Transport in Animals Flashcards
Circulatory Systems
Circulatory Systems
- can be either closed or open
Single Closed Circulatory, heart with two chambers, blood passes through heart once every cycle
Double Closed Circulatory, heart with four chambers, blood passes through heart twice every cycle
Structures and Their Functions
Structures and Their Function
Arteries, carry blood away from heart to rest of body, thick walls withstand high blood pressure, elastic tissue allows stretch and recoil which smoothens blood flow, smooth muscle enables blood flow to vary (constrict blood flow), lined with smooth epithelium to reduce friction and ease blood flow
Arterioles, branch off arteries, thinner and less muscular walls, feed blood into capillaries
Capillaries, smallest blood vessels, site of metabolic exchange, one cell thin for fast exchange
Venules, Larger than capillaries but smaller than veins
Veins, carry blood from body to heart, wide lumen to maximise volume of blood to heart, thin wall as low blood pressure, valves prevent backflow, no pulse so little elastic and smooth muscle is needed
Tissue fluid, contains dissolved oxygen and nutrients, exchange for waste products like carbon dioxide, enables exchange of substances between blood and cells
- Hydrostatic pressure is created when blood is pumped from arteries into arterioles and into capillaries, hydrostatic pressure forces substances out of capillaries that are small enough (tissue fluid), fluid is acted on by osmotic pressure and some is pushed back into capillaries, potential of the tissue fluid is negative but it is less negative in comparison to the blood (the blood contains more solutes).
- Remaining tissue fluid is carried back via the lymphatic system
- Lymphatic system contains the lymph fluid, similar to tissue fluid, contains less oxygen and nutrients as its main purpose is to carry waste
Mammalian Heat and Cardiac Cycle
Mammalian Heart and Cardiac Cycle
- Heart is myogenic, able to initiate its own contraction
- Sinoatrial node (pacemaker) is located in the right atrium
- Ventricles do not start contracting till the atria have finished contracting due to presence of tissue at the base of atria which is unable to conduct the electrical signal
- electrical wave eventually reaches the atrioventricular node located between the two atria, which passes the electrical excitation to the ventricles down the bundle of His to the apex of the heart
- Bundle of His branches into Purkyne fibres which carry the wave upwards, causes ventricles to contract thus emptying them
Stages of the cardiac cycle
Atrial Systole, atria contract, forces atrio-ventricular valves to open and blood to flow into the ventricles
Ventricular Systole, Contraction of ventricles causes atrio-ventricular valves to close and semi-lunar valves to open, allowing blood to leave the left ventricle through the aorta and right ventricles through pulmonary artery
Cardiac Diastole, atria and ventricles relax, elastic recoil of hear lowers pressure inside heart chambers, blood is drawn from the arteries and the veins, causing semilunar valves to aorta and pulmonary arteries to close, preventing backflow.
Haemoglobin
Haemoglobin
- water soluble, globular protein, tow alpha and two beta polypeptide chains each containing a haem group, each molecule can carry four oxygen molecules
- affinity for oxygen depends on the oxygen concentration
- greater the amount of dissolved oxygen in cells the greater the partial pressure
- During respiration oxygen is used up so partial pressure decreases, thus decreasing the affinity for oxygen of haemoglobin, oxygen is released in the respiring tissue where it is needed (unloading), haemoglobin returns to lungs where it binds to oxygen (loading)
Saturation, after binding to the first oxygen molecule the affinity of haemoglobin for oxygen increases due to change in shape, thus making it easier for other oxygen molecules to bind
Fetal Haemoglobin, needs to be better at absorbing oxygen because by the time oxygen reaches the placenta, the oxygen saturation in the blood has decreased, must have a higher affinity for oxygen in order to survive at low partial pressures
Partial Pressure of Carbon dioxide, carbon dioxide is released by respiring cells which require oxygen. Therefore, in presence of carbon dioxide the affinity for oxygen of haemoglobin decreases, releasing oxygen for respiring cells (Bohr effect)
