BMS100 Clinical Physiology II PDF, Fall 2022

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 Cardiovasc...

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