Sally was preparing vegetables for the evening meal when she cut herself with the knife. The cut bled profusely so she promptly put plaster on the cut and carried on preparing the food. A little while later she looked at the cut and noticed it had stopped bleeding. She was unsure as to the processes involved in the cessation of bleeding. In the space below summarise the process of haemostasis (the cessation of bleeding). In your summary you should include what happens during the three phases of haemostasis.
For answers see PowerPoint file provided
Blood pressure (BP) and its importance in health and disease. What is meant by the term blood pressure?
Blood pressure is the force of blood against the walls of arteries. Blood exerts pressure throughout the cardiovascular system, but is greatest within the arteries where it is generally measured and used as an indicator of good health. Blood pressure is the force exerted by the blood against the arterial walls and is determined by how much blood is pumped and the resistance to blood flow.
What are the two measurements taken in relation to blood pressure measurement? What are the 'healthy' values for each?
Systolic blood pressure is the pressure generated as blood is ejected from the heart during ventricular systole. 120mmHg During ventricular relaxation (diastole), the arterial blood pressure decreases and represents diastolic blood pressure. 80mmHg
How is mean arterial pressure (MAP) calculated and why is it important? The average pressure during the cardiac cycle is called the mean arterial pressure (MAP), and is important as it determines the rate of blood flow through the systemic circuit. Determination of MAP is not simply the average of systolic and diastolic pressure since diastole generally lasts longer than systole. However, MAP can be estimated in the following way: MAP = Diastolic blood pressure + 1/3 pulse pressure
For example if an individual has a blood pressure of 120/80 mmHg. pulse pressure = 120-80 = 40 mmHg
= 80 mmHg + 1/3 of 40
= 80 mmHg + 13
= 93 mmHg
How can systolic and diastolic blood pressure be recorded non-invasively and how does this method work? Recorded from the brachial artery by the use of a sphygmomanometer and stethoscope (see figure below). This method works on the principle that streamlined flow in an artery is silent but turbulent flow, which occurs when flow is intermittent, produces a tapping sound which can be heard through a stethoscope. The tapping sounds are called the KOROTKOFF sounds. The sphygmomanometer cuff is placed around the upper arm and when inflated it exerts pressure on brachial artery and thus can influence flow through it. When the pressure in the cuff is below diastolic blood pressure (DBP) flow is relatively unimpeded and thus is silent. When the pressure in the cuff is between the DBP and the systolic blood pressure (SBP) there is intermittent turbulent flow which sets up vibrations causing a tapping sound to be heard. When the pressure in the cuff is above SBP there will be no flow and hence silence.
High blood pressure (hypertension) is known as the 'silent killer' why is this? Hypertension is (140/90mmHg) seldom causes symptoms until secondary complications develop in the arteries, kidneys, brain, eyes or elsewhere. E.g. heart attack, stroke, kidney damage. Increased risk of cardiovascular problems e.g. atherosclerosis
Part C ECG and the cardiovascular system
Analyse the Following ECG traces:
Hint: When analysing ECG traces, consider the following:
1. What is the heart rate? Is it within the normal range of 60-100 beats per minute? 2. Is the rhythm regular?
3. Are all normal waves present in a recognizable form?
4. Is there one QRS complex for each P wave?
5. Are the P-R intervals constant in length?
1. What factor or factors could increase the size of the QRS complex of an ECG? Increased size of the QRS means an increase in the...
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