Describe the components of plasma and explain their function

Plasma is the liquid component of blood, in which the red blood cells, white blood cells, and platelets are suspended. Plasma is mostly made up of water around 90-92% this helps with the transport of blood cells around the body, as it can flow easily. Plasma also contains dissolved salts (electrolytes) and proteins; it is a yellow coloured fluid that carries all blood cells.
Albumin is a protein contained in plasma, it helps keep fluid from leaking out of blood vessels and into tissues; this is useful for people that has lost large amounts of blood as it binds to and carries substances such as hormones and certain drugs. Plasma also contains clotting factors, such as fibrinogen, which control bleeding during an injury. (NHS, 2010)
Plasma contains other dissolved substances such as glucose, mineral ions, hormones and carbon dioxide; nutrients such as glucose and mineral irons, which have been digested and not used by the cells, will be transported to the kidneys and excreted as urine. During exercise excess carbon dioxide that has been formed will be transported by the plasma to the lungs and exhaled as a waste product.
figure 4

Describe the role of the nervous system in generating breathing rhythm

Breathing is automatic and is under the control of the brain and the automatic nervous system (ANS), this controls the functions that we do not think about but are necessary for life such as breathing, heart rate and blood pressure. The sympathetic side to the (ANS) is usually used when the body feels pressure, the parasympathetic helps the body to relax and conserve energy, and these both form part of the (ANS). The breathing rhythm is set to meet the needs of the body, the more carbon dioxide in the blood flow to the brain, will result in an increase of breathing in order to remove it, to speed up the reaction a signal is also sent to the heart, to increase the heart rate. This is all controlled by the medulla oblongata and the pons, which make up part of the brain stem.
(Wright, 2007)
Figure 3

Evaluate the conditions required for effective gaseous exchange

The exchange of gases is vital for our survival, gaseous exchange happens in thelungs, in the alveoli. For effective gaseous exchange a large surface area is needed to ensure an efficient gas exchange area, this is why the alveoli are tiny sacs bunched together to increase the area so that more gases can be diffused. The body would have to work harder to increase the oxygen intake and its supply of oxygen to the muscles if the surface area was smaller.
The thinner the cell wall the quicker diffusion can take place, the alveoli are made up of flattened epithelial cells making them only one cell thick, the capillaries are also only one cell thick, with the distance between the alveoli and capillaries being so thin it allows the gases to reach their destination quicker, letting oxygen diffuse into the blood and bind with the haemoglobin, making oxy-haemoglobin and then get transported around the body, carbon dioxide can diffuse back into the alveoli as a waste product ready to be exhaled. If the diffusion area were thicker this process would take longer.
The area needs to be moist, as gases need to be in solution to diffuse across a membrane, oxygen and carbon dioxide dissolve in this membrane. This makes it easier for the transportation as water can diffuse in and out of the alveoli. If the area weren’t moist the alveoli would dry out making diffusion harder. The water also contains a soapy surfactant, which reduces its surface tension and stops the alveoli collapsing. (Wright, 2007)
A steep concentration gradient of the gases needs to be maintained. Gases will always move from a high concentration to a low concentration, in a constant strive for equilibrium. This gradient is maintained by blood flow on one side carrying oxygen away quickly and by airflow on the other side. Oxygen can diffuse down its concentration gradient from the air to the blood, and carbon dioxide can diffuse down its concentration gradient from the blood to the air. (Wright, 2007