Exercise physiology Flashcards
describe the phosphagen energy system
Phosphagen energy system - immediate energy source
* Immediate and fast, only lasts ≤10s
Stores in muscles therefore instantly available
- High conc of creatine phosphate (phosphocreatine) present in muscle
- Phosphocreatine decomposition (phosphorous bond) releases lotta energy - used to generate ATP - energy transfer occurs within fraction of second
- Catalysed by creatine kinase
describe the glycogen-lactic acid system
Glycogen-lactic acid system - non-oxidative anaerobic source
* Anaerobic glycolysis can provide energy for couple of min at most
No O2 and is inefficient pathway
- During heavy exercise, insufficient O2 means cells require/use anaerobic metabolism - glycogen stores in the skeletal muscle cells are broken down to glucose
*ATP generated from glucose via glycolytic pathway - less efficient in ATP generation than aerobic metabolism - Excess pyruvate is converted to lactate in reaction with (NADH) + (H+)
During 100m sprint blood lactate levels can rise from 1.6 to 3.8 mM - drop in pH and muscles begin to fatigue
describe the aerobic energy system
Aerobic system - oxidative energy source
* Aerobic metabolism uses O2
*Produces sustained supply of ATP
- In sustainable exercise almost all energy required is derived from aerobic metabolism
- Requires O2 (oxidative phosphorylation)
*Volume of O2 consumed = VO2
how do we measure oxygen consumption of muscle?
VO2= the rate of O2 uptake by muscels (cardiac or skeletal)
VO2 max= is the maximum amount of o2 someone can utilise at maximal effort/during dynamic excercise; it is the best indicator of cardiovascular fitness/aerobic endurance
so VO2 max is reached when o2 consumption remains at steady state despite an increase in workload
e.g. mildy fit adults have a VO2 max of 30-40ml O2/(min x kg) n.b. the fitter the person the higher this value
COPD patient 10-20 O2/ (min x kg)
what is the anaerobic threshold
anaerobic threshold (AT) aka lactate threshold= is the point where lactate (lactic acid) begins to accumulate in bloodstream
AT further increases in work that are not accompanied by o2 uptake are supplemented by anaerobic mechanisms
n.b. lactic acid is produced faster than it can be metabolised, metabolic acidosis develops + exercise endurance is reduced
atheletes have a high AT
when u excerices there is an increase in regional muscle vasodilation (as muscles need more nutrients/o2 therfore need more blood).
Explain the mechanism of regional muscle vasodilation:
mechanism of regional muscle vasodilation:
*muscle hypoxia triggers it {a state in which oxygen is not available in sufficient amounts at the tissue level to maintain adequate homeostasis}
Autonomic Nervous System: This part of the nervous system uses neurotransmitters like norepinephrine which, in muscle areas, can activate beta-adrenergic receptors to cause vasodilation.
Neurotransmitters: Substances like Nitric Oxide (NO) and Vasoactive Intestinal Peptide (VIP) are released from nerve endings to help dilate blood vessels.
2. Local Metabolic Factors
As muscles work harder, they produce byproducts such as carbon dioxide, lactate, K+ and adenosine that directly cause the blood vessels to widen.
pH Changes: The buildup of acids (e.g., lactic acid) reduces pH levels, contributing to vasodilation.
3. Endothelial Factors
Endothelial Cells: These cells line the blood vessels and produce Nitric Oxide (NO) in response to increased blood flow, leading to vessel relaxation and dilation.
Prostacyclin (PGI2): Another substance from endothelial cells that aids in widening the blood vessels.
4. Hormonal Control
Hormones like bradykinin and histamine, released locally or throughout the body, can also cause blood vessels in muscles to dilate.
5. Myogenic Response
Blood vessels automatically adjust their diameter in response to changes in blood pressure to protect underlying muscle tissue.
Clinical relevance:
Understanding how blood flow is increased to muscles helps in managing diseases that impair circulation, like peripheral artery disease, or in treating muscle injuries. Treatments might aim to use drugs that enhance these natural processes to improve blood flow.
- Athletes have an increased resting EDV (end-diastolic volume) and therefore increased ______
- Resting CO in athletes is identical to non-athletes due to an increased resting SV and compensatory bradycardia
- Athletes have an increased resting EDV (end-diastolic volume) and therefore **increased SV **
define tidal volume
Tidal volume = volume of air moves in or out of the lungs with each respiratory cycle - measures around 500 mL in an average healthy adult man and approximately 400 mL in a healthy woman
during exercise we have:
*increased CO2
* increased H+
* increased temperature
what happens to the affinity of Haemoglobin (Hb) when we are exercising
the affinity of Hb is reduced/decreases; as we need the oxygen to be breaking free from the Hb and delivered to tissues who need it as theyre respiring a lot!
i.e. oxyhaemoglobin level decreases (as Hb affinity for o2 reduced)
what is oxygen debt and how does our body recover from it?
Amount of o2 consumed during recovery in excess of that which would ordinarily be consumed= so u work up an “o2 debt”
- Initially there is a progressive rise in O2 consumption until it matches demands
- O2 deficit is met by phosphocreatine and glycolytic systems to supply ATP
- After exercise, O2consumption declines slowly and may not reach resting levels for >1 hour
- Initially, ATP and phosphocreatine are used up and these need to be re-synthesised using O2
what are baroreceptors and where are they located?
Baroreceptors constantly monitor how much blood you have in your blood vessels and what the pressure is inside them
Baroreceptors are mechanoreceptors located in blood vessels near the heart that provide the brain with info by detecting the level of stretch on vascular walls. As blood volume increases, vessels are stretched and the firing rate of baroreceptors increases
