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11 Cards in this Set

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Explain the events of the cardiac cycle.

(a) SA (sino atrial) node/pacemaker receives signal to fire;




when ventricle 70 %/almost full;




AV (atrio ventricular) valve opens and blood fills ventricle (to maximum) / atrialsystole;pressure increase in ventricle closes AV valve / ventricular systole;




AV node fires;




Purkinje fibres carry impulses to all areas of ventricles for simultaneous firing;




pressure increase causes semilunar valve to open;




blood pumped from ventricle to aorta/systole sound / ventricular diastole;




pressure lowers in ventricle closing semilunar valve / diastole sound;pressure in ventricle lower than atria so AV valve opens;




increases blood ventricular volume;both atria and ventricles are relaxed / diastole;atria receives blood from veins;




cycle repeats; [6 max]

Describe mechanisms that control heart beat

myogenic/ initiated in heart muscle itself




SA node sends impulse to atria




Stimulus to the AV node




Purkinje fibers conduct impulses to lower ventricles




adrenaline sends signal to heart and makes it beat faster

Outline the condition atherosclerosis and how it may cause coronary thrombosis. [4]

atherosclerosis – progressive degeneration of artery walls;




atheroma / lipids / cholesterol deposited on endothelium / wall;




fibrous tissue may also be laid down;blood flow is impeded causing platelets to stick;




clotting factors may then be released;a clot or thrombus may form;




if in coronary artery / arteriole flow of blood to part of heart muscle is reduced / stopped;




myocardial infarction / heart attack / cardiac arrest / heart failure; [4 max]

Explain the roles of the atria and ventricles in the pumping of blood.

The right atrium collects blood from the superior and inferior vena cava and the left atrium collects blood from the pulmonary veins.




This blood then flows into the right and left ventricle which pump the blood into the arteriesWhen the atria contract the blood flows through the atrioventricular valves which are open, into the ventricle




At this stage the semilunar valves are closed so the ventricle fills with blood. The ventricles then contract which causes a rise in pressure.




This rise in pressure first causes the atrioventricular valves to close preventing back flow of blood into the atria.

Describe the mechanism of ventilation in the human lung.

consists of inhaling and exhaling air / exchanging stale air with fresh air (with the environment)




external intercostal muscles contract moving the rib cage up/out




diaphragm contracts




increaes volume of thorax / lowers lung pressure relative to air pressure / pulls air in




diaphragm relaxes




abdominal muscles contract




internal intercostal muscles contract moving the rib cage down/inforce air out / decreases volume of thorax / raise lung pressure relative to air pressure

Explain the need for, and mechanism of, ventilation of the lungs in humans.

Need:


draws fresh air / oxygen into the lungs




removal / excretion of carbon dioxide




maintains concentration gradient of oxygen / carbon dioxide / respiratory gases




Inhaling:


diaphragm contracts




(external) intercostal muscles contract




increased volume (of thorax / thoracic cavity)




decreasing air pressure in lungsair




rushes in down air pressure gradient




Exhaling:


converse of the above causes exhalation




abdominal muscles contract during active exhalation




elastic recoil of lungs helps exhalation

State the differences between ventilation and gas exchange in humans.

ventialation:


movement of air




movement in and out of the lungs




caused by muscles




an active process




involves mass flow / involves flow along air passages




gas exchange:


movement of carbon dioxide and oxygen




(occurs when) oxygen moves from lungs / alveoli to red blood cells / carbon dioxide moves to lungs / alveoli from red blood cells




(occurs when) oxygen moves from red blood cells to tissues / carbon cioxide moves to red blood cells from tissues




a passive process / diffusion




takes place across a surface

Outline the events that occur within the heart, which cause blood to move around the body

blood is collectred in the atria




blood is pumped from the atria to the ventricles




opened atrio-ventricular valves allow flow from the atria to the ventricles




closed semi-lunar valves prevent backflow from the arteries to the ventricles




blood is pumped out from the ventricles to the arteries




open semi-lunar valves allow flow from ventricles to arteries




closed atrio-ventricular valves prevent backflow to the atria




pressure generated by the heart causes blood to move around the body




pacemaker (SAN) initiates each heartbeat

Describe the features of alveoli that adapt them to gas exchange.

A. large total surface area;


B. wall of single layer of flattened cells;


C. moist lining;


D. walls elastic;


E. dense network of capillaries;


F. capillary walls are thin / one cell thick;


G. short distance (for gases to travel);

Describe the structure of the ventilation system, including the alveoli [8]

- ventilation occurs within the lungs,


- trachea divides to form two bronchi


-alveoli connected to bronchioles


-diaphragm and intercostal muscles


-very small in diameter,


-many alveoli, increasing surface area


-wall of alveolus is a single layer of cells


-surrounded by a network of capillaries

Emphysema

A. Cause - carcinogens


B. Consequences - walls of alveoli damaged, no gas exchange possible, damage to bronchi/bronchioles


C. Treatment - inhalers, oxygen tubes