Gas Exchange 1/4/15 9:59 AM

O2 in

CO2 out

Adaptation of the alveolus ( singular form of alveoli)

-Need a large surface area

-Has to be moist, because materials can only diffuse in the same state

( liquid into liquid) the gas first dissolves into the outer liquid then diffuses in.

therefore it secrets fluid which also acts a detergents, preventing the sticking

together of the alveoli

-Needs to have a good transport system has to have a rich blood supply

( rich capillary network)

- small spaces for diffusion therefore thin walls.

All of the gas exchange happens with diffusion, so therefor there has to be a

concentration gradient, therefore a good transport system

3 mechanisims

ventilation breathing- moving air in and out using muscles

Gas exchange - O2 in CO2 out

Cell Respiration – releasing energy to form ATP with the use of oxygen which

produces CO2

Internal Intercostal muscles and external intercostal muscles on the ribs

Diaphragm is the muscle that separates the abdomen ( intestine) and

thoracic cavity

So when the diaphragm contracts it lowers the arch

When you inhale the

External intercostal muscle contracts moving the ribs up and out

The diaphragm contracts becoming flatter

The volume increase in the thoracic cavity

The pressure then decreases below atmospheric pressure

So the air want to come in because of pressure gradient

Therefore the lungs inflate

Air goes from high pressure in the chest cavity to less pressure to the lungs

which is now expands because of the contracts of muscles, so it comes via

the trachea into the lungs

When you exhale the

External intercostal muscle relaxes moving the ribs up and in

Abdominal muscle contract moving diaphragm into a dome shape

Volume decrease of the thorax

Pressure increases rises above atmospheric pressure

Air moves out to equalize till the lungs are back to atmospheric pressure

Diagram relaxes and the eicm relaxes too

No muscles in the lungs, it all has to with pressure

Because gas exchange is a passive process, a ventilation system is needed

to maintain a concentration gradient within the alveoli

This requires a high concentration of oxygen - and a low concentration of

carbon dioxide - in the lungs 

A ventilation system maintains this concentration gradient by continually

cycling the air in the lungs with the atmosphere

concentration gradients,

20% oxygen in 16% oxygen out

Adaptation of the alveolus ( singular form of alveoli)

Gas Exchange 1/4/15 9:59 AM1/4/15 9:59 AM

Hemoglobin is a protein which carries oxygen in the blood

The cell in which it is found are called erythrocytes

This cell has a

-plasma membrane

-inside is cytoplasm

- no nucleus

- few organelles

- has lots and lots of hemoglobin

Hemoglobin can bing to 4 oxygen molecules at one time and one carbon

dioxide molecule

Hemoglobin has

4 polypeptides

each have a haem group near the center

and each haem has a iron near it

and can transport 4 O2 molecules

each oxygen molecule adds to hemoglobin’s affinity to bond with another

oxygen until full

partial pressure is the pressure exerted by one gas in a mixture of gases

Myoglobin is similar but found in the muscles

Only has one haem group

Faster saturation as only needs one oxygen to be saturated

Stores oxygen in muscles to delay anaerobic respiration

Fetus hemoglobin has a higher affinity for oxygen

Therefore the oxygen will move from adult hemoglobin to fetal hemoglobin

in the capillaries of the uterus

Bohr Shift- Cells with increased metabolism (e.g. hypoxic tissue) release

greater amounts of carbon dioxide into the blood

Carbon dioxide lowers the pH of the blood (via its conversion into carbonic

acid) which causes hemoglobin to release its oxygen

This is known as the Bohr effect – a decrease in pH shifts the oxygen

dissociation curve to the right in tissues

Hence more oxygen is released at the same partial pressure of oxygen,

ensuring respiring tissues have enough oxygen when their need is greatest

Carbon dioxide transport

1st – a small percent dissolves into your blood plasma

2nd – 15-20 % carbon dioxide bonds with hemoglobin ( but only one) this

therefore lowers the affinity for oxygen , causing the Bohr shift

3rd- around 70% of CO2 enters the erythrocytes and converts into hydrogen

carbonate, and then moves to the blood plasma to be transported and will

not affect the PH of your blood

first t diffuses into the cell, then reacts with water ( sometimes catalysesd by

carbonic anhydrase) which produces carbonic acid, this quickly disassociates

to become hydrogen carbonate and hydrogen ions. The carbonate diffuses

out of the cell, while chlorine comes in to counterbalance the charge change,

this is the chloride shift, and then the h binds with the hemoglobin so it does

not change the PH of the blood. This is a buffering the ph.

Affect of exercise on ventilation

The use of muscles and ATP causes cell respiration to change drastically,

therefore consuming a lot more oxygen and making more CO2

Ventilation is controls by your medulla oblongata which is in your brainstem.

There are two mechanisms that determine when the rate needs to increase.

–Receptor cells ( chemoreceptors) located in you aorta ( Heart) and carotid

arteries detect a decrease in the CO2 levels because of the change in ph. So

when detected send an action potential message to the medulla.

- the medulla also has thee chemoreceptors, and when the blood passes

through the capillaries in the medulla, a decrease in PH is detected.

Blood is around 7.4 ( but when exercising heavily the buffering is not that

efficient and more CO2 builds up in the plasma and more H ions build up

increasing the concentration of H which decreases the PH. This changes to

around 7.0

To increase ventilation, the medulla sends action potential to the diaphragm,

intercostal muscles and abdomen telling it to fasten up, therofre changing

the frequency.

When physical exertion decrease the PH starts changing back which is then

detected by the same chemoreceptors, and action potential is sent again

decreasing the rate

Asthma

Asthma is a common, chronic inflammation of the airways to the lungs (i.e.

bronchi / bronchioles)

Inflammation leads to swelling and mucus production, resulting in reduced

airflow and bronchospasms

During an acute asthma attack, constriction of the bronchi smooth muscle

may cause significant airflow obstruction, which may be life threatening

Common asthma symptoms include shortness of breath, chest tightness,

wheezing and coughing

Asthma may be caused by a number of variable and recurring environmental

triggers, including:

Allergens (e.g. pollen, moulds)

Smoke and scented products (e.g. cigarettes, perfumes)

Stress and anxiety

Food preservatives and certain medications

Arthropods (e.g. dust mites)

Cold air

Exercise (increased respiratory rate)

High Altitudes

There is not less oxygen at higher altitudes

There is just less pressure , so the molecules are more spread out. This

therefore is less dense air, making oxygen diffusion less efficient.

At high altitude physical activity can cause fatigue, vision problems, nausea,

and high pulse. This is called mountain sickness

Our bodies compensate with faster ventilation.

Is however is not a long term solution, so acclimatization occurs.

-increase in erythrocytes

- increase in hemoglobin

- increase in amount and size of hemoglobin

- increase surface area, and size of lungs

- increase of myoglobin in muscle tissues

1/4/15 9:59 AM