Lec 13 exam notes

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23 Apr 2012
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LEC 13 exam notes!
Circulatory System (Network) Analysis
Organ Function:
Heart – Pump Blood
Kidney – filter and adjust volume and content of blood plasma, indirectly control
blood pressure
Spleen – filter and remove old red cells and platelets, site of maturation of white
blood cells
Thymus – site s of maturation of white blood cells, major site of antigen presentation
and memory formation in B cell populations
Tonsils (4 types) – site of storage and maturation of white blood cells
*note: redundancy in System!
The Heart as a Muscular Pump
• The heart is made of cardiac muscle tissue called myocardium
• What makes cardiac muscledifferent from skeletal muscle?
Neural input: involuntary, autonomic
Neural conduction: gap junctions …very fast, contract as a unit i.e. no fibre recruitment like skeletal
muscle
(in wave-like action)
Metabolism: VERY high oxidative
capacity (lots of mitochondria) – fatigue resistant
*has to beat for a lifetimes -- 100,000/day Roughly 3 BILLION total
The Heart as a Muscular Pump
The right side of the heart (pulmonary circuit)
– Contains blood rich in carbon dioxide
• Returns from the tissues
• Flows out to the lungs
The left side of the heart (systemic circuit)
– Contains blood rich in oxygen
• Returns from the lungs
• Flows out to the tissues
*physicians can diagnose valve problems with a stethoscope
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The Heart – Controlling Direction of Blood Flow with Valves
“LUB” – enter atria “DUB” – leave ventricles
Tricuspid, mitral Pulmonary, aortic
Atrioventricular (AV) valves are located between each atrium and ventricle.
Semilunar valves are located between each ventricle and its artery.
Give rise to the typical “lub dub” sounds of the heartbeat
The Heart – Controlling Direction of BloodFlow with Valves
Just as in large veins, there can be problems with heart valves.
Example:
• Stenosis – narrowing of a valve. May be congenital, due to calcification, or scarring
from rheumatic fever. Vary in terms of seriousness … can cause fatigue and
shortness of breath, exercise intolerance, or in more serious cases heart failure,
fluid buildup in lungs (pulmonary edema and hypertension) and death. Sites where
this tends to occur:
• Aortic valve: between left ventricle and aorta
• Mitral valve: between right atria and ventricle
*doctors can hear these abnormalities!
Artificial Heart Valves
Issues:
• durability – supposed to last 20+ years
• clot formation – requires consistent anticoagulant therapy
• getting stuck
• resistance to flow; vulnerability to backflow and regurgitation
Biological values are an alternative (usually porcine, or pig)
• refered to as xenotransplantation (between species) – requires
immunosupression therapy
*need blood thinners & immune suppressive drugs!*
The Heart as a Muscular Pump
• The cardiac cycle
–– Contraction of the atria
– Followed by contraction of the ventricles
-Followed by a rest when neither chamber is contracting
• Contraction is called systole systolic blood pressure
• Relaxation is called diastole diastolic blood pressure
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