The Respiratory System

Respiration is essential to human life; it provides oxygen and the energy which keeps us alive

The respiratory system supplies the blood with oxygen the blood then carries oxygen to all parts of the body, the respiratory system takes oxygen in through breathing (pulmonary ventilation) we inhale oxygen and exhale carbon dioxide through the nose (diffusion of gases) this process takes place between 15 and 25 times each minute.

Oxygen is inhaled through the nose and to the pharynx where the air is then passed through the larynx and to the trachea the bronchus then leads away from the trachea and to the lungs, this single bronchus splits into smaller bronchi which are narrow airways which make up the lungs known as the bronchial tree these supply air to a single lobe and then again to tertiary bronchioles which each supply a single part of that lobe. These tertiary bronchioles lead to the alveoli.
Alveoli is a thin walled sac with a moist inner surface that allows gases to be exchanged between the air and blood. Alveoli in a cluster look like a bunch of grapes there are lots of them so there is a greater surface area for the gas exchange to take place. We breath in around 21% of oxygen but we only breath out around 16% the remaining 5% passes through the walls of the alveoli through the thin walls and capillaries and into the blood. At the same time carbon dioxide passes in the opposite direction.

The respiratory system and exercise

In the short term the body has a number of responses to exercise such as:
Tidal volume increases
Breathing rate increases and becomes deeper and more regular
Heart beat increases supplying the demand for O2 in the working muscles
Gaseous exchange in the alveoli increases

The more muscles contract the more energy they use, to replace the energy the body needs to do more aerobic respiration, it needs to take more oxygen and breathe out more carbon dioxide. The body does this by increasing the breathing rate; this is a physiological adaptation that helps the body cope with exercise.
During exercise carbon dioxide levels rise these decrease the Ph levels in blood, there are receptors in the medulla, aortic bodies and carotid bodies called chemo receptors these detect changes in the ph of blood, if they detect and increase or decrease they send a signal to the medulla to send more frequent nerve impulses to the intercostals muscles and diaphragm, this then increases the rate and depth of breathing. Gaseous exchange then takes place co2 levels drop and extra o2 is supplies for the muscles.










references
cgp powerpoint respiratory handout
www.youtube.com
cgp handout physiological adaptations