Systems Physiology SBEG103 Fall 2024 Lecture 7 PDF

Systems Physiology SBEG103 Fall 2024 Lecture 7: the cardiovascular system (CVS) Prof Aliaa Rehan Youssef [email protected]  What are our objectives for today? Describe the function of different components of the cardiova...

Systems Physiology SBEG103 Fall 2024 Lecture 7: the cardiovascular system (CVS) Prof Aliaa Rehan Youssef [email protected]  What are our objectives for today? Describe the function of different components of the cardiovascular system Introduce How heart function is regulated Give Examples On devices relevant to the cardiovascular system What is the cardiovascular system? Cardiovascular = Heart, Arteries, Veins, Blood The heart is a double pump heart®arteries ®arterioles ­ ¯ veins¬venules ¬capillaries  The Heart 4 chambers – 2 Atria – 2 Ventricles 2 systems – Pulmonary – Systemic  What does the cardiovascular system do? Function: – Transportation – Blood = transport vehicle – Carries oxygen, nutrients, wastes, and hormones – Movement provided by pumping of heart  Key components of the CVS Heart Blood Vessels Blood Acts as a hydraulic These are the pipes This is the fluid being pump, similar to those (arteries, veins, and transported. used in fluid capillaries) through It consists of red blood mechanics. which blood flows. cells (carrying oxygen), It has four chambers— Arteries carry blood white blood cells two atria and two away from the heart, (immune response), ventricles—that work veins return blood to platelets (clotting), and together to maintain the heart, and plasma (the liquid the pressure and flow capillaries facilitate the component). of blood. exchange of gases and nutrients at the cellular level.  Heart: what is it? Outermost = Pericardium & Epicardium – Pericardium is a membrane anchoring heart to diaphragm and sternum – Pericardium secretes lubricant (serous fluid) – Epicardium is outermost muscle tissue Middle = Myocardium – Contains contractile muscle fibers Innermost = Endocardium – Lines Cardiac Chambers Heart: what is it?  Heart: what in it? Cardiac Chambers Human heart has 4 chambers – 2 Atria Superior = primary receiving chambers, do not actually pump Blood flows into atria – 2 Ventricles Pump blood Contraction = blood sent out of heart + circulated Chambers are separated by septum… – Due to separate chambers, heart functions as double pump CARDIAC CYCLE  …To the rest of the body Deoxygenated …To the lungs Blood Oxygenated Blood  Circulation: Pulmonary Circulation Pulmonary = Deoxygenated Blood Involves Right Side of Heart Pathway: 1. Superior / Inferior Vena Cava 2. Right Atrium à Tricuspid Valve 3. Right Ventricle à Pulmonary Semilunar Valve 4. Left Pulmonary Artery 5. Lungs  Circulation: Systemic Circulation Systemic = Oxygenated Blood Involves left side of heart Pathway: 1. Left pulmonary vein 2. Left atrium à Bicuspid valve 3. Left ventricle à Aortic semilunar valve 4. Aorta 5. All other tissues  Circulation control Cardiac Valves [4 main valves] When the heart is relaxed… – Blood passively fills atrium – Flows right past tricuspid / bicuspid valves – Semilunar valves remain shut When the heart contracts (pumps)… – Tricuspid / bicuspid valves swing up and shut – Blood ejected out of ventricle – Semilunar valves open up Cardiac Cycle The double pump Conduction System  Conduction System Inherent and rhythmical beat is due to autorhythmic fibers of the cardiac muscle. These fibers have 2 important function - Act as pace maker - Form the conduction system  Conduction System SA node would initiate action potential about every 0.6 sec or 100 times/min Conduction System: Physiologic Characteristics Automaticity Excitability Conductivity Rhythmicity Contractility Tonicity Which system does the CVS mimic? The cardiovascular system (CVS) as a hydraulic system The cardiovascular system forms a system similar to a complex engineering network. It is responsible for the transport of fluids (blood), throughout the body. This system ensures that oxygen, nutrients, and waste products are efficiently exchanged between tissues and the environment. A drive technology where a fluid is used to move the energy from e.g. an electric motor to an actuator, such as a hydraulic cylinder. The fluid is theoretically uncompressible and the fluid path can be flexible in the same way as an electric cable. Heart as a mechatronic system Regulation of survival meschansisms Stimulus: Neural, chemical, or mechanical Control: Local, and central How fast response is needed? Neural, hormonal  Cardiac receptors Mechanically (Baroreceptors ) and chemically sensitive receptors located in atria and in ventricles. Under normal circumstances, cardiac receptors sense changes in wall motion or diastolic pressure A fine tuning of the cardiovascular system occurs accordingly  Cardiac receptors: Baroreceptors Baroreceptors are located in the carotid sinus and in the aortic arch. Sense pressure changes by responding to change in the tension of the arterial wall. The baroreflex mechanism is a fast response to changes in blood pressure.  Cardiac receptors: chemoreceptors Central chemoreceptors: Located within the medulla sensitive to the pH of their environment. Peripheral chemoreceptors: The aortic and carotid bodies Act principally to detect variation of the oxygen concentration in the arterial blood Monitor arterial carbon dioxide and pH.  Signal transmission Local: SA and AV nodes node Central: sympathetic and parasymapthetic  How heartrate is regulated by the medulla? ANS Sensory Input: The brainstem receives sensory input from various sources, including chemoreceptors, baroreceptors, and mechanoreceptors. These sensors detect changes in factors like blood oxygen levels, carbon dioxide levels, blood pressure, and stretch of the blood vessels and heart. Integration: The cardiorespiratory center in the medulla integrates this sensory information. It continuously assesses the body's needs and responds to maintain homeostasis. For example, if oxygen levels in the blood drop or carbon dioxide levels rise, the center will initiate adjustments to restore balance. Autonomic Nervous System: Sympathetic Nervous System: When the cardiorespiratory center in the brainstem detects a need for increased cardiac output, such as during exercise or in response to stress or a perceived threat, it signals the sympathetic nervous system. SNS releases chemical neurotransmitters (norepinephrine), which acts on the heart's beta-adrenergic receptors. This results in an increase in heart rate and force of contraction. Parasympathetic Nervous System: when the body is at rest or the cardiorespiratory center determines that it's necessary to lower heart rate, it signals the parasympathetic nervous system. The PNS releases chemical neurotransmitters (acetylcholine), which acts on the heart's muscarinic receptors, causing a decrease in heart rate.  Heart Rate (HR) Regulation The heart rate can be increased or decreased by impulses brought to the heart through two nerves from the medulla of the brain Local regulation: basal heart rate is determined within the heart by the pacemaker External regulation Stimulus: changes to blood pressure levels or CO2 concentrations (and thereby blood pH) Neural regulation: Nerve signals from the brain can trigger rapid changes Hormonal regulation: endocrine signals can trigger more sustained changes  Heart Rate (HR) Regulation When the heart rate changes, there are steps taken to try and return it to a normal rhythm. The relevant receptors send an impulse to the cardiac control centre that the HR is decreased, located in the medulla oblongata. The impulse then gets sent to the sinoatrial (SA) node along the sympathetic neurone where depolarisation occurs. The SAN releases noradrenaline which results in an increased heart rate Conversely, decreasing the heart rate is the opposite to the steps above. How heartrate is regulated by the medulla? Chemoreceptors Changes (high/low)in blood oxygen, pH or low carbon dioxide are detected Impulses are sent from the chemoreceptors to the medulla – this will send the impulse down parasympathetic/sympathetic neurones. This causes acetylcholine/ noradrenaline to be released in the cardiac muscle, binding to receptors on the SAN. The heart rate will slow/increase to return the oxygen, carbon dioxide and pH of the blood to normal levels.  Regulation of blood pressure Blood pressure regulation: – complex process. – Several mechanisms work in unison to maintain homeostasis. Rapid adjustments in blood pressure are typically neurally mediated by the baroreceptor reflex. Intermediate and long term regulation of blood pressure is predominantly mediated by vasoactive compounds. How heartrate/ Blood Pressure (BP) is regulated by the medulla? Baroreceptors If high blood pressure is detected impulses are sent from the baroreceptors to the medulla this will send the impulse down parasympathetic neurons. This causes acetylcholine to be released in the cardiac muscle, binding to receptors on the SAN. The heart rate will slow to decrease the blood pressure.  Example: Low blood pressure If low blood pressure is detected, impulses are sent down sympathetic neurones by the medulla. This causes noradrenaline to be realised in the cardiac muscle, binding to receptors on the SAN. The heart rate will speed up to increase the blood pressure.  Actuator Cardiac muscles: straited muscles Blood vessels: smooth muscles Cardiac muscle  Cardia muscle The basic contractile units the sarcomere Slides like skeletal muscle Passive Proteins (such as The titin filament) contains several spring sections, each with their own stiffness. The titin is the main determinant of muscle stiffness in diastole Heart Attack Devices  Heart Sounds Produced from blood turbulence caused by closing of heart valves S1 – ATRIOVENTRICULAR VALVE CLOSURE S2 – SEMILUNAR VALVE CLOSURE S3 – RAPID VENTRICULAR FILLING S4 – ATRIAL SYSTOLE iSthethoscope  Electrocardiogram (ECG) Can trace conduction of electrical signals through the heart Aberrant ECG patterns indicate damage ECG  Pacemakers A pacemaker helps monitor and control heartbeat. The electrodes detect your heart's electrical activity and send data through the wires to the computer in the generator. If the heart rhythm is abnormal, the computer will direct the generator to send electrical pulses to your heart. – Device that control heart rhythm – It uses low-energy electric pulses to regulate heart beats – Functional electric stimulation (FES)  Composition Three parts: 1. a pacemaker with body sensors, 2. pacing leads carrying pacing impulses, 3. a programmer.  Basics  Provide the rhythm heart cannot produce  Either temporary or permanent  Consists of external or internal power source and a lead to carry the current to the heart muscle  Batteries provide the power source  Pacing lead is a coiled wire spring encased in silicone to insulate it from body fluids 81  Types Pacing: Rate-responsive: Monitors the heart Speeds up or slows rhythm down the heart rate Sends only electrical depending on how pulses to the heart if it active the patient is. is beating too slowly or It monitors the if it misses a beat. sinoatrial node rate, breathing, blood temperature, and other factors to determine the activity level.  sensor detects a physical or physio- logical parameter that is related to metabolic demand. physician adjusts the An algorithm relates ‘algorithm’ to achieve changes in the sensed the clinically desired parameter to a change rate response. in pacing rate. Artificial heart is a prosthetic device that is implanted into the body to replace the original biological heart. Thank You