transport in mammals

Explain how the structure of the tunica media is different from the structure of the tunica media in a muscular artery and relate the difference to the function of the aorta

• tunica media of aorta contains more elastin / less smooth muscle;

• aorta stretch; during ventricular systole;

• aorta recoils; maintain high blood pressure; evens out flow of blood;

State the changes that will occur in the cardiovascular system as a result of reduced nicotine levels.

• blood pressure decreases;

• platelets no longer sticky / lower risks of thrombosis / lower risks of blood clotting;

• endothelial repair more successful;

• heart rate decreases;

Compare the structure of a muscular artery with the structure of an arteriole.

similarities

• tunica intima;

• tunica media / smooth muscles;

differences

• wider lumen;

• more smooth muscles;

• thicker tunica media;

• more elastic fibres;

• no elastic lamina;

• more collagen fibres;

Explain, with reference to their functions, the difference in the thickness of the walls of the left ventricle and right ventricle of the heart.

• right ventricle pumps blood to lungs, left ventricle pumps blood to the rest of the body;

• shorter distance;

• less resistance;

• less force / pressure;

Describe the roles of sinoatrial node (SAN) and the atrioventricular node (AVN) in the initiation and control of the cardiac cycle.

SAN

• pacemaker / initiate heart beat / initiate cardiac cycle;

• release waves of excitation / electrical impulse;

• spread across atria, lead to systole;

AVN

• allow delay ~0.1s;

• passes impulse to Purkyne fibres / down septum;

• further detail eg. atria contract before ventricles / ventricles to fill;

Explain why it is important for the control of the cardiac cycle that there isa short delay at the AVN after impulses have been sent out by the SAN.

• atria and ventricles not in systole at the same time;

• ventricles contract after atria;

• idea allow atria to empty completely, allow ventricles to fill;

Compare the percentage saturation and volume delivered to tissues of oxygen for day 1 at 1530m and day 14 at 5700m

• decrease in percentage saturation, same quantity of oxygen delivered to tissues;

• high altitude lower partial pressures of oxygen in atmosphere;

• in lungs, less oxygen binds to haemoglobin;

• hemoglobin has lower affinity for oxygen;

• increased production of haemoglobin; density of red blood cells;

• more haemoglobin to bind to oxygen so same quantity as at sea level;

Describe the differences between blood arriving at the arterial end of the capillary network and the tissue fluid surrounding the body cells

• red blood cells;

• more white blood cells;

• has platelets;

• more plasma proteins;

• higher concentration of oxygen;

• higher concentration of glucose / amino acids;

• lower concentration carbon dioxide / urea;

• higher pressure;

Explain how the control of the heartbeat by the sinoatrial node can be disrupted by AF, resulting in rapid and irregular atrial contractions.

• normally only SAN sends out impulse;

• ref. to extra impulse;

• atrial systole occur when it should be diastole;

• impulses interfere;

• SAN no longer able to act as pacemaker;

• rapid since extra contractions;

Describe the role of carbonic anhydrase in the transport of carbon dioxide.

• catalyse reaction between water and carbon dioxide in red blood cells;

• form carbonic acid which dissociates to form HCO3- and H+;

• HCO3- diffuses into plasma;

• enzyme maintains steep concentration gradient for CO2 to diffuse into red blood cells;

• helps remove large quantity of carbon dioxide;

• in lungs, HCO3- converted back to CO2 to be excreted;