BMS 100 Clinical Physiology II PDF

Clinical Physiology II Fundamental Physiologic Basis of the Vital Signs Dr. Maria Shapoval BMS 100 Week 2 The Vital Signs Modeling the cardiovascularcardiorespiratory system Blood pressure Heart rate Respiratory rate Major pulses Post-learning: Elements of thermoregulation Temperature The Cardi...

Clinical Physiology II Fundamental Physiologic Basis of the Vital Signs Dr. Maria Shapoval BMS 100 Week 2 The Vital Signs Modeling the cardiovascularcardiorespiratory system Blood pressure Heart rate Respiratory rate Major pulses Post-learning: Elements of thermoregulation Temperature The Cardiovascular System – A Model • A pump • Flexible, muscular vessels • A very large number of tiny vessels • Large-capacity vessels The Cardiovascular System – A Model • A pump ▪ The heart • Flexible, muscular vessels ▪ Arteries and arterioles • A very large number of tiny vessels ▪ capillaries • Large-capacity vessels ▪ Venules and veins The Cardiovascular System – A Model • A pump ▪ The heart • Flexible, muscular vessels ▪ Arteries and arterioles • A very large number of tiny vessels ▪ capillaries • Large-capacity vessels ▪ Venules and veins The Systemic and Pulmonary Circulations Pulmonary Circulation Systemic – role • Left heart applies high pressure to high-O2, low-CO2 blood • Systemic veins return low-O2, highCO2 blood to the right heart • Systemic arteries + arterioles deliver this blood to most tissues • Systemic capillaries allow tissues to extract O2 from and deliver CO2 to blood The Systemic and Pulmonary Circulations Pulmonary Circulation Systemic – role • Left heart applies high pressure to high-O2, low-CO2 blood • Systemic veins return low-O2, highCO2 blood to the right heart • Systemic arteries + arterioles deliver this blood to most tissues • Systemic capillaries allow tissues to extract O2 from and deliver CO2 to blood The Systemic and Pulmonary Circulations Pulmonary – role • Right heart applies moderate pressure to low-O2, highCO2 blood • Pulmonary arteries + arterioles deliver this blood to the lung Systemic Circulation • Pulmonary veins return high-O2, lowCO2 blood to the left heart • Pulmonary capillaries allow lung tissue to deliver O2 to and extract CO2 from blood The Systemic and Pulmonary Circulations Pulmonary – role • Right heart applies moderate pressure to low-O2, highCO2 blood • Pulmonary arteries + arterioles deliver this blood to the lung Systemic Circulation • Pulmonary veins return high-O2, lowCO2 blood to the left heart • Pulmonary capillaries allow lung tissue to deliver O2 to and extract CO2 from blood Think-Pair-Share • 4 minutes – apply the labels to the correct structure in the table • 5-minutes – turn to the person next to you and check your work ▪ Bonus vessels – for those of you that remember your undergrad anatomy or physiology well • Put an “S” if the vessel is systemic, or a “P” if pulmonary Vessel Label “S” / “P” D Aorta Pulmonary artery Pulmonary capillaries Vena cava A E B F Pulmonary Vein Hepatic vein (bonus) Portal hepatic vein (bonus) Gastric capillaries (bonus) Hepatic capillaries (bonus) Hepatic artery (bonus) G C H I J The Cardiovascular System – Basic Features • The heart – a 2-phase pump ▪ Relaxation – pressure within the heart drops and draws blood from veins (refills) • Diastole ▪ Contraction – applies pressure to blood and ejects a proportion of it from the heart → arteries • Systole • Arteries and arterioles • Capillaries • Veins and venules Cardiac Cycle – The Basics Heart – four chambers and two sides • Left side: ▪ Left atrium: receives blood from the pulmonary vein → passes blood to left ventricle (atrial systole) → ▪ Left ventricle: applies pressure to blood (ventricular systole) → ejects a proportion into the arteries of the aorta • Right side: ▪ Right atrium: receives blood from veins of the vena cavae → passes blood to the right ventricle → ▪ Right ventricle: applies pressure to blood → ejects a proportion into the pulmonary artery Cardiac Cycle – The Basics • Match each step in the previous slide to the events pictured here • Note that the events of the left and right sides of the heart occur at almost exactly the same time ▪ i.e. left atrial systole occurs at almost the same time as right atrial systole Basics of Fluid Movement Through Tubular Structures • Flow = volume of fluid that passes through a tube over a unit of time ▪ Units – mL/sec, L/min, mL/min • Pressure = the force that fluid exerts on the walls of its container ▪ This is a type of potential energy • Pressure gradient = a difference in pressure between two areas in space ▪ One higher pressure, one low pressure Basics of Fluid Movement Through Tubular Structures • When there is a pressure gradient that exists across two points of a tube, fluid flows from areas of high pressure to low pressure • This is the job of the ventricles ▪ Apply pressure (potential energy) which is converted to kinetic energy → • Forward movement of blood • “Bulging” of the walls of large (elastic) arteries What Does The Heart Do? • Two tightly related things: ▪ Applies pressure to blood during ventricular systole • This pressure establishes the pressure gradient that drives blood forwards in the cardiovascular system ▪ Sends a proportion of its full (diastolic) volume into the arteries (pulmonary artery and aorta) every single systole • Stroke volume (SV) SV X heart rate (HR) = flow (cardiac output or CO) SV X HR = CO 70 mL X 70 beats/min = 4900 mL/min The Cardiovascular System – Basic Features • The heart – a 2-phase pump • Arteries and arterioles ▪ Arteries – larger, more elastic vessels that conduct blood away from the heart to large organ/tissue “beds” • Pressure “reservoirs” ▪ Arterioles – smaller, muscular vessels that feed capillary tissue beds • Constrict or dilate to modify flow to each bed • Capillaries • Veins and venules Arteries • The left ventricle alternates between a high pressure (120 mm Hg) during systole and a low pressure (0 mm Hg) during diastole • However, your blood pressure (the pressure in the elastic arteries) never drops the ventricular diastolic level ▪ Why? Arteries • Your large elastic arteries are full of elastic fibres ▪ Within the smooth muscular wall ▪ In membranes around the muscular wall • Every ventricular systole, the elastic arteries stretch • During ventricular diastole, that potential energy stored in the “stretch” ▪ drives blood forwards ▪ maintains overall arterial blood pressure Elastic Arteries and BP Arterioles • Let’s say you’re running a race – where do you need to divert oxygen-rich blood? ▪ Liver and GI tract? ▪ Legs? • Your large vessels are unable to divert blood from one organ to another ▪ Your arterioles constrict (limit flow) or dilate (increase flow) in different organs/tissue beds depending on: • Overall blood pressure • Metabolic needs of the tissue Arterioles Arterioles dynamically constrict or dilate depending on • Tissue need for blood (accumulation of metabolites) • Neurologic or hormonal signals ▪ If overall BP is low, then arterioles in many beds constrict ▪ Why does arteriole constriction increase pressure in the larger arteries overall? • We will discuss this in great detail during week 4 The Cardiovascular System – Basic Features • The heart – a 2-phase pump • Arteries and arterioles • Capillaries ▪ Very small vessels that allow exchange of gases, nutrients, metabolites, wastes between blood and tissues ▪ This exchange is fundamentally different in pulmonary vs. systemic capillaries • Veins and venules Two capillary beds: • Which is pulmonary? Systemic? • What substances are exchanged? ▪ What is the direction of the exchange, in terms of between tissue and blood? The Pulmonary System • Similar to the cardiovascular system: ▪ The muscular and elastic components of the pulmonary system are built to optimize flow • However, in the pulmonary system the substance that flows through these components is atmospheric air, not blood ▪ The capillaries are built to optimize exchange of molecules through the process of diffusion • However, the goal is to exchange molecules between the atmosphere and the blood • Atmosphere: high O2, low CO2 ▪ compared to metabolically active tissue The Pulmonary System – Air Flow (Ventilation) The Pulmonary System – Diffusion and Gas Exchange Fill it in together (in pairs): Pulmonary System Pump Substance being pumped Gas diffusing out of blood Gas diffusing into blood pH in capillary blood Major muscle of ventilation -? Systemic Circulation The Cardiovascular System – Basic Features • The heart – a 2-phase pump • Arteries and arterioles • Capillaries • Veins and venules ▪ Limited focus for today • Assessing the venous system will be discussed later in Clinical Physiology and Clin Med ▪ Veins return blood to the heart ▪ Systemic veins store 60% of the blood volume (~ 5 L) Control of the Cardiorespiratory Apparatus • Pressure sensors ▪ Baroreceptors • Gas sensors ▪ Chemoreceptors for: • CO2 • O2 • pH sensors ▪ Detects H+, in the form of CO2 levels within the brain: H20 + CO2 H2CO3 H+ + HCO3- Control of the Cardiorespiratory Apparatus Major baroreceptors: • carotid arteries • arch of the aorta Pressure drops → message sent to the brainstem via nerves → 1. Activation of the sympathetic nervous system → release of epinephrine, norepinephrine 2. Epi and NE → Elevation in HR and constriction of arterioles Aortic arch Control of the Cardiorespiratory Apparatus Gas sensors and pH sensors • Peripheral – same location as baroreceptors ▪ Detects CO2 and O2 • Central (detects pH and CO2) ▪ Distributed throughout brainstem • A drop in arterial O2 or an increase in arterial CO2 leads to: ▪ An increase in respiratory rate ▪ An increase in volume ventilated each breath Aortic arch Regulation Of The Respiratory System Is Very Complex System/region or Sensor Details Cerebral Cortex Voluntary control of respiratory rate Hypothalamus Regulates respiratory rate based on emotional state, pain, body temperature set-points → tells the brainstem to change ventilation Proprioceptors When your muscles and joints move, sends a signal to your brainstem → your ventilation changes in anticipation of increased MSK oxygen and carbon dioxide exchange needs Chemoreceptors Increase ventilation when arterial oxygen drops and carbon • Peripheral dioxide increases • Central → Very strong influence on ventilation Regulation Of The Respiratory System Is Very Complex • The factors that influence ventilation in the previous table mostly modulate the activity of the brainstem ▪ Medulla and pons • The medulla and pons in turn regulate the activity of the major muscles of ventilation The Vital Signs • All vital signs are highly variable across individuals, level of cardiovascular “fitness”, and across the lifespan • In general: ▪ Normal heart rates in adults range between 60 and 100 beats/min AT REST ▪ A healthy blood pressure is considered to be less that 140 mm Hg systolic and 90 mm Hg diastolic AT REST • Many people have “low” blood pressures – whether it is pathologically low depends on the person’s baseline • A blood pressure less than 90 mm Hg systolic and 60 mm Hg systolic is low enough to be considered abnormal in most The Vital Signs • All vital signs are highly variable across individuals, level of cardiovascular “fitness”, and across the lifespan • In general: ▪ The respiratory rate likely varies the most widely across individuals ▪ At rest, a normal respiratory rate is usually between 12 and 20 breaths/min Hypothetical – 1 L Blood Loss Ouch! • Predict the immediate (1-2 seconds) impact of the loss of 1 L of blood on the vitals, and explain why: ▪ Heart rate ▪ Blood pressure ▪ Respiratory rate • Predict how the body will quickly compensate for the injury in the minutes after and explain why: ▪ Heart rate ▪ Blood pressure ▪ Respiratory rate