Circulatory system Flashcards
(32 cards)
Describe the Structure of an artery
- The artery is made of smooth inner lining(endothelium), to prevent turbulence in flow of blood.
- Small lumen to maintain pressure
- High ratio of elastin fibers to allow walls to stretch and recoils as blood is pumped in the artery, to maintain pressure.
- High amounts of collegen which prevents rupturing of wall and provides strength
Describe the Structure of an Vein
- Semi Lunar valves present to prevent back flow of blood
- Endothelium(Smooth inner lining) to prevent turbulence flow
- Thin walls as blood flows at low pressure, hence only few elastin and collagen is needed
- Large lumen
Describe the Structure of Capillary
-Only endothelium is present. One cell thick for short diffusion surface.
Semi permeable walls to allow to exchange of oxygen,CO2 and glusoce.
Differentiate between arterioles and venules
Arterioles carry oxygenated blood from arteries to capillaries. The consist of only endothelium and some muscle fibres. Serves to regulate the quantity of blood that enters capillaries.
The venules carries deoxygenated blood from the capillaries to the veins. They are consist of collagen and are thick and non elastic. Allows blood to drain into veins
Why is the heart described as closed and double?
The heart is a closed system because at no point is blood outside the blood vessel unless there is a cut.
Double circulation means blood travels through the heart twice through the pulmonary and systematic circulation.
Differentiate between pulmonary and systematic circulation
Pulmonary Circulation: Deoxygenated blood travels from the heart to the lungs via the pulmonary artery and returns via the pulmonary vein.
Systematic Circulation: Blood from the heart is pumped into the aorta to be carried to all the organs in the artery, except the lungs. Deoxygentaed blood is then carried to the vena cava through the veins.
Differentiate between the right and left side of the heart
The right heart pumps deoxygenated blood through the pulmonary circuit (to the lungs) while the left side pumps oxygenated blood through the systematic circuit (to the rest of the body)
Describe the inner structure of the heart
The heart is divided into 4 chambers. The two top thin walls are called the atria. The collect blood from veins and pump the blood into the lower ventricles. The right atrium collects blood form the vena cava (the body) and the left atrium collects blood from the pulmonary vein (from the lungs).
The lower chambers are called the ventricles. The are surrounded by thick muscles. They collect blood from the atria to be pump blood into the arteries. The right ventricle pumps deoxygenated blood to the pulmonary artery. The left ventricle pumps blood to the aorta.
The muscular wall of the left ventricle is greater than that of the right ventricle because the left ventricle has to pump blood to the entire body while the right atrium has to pump to the lungs which are nearby.
State the valves in the heart and their function
Valves prevent the back flow of blood. The values called atrioventricular values, separate atrium from ventricles. The values that separate the right atrium and right ventricle is call the tricuspid valve. The valve that separate the left atrium from the left ventricle is called the bicuspid valves.
The semi-lunar valves separate the ventricles from the arteries.
Describe the two phases of the cardiac cycle?
Systole and Diastole. Systole refers to the contraction of the atrium or ventricles. Diastole refers to the relaxation of the atrium or ventricles; blood enters. It begins with the contraction of the atria. It causes blood to rush into the ventricles and the AV valves to open. This is atrial systole. When the ventricles are full, ventricles systole begins. Contaction begins in the base of the ventricles and pressure becomes greater than that of the atrium, hence the AV valves close and the SL valves to open
Explain the cardiac cycle from the P wave to the QR complex
The SAN nodes fires off to causes the atrium to contract and begin atrial systole. This makes the pressure in the atrium to increase and causes the AV valves to open and blood flows into the ventricles. As atrial systole comes to an end and diastole begins, the pressure gradient reverses and causes the AV valves to close, producing the first heart sound, S1.
Ventricular Systole begins when the van begins to contract. Contraction begins at the base of the van and this is shown by the QR complex.
Explain the cardiac cycle from the RS complex to the T wave
As the vans start to contract, pressure builds up in the van and this is shown by the RS complex. When the pressure builds up to a point that is greater than the aorta and pulmonary artery, the semi-lunar valves open and rapid blood ejection begins. This is shown by the T wave. As ventricular systole comes to an end, pressure in the vans fall and this cause the SL valves to close, producing the second heart sound, S2. this starts ventricular diastole.
Why is the heart myogenic?
The heart is myogenic as it gives rise to its own contractions without interference of the nervous system. Specialized cells called cardiac cells initiate signals across the heart that makes it contract in a specific way. It ensure the ventricles contract after the atrium.
What are the names of the fibers that control the contraction of the heart
SAN ( Sino atrial node)
AVN (atrio ventricular nose)
Purkyne fibers
Role of the SAN
The SAN starts the cardiac cycles and is referred to the pacemaker of the heart. Every time it contracts, it sets up a wave of electricity impulse that spreads across the atrial walls, allowing it to contract with the SAN node
Roles of the AVN and purkyne fibres
The fibers in between the atria and ventricles cannot conduct the excitement wave released by the SAN. Instead, electric waves travel to the AVN. The AVN creates a delay in the contraction of the vans. The AVN carries the impulse down the septum along the purkyne fibers to the base of the heart. The impulse then travels up the walls of the ventricles, cause the ventricles to contract.
Define stroke volume
Stroke volume is the amount of blood ejected by each ventricle by the contraction
How does exercise affect cardiac output?
During exercise, there is a drop in oxygen amounts in the blood. The cells of the blood vessels react to this by creating nitric oxide. Nitric oxide relaxes the muscles of the arterioles and allows more blood the into the vein and hence the heart. The heart compensates by pumping more vigorously. The stretching of the heart muscles makes the SAN fire off more rapidly
What is cardiac output?
Cardiac output = stroke volume * heart rate
The amount of blood that leaves the heart over a given time.
Differentiate between sympathetic and parasympathetic nerves running to the heart?
The sympathetic nerve carries nerve impulses to the wall of heart muscles while parasympathetic nerves (vagus) nerves sends impulses to the SAN and AVN. If an action potential travels through the sympathetic nerves, to increases the heart rate and stroke volume, while if it run along the vagus nerve, it does the opposite.
State the role of baroreceptors
Baroreceptors are stretch receptors in the aorta and carotid arteries. If blood pressure rises in the heart, the aorta walls stretches to activate the baroreceptors to send a signal to the brain. the brain then sends an impulse via the vagus nerve to slow the heart rate. Low pressure has the opposite effect. The lack of stretching will make the brain send a signal along the sympathetic nerve to increase heart rate
Define blood pressure
blood pressure is the pressure of the circulating blood exerts on the walls of the blood vessels. It is divided in two types: systole and diastole blood pressure. Systole pressure is the highest of the two and is caused by the contraction of the left ventricle while diastole is the pressure of the relaxation of the ventricular muscles. Its is the most important number
what is atherosclerosis?
Atherosclerosis is the thickening of the blood vessels caused by high build up of cholesterol in the artery walls forming plagues
what is hypertension?
Hypertension is a persistently high diastole pressure (high blood pressure)