - Change in the blood pH
Temperature- temp increases = the curve moves to the right
Carbon Dioxide – increased PCO2
2.3 What are the ways in which carbon dioxide is transported in the blood?
(3)
1. Dissolved CO2 (±10%)
2. CO2 bound to hemoglobin (±20%)
3. Bicarbonate (HCO3¯)(±70%)
2.4 Explain how carbon dioxide is converted to bicarbonate in red blood cells.
(7)
A high PCO2 causes CO2 to combine with water, forming carbonic acid.
This reaction is rapidly catalyzed by the enzyme Carbonic Anhydrase
The carbonic acid then dissociates into bicarbonate ion and hydrogen ion.
The hydrogen ion then binds with hemoglobin
The bicarbonate ion diffuses out of the red blood cell into the blood plasma
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Because bicarbonate carries a negative charge (anion), removal of a negatively charged
molecule from a cell = electrochemical imbalance
Therefore the negative charge must be replaced
Bicarbonate is replaced by chloride (Cl¯) which diffuses from the plasma into the red blood cell
This is called chloride shift
 the shift of anions into red blood cells as blood moves through tissue capillaries
The release of CO2 from the blood into the alveoli is removed from the body in expired gas
(CO2 we breathe out)
Question 3
[14]
3.1 Explain the use of the ventilatory threshold during exercise.
(6)
Reflects aerobic fitness without the need to directly measure maximal oxygen uptake
Point during exercise training at which pulmonary ventilation becomes disproportionately high
with respect to oxygen consumption during an incremental exercise test
Used as a guide to determine exercise intensity
Therefore: Ventilatory threshold = intensity of exercise that shows a larger ventilation than
required to do work.
At this point, the contribution of anaerobic metabolism becomes significant to produce larger
concentrations of lactic acid.
Lactic acid accumulates, reducing pH & increasing metabolic acidosis.
Because one of the functions of the respiratory system is acid-base balance, respiration must
increase to compensate for the increased acidosis.
The point were ventilation deviates from linearity is termed the ventilatory threshold (T VENT).
3.2 What is exercise induced hypoxemia?
(2)
Low arterial PO2 vales during exercise
3.3 Explain the possible causes of exercise induced hypoxemia.
(6)
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Failure of pulmonary system?
Ventilation perfusion mismatch?
Indicates matching of blood flow to ventilation
– Ideal: ~1.0
– Light exercise improves
– Heavy exercise = inequality
Diffusion limitations during exercise ?
Reduced amount of time that red blood cells spend in the pulmonary capillaries...caused by
high cardiac outputs from athletes  less time for gas equilibrium to be achieved
Question 4
[16]
4.1 How does the anterior hypothalamus respond to an increase in core temperature? (3)
Increased evaporative heat loss
Increased skin blood flow
Allows increased heat loss
4.2 How does the posterior hypothalamus respond to a decrease in core temperature? (3)
Responds to decreased core temperature
Shivering and increased norepinephrine secretion
Increased heat production
Decreased skin blood flow
Decreased heat loss
4.3 What are the 4 ways that heat can be lost in the body?
(4)
Radiation
Convection
Conduction
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Evapouration
4.4 What are the primary adaptations that occur with heat acclimatization?
(6)
Adaptations occur within 7–14 days:
Increased plasma volume
Earlier onset of sweating
Higher sweat rate
Reduced sodium chloride loss in sweat
Reduced skin blood flow
Increased cellular heat shock proteins
END OF PAPER
TOTAL: 65 MARKS
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