FACULTY OF SCIENCE & AGRICULTURE
DEPARTMENT OF BIOKINETICS & SPORTS SCIENCE
SHMD 339 – Exercise Physiology 3
TEST 3
DURATION: 2 Hours
MARKS: 100
Internal Moderator
Mrs. S Currie
Lecturer
Ms. K Frames
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. Write neatly.
6. Do not use tipex.
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Question 1
[10]
Choose the correct answer and write only the letter of the corresponding answer.
1.1 Hemoglobin is a protein found in
a. Erythropoietin.
b. Erythrocytes.
c. Epinephrine.
d. Myoglobin.
1.2 Myoglobin is found in the:
a. Muscles.
b. Blood.
c. Hemoglobin.
d. Erythrocytes.
1.3 Oxygen binding with hemoglobin is called:
a. Myoglobin.
b. Unloading.
c. Loading.
d. Affinity.
1.4 As breathing frequency increases, minute ventilation will:
a. Increase.
b. Decrease.
c. Drift slightly downwards.
d. Stay the same.
2
1.5 Incremental exercise will result in a:
a. Linear decrease in ventilation.
b. Plateau in ventilation.
c. Linear increase in ventilation.
d. Upward drift in ventilation.
1.6 Shivering is a result of the action of which hormones?
a. Thyroxine and human growth hormone.
b. T3 and insulin.
c. Insulin and adrenaline.
d. Thyroxine and catecholamines.
1.7 The measure of the body’s perception of how hot it feels is called the:
a. Heat scale.
b. Relative humidity.
c. Ambient air.
d. Heat index.
1.8 Guidelines for adequate rehydration after exercise are:
a. 1 kg body weight = 2L fluid replacement.
b. 1.5 kg body weight = 1L fluid replacement.
c. 1 kg body weight = 1.5L fluid replacement.
d. 1 kg body weight = 0.5L fluid replacement.
1.9 Prolonged exercise in the heat may result in:
a. Hypothermia.
b. Hyperthermia.
c. Hyponatremia.
d. Hypernatremia.
3
1.10
A reduction in thermotolerance with age is due to:
a. Degeneration of the neurovascular system.
b. Deconditioning with age and lack of acclimatization.
c. Deconditioning of the muscular tissue to heat.
d. Hormonal imbalances from the anterior and posterior pituitary glands.
Question 2
[10]
Answer the following statements with either true or false:
2.1 Each hemoglobin molecule can hold up to 4 molecules of oxygen. T
2.2 Hemoglobin is 100% saturated with oxygen at sea level. F
2.3 Hemoglobin saturation is determined by its affinity for oxygen. T
2.4 At the onset of constant-load submaximal exercise, ventilation increases rapidly. T
2.5 A higher ventilation during prolonged, sub maximal exercise is due to an increased PCO2. F
2.6 Patients with severe lung disease have a high arterial PO2 .F
2.7 At the start of exercise, the increase in ventilation is faster than the increase in metabolism. F
2.8 Voluntary heat production accounts for 30-40% of the body’s energy expenditure. F
2.9.Heat production increases linearly with exercise intensity. T
2.10 Heat shock proteins protect against heat stroke. T
Question 3
[37]
3.1What is the amount of hemoglobin found in normal, healthy males and females?
(2)
Healthy male can transport 200ml of O2
Healthy female can transport 174ml of O2
3.2 Explain the oxyhemoglobin dissociation curve, focusing on:
a. the use of the oxyhemoglobin dissociation curve.
An important tool for understanding how our blood carries and releases oxygen.
Relates oxygen saturation (SO2) and partial pressure of oxygen in the blood (PO2)
Determined by what is called "hemoglobin's affinity for oxygen“
how readily hemoglobin acquires and releases oxygen molecules from its surrounding tissue.
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b. the flat portion of the curve.
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.
c. the steep portion of the curve.
(12)
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.
3.3 List the factors that affect the oxyhemoglobin dissociation curve.
(6)
Increased pH
Increased temperature
Increased PCO2
3.4 Explain how exercise affects the oxyhenmoglobin dissociation curve.
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(3)
During exercise, the oxyhemoglobin dissociation curve will shift to the right to allow for more
oxygen to be unloaded into active muscles. This is because the pH in the body is decreased (from
increased lactic acid) and an increase in body temperature from exercise.
3.5 Describe the ways in which carbon dioxide can be transported in the blood.
(3)
1. Dissolved CO2 (±10%)
2. CO2 bound to haemoglobin (±20%)
3. Bicarbonate (HCO3¯)(±70%)
3.6 Explain how carbon dioxide is converted into bicarbonate.
(5)
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
3.7 Explain bicarbonate exchange.
(6)
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
When blood reaches the pulmonary capillaries:
PCO2 of the blood is greater than that of the alveolus = CO2 diffuses out of the blood across the
blood-gas interface
At the lungs:
Binding of O2 to hemoglobin causes a release of the hydrogen ions (which are bound to
hemoglobin) to promote the formation of carbonic acid
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In conditions where PCO2 is low (at the alveolus), carbonic acid then dissociates into CO2 and
H2O
The release of CO2 from the blood into the alveoli is removed from the body in expired gas
(CO2 we breathe out)
Question 4
[22]
4.1 Describe the ventilatory threshold and how it is used.
(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 where ventilation deviates from linearity is termed the ventilatory threshold (TVENT).
4.2 How do trained and untrained athlete’s ventilatory responses differ?
Trained:
Decrease in arterial PO2 near exhaustion
pH maintained at a higher work rate
Ventilatory threshold occurs at higher work rate
Untrained: able to maintain PO2 in arteries within 10–12 mmHg of resting value
Trained: PO2 decreases by 30- 40 mmHg during heavy exercise
*low arterial PO2 vales during exercise = exercise induced hypoxemia
* Low arterial Po2 values are also seen in patients with severe lung disease
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(3)
4.3 What are the physiological responses to prolonged exercise in a hot environment?
(3)
Hot environments hamper heat loss from the body
Increase in body temperature which directly affects respiratory control centre
= Minute ventilation increases (with increased breathing frequency)
Ventilation tends to drift upwards
Little change in PCO2
Higher ventilation not due to increased PCO2
4.3 What is hypoxemia and how does it relate to exercise?
(4)
Low arterial PO2 vales during exercise = exercise induced hypoxemia
Means that while exercising, the transport of oxygen throughout the body becomes lower than
optimal, resulting in earlier fatigue as muscle struggles to get enough oxygen.
4.4 Explain the possible causes of hypoxemia in athletes.
(6)
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 5
[21]
5.1 List the 4 ways that heat can be lost from the body.
(4)
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Radiation
Evaporation
Convection
Conduction
5.2 What are the thermoregulatory functions of the anterior hypothalamus?
(3)
Responds to increased core temperature
Begin to sweat:
Increased evaporative heat loss
Increased skin blood flow
Allows increased heat loss
5.3 Give 4 ways that dehydration can be prevented during and after exercise.
(4)
Hydrate prior to performance
400–800 ml fluid within three hours prior to exercise
Consume 150–300 ml fluid every 15–20 min
Volume adjusted based on environmental conditions
Ensure adequate rehydration
5.4 How does exercise accelerate muscle fatigue?
(4)
Rapid onset of muscle fatigue in hot/humid environments
Heat-related muscle fatigue due to:
High brain temperature reduces neuromuscular drive
Reduction in motor unit recruitment
Accelerated muscle glycogen metabolism and hypoglycemia
Increased free radical production
Damage to muscle contractile protein
5.5 What are the primary adaptations to heat acclimatization?
Increased plasma volume
Earlier onset of sweating
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(6)
Higher sweat rate
Reduced sodium chloride in sweat
Reduced skin blood flow
Increased heat shock proteins in tissues
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