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venous return
the volume of blood flowing back to the heart through the systemic veins, occurs due to pressure generated by contractions of the left ventricles.
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the skeletal muscle pump
at rest, the venous valves in the lower limbs are open and blood flows towards the heart. Contraction of the leg muscles pushes the blood through the proximal valve while closing the distal. As the leg relaxes the proximal valve closes and the distal valve opens
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the respiratory pump
during inhalation the diaphragm moves downwards which causes a decrease in pressure in the thoracic cavity and an increase in pressure in the abdominal cavity. As a result abdominal veins are compressed and a greater volume of blood moves into the thoracic veins and into the right atrium
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circulation time
is the time required for a drop of blood to pass from the right atrium, through the pulmonary circulation, back to the left atrium through the systemic circulation down to the foot and back to the right atrium
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cardiac accelerator nerve
how sympathetic impulses reach the heart from the CV centre in the medulla oblongata. Increase heart rate and contractility
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vagus X nerve
parasympathetic nerve that carries impulses from the CV centre decrease the heart rate and contractility.
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vasomotor nerve
the CV centre also continually sends impulses to smooth muscle in blood vessels via this nerve.
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vasomotor tone
the vasomotor region of the cardiovascular centre continually sends impulses over these routes to arterioles throughout the body. The result is a moderate state of tonic contraction or vasoconstriction
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baroreceptor
pressure sensitive sensory recepters are located in the aorta, internal carotid arteries. They send impulses to the CV centre to help regulate blood pressure.
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Baroreceptor reflexes: carotid sinus reflex
this helps regulate blood pressure in the brain
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Baroreceptor reflexes: aortic reflex
which regulates systemic blood pressure. nerve impulses from aortic baroreceptors reach the cv centre via sensory axons of the Vagus X nerves
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chemoreceptor reflexes
sensory receptors that monitor the chemical composition of blood. They detect changes in blood level of O2 CO2 and H+
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Renin- angiotensin-aldosterone (RAA) system
when blood volume drops or flow to kidneys decreases, renin is secreted into the blood stream. In sequence the renin and angiotensin converting enzymes act on their substrates to produce the active hormone angiotensin 2, which raises blood pressure
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Epinephrine and norepinephrine
in response to sympathetic stimulation the adrenal medulla secretes these. These hormones increase cardiac output by increasing the rate and force of heart contractions. They also cause vasoconstriction of arterioles and veins and vasodilation of arterioles in cardiac and skeletal muscle
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Antidiuretic hormone
is produced by the hypothalamus and is released by the posterior pituitary gland in response to dehydration or decreased blood volume. It causes vasoconstriction.
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atrial natriuretic peptide (ANP)
released from cells in the atria of the heart, ANP lowers blood pressure by causing vasodilation and by promoting loss of salt and water in urin which reduces blood volume
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autoregulation
the ability of tissue to automatically adjust its blood flow to match its metabolic demandes
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pulse
the alternating expansion and recoiling of elastic arteries after each systole of the left ventricle creates a traveling pressure wave
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sphygmomanometer
the device used to measure blood pressure
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systolic blood pressure
the force of blood pressure on arterial walls just after ventricular contraction
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diastolic blood pressure
represents the force exerted by the blood remaining in the arteries during ventricular relaxation
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kortokoff sounds
the sounds heard while taking blood pressure
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pulse pressure
the difference between systolic and diastolic pressure, usually 40 mmHg
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shock
is a failure of the cardiovascular system to deliver enough oxygen and nutrients to meet cellular metabolic needs
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hypovolemic shock
due to decreased blood volume. A common cause is acute (sudden) hemorrhage. It may be external or internal. Loss of other body fluids may also cause this
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cardiogenic shock
due to poor heart function. The heart fails to pump adequately. Most often because of a myocardial infarction (heart attack)
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vascular shock
due to inappropriate vasodilation
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obstructive shock
due to obstruction of blood flow
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circulatory routes
blood vessels are organized into these and carry blood to specific organs in the body.
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pulmonary circulation routes
need not be pumped as far as in the systemic routes. They carry blood to and from the lungs. These arteries are larger, with thinner walls and less elastic tissue. The resistance is very low meaning it requires very low pressure
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hepatic portal circulation
carries venous blood from the gastrointestinal organs and the spleen to the liver.
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hypertension
persistently high blood pressure. it is the most common disorder affecting the heart and blood vessels and is the major cause of heart failure, kidney disease and stroke
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aneurysm
a thin, weakened section of the wall of an artery or a vein that bulges outward, forming a balloon like sac . Common causes are syphilis, artherosclerosis, congenital blood defects and trauma
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deep venous thrombosis
the presence of a thrombus (blood clot)in a deep vein of the lower limbs
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hypotension
low blood pressure, most commonly used to describe an acute drop in blood pressure, as occurs during excessive blood loss
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occlusion
the closure or obstruction of the lumen of a structure such as a blood vessel
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phlebitis
inflammation of a vein involving clot formation
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thrombophlebities
inflammation of a vein involving clot formation
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