Blood - Editors
The main reason for this particular blog is to teach myself about cardiovascular physiology in preparation for an exam next week... So I hope others will find this useful too!
Primary aims of circulation are to transport Oxygen and nutrients to tissues, whilst removing carbon dioxide and waste products of metabolism. The rate of flow is primarily determined by organ demand.
Structure of the heart
The heart is a muscle on a fibrous skeleton, with pumps on the left and right. Each side has an atrium and a ventricle. Blood enters through the atria, and is ejected from the ventricles. Coordinated pumping of all four chambers is essential. The right side is a low pressure pulmonary pump (going to the lungs), whereas the left side is a high pressure systemic pump (going to the rest of the body).
Cardiac muscle is formed of myocytes, specialised involuntary striated muscle, which is highly fatigue resistant. There are large numbers of mitochondria present, giving the heart a good blood supply.
Myocytes are interconnected by gap junctions, permitting rapid transmission of impulses from cell to cell. Electrical stimulation causes a full contractive force, which can be increased by adrenaline (epinephrine) and the Sympathetic Nervous System (SNS). These cells are able to produce action potentials automatically.
Metabolism in the heart is 99% aerobic (60% free fatty acids, 35% carbohydrates and 5% arachidonic acid) and 1% anaerobic.
Blood vessels
Arteries - carry oxygenated blood away from the heart (except pulmonary artery), are muscular with elastic recoil, and are resistance vessels.
Veins - carry deoxygenated blood to the heart (except pulmonary vein), have no muscular layer, low resistance, skeletal muscle pumps with valves to maintain flow.
Microcirculation - arterioles, venules and capillaries, which are one cell thick, autoregulated, allowing bidirectional flow of gases and metabolites across cell wall.
Blood pressure
Blood pressure is generated by cardiac contraction, a result of systolic squeeze and diastolic relaxation. This is pulsatile in the arteries. The cardiac cycle itself is 1/3 systolic and 2/3 diastolic and is regulated by the renin-angiotensin system. When the volume of blood is low, the kidneys secrete renin, which stimulates the production of angiotensin, causing blood vessels to restrict, resulting in increased Blood Pressure. Blood pressure is affected by many extrinsic factors and mean blood pressure increases with age.
Blood volume
There are 42 litres of blood in the body (60% and 50% of which is water in males and females respectively). Of the 42 litres, 25 litres is intracellular and 17 litres is extracellular. The cardiac output (Q) is calculated by multiplying stroke volume (the volume of blood pumped out per beat by the left ventricle, equivalent to 70ml x 70 b.p.m.) and heart rate together.
Electrical impulses
Signal is initiated in the SA node (sino-atrial), which is located in the wall of the right atrium, generating sinus rhythm and functioning as a pacemaker. The atria are electrically isolated from ventricles, with the AV node (atrio-ventricular) being the only conductive point. Purkinje fibres rapidly carry signal from the AV node to the ventricles.
Autonomic nervous system (ANS)
Made up of the sympathetic Nervous System (fight or flight, adrenaline/noradrenaline) and the parasympathetic nervous system (rest and digest, acetylcholine). This provides autonomic control of heart rate. Adrenaline and noradrenaline increase the opening of calcium and sodium channels, causing an increase in SA node firing. Acetylcholine increases opening of potassium channels, causing a decrease in SA node firing. Baroreceptors compensate for a fall in blood pressure from a supine to standing position by signalling to the medulla oblongata, which controls vasoconstriction and dilation.
Oxygen
The quantity of oxygen transported to tissues is determined by multiplying oxygen content by cardiac output.
Factors affecting this are split into central (effective respiratory gas exchange, adequate CV reserve, haemoglobin to transport oxygen) and peripheral (regional blood flow, microcirculation, oxygen-haemoglobin affinity, tissue oxygen extraction).
The quantity of oxygen consumed by tissues, VO2, which is the difference between amount of oxygen delivered to tissues and the amount of oxygen returned to the heart, is determined by the Fick equation.
The main reason for this particular blog is to teach myself about cardiovascular physiology in preparation for an exam next week... So I hope others will find this useful too!
Function of circulation
Circulatory system
There are two distinct circulations present within the system, the pulmonary system from the right side of the Heart (8% of blood), the systemic system from the left side of the heart (85% of blood, 65% of which is in veins (and that's where our similarity ends)) and the heart, which pumps the remaining 7% of blood.
Structure of the heart
The heart is a muscle on a fibrous skeleton, with pumps on the left and right. Each side has an atrium and a ventricle. Blood enters through the atria, and is ejected from the ventricles. Coordinated pumping of all four chambers is essential. The right side is a low pressure pulmonary pump (going to the lungs), whereas the left side is a high pressure systemic pump (going to the rest of the body).
Cardiac muscle is formed of myocytes, specialised involuntary striated muscle, which is highly fatigue resistant. There are large numbers of mitochondria present, giving the heart a good blood supply.
Myocytes are interconnected by gap junctions, permitting rapid transmission of impulses from cell to cell. Electrical stimulation causes a full contractive force, which can be increased by adrenaline (epinephrine) and the Sympathetic Nervous System (SNS). These cells are able to produce action potentials automatically.
Metabolism in the heart is 99% aerobic (60% free fatty acids, 35% carbohydrates and 5% arachidonic acid) and 1% anaerobic.
Blood vessels
Arteries - carry oxygenated blood away from the heart (except pulmonary artery), are muscular with elastic recoil, and are resistance vessels.
Veins - carry deoxygenated blood to the heart (except pulmonary vein), have no muscular layer, low resistance, skeletal muscle pumps with valves to maintain flow.
Microcirculation - arterioles, venules and capillaries, which are one cell thick, autoregulated, allowing bidirectional flow of gases and metabolites across cell wall.
Blood pressure
Blood pressure is generated by cardiac contraction, a result of systolic squeeze and diastolic relaxation. This is pulsatile in the arteries. The cardiac cycle itself is 1/3 systolic and 2/3 diastolic and is regulated by the renin-angiotensin system. When the volume of blood is low, the kidneys secrete renin, which stimulates the production of angiotensin, causing blood vessels to restrict, resulting in increased Blood Pressure. Blood pressure is affected by many extrinsic factors and mean blood pressure increases with age.
Blood volume
There are 42 litres of blood in the body (60% and 50% of which is water in males and females respectively). Of the 42 litres, 25 litres is intracellular and 17 litres is extracellular. The cardiac output (Q) is calculated by multiplying stroke volume (the volume of blood pumped out per beat by the left ventricle, equivalent to 70ml x 70 b.p.m.) and heart rate together.
Q = SV x HR
Electrical impulses
Signal is initiated in the SA node (sino-atrial), which is located in the wall of the right atrium, generating sinus rhythm and functioning as a pacemaker. The atria are electrically isolated from ventricles, with the AV node (atrio-ventricular) being the only conductive point. Purkinje fibres rapidly carry signal from the AV node to the ventricles.
Autonomic nervous system (ANS)
Made up of the sympathetic Nervous System (fight or flight, adrenaline/noradrenaline) and the parasympathetic nervous system (rest and digest, acetylcholine). This provides autonomic control of heart rate. Adrenaline and noradrenaline increase the opening of calcium and sodium channels, causing an increase in SA node firing. Acetylcholine increases opening of potassium channels, causing a decrease in SA node firing. Baroreceptors compensate for a fall in blood pressure from a supine to standing position by signalling to the medulla oblongata, which controls vasoconstriction and dilation.
Oxygen
The quantity of oxygen transported to tissues is determined by multiplying oxygen content by cardiac output.
delivery O2 = CaO2 x Q
Factors affecting this are split into central (effective respiratory gas exchange, adequate CV reserve, haemoglobin to transport oxygen) and peripheral (regional blood flow, microcirculation, oxygen-haemoglobin affinity, tissue oxygen extraction).
The quantity of oxygen consumed by tissues, VO2, which is the difference between amount of oxygen delivered to tissues and the amount of oxygen returned to the heart, is determined by the Fick equation.
consumption O2 = Q x (CaO2 - CvO2)
If you would like more information on Osteopathy, your suitability to certain exercise/sport, or are unsure whether osteopathy can help with any problems you may have, it may be worthwhile coming to see us at Hashim Saifuddin Osteopathy, where we can explain your problems to you, why they occur and whether or not you are suitable for osteopathic treatment. Often this can be done via email or on the phone.
Visit http://www.hashim-osteopathy.co.uk/ for more information or feel free to email me on [email protected]
Thanks for reading!
Hashim Saifuddin (M.Ost DO ND)
GOsC Registered Osteopath
Osteopathy / Sports Osteopathy
Visit http://www.hashim-osteopathy.co.uk/ for more information or feel free to email me on [email protected]
Thanks for reading!
Hashim Saifuddin (M.Ost DO ND)
GOsC Registered Osteopath
Osteopathy / Sports Osteopathy
