1. Explain in detail how (physiologically) the following systems adapt, in the short term, to exercise. Please also make brief comment about long term adaptation in each case.
(a) The Cardiovascular System
The cardiovascular system should regulate the changes to meet the bodys increased demands and perform efficiently The short-term response to exercise includes the following:
Cardiac output is the product of stroke volume and heart rate. The cardiac output increases in a linear manner with increase in the rate of work to meet the increase in oxygen demand, but only up to its maximum capacity. The output at rest is normally 5L/min, but it can increase up to 20-40L/min during strenuous activity.
The blood flow pattern changes when an individual shifts from resting to exercising. During rest, the skeletal muscles and the skin receive 20% of the total cardiac output. More blood goes to the skeletal muscles during exercise, and as the temperature rises, more blood goes to the skin. This is made possible by redistributing blood away from regions of lower demand like splanchnic organs to allow 80% of the output to go to skin and active skeletal muscles at maximum work rate (Rowell 1986)
There is an increase in the mean arterial pressure in respond to strenuous exercise mainly due to increased systolic pressure since the diastolic pressure remains constant. the systolic blood pressure rises in a linear manner up to a peak of 200-240 mm/Hg. There is a drop of blood pressure below the pre-exercise resting levels during the first 3hours of exercise.
During rest and exercise, the coronary blood flow, and the demand of myocardium are coupled. The increased coronary blood flow during exercise is a result of coronary vasodilation and increased perfusion pressure of coronary artery. Most significant, increased sympathetic nervous system stimulation results in an increase of the circulating catecholamines. The response will trigger metabolic processes that increase coronary vasodilation and coronary artery perfusion pressure to meet the myocardium demand for exercise.
Stroke volume increases with the intensity of the exercise up to 40-60%of the maximum capacity after which it remains constant. All this occurs because the left ventricle completely fills thus stretching further to produce a more forceful contraction.
Long-term changes are in the hearts structure which augments the stroke volume. The adaptive responses include cardiac muscles hypertrophy which permits more force exertion on each heart beat. The increased thickness of septal and posterior left ventricular walls results in forceful contraction thus ejecting more blood.
(b) The Respiratory System
Pulmonary ventilation increases immediately due to feedback from proprioceptors located in the joints and muscles of the active limbs and stimulation of respiratory centre in the brainstem. During strenuous exercise increase in hydrogen ions (H+), CO2 production, blood and body temperatures cause a further increase in pulmonary ventilation. At low exercise intensity, the increased ventilation is a result of increased tidal volume while at higher intensities the rate of respiration also increases
The rate of respiration increases with an increase of oxygen and carbon dioxide being transported. The increase is also attributed to the influence of sympathetic nervous stimulation of the respiratory muscles. The rate of respiration increases up to 32 breaths per minute to allow more oxygen supply to the lungs and delivery of blood to the active muscles.
Working muscles have an increase in the oxygen demand and, therefore, more oxygen should be delivered. During strenuous exercise, veins constrict due to sympathetic nervous stimulation to return additional blood to the heart. This blood contains CO2 from the muscles, and it increases the hearts stroke volume by 30-40%.
Permanent changes in respiration
The long-term changes in the respiratory system are in the maximum pulmonary ventilation rate which is a result of increased respiratory rate and tidal volume and increased pulmonary diffusion due to increased pulmonary blood flow to the upper portions of the lungs.
2. With reference to the lung-function aspects of the practical, define the following terms:
- Tidal volume - is the amount of air that gets out of the lungs with each expiration or moves into the lungs with each inspiration.
- Volume expired - refers to the amount of air that is expired in one minute.
3. Suggest how individual subjects on the exercise bikes may vary. State what variation in expired air volumes these differences might cause and provide a brief anatomy & physiology-based rationale.
For subjects on exercise bikes, there is an increase in the tidal volume which is attributed to the ability of the lungs to contract and expand. The volume also expired increases because the respiratory rate and the tidal volume increased. Tidal volume and minute volume interacts with tissues in the lungs that exchange CO2 for oxygen. During exercise, to move air into the lungs, the tidal volume should increase to facilitate gas exchange and reduce the air proportion belonging to the dead space.
4. How did you decide on the resources to be used in your reference list and how did you explore each resource?
I chose the resources I used based on the content of the work that was needed in the report. I explored these resources via the internet and mostly I used the library physiology books narrowing into the relevant topics.
List of References
1.Guyton, A. and Hall, J. (2000). Textbook of medical physiology. Philadelphia: Saunders.
2.NursingLink, (2016). Exercise Physiology Basics. [online] Available at: http://nursinglink.monster.com/training/articles/354-exercise-physiology-basics [Accessed 2 Mar. 2016].
3.Susan M. Barman., Scott Boitano., and Heddwen Brooks., (2009). Ganong's Review of Medical Physiology, 23rd Edition. McGraw-Hill Publishing.
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