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BLOOD VESSELS, Major arteries branch into minor arteries and then into,…
BLOOD VESSELS
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BLOOD FLOWS THROUGH THE BODY VIA BLOOD VESSELS THROUGH THE CIRCULATORY SYSTEM MOVING TO REGIONS OF LOWER PRESSURE.
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Within the major artery- aorta- and throughout our arteries we have a similar blood pressure. This is the blood pressure that we measure.
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Blood pressure depend on total volume of blood within the cardiovascular system - about five litres at any time when well-hydrated.
If we are not well-hydrated our arteries will contract to bring our blood pressure up to an appropriate level so that we have the force that we need to support our capillaries to function.
Conversely, our arteries will dilate if we have too much fluid in our system in order to bring our blood pressure down to an appropriate level.
This is controlled by the cardiovasular centre of the brain. Sits within mid-brain/ medulla oblongata.See slide for more information.
Vascular resistance is the opposition to blood flow due to friction between the blood and the walls of the blood vessels. It depends on:
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CAPILLIARY NETWORK
Capillaries are:
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Known as exchange vessels because they permit the exchange of nutrients between the body's cells and the blood.
Able to auto-regulate. Auto-regulation is the ability of a tissue to automatically adjust its blood flow to match its metabolic demands.
Able to do that because of muscle fibers on the outside of the capillary network to enable it to control its blood pressure.
BLOOD FLOW
Several interconnected negative feedback systems control blood pressure and blood flow by adjusting heart rate, stroke volume,vascular resistance and blood volume.
The cardiovascular centre in the medulla oblongata helps regulate heart rate- pulse and stroke volume - amount of blood ejected from the heart with each beat.
The cardiovascular centre also controls the neural
(nervous system) and hormonal (endocrine system) negative feedback systems that regulate blood pressure and blood flow to specific tissues.
The cardiovascular centre also receives input from three main types of sensory receptors: proprioceptors, barorecepters and chemoreceptors.
Proprioceptors monitor movements of joints and muscles, provide input to the CV center during physical activity to cause a rapid increase in heart rate. Our muscles might need more energy and oxygen so the heart beats faster to bring those nutrients. Waste products can also exit as quickly as possible to minimise things like lactic acid build up.
• Baroreceptors (pressure receptors) are located in the aorta, internal carotid arteries and other large arteries in the neck and chest. They send impulses to the cardiovascular center to regulate blood pressure. Sending feedback to the CV system.
• Chemoreceptors (chemical receptors) monitor blood levels of O2, CO2, and H+ are located in the two carotid bodies in the common carotid arteries and in the aortic body in the arch of the aorta. The CV center responds by increasing sympathetic stimulation of arterioles and veins, producing vasoconstriction and an increase in B.P.
Several hormones help regulate blood pressure and blood flow by altering cardiac output, changing vascular resistance, or adjusting the total blood volume. The following hormones are involved:
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Pressure drops with each split of the artery. The further you go from the heartbeat the lower the pressure.
Arterioles take blood towards capiliary networks. Gas and nutrient exchange occurs in capiliary network.
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