Lesson 3 Flashcards
- What do we call the contraction of the heart? What do we call the relaxation of the heart?
The word systole refers to the contraction of the heart. Both atria contract at the same time, then both ventricles contract. The word diastole refers to the relaxation of the heart. After contraction of the four chambers occurs, the heart relaxes.
- What are the two heart sounds and what is each caused by?
The two heart sounds are termed “lub dub”. The first sound the “lub” is a longer lower pitched sound caused by vibrations that occur when the AV valves close. The “dub” sound is a shorter and sharper sound caused by the closure of the semi-lunar valves.3 wha
- What is another name for the SA node? Where is it located? What is its function?
The SA node, the sinoatrial node, is the pacemaker of the heart initiating the heartbeat. It is located in the upper dorsal (back) wall of the right atrium. This nodal tissue has properties of both muscle and nervous tissue and is unique to the heart.
Where is the AV node located? What is its function?
The AV node, the atrioventricular node, is located in the base of the right atrium. It initiates the contraction of the ventricles. The actions of the SA node and the AV node, the atrioventricular bundle and the Purkinje fibers are referred to as intrinsic control of the heart rate. Refer to Figure 5.6 on page 83 of the textbook.
6.What part of the brain is responsible for extrinsic control of the heart rate, and what part of the nervous system works with the brain to control the heart rate? What hormones also affect heart rate?
- The medulla oblongata located at the base of the brain, is the extrinsic control centre for heart rate. The medulla oblongata along with the autonomic system controls heart rate under extreme or abnormal circumstances. The hormones, epinephrine and norepinephrine can also affect heart rate.
- What is an electrocardiogram (ECG)?
- An ECG is a recording of the electrical changes that occur in the myocardium (heart muscle) during a cardiac cycle.
- What is a pulse? Where do we normally feel for a pulse? What is the pulse rate usually?
- A pulse is what we feel with each beat of the heart, as the arterial wall expands and recoils with the surge of blood that rushes through it. We normally feel for a pulse at sites of large arteries that are easily felt, such as the carotid artery in the neck or the radial artery in the forearm near the wrist. The pulse rate should be the same as the heart rate because the arterial walls should pulse with every contraction of the left ventricle. The pulse rate should therefore be approximately 70 beats per minute, but may vary between 60 to 80 beats per minute.
- What is blood pressure? What does systolic pressure represent? What does diastolic pressure represent? Where do we normally take blood pressure and what numbers represent the average blood pressure?
- Blood pressure is the pressure of blood against the wall of a blood vessel. Systolic pressure represents the pressure exerted against the arterial walls as blood is forced from the heart. It is the highest blood pressure. Diastolic pressure represents the pressure exerted against the arterial walls when the heart is relaxed. It is the lowest blood pressure. We normally take a blood pressure reading at the site of the brachial artery. The average blood pressure reading is approximately 120/80 mmHg.
- Describe the difference in blood flow between arteries, capillaries and veins.
- Blood flow through the arteries is fast and associated with a great deal of pressure due to the contraction of the heart. Blood flow through capillaries is much slower than arteries because there are more capillaries than arteries to handle the same volume of blood (increase in total cross-sectional area), and because the effect of the force of contraction of the left ventricle is less the further away you are from the heart. Blood flow through veins is slow as well but not as slow as capillaries because of the reduced cross-sectional area due to the fact that there are fewer veins than capillaries. Blood flow happens step-by-step as blood flows from one valve to another. We refer to blood pressure as being minimal in veins.
- What is the significance of blood flow in capillaries?
The slow movement of blood in numerous capillaries, ensures that there is plenty of time for substances to be exchanged between the capillary and the surrounding tissue.
- How is blood flow aided in veins?
Blood flow is aided in veins by three factors: skeletal muscle contraction, valves, and respiratory movements.
- What do we refer to the heartbeat as? What is considered to be a normal rate per minute for an adult at rest?
The heartbeat is also referred to as a cardiac cycle. A normal adult rate at rest is between 60-80 beats per minutes, 70 being the average.
