Case 1 + 2 - heart Flashcards
Dorsal motor nucleus of the Vagus (DMNV)- nervous effect on cardiac output
In the medulla oblongata. When activated it inhibits the SA node which decreases heart rate, decreasing cardiac output and mean arterial pressure. Parasympathetic and mediated via vagus nerves
Rostral ventrolateral medulla (RVLM)- nervous effect on cardiac output
In the medulla oblongata. When activated by sympathetic outflow, mediated by the nerves. It stimulates the SA node causing heart rate, cardiac output and mean arterial pressure to increase. Also causes the constriction of smooth muscle in the blood vessels. Vasoconstriction increases mean arterial pressure
Nucleus tractus solitarius (NTS)- nervous effect on cardiac output
When there is an increase in blood pressure this will be detected in the baroreceptors in the ceratoid sinus and aortic arch. This will fire action potential along the Glossopharyngeal nerve and vagus nerve respectfully, to the Nucleus Tractus Solitarius (NTS) in the medulla Oblongata. This will then stimulate the DMNV to produce its effect, and inhibit the RVLM.
The effects of posture on arterial blood pressure
When you stand up blood pools in your legs and less returns to your heart, decreasing blood pressure in the aorta. This will be detected by baroreceptors which will stretch less. Less firing to the NTS, less stimulation of DMNV and less inhibiting RVLM. This will increase cardiac function, heart rate, cardiac output and finally blood pressure. Vasoconstriction also occurs due to the RVLM, this increases the resistance and blood pressure. There will be an increase in sympathetic which increases peripheral resistance, and a decrease in parasympathetic which increases heart contraction. This will readjust the blood pressure back to normal. Increasing the blood supply to the brain
Stopping blood loss from blood vessels
The smooth muscle in the blood vessel constrict when the blood vessel is broken, this increases blood pressure but reduces blood flow and blood loss. This causes nervous reflexes initiated by pain and local myogenic contraction of blood vessels. Platelets releasing thromboxane A2 and serotonin which cause vasoconstriction. The thrombin generated in the coagulation cascade triggers the endothelium to release endothelin-1 which is a vasoconstrictor. This whole process is the vascular spasm. Platelets will plug the hole
Blood as a pump
The left and right side of the heart act as two pumps. The pump on the right side of the heart send blood to the lungs, when they contract to be oxygenated. When the left ventricle contract the blood is sent around the body.
The walls of the heart
The walls of the ventricles are much thicker than the walls of the atria, because the ventricles need to develop more force when they contract, as in the left ventricle the blood needs to go around the whole body. For the right ventricle, the force generated needs to be relatively small because the blood is only going to the lungs which aren’t very far away. If too high a pressure is developed, tissue fluid would accumulate in the lungs hampering gas exchange. In the atria the blood is only going to the ventricles.
The walls of the arteries
Have a small lumen with thick walls, especially the tunica media. The walls are thick because the blood us at high pressure, so they need to be strong, so they don’t burst. There is lots of elastic fibre in the tunica media which allows walls to stretch as pulses of blood surge through at high pressure, this makes the artery wider reducing the pressure. It recoils when low pressure blood goes through so the artery becomes narrower and the pressure increases. This evens out the flow of blood.
The walls of the capillaries
They are small allowing them to get as close as possible to the cells, the walls are only one cell thick, so the oxygen does not have to diffuse far. The pressure of blood is low in the capillaries. The walls are made up of only a single layer of endothelial cells.
The walls of the veins
The vein walls are thin as blood pressure is low, so they do not have to withstand a high force. To keep blood flowing in the right direction, semilunar valves allow blood to move towards the heart and not away from it. Blood is returned in the veins by tensing muscles raising the pressure
Acute inflammation
When a tissue is damaged, the damaged cells release chemicals which are a distress signal. This causes increased blood flow and blood vessels become leaky. The distress signals also attract white blood cells to clear the germs and dead cells. Once the wound has healed, the process stops and recovery follow
Chronic inflammation
The same steps as acute inflammation but with no recovery. Leads to a negative effect on organs and tissues
Pulmonary arteries
The pulmonary trunk carries deoxygenated blood from the right ventricle. It splits into the left and right pulmonary artery which take blood to the left and right lung respectively, the blood is then oxygenated.
Pulmonary vein
The pulmonary veins take oxygenated blood from the lungs to the left atrium where its pumped to the left ventricle and then around the body through the aorta. There is a pulmonary vein on both the left and right side.
Mechanical events that happen during the cardiac cycle
1) Ventricular filling- occurs during ventricular diastole (relaxation). Pressure is low and blood flows in from the venous system
2) Atrial contraction- atrial systole, this contraction will push blood from the atrium to the ventricle
3) Isovolumetric ventricular contractions- ventricles are stimulated electrically to contract, this squeezes the blood. All valves close, pressure increases, volume doesn’t change.
4) Ventricular ejection- ventricular systole, pressure is higher than the arteries and the blood moves down the pressure gradient from the ventricles to the arteries
5) Isovolumetric ventricular relaxation- ventricles relax, all valves close, pressure decreasing, volume not changing.
