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Physiology > Lecture 27: Acid Base Balance During Exercise > Flashcards

Lecture 27: Acid Base Balance During Exercise Flashcards

1
Q

Define an ion.

A

An atom with one extra electron

Therefore has an electrical charge

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2
Q

Define an acid.

A

Something that can liberate hydrogen

Causes increased hydrogen in a solution

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3
Q

Define a base.

A

Something that accepts hydrogen molecules

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4
Q

What is pH?

A

The concentration of hydrogen ions

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5
Q

What is the survival range for pH?

A

6.8 –> 7.8

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6
Q

What are the pathological effects of a pH that is too low?

A

Low pH (acidosis): coma due to decreased CNS activity

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7
Q

What are the pathological effects of a pH that is too high?

A

High pH (alkalosis) spasm of respiratory muscles

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8
Q

What value is given for normal pH?

A

7.4

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9
Q

Why are there fewer bases with lower pH?

A

Because increased H+ concentration due to increased acid content (acidosis) causes more bases to combine with hydrogen

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10
Q

What are the three types of acid in the body? Give examples of each type and how they are produced.

A

Volatile Acids

CO2 + H20 –> H2CO3 –> H + HCO3 (Carbon dioxide liberates pH when combined with water)

Fixed Acids

Produced from amino acid metabolism
Sulfuric acid and Phosphoric acid

Organic Acids

Metabolism of fats and carbohydrates
Lactate

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11
Q

In sport, when are people most at risk of acidosis?

A

Sport lasting under 45 seconds
100% effort
Sprint finish

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12
Q

How can increased H+ (acidosis) inhibit skeletal muscle and aerobic/anaerobic performance?

A 
H+ binds to troponin (vs. calcium)
Inhibits enzymes (involved in aerobic/anaerobic pathways)
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13
Q

What is more acidic at maximum intensity exercise, the muscle or the arteries?

A

The muscle

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14
Q

Why does muscle pH decline more than in the arteries?

A

Inferior buffering capacity

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15
Q

What are the 3 exercising factors that determine pH production?

A

Duration
Intensity
Muscle mass

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16
Q

What is the first line of defence in regulating pH during exercise?

A

Cellular buffers:

Bicarbonate
Proteins
Phosphate

Blood buffers:

Bicarbonate
Proteins
Haemoglobin

17
Q

What is the second line of defence against acidosis during exercise?

A

Increased ventilation

18
Q

Give one or two constituents (e.g. carbonic acid) that act as buffers for each system.

A

Bicarbonate & Phosphate system:
Sodium Bicarbonate & Sodium Phosphate (strong acid –> weak acid)
Carbonic acid (weak acid –> strong acid)
Protein system:
NH3 & COO (accept H+)

19
Q

What is the major buffering system in the muscle?

A

Proteins

20
Q

What is the major buffering system in the blood?

A

Bicarbonate

21
Q

At what exercise intensity does bicarbonate begin to decrease and lactic acid begin to increase?

A

Between 50% - 75%

22
Q

Define a buffer.

A

A chemical that either liberates hydrogen during alkalosis, or removes hydrogen during acidosis
Neautral pH

23
Q

What have studies shown as the effects of sodium buffers on performance?

A

Can increase time to fatigue at high exercise intensities

24
Q

What are the drawbacks of using sodium buffers?

A

Can cause nausea, vomiting and alkalosis

25
Q

What is the effect of increased pulmonary ventilation on pH?

A

Activates carbonic anylase
Converts carboxylic acid back into CO2 and water
There is a lower concentration of CO2 in the alveoli due to increased ventilation, therefore CO2 can enter lungs and be exhaled

26
Q

What receptors input to the respiratory control centre?

A 
Central chemoreceptors (medulla; PCO2 & H+; in cerebrospinal fluid) 
Peripheral chemoreceptors (aortic and carotid bodies; PCO2, PO2, K+, H+; in blood)
27
Q

How can physiological adaptations reduce acid build up during exercise?

A

Delayed pH drop
Delayed ventilatory threshold
Increased buffering capacity

28
Q

Which organ is the major long-term acid-base balance regulator?

A

The renal system

29
Q

How does the renal system respond to increased acidosis?

A

Increases bicarbonate secretion

Physiology (16 decks)

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