21- Exercise Physiology

Question 1

Three functions of exercise

Answer 1

most essential aspect during muscular activity is coordination of 3 functions

1. Communication (signals from brain)
   - brain must stimulate muscles
2. Energy Production (ATP)
   - fuel available for the energy
3. O2 and CO2 transport
   - O2 provided and waste products eliminated (CO2 gets eliminated)

Question 2

exercise is voluntary movement which requires what parts of the brain to originate the signal

Answer 2

• cortex
• basal ganglia
• cerebellum

Question 3

once you have an idea to exercise of get up.. what happens from there

Answer 3

two steps

1. PLAN
   - cortical association areas go to basal ganglia and lateral cerebellum
   - this signal goes tot he premotor and motor cortex for execution
2. EXECUTE
   - movement occurs and this includes the intermediate cerebellum as well

• movement signal via corticospinal tracts
• cerebellum provides feedback to adjust and smooth movements

Question 4

Corticospinal tract

Answer 4

all participate in sending appropriate cycles from proper posture to fine tune to regulate complex movement then others actually stimulate muscle

• 31% of its neurons are from the primary motor cortex
• 29% from the premotor and supplementary motor cortex
• 40% from neurons in primary somatic sensory cortex and posterior parietal cortex

Question 5

basal ganglia

Answer 5

composed of several nuclei and biochemical pathways

• dopaminergic
• cholinergic
• gabaergic systems

influence motor cortex
-thalamus

diseases

• hyperkinetic (parkinsons)
• hypokinetic (akinesia) muscle conditions

Question 6

possible reason for ataxia

Answer 6

disease of cerebellum

Question 7

muscle strength (Kg/cm^2)

Answer 7

• determined by its size
• increased through training or anabolic steroids

ex: weight lifting

Question 8

muscle power (Kg-meters)

Answer 8

• differs from strength
• (power = force x distance) over a period of time
• power output declines with duration of muscle contraction

ex: high jump or running 100-meter dash

Question 9

muscle endurance

Answer 9

• time a task can be sustained

- dependent on muscle glycogen store

Question 10

what energy is used for exercise

Answer 10

ATP

• source of energy for muscle contraction
• bonds:
• -last 2 phosphate radicals
• -adenosine molecule
• -high energy phosphate bonds
• -each bond storing 7300 calories of energy/mole ATP

–removing both bonds results in release of 14,400 calories of energy and formation of ADP and AMP

-can sustain maximal muscle power for 3 seconds so you need a continuous supply of ATP

Question 11

different pathways that generate ATP

Answer 11

1. phosphocreatine —> createine
2. Glycogen —> lactic acid
3. glucose/fatty acids/amino acids + O2 —> CO2 + H2O+ Urea

all of these end up breating ATP which is used for muscle contraction

Question 12

Phosphagen system of energy

Answer 12

Phosphagen system:
Stored ATP plus phosphocreatine which is broken down to creatine and phosphate releasing of 10,300 calories/mole.

-fastest system (as compared to glycogen-lactic acid system and aerobic system)

Question 13

phosphagen system vs glycogen-lactic acid system vs aerobic system

Answer 13

phosphagen system: used for power surgest of a few seconds (weight lifting, 100m dash) — 4moles of ATP/min

Glycogen-lactic acid system: used for intermediate athletic activities (tennis, 400-m dash) — 2.5 moles of ATP/min

Aerobic System: used for prolonged athletic activity (jogging, 10,000 meter skating) — 1 mole of ATP/min

Question 14

glycogen with oxygen

Answer 14

Glycogen
(through glycolysis) split into glucose
-Two pyruvic acid molecules
-Pyruvic acid enters mitochondria and reacts with oxygen to form ATP molecules

Question 15

glycogen without oxygen

Answer 15

pyruvic acid coverted to lactic acid (anaerobic metabolism

Forms ATP 2.5 times more rapidly than oxidative pathway but only 50% of the rate of phosphagen energy system

Provide maximum muscle activity for about 1.5 minutes

Question 16

exercise intensity and O2 consumption

Answer 16

• Work intensity and oxygen consumption are proportional until oxidative pathway maximum is reached
• Increased work beyond maximum oxygen consumption due to anaerobic metabolism

Question 17

ATP from oxidative pathway

Answer 17

Glucose, Fatty Acids, Amino Acids

• Oxidation in mitochondria to form ATP
• slower than phosphogen and glycogen-lactic acid systems

Provides for endurance of muscle
-32 ATP molecules/glucose

Question 18

what does increased epinephrine cause

Answer 18

increase in…
• Glucose output from the liver
• Output of fatty acid from adipose tissue

– high carbohydrate diet increases stored glycogen

Question 19

Post exercise oxygen consumption

Answer 19

• Post Exercise
– Oxygen consumption above rest

Oxygen debt

– Alactacid phase
—-Reconstituting the phosphagen system

– Lactic acid phase
—-Conversion of lactic acid
to glucose

*Oxygen consumption remains elevated after exercise to reconstitute the phosphagen system and convert lactic acid to glucose

Question 20

Cardiovascular Adjustments to Exercise

Answer 20

Note all variables are linearly related to work rate to about 60% maximal O2 consumption, but particularly stroke volume plateaus thereafter.

Question 21

Systolic Blood Pressure and Peripheral Resistance during exercise

Answer 21

• Tissue perfusion enhanced by increased systolic blood pressure and decreased peripheral resistance.

-diastolic changes very little during exercise

Question 22

rhythmic muscle blood flow during exercise

Answer 22

Locally mediated vasodilation

increases blood flow to the muscles which is rhythmic due to capillary compression during muscle contraction

Question 23

Cardiac output distribution during exercise

Answer 23

• Cardiac output to the muscle is about 20% at rest
• Can increase up to 75% during exercise

-blood flow to abdomen is sacrificed for blood flow to muscles during exercise

Question 24

Mechanism of cardiovascular changes during exercise

Answer 24

• Brain “Exercise” centers and feedback from contracting muscles to medullary cardiovascular neurons regulate cardiovascular responses to exercise.
• There is a decrease in parasympathetic output to the heart and Increase sympathetic output to the heart and blood vessels
• Chemical changes in the muscles induce local vasodilation.

Question 25

Pulmonary adjustments to exercise

Answer 25

Pulmonary responses to exercise – Meet increased needs for gas exchange – Exercise increases breathing by unknown mechanism Low work rates – IncreasedVentilationby increased tidal volume – More fresh air reaches the lung with each breath – Decreased dead space to tidal volume ratio Limit – Hightidalvolumes,lung compliance is reduced – Additional increases in ventilation are achieved to a greater extent by increasing breathing frequency

Question 26

arterial blood gases during exercise

Answer 26

Homeostasis – 60% of maximal exercise capacity – Signal for the hyperpnea not from increased stimulation of carotid and intracranial chemoreceptors – During exercise above 60% of maximal capacity, • Lactacidosis • Hyperventilation of unknown cause

Question 27

alveolar to capillary gas exchange during exercise

Answer 27

DLCO increasing – Recruitment of alveolar –capillary units – Increases the surface area for gas exchange. Increase in the A-a PO2 difference – Hyperventilation Increase in PAO2 – Driving pressure for diffusion of oxygen

Question 28

Increased demands for alveolar to capillary gas exchange during exercise

Answer 28

• At Rest – Arterial-venous content difference is 5 vol% – Mixed venous PO2 is 40 mmHg ``` • During Exercise – Need for exchange is increased – Greater extraction of oxygen ---Decrease O2 bound to hemoglobin in venous blood ---Blood vessel (vasodilation) dilation – Arterial-venous content difference may exceed 15 vol% – Mixed venous PO2 is less than 20 mmHg ```

Question 29

Classification of exercise hyperpnea theories

Answer 29

1) Neural, feed-forward : signal originates in the brain 2) Neural feedback: signal originates in muscles 3) Humoral: blood-born feedback

Question 30

Exercise: Body Temperature

Answer 30

• Temperature control center receives input from thermo receptors in the skin (environmental temperature) • The hypothalamus (body temperature). • Regulation of body temperature during exercise – Hydration – Electrolyte balance ``` • Work results in conversion of energy to large amounts of heat – 98.6 ° (degrees) - 102° Fahrenheit • Heat loss – Vasodilation of arterioles in the skin – Heat transfer from the blood to the skin – To environment ---Sweating ---Evaporation ``` • Sweat production – Increased by the thermal control center in the hypothalamus – Increasing activity of sympathetic nerves to the sweat glands in the skin.

Question 31

neuroendocrine responses to exercise

Answer 31

Principal pathways activated by stress: -hypothalamic-pituitary-adrenal axis and sympathetic nervous system increases in: - growth hormone - TSH - cortisol - catecholamines - glucagon - endorphins stimulation of: - hepatic glycogenolysis and gluconeogenesis - muscle glycogenolysis Suppressed release of: -insulin

Question 32

exercise: effects of physical training

Answer 32

Training : Enhances Athletic Performances – 2-3 days a week (4-6 weeks) Increase of work rate related to Intensity and Duration – Increase in maximal cardiac output primarily in stroke volume – Increased muscle and myocyte size – Increased vascularization of the heart Increased vascularization of skeletal muscle including – Locomotor muscles – Respiratory muscles – Enhanced blood delivery – Reduced diffusion distance for diffusion of gas ---Between the vasculature and the muscle Little evidence of respiratory system enhancement Enhances endocrine, thermoregulatory and metabolic responses to exercise - changes in sympathetic nerve activity - enhance mobilization of glucose and fatty acids - elimination of heat

Question 33

limiting factors of exercise

Answer 33

Limiting factors to maximal O2 consumption Fatigue (mental or physical) – Boredom – Staleness – Drugs – Illness. – Depletion or non-availability of stores of energy – Accumulation of metabolic waste products – Alteration of physical-chemical state – Breakdown of homeostasis Highly elite endurance athletes can have a PaO2 of 60 mmHg during maximal exercise - at rest respiratory muscles only consume 2% of total O2 - at maximal exercise the respiratory muscle consumes nearly 25% of O2 consumption

Question 34

forced vital capacity

Answer 34

as much as you can breathe in at once (forcefully)

Question 35

forced exhaled volume

Answer 35

amount you can exhale at once (forcefully)

Question 36

during exercise, muscle capillary PO2 and PCO2 decrease and increase respectively relative to rest. These changes cause...?

Answer 36

- dissociation curve of capillary blood shifts to the right cause of a high CO2 - at any given O2 content, the diffusion gradient for O2 from the capillaries to tissues is greater than at rest