simple notes
· Anatomy terms
o Pericardium: tough membranous sac that surrounds the entire heart
o Myocardium: muscle around the heart
o Myocardial cells: cardiac muscle cells
o Intercalated disks: specialized cell junctions in myocardium where one muscle connects to the next
o Fiber type: similar to type 1 muscle fibers, highly oxidative, many mitochondria
§ Only blood supply: coronary blood vessels
· Cardiac conduction system
o Myocardial cells can spontaneously depolarize
o Intrinsic control- rate of depolarization is set by cells in upper right atrium
§ Spontaneous rhythmicity- cardiac muscle can generate own electrical signal, no external stimulation needed
§ Contraction is rhythmical
§ Intrinsic heart rate: 100 bpm
§ Components of cardiac conduction system
· SA node (pacemaker)
· AV node
· AV bundle
· Purkinje fibers
o Extrinsic control- ANS and hormones
§ Alters heart rate and force of contraction
§ Sympathetic N.S: fight or flight
· Increases depolarization of SA node and increases heart rate
§ Parasympathetic N.S: rest and digest
· Vagus nerve: connects brain to heart, carries impulses to SA and AV nodes, releases ACh
· ACh: decreases heart rate
§ Endocrine system
· Norepinephrine and epinephrine released from adrenal medulla
o Increase heart rate and contractility of heart
· Cardiac Cycle
o All mechanical and electrical events during one heartbeat
o Diastole: filling
o Systole: contract
o Exercise shortens time for chambers to fill and contract
o Pressure: driving force that moves blood from one chamber to next
o P wave: atrial depolarization (SA node-AV node)
o QRS complex: ventricular depolarization (AV bundle – Purkinje fibers)
o T wave: ventricular repolarization
o Electrocardiogram: electrical activity of heart
o AV valves: tri + bicuspid valve
o Semilunar valve: pulmonary + aortic valve
o Four phases
§ Atrial diastole
· Atria fills, AV valve open, Atrium pressure greater than ventricular pressure, blood fills ventricles
§ Atrial systole
· SA node activates AP, atria contract, atrial depolarization, push more blood from atria into ventricles
§ Ventricular diastole
· AV valves close, no change in amount of blood, pressure in ventricles build
· End diastolic volume: total volume of blood at end of diastole
§ Ventricular systole
· Electrical contraction at Av node and travels down Purkinje fibers
· Delay in Av node for atria to finish depolarizing
· Pressure in ventricles greatestthan pulmonary
· SL valves pen
· End systolic volume: amount of blood left in ventricles at end of systole
· Heart sounds
o First sound: Lubb, AV valve closes
o Second sound: Dupp, SL valves close
· Pumping of heart during exercise
o Heart contracts as one unit due to myocardial cells connected by intercalated discs
o During exercise, filling time decreases, contractility increases to compensate
· Cardiac output: total volume of blood pumped by the ventricle per minute, HR x SV
o Heart rate: BPM
o Stroke volume: volume of blood pumped per beat, EDV – ESV
§ Preload: stretch of ventricle from blood filling, EDV high
· high venous return & plasma volume
§ Afterload: force that ventricle has to overcome to eject is blood, ESV low
· low TPR (MAP), high vasodilation
§ Contractility: ability of heart muscle to contract
· High myocardium/heart dimensions
· catecholamines
§ frank sterling mechanism: relationship between preload and contractility, linear
· Ejection fraction: fraction of blood pumped out of left ventricle in relation to amount of blood that was in ventricle before contraction
o SV/EDV
o indicates pumping ability of heart
· layers of vessels
o Tunica interna: thin single layer
o Tunica media: inner layer of smooth muscle and elastic (vasodilation/constr)
o tunica externa: collagen fibers and structure
o
· Arterioles
o smallest of arteries, lead to capillaries
o greatest control of circulation
o resistance vessels
o responsible for vasoconstriction and dilation
· Venules
o smallest of veins connecting to capillaries
· Blood pressure
o pressure exerted by blood on arterial walls
o systolic: high pressure during ventricular systole
o diastolic: lowest pressure during ventricular diastole
o MAP: average pressure exerted by blood as it travels through arteries
§ 2/3 DBP + 1/3 SBP
o Aorta/arteries have highest pressure
o reason for pressure difference: blood vessels providing resistance to bf
§ radius/length of blood vessel, viscosity
· Distribution of blood
o At rest, liver and kidneys get half of CO
o During exercise, muscles get the most
· Intrinsic control of blood flow
o ability of local tissues to dilate/constrict arterioles to alter regional bf depending on immediate needs of tissue
o factors: increases O2 demand, high levels of H+, nitric oxide, decreased bp
· Extrinsic control
o redistribution at system/organ level, regulated by SNS, vasoconstriction, decreased bf
o vasomotor tone: maintain slight vasoconstriction to maintain blood pressure + bf
· Muscle blood flow
o exercise increases SNS, need vasodilation
o functional sympatholysis: NO released to increase vasodilation where needed
· venous blood flow
o Most of blood volume is on venous side
o venous system acts as reservoir
o muscle pump: rhythmic mechanical compressions of veins during exercise, pushes blood in veins back to heart
· Control of bp
o baroreceptors: pressure sensors, sense stretch of vessels
o L: aortic arch and carotid arteries
· blood
o transportation, temp. regulation, acid base balance
o erythrocytes: RBC’s
o Hemoglobin: protein on RBC’s that bind to oxygen
o viscosity: thickness of blood
· Hemodynamics review
o for stroke volume we want:
§ high contractility
· good cardio dimensions and low catecholamines?
§ Low afterload
· low TPR
· high vasodilation
§ High preload
· high venous return
· high plasma volume
◦ Heart Rate- Inc. then plateau
◦ Anticipatory response: Inc. SNS, NE/E
◦ Inc. then plateau as near max. exercise reached: steady state heart rate (plateau)
◦ HR max: used in clinical exercise testing to prescribe exercise intensity in physical training and rehabilitation settings
◦ Constant daily, changes yearly
◦ Hrmax=220-age
◦ Heart rate variability = a measure of the rhythmic fluctuation in HR that occurs because of continuous changes in the sympathetic-parasympathetic balance that controls sinus rhythm
◦ Stroke Volume- Inc. to 40-60% VO2 max then plateaus
◦ Untrained: 60-70 to 110-130
◦ Increases in upright position
◦ Can increase with less time because contractility increases
◦ Factors that inc. SV
◦ Inc. Preload: inc. venous return, EDV, frank sterling mechanism
◦ Inc. contractility: inc. SNS activity, NE/E
◦ Dec. Afterload: TPR decreases vasodilation
◦ If ejection fraction inc., EDV does not have to inc. to inc. contractility
◦ Plateaus: venous return/EDV can’t keep up with inc. HR
◦ Difficult to measure
◦ Echocardiography (sound waves) & radionuclide technique (tagging RBC’s w radioactive tracers)
◦ Cardiac Output- Inc.
◦ Resting 5.0 to 20-40 during exercise
◦ Increases linearly to meet increased demand for O2
◦ When resting CO Inc: SV dec. and HR inc.
◦ When exercising CO inc: SV and HR inc. until SV plateaus
◦ Ficks equation: oxygen consumption of tissue depends on BF to tissue and amount of oxygen that tissue extracts from the blood
◦ VO2=CO x (diff in conc. of oxygen in blood of arterial vs. venous blood)
◦ Blood Pressure- Inc.
◦ SBP and MAP inc.
◦ DBP stays same or decreases due to functional sympatholytic
◦ Upper body causes greatest response
◦ Valsalva maneuver causes spike in BP: inc. intrathoracic pressure, This maneuver occurs when a person tries to exhale while the mouth, nose and glottis are closed
◦ Blood Flow- Inc.
◦ Inc due to CO and BP
◦ Blood
◦ (a-v)O2 difference increases, Venous O2 content changes (getting in same amount of O2, extracting more)
◦ PV dec. due to sweat
◦ Inc. Viscosity, stickier blood
Chapter 7 Simple
· Pulmonary Ventilation- breathing
o Gas exchange occurs at: respiratory bronchioles & alveoli
o Inspiration: active process w/ diaphragm and external intercostal muscles
§ Ribs (up + out) & sternum (up + forward) moved by: external intercostal muscles
§ Purpose: make cavity big, increase lung volume
§ Boyles law: pressure and volume
o Expiration
§ At rest: uses inspiratory muscles and elastic recoil of lung tissue, dec. V of thorax
§ Forced breathing: uses internal intercostal muscles, pulls ribs down and inward
· Respiratory Pump: changes in pressure help increases venous return
o Regulation- Involuntary
§ Motor neurons regulated by respirator center in brainstem
· cortex can override for voluntary control of breathing
§ Changing chemical environment
· PCO2 strongest regulation of breathing (can cross blood brain barrier)
· CO2 and H+ levels
§ Chemoreceptors (aortic arch, carotid) sensitive to changes in PO2, PCO2, H+
· Pulmonary diffusion- gas exchange in lungs between alveoli and capillary blood
o Functions
§ 1. replenishes bloods oxygen supply
§ 2. removes CO2 from venous blood returning
o Blood flow to lungs matches blood flow to systematic circulation, 4-6 L/min
o Highest pressure in aorta
o Lower change in pressure and resistance across pulmonary circulation
o Pressure= flow x resistance
· Transport of CO2 and O2 via blood
o Oxygen transported via: hemoglobin
§ One molecule of hemoglobin carries 4 molecules of oxygen
§ binding of oxygen to hemoglobin depends on: PO2 in blood + bonding strength
§ Oxygen dissociation curve
· flat upper portion: large changes in PO2- small changes in hemoglobin sat.
· Steep middle portion: small changes in PO2- large changes in hemoglobin sat., unloading phase
· pH impacts unloading: pH more acidic during exercise-more O2 unloaded
· Blood temp increases- more O2 unloaded
§ Carbon dioxide
· CO2 is transported via
o 1. Bicarbonate ions: common, releases H+, Bohr effect, makes blood more acidic, increases O2 unloading
o 2. dissolved in plasma
o 3. bound to hemoglobin, doesn’t compete with oxygen
o Oxygen carrying capacity: max amount of oxygen blood can transport
· Capillary diffusion- gas exchange at muscles
o More oxygen is unloaded to active muscles is due to: PO2 is lower in arterial blood
o Myoglobin: transports oxygen to mitochondria
o Factors that influence rate of oxygen deliver/uptake
§ oxygen content of blood: reduction in bloods normal oxygen carrying capacity or reducing in PO2 of arterial blood- decrease
§ blood flow: exercise increases blood flow- increases
§ Local conditions (pH, temp): exercise incr. muscle acidity + temp- increases
· Pulmonary Volumes
o Spirometry: measure volume of air in lungs
o Residual volume: Volume of air remaining in lungs after max expiration
o ERV: max volume of air expired from resting end-expiratory volume
o Tidal volume: quiet breathing, breathing at rest
o IRV: max volume of air inspiration from resting end-inspiratory level
o Inspiratory capacity: sum of TV & IRV, max volume of air inspired from end-expiratory
o Vital capacity: max volume of air expired from max inspiratory level
o Total lung capacity: sum of all, volume of air in lungs after max inspiration
· Partial pressure of gases
o Partial pressures: individual pressures of each gas
o Daltons Law: total pressure of mixture is equal to sum of partial pressures
o Nitrogen=79.04%, Oxygen=20.93%, CO2=0.03%
§ constant w/ altitude changes, changes due to atmospheric pressure
o Henrys Law: gases dissolve in liquids in proportion to their partial pressure
§ Pressure gradient of gases between blood and alveoli
o Ficks law: rate of diffusion depends on ration of SA & difference in partial pressures
§ rate of diffusion inversely proportion to thickness of tissue it diffuses through
o Oxygen diffusion Capacity: rate at which oxygen diffuses from alveoli into blood
§ can increase during exercise x3 resting rate due to greater PP gradient
· Laws
o Boyles Law: inverse relationship between pressure and volume
o Daltons Law: total pressure of mixture is equal to sum of partial pressures
o Henrys Law: gases dissolve in liquids in proportion to their partial pressure
o Ficks law: rate of diffusion depends on ration of SA & difference in partial pressures
Respiratory responses to acute exercise Simple
· Basics
o Initial respiratory response: neural- respiratory control centers in brain
o Second phase response: changes in chemical status in arterial blood
o Post-exercise ventilation takes longer to return to normal due to acid base balance, PCO2, blood temp
· Breathing irregularities
o Dyspnea: shortness of breath
§ build up of CO2 and H+
o Hyperventilation: increase in ventilation
§ decrease in CO2, increase in pH, reduce ventilatory drive
o Exercise-Induced asthma: lower airway obstruction
§ Bronchospasm: reduction in lung function
o Valsalva maneuver: close glottis, increase intrathoracic pressure, restrict venous return
· Energy metabolism during Ventilation
o VE: volume of air expired
o VO2: amount of oxygen consumed by tissues
o VO2max: max amount of oxygen someone can utilize during max intensity
o Ventilatory equivalent for oxygen (Ve/VO2): ration between volume of air ventilated and amount of O2 consumed by tissues in given amount of time
§ ratio remains constant showing that breathing is matched to oxygen needed
o Ventilatory Threshold: ventilation increases disproportionally to oxygen consumption, 55-70% VO2 max
§ results form increase in lactate
§ reflects respiratory response to increased CO2 levels
· Respiratory Limitation in exercise
o Maximal voluntary ventilation: maximal capacity to voluntarily move air in and out of lungs, hard to reach, mentally stop or VO2 max reached beforehand
· Acid base balance
o exercise increase H+, lowers pH
o Regulations: body fluid is more basic, tissue pH is alkaline
o pH is controlled by: chemical buffers in blood, pulmonary ventilation, kidney function
o 3 major chemical buffers
§ bicarbonate: combines with H+ to form carbonic acid to eliminate free H+
· Carbonic acid turns into CO2 and water in lungs
· Amount of acid buffered = amount of bicarbonate that combines w H+
§ inorganic phosphates:
§ proteins
o Blood lactate is removed quicker w/ active recovery because it keeps bf elevated and enhances lactate diffusion
Lecture 5 Simple