Blood PressureBlood Pressure
=force exerted by the blood against =force exerted by the blood against the walls of the blood vessel; the walls of the blood vessel; Changes throughout cardiac cycleChanges throughout cardiac cycle– Systolic Blood pressure=maximal Systolic Blood pressure=maximal
pressure achieved by ventricular pressure achieved by ventricular contractioncontraction
– Diastolic Blood pressure=lowest Diastolic Blood pressure=lowest pressure remaining in blood vessels pressure remaining in blood vessels after ventricle contractsafter ventricle contracts
Blood flow - amount of blood flowing at Blood flow - amount of blood flowing at any given time. Dependent on Cardiac any given time. Dependent on Cardiac output (CO).output (CO).
Blood pressure - force per unit area Blood pressure - force per unit area exerted on wall of blood vesselexerted on wall of blood vessel
Autonomic Nervous System Autonomic Nervous System – Sympathetic – causes Sympathetic – causes
vasoconstriction of arteriolesvasoconstriction of arterioles Increases blood pressureIncreases blood pressure
– Parasympathetic – causes Parasympathetic – causes vasodilationvasodilationDecreases blood pressureDecreases blood pressure
Blood PressureBlood Pressure
Systolic pressureSystolic pressure Diastolic pressureDiastolic pressure Pulse pressure = systolic - diastolicPulse pressure = systolic - diastolic MAP = Diastolic + (Pulse pressure/3)MAP = Diastolic + (Pulse pressure/3) Hypotension - Low blood pressure Hypotension - Low blood pressure
(Nutritional, anesthesia)(Nutritional, anesthesia) Hypertension - High blood pressure Hypertension - High blood pressure
(increased peripheral resistance, high (increased peripheral resistance, high blood viscosity)blood viscosity)
Blood PressureBlood Pressure
PressurePressure
Systemic circulation-high hydraulic Systemic circulation-high hydraulic pressure required to overcome pressure required to overcome gravitational forces and resistance gravitational forces and resistance
Arteriole-vessels with high resistance Arteriole-vessels with high resistance to reduce pressure before reaching to reduce pressure before reaching capillary bedscapillary beds
Pulmonary Circulation-low pressure, Pulmonary Circulation-low pressure, due to low resistance to blood flowdue to low resistance to blood flow
Effects of High Blood PressureEffects of High Blood Pressure
Abnormally high blood pressure Abnormally high blood pressure within veins-can cause leaking of within veins-can cause leaking of fluid from blood vesselsfluid from blood vessels– Result-edemaResult-edema– Congestive heart failureCongestive heart failure
Right heart failure-leaking of fluid from vena Right heart failure-leaking of fluid from vena cavacava
– Pleural effusionPleural effusionLeft heart failure-leaking of fluid within lungs Left heart failure-leaking of fluid within lungs
– Pulmonary edemaPulmonary edema
Distribution of Blood FlowDistribution of Blood Flow
Pulmonary Circulation – 15%Pulmonary Circulation – 15% Systemic Circulation – 80%Systemic Circulation – 80%
– 65% in veins65% in veins– 10% in arteries and arterioles10% in arteries and arterioles– 5% in capillary beds5% in capillary beds
Heart – 5%Heart – 5%
Functions of the CV SystemFunctions of the CV System
Maintain blood pressure within the Maintain blood pressure within the arteriesarteries
Maintain blood flow to the tissuesMaintain blood flow to the tissues Maintain normal blood pressures Maintain normal blood pressures
within the capillaries and veinswithin the capillaries and veins
=Perfusion=Perfusion
PerfusionPerfusion
Allows delivery of oxygen and Allows delivery of oxygen and nutrients (i.e. glucose)nutrients (i.e. glucose)
Removal of waste productsRemoval of waste products– Carbon dioxideCarbon dioxide
Transport of hormonal messages Transport of hormonal messages from one part of the body to anotherfrom one part of the body to another
Forces Forces
Heart must adjust contractility Heart must adjust contractility (inotropic state) based on forces (inotropic state) based on forces working on the heart.working on the heart.– PreloadPreload– AfterloadAfterload
AfterloadAfterload
=Sum of forces the ventricles must =Sum of forces the ventricles must contract against to make blood flow contract against to make blood flow forwardforward
Increased systemic blood pressureIncreased systemic blood pressure– Increases or Decreases Afterload????Increases or Decreases Afterload????– Chronic blood pressure-increases the Chronic blood pressure-increases the
work of the heart-heart enlarges!work of the heart-heart enlarges!
PreloadPreload
=Amount of blood in the heart just =Amount of blood in the heart just prior to contraction of the ventricleprior to contraction of the ventricle
=Venous Return or amount of blood =Venous Return or amount of blood returning to the heartreturning to the heart– Leaky valves-regurgitate blood back into Leaky valves-regurgitate blood back into
the atriumthe atrium Increases or Decreases Preload??Increases or Decreases Preload??
Inotropic StateInotropic State
Adjustments in contractility based on Adjustments in contractility based on Calcium and contractile protein Calcium and contractile protein interactionsinteractions– Sympathetic tone (norepinephrine-Sympathetic tone (norepinephrine-
neurotransmitter)neurotransmitter)– Increases heart rate and contractility by Increases heart rate and contractility by
increasing Calcium availabilityincreasing Calcium availability– Starling’s law-increased contractility Starling’s law-increased contractility
with stretching of sarcomerewith stretching of sarcomere
The Cardiac CycleThe Cardiac Cycle
““Pacemakers” of the heart-send Pacemakers” of the heart-send electrical signal through heart electrical signal through heart – Systole-ventricular contractionSystole-ventricular contraction– Diastole-Heart is relaxed allowing filling Diastole-Heart is relaxed allowing filling
of the heartof the heart
**Based on Ventricle, although atria also **Based on Ventricle, although atria also contract and relax contract and relax
The Cardiac CycleThe Cardiac Cycle
End of Diastole-maximal ventricular End of Diastole-maximal ventricular fillingfilling
Electrical signal-triggers ventricular Electrical signal-triggers ventricular contraction.contraction.
Pressure in Ventricle > Atria = closes Pressure in Ventricle > Atria = closes AV valves; semilunar valves not open AV valves; semilunar valves not open yetyet
The Cardiac CycleThe Cardiac Cycle First Heart SoundFirst Heart Sound =closure of AV valves =closure of AV valves
Semilunar Valves open once pressure in Semilunar Valves open once pressure in ventricle is greater than aorta or ventricle is greater than aorta or pulmonary arterypulmonary artery
Stroke Volume = amount of blood ejected Stroke Volume = amount of blood ejected (end diastolic volume-end systolic volume)(end diastolic volume-end systolic volume)
Second Heart SoundSecond Heart Sound= Closure of the = Closure of the Semilunar valvesSemilunar valves
The Cardiac CycleThe Cardiac Cycle
Semilunar Valve-openSemilunar Valve-open AV valves-closedAV valves-closed Ventricle RelaxesVentricle Relaxes Once pressure in the ventricle is less than Once pressure in the ventricle is less than
the atrium-AV valves open allowing filling the atrium-AV valves open allowing filling of ventricleof ventricle
Third heart soundThird heart sound =passive filling of the =passive filling of the ventricleventricle– Normal to hear in horses and ruminants-not Normal to hear in horses and ruminants-not
carnivorescarnivores
Ventricular FillingVentricular Filling
Initial, rapid filling phase-passiveInitial, rapid filling phase-passive Slow-filling phase-atrial contractionSlow-filling phase-atrial contraction
Fourth heart soundFourth heart sound =atrial =atrial contractioncontraction– Normal in ruminants and equine, not in Normal in ruminants and equine, not in
carnivorescarnivores
Cardiac MuscleCardiac Muscle
Striated muscleStriated muscle Impulse from cell to cellImpulse from cell to cell Automaticity-cells can become self-Automaticity-cells can become self-
excitableexcitable– Small portion of the muscle cellsSmall portion of the muscle cells
Activation of cellActivation of cell
Depolarization=Opening of fast Depolarization=Opening of fast sodium channelssodium channels
Wave of depolarizations travels down Wave of depolarizations travels down myocardium-Ca++ channels open in myocardium-Ca++ channels open in sarcoplasmic reticulumsarcoplasmic reticulum– Crosslink of myocardiumCrosslink of myocardium
Refractory Period-resting between Refractory Period-resting between depolarization, unable to contractdepolarization, unable to contract
Cardiac Impulse PropagationCardiac Impulse Propagation
Automatic Tissues-generate action Automatic Tissues-generate action potentialspotentials
Sequence of activationSequence of activation– Sinoatrial (SA) node-fastest rate!Sinoatrial (SA) node-fastest rate!
Atrial ContractionAtrial Contraction
– AV nodeAV node– Bundle of HisBundle of His– Rt. And Lt. Bundle Branch to v. apexRt. And Lt. Bundle Branch to v. apex– Purkinje fibers to myocardiumPurkinje fibers to myocardium
THE WHOLE THE WHOLE PICTUREPICTURE
CHARGE
INSIDE CELL
TIME
Na + influx creates (+) internal charge
+
0
-
0
12
3
4Resting
cell
Depolarization
Repolarization K+ leaves
cell and cell
returns to it’s resting
or repolarized
state
**Purple numbers indicate phase numbers
Action PotentialAction Potential
0-Sodium enters cell 0-Sodium enters cell via fast channelsvia fast channels
1-fast sodium 1-fast sodium channels closechannels close
2-Ca and Na enter cell 2-Ca and Na enter cell via slow channelsvia slow channels
3-K exits cells 3-K exits cells 4- Na and K 4- Na and K
equilibriumequilibrium
Intrinsic RateIntrinsic Rate
SA node-fastestSA node-fastest AV note-40-60 bpmAV note-40-60 bpm Sympathetic and Parasympathetic Sympathetic and Parasympathetic
Nervous System-alter the intrinsic Nervous System-alter the intrinsic raterate– SNS-increase rate of depolarizationSNS-increase rate of depolarization– PNS-decrease rate of depolarizationPNS-decrease rate of depolarization
Heart Rate RegulationHeart Rate Regulation
Baroreceptors-in blood vessels and Baroreceptors-in blood vessels and heart chamberheart chamber– If blood pressure decreasesIf blood pressure decreases
Brain>>Increased Sympathetic nervous Brain>>Increased Sympathetic nervous systemsystem
Increases Heart rate and vasoconstricts to Increases Heart rate and vasoconstricts to increase blood pressureincrease blood pressure
– If blood pressure increases?If blood pressure increases?
Excitation-Contraction CouplingExcitation-Contraction Coupling
See muscle physiology!!See muscle physiology!! Ca++ influxCa++ influx Myofibrils couple via Myofibrils couple via
troponin/tropomysin complextroponin/tropomysin complex
The Electrocardiogram (ECG)The Electrocardiogram (ECG)
Recording of electrical activity of the Recording of electrical activity of the heartheart
Waves-positive vs. negative Waves-positive vs. negative depending on the direction the depending on the direction the impulse is travelingimpulse is traveling
P wave-P wave-– Atrial depolarizationAtrial depolarization
QRS complexQRS complex– Ventricular Ventricular
depolarizationdepolarization T wave-ventricular T wave-ventricular
repolarizationrepolarization
ECGECG
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