21- Exercise Physiology Flashcards
Three functions of exercise
most essential aspect during muscular activity is coordination of 3 functions
- Communication (signals from brain)
- brain must stimulate muscles - Energy Production (ATP)
- fuel available for the energy - O2 and CO2 transport
- O2 provided and waste products eliminated (CO2 gets eliminated)
exercise is voluntary movement which requires what parts of the brain to originate the signal
- cortex
- basal ganglia
- cerebellum
once you have an idea to exercise of get up.. what happens from there
two steps
- PLAN
- cortical association areas go to basal ganglia and lateral cerebellum
- this signal goes tot he premotor and motor cortex for execution - EXECUTE
- movement occurs and this includes the intermediate cerebellum as well
- movement signal via corticospinal tracts
- cerebellum provides feedback to adjust and smooth movements
Corticospinal tract
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
basal ganglia
composed of several nuclei and biochemical pathways
- dopaminergic
- cholinergic
- gabaergic systems
influence motor cortex
-thalamus
diseases
- hyperkinetic (parkinsons)
- hypokinetic (akinesia) muscle conditions
possible reason for ataxia
disease of cerebellum
muscle strength (Kg/cm^2)
- determined by its size
- increased through training or anabolic steroids
ex: weight lifting
muscle power (Kg-meters)
- 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
muscle endurance
- time a task can be sustained
- dependent on muscle glycogen store
what energy is used for exercise
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
different pathways that generate ATP
- phosphocreatine —> createine
- Glycogen —> lactic acid
- glucose/fatty acids/amino acids + O2 —> CO2 + H2O+ Urea
all of these end up breating ATP which is used for muscle contraction
Phosphagen system of energy
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)
phosphagen system vs glycogen-lactic acid system vs aerobic system
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
glycogen with oxygen
Glycogen
(through glycolysis) split into glucose
-Two pyruvic acid molecules
-Pyruvic acid enters mitochondria and reacts with oxygen to form ATP molecules
glycogen without oxygen
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
exercise intensity and O2 consumption
- Work intensity and oxygen consumption are proportional until oxidative pathway maximum is reached
- Increased work beyond maximum oxygen consumption due to anaerobic metabolism
ATP from oxidative pathway
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
what does increased epinephrine cause
increase in…
• Glucose output from the liver
• Output of fatty acid from adipose tissue
– high carbohydrate diet increases stored glycogen
Post exercise oxygen consumption
• 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
Cardiovascular Adjustments to Exercise
Note all variables are linearly related to work rate to about 60% maximal O2 consumption, but particularly stroke volume plateaus thereafter.
Systolic Blood Pressure and Peripheral Resistance during exercise
• Tissue perfusion enhanced by increased systolic blood pressure and decreased peripheral resistance.
-diastolic changes very little during exercise
rhythmic muscle blood flow during exercise
Locally mediated vasodilation
increases blood flow to the muscles which is rhythmic due to capillary compression during muscle contraction
Cardiac output distribution during exercise
- 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
Mechanism of cardiovascular changes during exercise
- 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.
Pulmonary adjustments to exercise
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
arterial blood gases during exercise
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
alveolar to capillary gas exchange during exercise
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
Increased demands for alveolar to capillary gas exchange during exercise
• 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
Classification of exercise hyperpnea theories
1) Neural, feed-forward : signal originates in the brain
2) Neural feedback: signal originates in muscles
3) Humoral: blood-born feedback
Exercise: Body Temperature
• 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.
neuroendocrine responses to exercise
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
exercise: effects of physical training
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
limiting factors of exercise
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
forced vital capacity
as much as you can breathe in at once (forcefully)
forced exhaled volume
amount you can exhale at once (forcefully)
during exercise, muscle capillary PO2 and PCO2 decrease and increase respectively relative to rest. These changes cause…?
- 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
