Flashcards in Cardiovascular System Part 2 Deck (57):
What is the Lymphatic System?
A key component of the immune system; it involves an extensive network of vessels. They collect excess interstitial fluid (comes lymph), and return it to the venous blood. It continuously picks up interstitial fluid and returns it to the heart.
What tissues and organs are involved in the lymphatic system and what do they do?
Lymph nodes, spleen, thymus, and tonsils. They remove viruses, bacteria, damaged cells, and cellular debris from lymph and blood stream. They defend the body against infection and cancer.
What does the right lymphatic duct do?
Drains the right upper portion of the body.
What does the Thoracic Duct do?
Drains most of the body.
What do Lymph Vessels do?
Return excess interstitial fluid to the blood.
What is the heartbeat produced by?
A cycle of contraction and relaxation of the atria and ventricles.
Where is the cardiac cycle initiated?
Within the heart.
What does the arterial blood pressure cycle through?
A high systolic and a low diastolic pressure.
What can some hearts do?
They have the ability to work independently of the circulatory system, allowing for heart transplants as it continues to contract outside the body.
What are Neurogenic Hearts?
Hearts that require external neural stimulus to beat (e.g. decapod crustaceans).
They need to be connected to the body to contract.
What are Myogenic Hearts?
(Humans) They have pacemaker cells. The membrane potential of pacemaker cells slowly depolarizes due to an increased inward current of Na+ and Ca2+, and a decreased outward current of K+.
Action potential is produced when L-type Ca2+ channels open at threshold, a large influx of Ca2+ causes rapid depolarization.
What is involved in the four-chambered pump of the mammalian heart?
Two atria (top of heart), two ventricles (bottom), atrioventricular valves (AV) between atria and ventricles, and semilunar valves (SL) between ventricles and aorta/pulmonary arteries.
What two circuits is blood pumped through?
Pulmonary circuit (right heart) and systemic circuit (left heart).
What does the Superior Vena Cava do?
Returns blood from head and upper limbs to the heart.
What does the Right and Left Pulmonary Veins do?
Return blood from lungs to heart.
What does the Inferior Vena Cava do?
Returns blood flow from trunk, legs to heart.
What does the Pulmonary Arteries do?
Sends blood to lungs from heart.
What does the Aorta do?
Returns blood to systemic circuit from heart.
True or False: Atrial/Ventricular Valves are active, as are the outflow valves.
False. Atrial/Ventricular Valves are passive, as are the outflow valves.
What happens when pressure reaches a valve?
If the greater pressure is behind the valve, it opens. If the greater pressure is in front of the valve, it closes.
What is systolic pressure?
Contraction of ventricles pushes blood into arteries at peak pressure. Highest blood pressure.
What is diastolic pressure?
Between contractions (right before the next contraction of the ventricles), blood pressure in the arteries falls to a minimum pressure. Lowest blood pressure.
What is the systole-diastole sequence called?
The cardiac cycle. It is triggered by the pacemaker cells within the cardiac cycle.
What is important about vertebrate heart walls?
They have thick, muscular myocardium that is sandwiched between the endocardium and epicardium. The myocardium consists of interlacing bundles of cardiac fibres arranged spirally; intercalated discs contain desmosomes and gap junctions. Impulses spread to all cells joined by gap junctions to form a functional syncytium.
What is the specialized electrical conducting system of the heart?
There may be other pacemakers (ectopic pacemakers), it's a specialized conduction system of the mammalian heart; spread of cardiac excitation. An AP is initiated at the SA node; spreads throughout both atria. Its spread is facilitated by two specialized atrial conduction pathways, the interatrial and internodal pathways, and the AV node is the only point where an action potential can spread from the atria to the ventricles. From the AV node, the AP spreads rapidly throughout the ventricles, hastened by specialized ventricular conduction system consisting of the bundle of Hid and Purkinje fibres.
What is an Electrocardiogram (ECG)?
Detection of the electricity of the heart; electrical currents generated by cardiac muscle can be detected using recording electrodes on the skin. This can be used to detect heart problems.
What does the P wave of an ECG represent?
What does the QRS complex of the ECG represent?
Ventricular depolarization (and atrial repolarization).
What does the T wave represent on the ECG?
What periods of the ECG have no current flow and what do they represent?
PR segment = AV nodal delay
ST segment = plateau phase
TP interval = passive ventricular filling while all chambers are at rest
What do the semilunar and atrioventricular valves do?
They stop blood from going from the ventricles back into the atrium.
Are atrial/ventricular valves tissues or muscles?
Tissues, they are passive and open/close depending on pressure.
What is the Electrical Control of the Heart in four steps?
1. Pacemaker generates a wave of signals to contract (fastest pacemaker prevails)
2. Signals are delayed in the region between the atria and ventricles
3. AV node cells are stimulated to produce a signal, which travels along Purkinje fibres to the bottom of the heart
4. Signals spread from the bottom of the heart upwards, causing the ventricles to contract
Before the P wave, what is the state of the ventricle and atrium?
Both are relaxed. There is slightly more pressure in the ventricle than the atrium.
Where is the blood entering the ventricles coming from?
The veins, the pressure is driven by the pressure from the veins.
What occurs in the P wave?
The atrium contract (atrial depolarization), and there is a slight increase in atrium pressure. The SA node propagates an AP, triggering the QRS complex.
What occurs in the QRS complex?
Ventricles start contractions, pressure of the ventricles surpasses the pressure in atrium. This makes the blood want to go back to the atrium/lungs, pressure in the atrium decreases and pressure in the ventricles increases so the AV valves close. This causes the first beat/sound (blood hitting the valve).
The pressure in the aorta is higher than the ventricles, so the blood wants to go to the ventricles from the aorta but this is the wrong direction, so when the ventricle contracts all valves are closed.
Isometric/isovolumetric ventricular contraction = the heart is contracting with no volume change (huge pressure change).
The ventricle will contract until the pressure is higher than the aorta, then the aortic valve will open, and there is a very fast reduction in the volume of the ventricle as blood quickly flows out.
What happens in the T wave?
Relaxation of the ventricle, repolarization, pressure goes down, isovolumetric/isometric ventricular relaxation. The pressure of the aorta passes the ventricle, aorta valve closes (second beat of the heart). The ventricle pressure goes down until it is lower than the atrium, and the cycle starts again.
What structure in the heart does the most work?
The ventricle; the aorta pressure is never close to zero because without pressure in the aorta there is no life.
What do arteries provide?
Rapid passage of blood from the heart to the tissues as large radii offer little resistance to flow; very large tubes, low resistance, high velocity. This is crucial to allow blood to flow at a high velocity and allow for life.
What do arteries serve as?
Pressure reservoirs as the arteries' elasticity enables then to expand during ventricular systole.
The elastic recoil is the driving force for the continued flow of blood during diastole.
What do the arteries do during cardiac systole?
The elastic arteries distend as more blood is ejected into them than drains off into the narrow, high-resistance arterioles.
What do the arteries do during cardiac diastole?
The elastic arteries recoil, continuing to drive the blood forward when the heart is not pumping. The arteries want to go back to their original size.
What is the maximum arterial blood pressure exerted on the arteries?
Systolic blood pressure, averages 120 mmHg in humans.
What is the minimum arterial blood pressure exerted on the arteries?
Diastolic blood pressure, averages 80 mmHg in humans.
What is arterial blood pressure expressed as?
A fraction; 120/80 mmHg.
What does the mean arterial pressure do?
It is the main driving force of blood flow.
Mean arterial pressure = diastolic pressure + (systolic pressure - diastolic pressure)
What is the Mean Arterial Pressure (MAP)?
It's determined by the cardiac output and peripheral resistance; the variables that affect it are:
1. Total peripheral resistance (TPA)
2. Cardiac output
MAP = Cardiac output * TPA (Ohm's Law); the amount of blood your heart is able to send to your arteries.
What is Cardiac output?
A measure of blood flow into the arterial system. Blood flow is directly proportional to pressure (flow = pressure/resistance), therefore an increase in flow will cause a proportional increase in pressure.
What is Total Peripheral Resistance?
Blood vessels provide resistance to the flow of blood because of friction between moving blood and the wall of the vessel. TPA refers to the vascular resistance of the flow of blood in the systemic circulation. Because of the small radii, arterioles provide great resistance to blood flow. If resistance increases, so does pressure. When arterioles vasoconstrict, TPA and MAP increase.
What is Cardiac Output determined by?
Heart rate and stoke volume. It is the volume of blood pumped by the heart per minuted (mL/min). Increasing either increases the cardiac output.
What is the heart rate?
Number of heart beats per minute.
What is stroke volume?
Volume of the blood pumped out of the heart with each beat (mL).
What is the most important factor controlling Total Peripheral Resistance?
The radius of the arterioles. Fluid flow obeys the hemodynamic flow law (Poiseuille's Law); Q (blood flow = deltaP/R
P = pressure, r = resistance.
Resistance is the hindrance to blood flow through a vessel caused by friction.
(R=resistance, n=viscosity, L=length, r=radius)
The major determinant of resistance is radius as resistance decreased with an increase in radii (by 16). Resistance is inversely proportional to the 4th power of the radius.
What is cardiac contraction a property of?
Cardiac contraction is myogenic, an intrinsic property of cardiac myoctyes (pacemakers).
What are the pacemaker cells?
Cells of the SA node.