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Physiology Lecture Notes
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The lecture notes for second year in Sports and Exercise Science (physiology).
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The Energy SystemsEnergy is needed for; physical movement, temperature maintenance and metabolic
activities. Physical movement requires ATP which is stored in the muscles so it is
available straight away, though is limited. Anything that lats longer than a few
seconds needs more ATP.
ANAEROBIC METABOLISM
The production of ATP without the use of oxygen. ATP is formed when ADP binds with
another phosphate molecule, the energy is stored between the second and third
phosphate bond so when the cells needs energy, it breaks the bond between them to
release the energy forming ADP and a singular phosphate molecule.
ATP-PC System
This system is made up of ATP and Phosphocreatine (PC). The PC is broken down by the
enzyme Creatine Kinase, therefore releasing a phosphate molecule. This is used to
regenerate ATP by rebuilding the ADP from which the phosphate was released during use.
It can sustain all-out exercise for up to 15 seconds, so if the activity continues beyond this
the body must rely on additional energy systems to regenerate ATP.
Lactate System
This system lasts from 15 seconds to 3 minutes. Simply, glycolysis is the breakdown of
glucose (using the Krebs Cycle). The body breaks down carbohydrates from food,
converting it into glucose, this is stored in the liver and muscles and glycogen). During the
Krebs Cycle, the glucose is broken down. This is done by a series of enzymatic reactions,
ending with a product of Pyruvic Acid. This is unable to be metabolised in the Citric Cycle
so it is converted into Lactate by the enzyme Lactate Dehydrogenase. During this
production of Lactate, NADH and H+ are oxidised into NADH+. Anything over the 3
minute marker will then need to use the aerobic system.
AEROBIC METABOLISM
Aerobic metabolism processes require oxygen to generate energy, and can be sustained
over the longest period of time as it is a lower intensity. The oxidative production of ATP
occurs in the mitochondria of the muscles. Stage 2: Krebs Cycle
Stage 1: Aerobic Glycolysis
- Converts glycogen to glucose (enzymes).
- 2 ATP to fuel, 4 made (2 for muscles. contraction).
- Pyruvate = end product of glucose breakdown.
- Converted to Acetyl CoA.
Stage 3: Electron Transport Chain
- Hydrogen ions from Krebs cycle are carried here
by carrier molecules.
- These ions undergo a series of chemical reactions.
- A gradient is created > as hydrogen ions move across this gradient, ADP adds
another Phosphate (phosphorylates) group to form ATP.
- Water is created as a by-product.
, Energy Continuum
- Energy systems are viewed as a continuum.
- High-intensity exercise lasting 8-15s requires the ATP-PC system to meet the energy
demands.
- As the duration increases the intensity of the demand decreases and the lactate system
is used.
- The point at which blood lactate builds up so it prevents effective muscle contraction
occurs between 30s and 180s (3mins) depending on the intensity of exercise and the
fitness of the athlete. This point is known as the Onset of Blood Lactate Accumulation
(OBLA).
- Once the duration of exercise goes beyond 3
minutes, the majority of energy comes from the aerobic
system.
OBLA Explanation
Onset is the level above which blood lactate is
produced faster than it can be used aerobically. It
occurs when the concentration of blood lactate
reaches approx. 4 Mmol/L.
Continued exercise above the lactate threshold results
in the accumulation of hydrogen ions in the muscle
tissue, causing fatigue and intramuscular pain.
Buffering Systems of Lactate
ATP-PC System Hormonal
Fuel - Phosphocreatine (PC) Carbon Dioxide
Duration - 8 to 10 seconds Kidney buffering
Intensity - High
By-products - Free creatine
Sporting Ex. - 100m sprint
Lactate System
Fuel - Carbohydrate
Duration - 30 to 90 seconds
Intensity - Medium
By-products - Lactic acid and ass. H+
Sporting Ex. - 400m / repetitive runs in rugby
Aerobic
Fuel - Carbohydrate / Fat / Protein
Duration - Hours
Intensity - Low
By-products - CO2 and H2O. Sporting Ex. - 10,000m / mountain hike
, Skeletal System Response
Response (short term)
- Exercise stimulates increased mineral uptake in bones due to weight bearing exercise
(e.g. calcium).
- Mechanical stress produces micro trauma at the periosteum (outer) of the bone /
damage to the bone.
- Effect is not achieved in non-weight bearing exercise (e.g. swimming).
- Movement stimulates the secretion of synovial fluid and makes the joints warmer. It then
becomes thinner, making movement more efficient by preventing friction.
- Range of movement (ROM) increases.
LONG TERM
Bone Growth
- Dynamic tissue, constantly shaped by osteoblasts (broken down by osteoclasts).
- As the body ages, osteoclast activity increases, breaking down the tissue to release
calcium and other minerals into the bloodstream.
- Research suggests weight-bearing exercise stimulates the activity of osteoblasts and
suppresses osteoclast activity, maintaining a healthy bone density.
Synovial Fluid
- A thick, straw-coloured liquid that acts as a lubricant and is found primarily in the
cavities of synovial joints.
- Exercise increases the amount of synovial fluid, decreasing its viscosity, keeping joints
healthy, while stopping cartilage from drying out.
- Research suggests exercise also increases the range of movement at the joints as more
synovial fluid is released into them.
Bone Strength
- Increase calcium stores (determining bone density).
- Technical stress around the insertion of ligament / tendon causes calcium to be stored
in that location.
- Calcium is also needed from transmitting electrical impulse in muscle cells for
contraction.
Increased Ligament Strength
- Attach bone to bone, stabilising the joint.
- Control range and alignment of movement.
- Connective tissue (collagen) becomes aligned, allows further stretch along the direction
of ligament.
Other Adaptations
- Increased thickness of hyaline cartilage (protecting the bone and storing synovial fluid).
More cartilage means more fluid and better protection.
- Increased production of synovial fluid. Regular exercise means a reduction in viscosity
and better joint lubrication. Also provides nutrients to the hyaline cartilage.
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