Sunday, January 07, 1996
In animal respiratory systems, the three main points are the gas exchange, the method of delivery and the exchange organ. In simple animals, diffusion exchanges the gases. As creatures became bigger and/or more active the respiratory system became more complicated.
Earthworms still diffuse oxygen through the skin, but they use blood to reach the inner cells.
Fish for example have gills to collect oxygen. Their gills are lungs which are like modified skin. The fish takes a mouthful of water and pushes it past the gills. The water goes toward the tail while the blood goes toward the head. This is called counter current exchange this maximizes the exchange so that the diffusion can occur all the way through the system. The opposite of this is parallel current exchange. (Check Book for Picture)
Insects have a weird respiratory system named the tracheal system. This is where there are tubes that carry air to individual cells. These tubes limit the size of insects. (See Book for Picture)
The human system of "passageways and lungs" collects oxygen and gets rid of carbon dioxide. After passing through the nose or mouth, pharynx, epiglottis, and larynx, it goes down the TRACEA which leads to the lungs. Cilia an mucus collects foreign dust particles. The airways branch and branch until they reach little sacs called ALVEOLI which have one cell thick walls that diffuse O2 and CO2. Remember that the cells get oxygen from the blood and give back carbon dioxide which diffuses out of the lungs and in comes oxygen.
The diaphragm moves up and down forcing air in and out of the alveoli. The diaphragm is relaxed in a dome position and flattens as it contracts. The brain controls breathing in the medulla oblongata. This occures unconciously and is regulated by O2 and CO2 sensors with priority given to the CO2 ones. Refer to the handout and know the functions of the terms listed.
Human respiration can be broken down into two parts: taking in air, transporting the gases. The air arrives via the negative breathing pressure. By increasing the chest cavity volume, we decrease the pressure and air flows in. Exhaling is the opposite. The gas transport uses the circulatory system. The hemoglobin was originally not needed as we were very calm creatures. The hemoglobin takes oxygen to form oxyhemoglobin. This goes to the tissues and via a diffusive process, breaks down. The CO2 goes back by turning into a bicarbonate ion. (H2O + CO2 H2CO3 H+ + HCO3-) This transformation is reversed in the lungs to release carbon dioxide.
This system is different in different animals. It was required to transport stuff in multi-cellular animals. It must transport CO2, O2, nutrients, wastes especially nitrogen, and hormones the chemical messangers. It must consist of a pump and vessels. The liquid used to transport the stuff is calleed blood. It consists of mainly water but includes inorganic molecules especially ions, organic molecules and blood cells.
Circulatory systems can be catagorized into two general catagories, open and closed. The open system found in a grasshopper (P.780) and other arthropods has a dorsal blood vessel and heart which pumps blood on the brain. The blood then oozes through the tissues back to the heart. This circulation is slow, but these animals use trachea tubes for their gases. A closed circulatory system is foun in earthworms and more evolved creatures. These vessels are all connected to form a loop. In vertebrates, their circulatory system can further be catagorized by the chambers of their hearts. Fis have two, reptiles have three and mammals have four. The chambers are separate except for blue babies who by genetic defectt have a hole in between chambers. These chambers are termed atria which receive blood and ventricles which pump out blood. Valves prevent backflow in the system.
The pulse that you feel is literally the artery expanding and rebounding. This increases and decreases as your condition changes. Normally, at rest and especially lying in bed just after waking up, the pulse is constant and 60 to 72 BPM. The pulse that increases when exercising does not continue to increase with a maximum of 220 BPM. The heart can first only beat so fast and the chambers can only take in so much blood so quickly to release it. The amount of blood that the heart pumps out in a minute is the cardiac output. This is controlled from the medulla and uses the sinoatrial node and then the atrioventricle node to make the heart contract.
The blood is made of a watery solute called PLASMA which comprises 55% by volume. RED BLOOD CELLS compries the 44% of the blood. These have no nucleus and only live for 120 days. Each cell has HEMOGLOBIN which contains iron and is a protein that collects oxygen. Hemoglobin can also carry carbon dioxide, but most carbon dioxide combines with sodium to fomr sodium hydrongen carbonate. WHITE BLOOD CELLS comprise 1% of the blood. PLATELETS prevent from bleeding to death by cloting blood.
Blood is catagorized into types depending on which antibodies (A or B) are present. ANTIGENS are foreign substances that make the immune system respond. ANTIBODIES are the things that react with antigens on the cell. (See Text P. 984 for picture on the A,B,AB,O Blood types. The Rh factor is the Rhesus factor which when the fetus's blood mixes with the mothers (being the opposite types of course) the antibodies form and the next baby's RBCs die from the antibodies.
ARTERIES carry blood away from the heart and are thick and flexible. The heart increases the artery pressure and you feel a pulse. The branches of arteries and veins are called atrioles and and venules respectively. The CAPILLARIES are the one cell thick vessels that diffuse stuff. The VEINS return the blood to the heart and have valces so that muscles can slowly push it back up.
The heart recieves blood from the VENAE CAVAE and into the right atrium. It is divided into the upper chambers, ATRIA, and lower muscle chambers, VENTRICLES. The blood leaves the heart by the AORTA and the left ventricle. The surge of blood as the ventricle compresses is called a PULSE. The same medulla oblangata controls heart rate. BLOOD PRESSURE is the pressure of the vessels that is exerted on the body. (Look at the graph in the book.) It is normally systelic120 mmHg (the high one) and diastolic pressure or low one is about 80 mmHg. The pulmonary vessels are reversed in terms of oxygen content. The artery is blue and the vein is red. These link from the output of the right ventricle to the left atrium.
The KIDNEYS remove liquid wastes from the body. The wastes go down the URETER tube and are stored in the UNRINARY BLADDER. Every filtering unit of the kidney is a NEPHERON. A lot of the ions, salts, glucose, water, amino acids, and vitamins are lost in the Bowman's capsule only to be reabsorbed downstream. This does active transport at this stage.
The system regulates salt while expelling nitrogenous wastes and amonia. The HYPOTHALAMUS uses antidiuretic hormon (ADH) to control the water in the blood.