Kinesiology 470-Exam #2 (Chapter 9: Cardiovascular Responses to Exercise)

Average Aortic Pressure

-Aortic pressure is inversely related to stroke volume -Aortic pressure increases --> decreased stroke volume since it's harder for the ventricle to overcome this pressure and require greater force -Represents "afterload" -High afterload results in a decreased stroke volume -Requires greater force generation by the myocardium to eject blood into the aorta -Reducing aortic pressure results in higher stroke volume -Vasodilation (arteriole dilation) during exercise reduces afterload

Relationship Between End-Diastolic Volume and Stroke Volume

-As EDV increases so does the stroke volume, tho the curve does flatten out -If we send more blood to the heart (EDV), we get more blood pumped out of the heart

Respiratory Pump increased EDV

-Changes in thoracic pressure pull blood toward the heart --> increased EDV -During exercise breathing gets deeper (changing thoracic pressure) and more forceful increasing pull on blood -One of the strongest mechanism to EDV

Electrical Activity of the Heart

-Heart doesn't need a CNS -Contraction of the heart depends on electrical stimulation of myocardium -Impulse is initiated in the right atrium and spread throughout the entire heart -May be recorded on an electrocardiogram (ECG)

Ventricular Contractility

-Increased contractility --> increases stroke volume -Circulation epinephrine and norepinephrine -Increases force of contraction in heart -Increases the amount of Ca++ in the heart muscle and sensitivity to Ca++ -More Ca++ = more cross bridges (CB's) = more force = increased SV -Muscles need Ca++ to contract

Physical Characteristics of Blood

-Plasma -Liquid portion of blood -Contains ions, proteins, hormones -Cells -Red Blood Cells (RBCs) -Contains hemoglobin to carry oxygen -White Blood Cells (WBCs) -Important in preventing infection -Platelets -Important in blood clotting -Hematocrit -Percentage of blood composed cells (RBCs mainly, just not plasma) -42% for males, 38% for females -Heavy parts (RBCs) go to the bottom, Plasma lighter part goes up top

Blood Flow through the Systemic Circuit

-Pressure gradient drives blood flow -Left ventricle is close to 100 mmHg -Right atrium is close to 0 mm Hg (100 mm Hg pressure difference) -This drives blood all throughout the body

ECG Interpretation

-Records the electrical activity of the heart -Put electrodes on the heart -P wave -Atrial depolarization -QRS Complex -Ventricular depolarization and atrial repolarization -T Wave -Ventricular repolarization

Hypertension

-Resting BP > 140/90 mm Hg -Primary ("essential") hypertension -Cause unknown -90% cases of hypertension -Secondary hypertension -Result of some other condition or disease -Risk factor for HYT -Left ventricular hypertrophy -Atherosclerosis and heart attack -Kidney damage -Stroke

Skeletal Muscle Pump Increases EDV

-Rhythmic skeletal muscle contractions force blood in the extremities back toward the heart -There's a lot of blood stored in veins -These muscle pushes the blood in the veins -One-way valves in veins prevent backflow of blood

Mehcnism of Frank-Starling Law

-Sarcomere is the contractile unit and we can measure the force -As sarcomere length increases with increased EDV so does tension and pressure so contraction increases -The sarcomere length increases where there's overlap which reduces force -As the muscle is stretched with increased EDV --> more forceful contraction -It can get stretched out too much that not that much blood is pumped out (heart failure)

The ANS tug-of-war and Exercise

-Sympathetic Nervous System- increases the SA-node firing rate --> Inc heart rate -Parasympathetic Nervous System- withdraw of vagal tone followed by increased firing of acceleration nerves -From rest to exercise, withdrawal of vagal tone --> parasympathetic system is slowing down -Sympathetic nervous system increased --> increased heart rate -Initially, there's no sympathetic nervous system response only the withdrawal of vagus tone increasing heart rate from 70 to 100 beats per minute then sympathetic nervous system increase due to increased exercise intensity

Ventricular Contractility: Effects of Sympathetic Stimulation on Stroke Volume

-Sympathetic Stimulation = Epinephrine and Norepinephrine release --> increases contractility -For every amount of EDV you increased contractility of that --> increased SV significantly versus if either contractility or EDV was acting alone

How is End-Diastolic Volume Regulated?

-The respiratory and skeletal muscle pump increase EDV -Venoconstriction -Constriction of smooth muscle around the veins in the skeletal muscles -There's a lot of blood in the veins so constricting it increased EDV -Via stimulation of the sympathetic nervous system -Signals comes from CVC in the brain

SA and AV nodes have spontaneous depolarizing cells

-This action potential of the SA and AV node look similar and act like neurons -These nodes have leaky ion channels that don't go to rest but allow slow depolarizations towards the threshold and fire without nervous input -The resting phase is still a slope towards depolarization instead of being flat -SA and AV nodes have inherent firing rates -SA nodes wants to fire at 100/min -AV node wants to fire at 40/min -The heart still beats closer to 100 bpm due to the SA node

Regulation of Stroke Volume

1. End-diastolic volume (EDV) -Volume of blood in the ventricles at the end of diastole ("preload") Increasing this increases the amount of blood pumped (more blood in the heart --> more blood is ejected out) --> stroke volume increases 2. Average aortic blood pressure Pressure the heart must pump against to eject blood ("afterload") -lower the average aortic pressure the higher the stroke volume 3. Strength of the ventricular contraction "contractility"-heart contracts with more force

TBL Assignment: CO during Exercise

1. There's a bigger demand for blood flow and oxygen to muscles during exercise the heart rate increases (cardiac output) in response to exercise due to input from the sympathetic nervous system (Autonomic nervous system) caused increased depolarization in the pacemakers cells -The nervous system -Parasympathetic system tone loses first- we get closer to 100 bpm ((acetylcholine is released to decrease heart rate, this neurotransmitter not released anymore), then sympathetic system works to increase heart rate past 100 bpm 2. Heart rate increased due to sympathetic nervous system and decreased parasympathetic nervous system, stroke volume also increases to volume of blood pumped in the heart (there a number of ways to increases this to increase cardiac output ( -vasoconstriction of inactive muscles + vasodilation of active muscles, venous return is increased through respiratory pump and muscle pump, End-diastolic volume increases stroke

Structure of the Heart

2-Pump system: 2 Atrium-ventricle pair -Right Side-Pulmonary Circuit, low pressure -Left Side- Systemic Circuit, high pressure 1-way valves prevent backflow 2 circuits: pulmonary, systemic

Introduction to Cardiovascular Responses to Exercise

A major change to homeostasis posed by exercise is the increased demand for oxygen During exercise, need for O2 may increase 15- to 25-fold Two major adjustments to meet increased oxygen demand: -Increased cardiac output (CO, blood pumped per min by the heart) to meet oxygen demand -Redistribute blood flow from inactive organs to active skeletal muscles (upregulate O2 consumption)

Factors That Influence Arterial Blood Pressure

Arterial Blood Pressure increases with: -Cardiac Output Increases -Stroke volume increases (Blood volume ejected per beat of the heart) -Heart rate increases -Blood Volume increases Blood -Viscosity Increases (doesn't really change much) -Peripheral Resistances increases

Changes in Muscle and Splanchnic Blood Flow during Exercise

As exercise intensity increases closer to VO2 max, muscle blood flow increase linearly while Splanchnic Blood Flow (to the gut) decreases

Describe the cardiac cycle: what happens in each phase and what is the timing?

At rest, Diastole and Systole are split pretty evenly for 70 bpm, diastole and systole finishes in 8/10 of a second (0.3 sec Systole, 0.5 seconds Diastole); most time spent in diastole -Systole is the strong pumping action of the heart -Diastole is when the heart is filling and relaxing During exercise, diastole is shorten a lot of more -There's a more even contribution between systole and diastole which is different compared at rest

Mean Arterial Pressure during Heavy Exercise

Blood Pressure : 180/80 mm Hg -MAP = 80 + .67 (180-80) = 80 + 67 = 147 mm Hg 1/3 changes to 2/3 because there's more time spent in systole

Relationships Among Pressure, Resistance, and Flow

Blood flow = (Difference in pressure 100 mm Hg) / (Resistance) -If resistance increases, blood flow decreases and vice verse -Directly proportional to the pressure difference between the two ends of the system -Inversely proportional to resistance Pressure -Proportional to the difference MAP and right atrial pressure (Difference in pressure) -Driving force in blood flow Increased flow during exercise mostly due to decrease in resistance Increasing the pressure to meet blood flow like 5x to meet demands would burst vessels, so resistance is modified instead since it's safer

Mean Arterial Pressure At Rest

Blood pressure: 120/80 mm Hg -Pulse Pressure = Systole BP - Diastole BP MAP at -Rest = Mean Arterial Pressure = Diastole BP + (1/3)(Pulse Pressure) -MAP = 80 mm Hg + .33 (120-80) = 80 + 13 = 93 mm Hg

Factors that Regulate Cardiac Output

Cardiac Rate increases when: -PNS system activity decreases -SNS system activity increases Stroke Volume increases when -Contraction strength increases (increased by SNS stimulation + stretch increases heart muscle tension- frank-starling) -EDV increases (increased by increased tension, muscle pump, respiratory pump) -decreased mean arterial pressure

Cardiac Tissue Has Specialized Structures

Cardiac muscle fibers: -High density of mitochondria (more and bigger mitochondria because it's very aerobic-compared to Skeletal muscle) -Intercalated discs; -Leaky membranes (allows rapid electrical transmission) -Rapid electrical transmission -Internal conduction system (act like neurons and become polarized to pump rhythmically on its own) uninuclear-one nucleus per cell

How does cardiac muscle differ from skeletal muscle in a) structure and b) function?

Cardiac muscle is shorter, connected tighter, branched, intercalated disks, involuntary, fibers are electrically coupled to contract al at once when a signal is sent, high density Skeletal muscle fiber are bigger and wider, and voluntary, multinuclear Cardiac muscle fibers: -High density of mitochondria (more and bigger mitochondria because it's very aerobic) Heart doesn't fatigue since it's so aerobic (no lactic acid buildup) -Intercalated discs; Leaky membranes (allows rapid electrical transmission) Rapid electrical transmission -Internal conduction system (act like neurons and become polarized to pump rhythmically on its own) Like its own little nervous system -Uninuclear- one nucleus per cell

Conduction System of the Heart

Contraction of the heart depends on electrical stimulation of the myocardium -Conduction System Sinoatrial Node (SA node) -Pacemaker, initiates depolarization causes atria to contract and triggers AV node depolarization -Atrioventricular node (AV node) -Passes depolarization to ventricles -Brief delay to allow for ventricular filling -Bundle Branches -To left and right ventricle -Purkinje fibers -Throughout ventricles

Pressure, Volume, and Heart sounds During the Cardiac Cycle

Diastole -Pressure in ventricles is low - -Filling with blood from atria -AV valves open when ventricular P < atrial P Systole -Pressure in ventricles rises -Blood ejected in pulmonary and systemic circulation -Semilunar valves open when ventricular P> aortic P Heart sounds First: closing of AV valves Second: closing of aortic and pulmonary valves Isovolumic contraction Phase: pressure is increasing even though there's no change in blood volume -Semilunar valves doesn't open until pressure increases and forces it open (Past 80 mm Hg) -Blood volume doesn't go to zero during contraction The initial increase in volume is due to atria contracting blood into ventricles

Phase Changes During the Cardiac Cycle

Diastole -Relaxation phase -Filling with blood -Pressure is low -Pressure is high in the atria -Filling with blood from atria -AV (btwn atria and ventricles) valves open when ventricular pressure is less than atrial pressure Systole -Pressure in ventricle rises -Blood ejected in pulmonary and systemic circulation -Semilunar valves open when ventricular pressure is greater than aortic pressure -2/3 blood is ejected from ventricles per beat Heart Sounds -First: closing of AV valves -Second: closing of aortic and pulmonary valves At rest, diastole longer than systole During exercise, both systole and diastole are shorter

How does the timing of the cycle change with heavy endurance exercise?

During exercise, 180 bpm means both systole and diastole cycle occur in a much shorter time frame, diastole shrink as exercise intensity increases, systole decreases but not as much (0..2 sec Systole, 0.13 sec diastole During exercise, diastole is shorten a lot of more -There's a more even contribution between systole and diastole which is different compared at rest

How is blood redistributed in the body during exercise?

During exercise, arterioles leading to active muscles increase in diameter (vasodilation) increasing blood flow, while decreasing to inactive muscles (vasoconstriction), higher command centers in the brain also send signals to vasoconstrict or vasodilate blood vessels Redistribution of -Blood Flor During Exercise Blood flow is 5 L/ min at rest -At rest, gut and stomach intestines have a decent amount of blood flow -Kidneys receive about 20 % of blood flow -Muscle and bones receive another 20% Blood flow during exercise is 25 L/min -Muscles receive close to 80-85% of the blood flow -Blood flow is shunted from other systems (digestive) and kidneys and moved to the muscles -Blood flow to the heart percentage stays the same since the increased blood flow is enough to support the heart at the same percentage (5 times as much)

Conduction System of the Heart 2

ECG is a composite of all Aps in the heart -As you move through the heart the APs are different throughout the heart, in a ECG trace you see a composite of these APs -Doesn't need CNS system to beat continuously because they have pacemaker cells

Layers of the Heart

Epicardium-outermost layer Myocardium- thickest layer, heart muscle (a lot of similarities with skeletal muscle) -Generate the force needed to pump the heart Endocardium-innermost layer -Protective layer of elastic and collagen fibers

Arterial Blood Pressure

Expressed as systolic/diastolic -"Normal" is 120/80 mmHg High is greater than or equal to 140/90 mmHg Systolic pressure (Top number) -Pressure in the arteries generated during ventricular contraction (systole) force against the arterial walls Diastolic pressure (bottom number) -Pressure in the arteries during cardiac relaxation (diastole)

TBL Assignment: ECG Issues

First-degree AV block, Hint: the electrical signal from atria to ventricles, through the AV node, is delayed. Distance BETWEEN THE P WAVE AND QRS COMPLEX IS LONGER MEANING IT'S TAKING LONGER to reach QRS complex Premature ventricular contractions Hint: the heartbeat is initiated by the Purkinje fibers rather than by the SA node. Sometimes there's no P Wave and a random QRS complex Third-degree AV block, the impulse generated in the SA node does not propagate to the ventricles Hint: Because the impulse is blocked, an accessory pacemaker in the lower chambers will typically activate the ventricles. SA Node and AV Node are out of sync so random P waves occur, close or not close the QRS complex, completely disconncected

Pressure Changes Across the Systemic Circulation

Large arteries have constantly high pressure due to the resistance as arteries get smaller and becomes arterioles, capillaries the pressure decreases The greatest pressure change occurs in the arterioles -The radius of the vessels are manipulated at this point resulting in a greater change in pressure

Mean Arterial Blood Pressure (MAP)

Mean Arterial Pressure (MAP) -Average pressure in the arteries during a cardiac cycle -Determines rate of systemic blood flow -Higher MAP = lower blood flow MAP = Diastolic + 1/3 (Pulse Pressure) MAP = C.O. x Total Peripheral Resistance -Total Peripheral Resistance represents the total vascular tone/resistance of the blood vessels -CO=Volume of blood pumped by heart per min -Resistance of the vessels (Resistances in the vessels which depends on vessel diameter, length, and blood viscosity) -Directly proportional

Effective Treatments of High-Blood Pressure

Medications -Diuretics, beta-Blockers, etc -Regular physical activity -Weight loss -Stress management -Decreased sodium intake -Decreased alcohol consumption

Nitric Oxide is an Important Vasodilator

Produced in the endothelium or arterioles Promotes smooth muscle relaxation -Vasodilation and increased blood flow Important in autoregulation -Works in conjunction with other factors One of the several factors involved in blood flow regulation during exercise -Increases muscle blood flow -Recruitment of capillaries

Pulmonary and Systemic Circuits

Pulmonary Circuit -Right side of the heart -Pumps deoxygenated blood to the lungs via pulmonary arteries -Returns oxygenated blood to the left heart via pulmonary veins Systemic Circuit -Left side of the heart -Pumps oxygenated blood to the whole body via arteries -Returns deoxygenated to the right side via veins

Pulse Pressure

Pulse pressure -Difference between systolic and diastolic -Pulse Pressure = Systolic BP - Diastolic BP

What Factors determine resistance?

Resistance -Depends upon: -Length of the vessel -Usually stays the same -Viscosity of the blood -Usually stays the same -Radius of the vessel (most important) -Changes a lot during exercise, and the change is not linear since its to the power of 4, small changes in radius can result in a big change to resistance -Resistance = (Length x Viscosity) / (Radius^4) Decreasing the radius of the vessel in half will increase resistance by a factor of 16

Regulation of Local Blood Flow during Exercise

Skeletal muscle vasodilation -Autoregulation -Blood flow increased to meet metabolic demands of tissue -If a vessel becomes hypoxic, arterioles will dilate automatically -Due to changes in O2 tension, CO2 tension, nitric oxide, potassium, adenosine, and pH -Nitric oxide is a potent vasodilator -This causes the smooth muscle (sensitive to changes) near this muscle to vasodilate to meet local control Vasoconstriction to visceral organs and inactive tissues -Need SNS stimulation to have vasoconstriction

Hemodynamics

Study of physical characteristics of the blood and blood flow throughout the body -Interrelationships among pressure, flow, and resistance

Cardiac Output

The amount of blood pumped by the heart each minute -Product of heart rate and stroke volume -Q = HR x SV -Heart rate= number of beats per minute -Stroke Volume = amount of blood ejected in each beat

Extra question: Does Covid-19 impact heart function? What happens and how might it a affect exercise capacity?

The heart experiencing damage from people recovering from Coivd-19 -Myocarditis(heart inflammation) shown in 60% of patients and they're recovering very slowly -Reduced exercise capacity for months

Length-Tension Relationship of Skeletal Muscle

There's an optimal length (maximizes cross-bridges form; acting and myosin) of muscle length that increases force of contraction -As we stretch the heart, this increased the forces --> increased stroke volume -Increasing EDV will increased heart muscle tension due to stretch with increased Blood volume (stretching the muscle increases how much actin and myosin can bind) -Increasing the length further forces decrease because you're decreasing the amount of myosin and actin cross bridges that can form

Myocardial Metabolism: Substrate Utilization

• At rest, heart used fatty acids for ATP production • During moderate exercise, there's and even split between fatty and carbs • Heart has the LDH that's more prone to converting lactate into pyruvate to be used in oxidative phosphorylation -During heavy exercise, more lactate is used

Myocardial O2 Use

• At rest, myocardial uses 70-80% available O2 • During exercise, flow must increase 5-7-fold to meet O2 demand • Vasodilation (drops pressure to increase blood flow) by ○ Adenosine ○ Hypoxia ○ Sympathetic Nervous System Hormones

Central Command Hardware

• Cardiovascular control center is in the brain stem ○ This influences blood vessels on the heart ○ Feedback area

What is the signal to turn on the Cardiovascular system at the start of exercise?

• Central Command Theory • Motor signals in the brain send parallel signals to muscles and CV center at onset of exercise -Fine tuned by other local factors with feedback on CV center

Changes in Rate Pressure Product during Exercise

• Double Product = HR x SBP

End-Diastolic Volume

• Frank-Starling mechanism ○ Greater EDV results in more forceful contraction dur to stretch of ventricles ○ Dependent on venous return § Venoconstriction □ Via SNS § Respiratory pump □ Changed in thoracic pressure pull blood toward heart § Skeletal muscle pump

The Heart's Blood Supply

• Heart is a muscle and still needs oxygen • Coronary Circulation ○ Right and left coronary arteries branch off the ascending aorta ○ Right Coronary Artery (RCA) mainly supplies the right atrium and ventricle -Left Coronary Artery (LCA) supplies the left atrium and ventricle and a small portion of the right ventricle

Nervous System Regulation of Heart Rate

• Heart is connected to CNS ○ Heart is innervated by both sympathetic and parasympathetic nervous system (Autonomic Nervous System) ○ Carotid and Aortic baroceptors collect info about pressure in the heart and send that feedback § Send signals directly to brain stem which can be integrated there or be sent to the higher brain

Summary of Cardiovascular Control During Exercise

• Higher brain centers - motor cortex --> send signal to muscles to contract, and send signals to CV control center • CV control center sends signals to the heart to beat faster and stronger, blood vessels to shunt blood to the working muscles • Chemoreceptor---> sense biochemical changes in blood (ions, metabolites) --> feedback to CV control center to increase or decrease output • Mechanoreceptors --> senses changes in touch, stretch, force, speed of movement --> feedback to CV control center --> increase in HR and change in blood vessel Receptor • Baroreceptors --> senses changes in blood pressure --> feedback to the CV control center

Impaired Cardiac Blood Supply

• Impaired flow --> angina pectoris (blood flow is not enough to keep up with oxygen demand) -If flow is severely impaired, myocardial infarction may result (cell death)

Central Command Theory

• Initial signal to "drive" cardiovascular system from higher brain centers ○ Due to centrally generated motor signals • Fine-tuned by feedback from: ○ Heart mechanoreceptors ○ Muscle chemoreceptors § Sensitive to muscle metabolites (K+, lactic acid) § Exercise pressor reflex ○ Muscle Mechanoreceptors § Sensitive to force and speed of muscular movement ○ Baroreceptors -Sensitive to changes in arterial blood pressure

Exercise Training Protect the Heat

• Regular exercise is cardioprotective ○ Reduces incidence of heart attacks ○ Improves survival from heart attack • Exercise reduces the amount of myocardial damage from heart attack ○ Improvements in heart's antioxidant capacity ○ Improved function of ATP-sensitive potassium channels