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“Little Cowboy”
Homeostasis and The Heart
Tissues and Organs Depend on Appropriate Blood Flow (Perfusion)
Supply = Demand
Starling’s Law: Intrinsic Control of HeartVenous Return determines “stretch”
of cardiac myocytes: Venous Return = Stretch Stretch = Force and Rate
Known as PreloadExercise Increases Venous
Return / Preload / Force & Rate
Extrinsic Control: Baroreceptor ReflexBaroreceptors: Sense stretch in
artery walls(Stretch = Pressure)Aorta Internal Carotid Artery
Afferent Signals to Cardioregulatory Centers: Medulla Oblongata
Perfusion homeostasis by addressing pressure problems:
Heart Rate Decreases
Pressure Increases
InhibitionOf PressureSignals
Baroreceptor Reflex…Efferent Signals from Autonomic
Nervous System:Parasympathetic: Decrease HRSympathetic: Increase HRAdrenal: Increase HR
How do you think pressure affects perfusion of vital tissues?
Decreased CO Threatens Vital OrgansCardiac Response:
Increase HR (to compensate for decreased pressure/SV)
Vascular Response:Direct more of the total blood
volume to vital tissuesAway from less vital tissues
Extrinsic Control: Chemoreceptor Reflexes Increased Metabolism produces more
CO2, acids, and Temp:
Chemoreceptors (mostly in the medulla oblongata) initiate:
SNS stimulation: Rescues from “metabolic buildup” by HR
PSNS stimulation: Slows the heart when CO2, acids and temp recover
Exercise = PreloadWorking muscles “squeeze” more
blood back to heart Increased Venous Return =
Increased PreloadStarling Law is important in
initial increases in Exercise CO
Exercise Stimulates SNSCardioregulatory centers + SNS:
Stimulate SA Node to increase HRStimulate Adrenal Medulla to
release Norepinepherine, which increases HR
Increase contractility and SVIncrease myocardial blood flow
Exercise increases CO2, H+ and Temperature
Chemoreceptors stimulate SNS and adrenal medulla
Increase HR and SV
Exercise Applications:Vital Organs: Heart, Lungs, Brain
(Kidney)How does Exercise affect the “Priority”
of blood flow to “vital organs”?What TWO tissues during exercise
have high priority for perfusion? (become vital organs)
Vital Tissues during Exercise:Working Muscles
Larger muscles = more blood volume = greater venous return
Skin (cooling)BrainHeartLungs
Meeting the Demand: More “Vital Organs”Cardiac Response:
Increased CO by Increased SV * HR
Preserving Blood flow to “HLB”Vascular Response:
Redistributing blood flow from less vital tissues…more later
Think About This: Explain the
difference between an “athlete’s” heart and an non-athlete’s heart:
Address Cardiac Output and Heart rate at rest and exercise.
Athlete vs. Non-Athlete
Ventricle Volume and Mass
Max SV = Max HR Max CO Resting HR Resting SV = Resting CO
More Thinking: How do you think
cardiac output is affected in paraplegic athletes?
What are the dominant muscles? Where?
Would swimmers be similar?
Upper Body Athletes:
Smaller Active Muscle Mass =
Venous Return SV = HR CO
At Maximum Exercise
Summarize: The HeartFunctions of the Heart:
Blood Pressure = PerfusionDirecting Blood: Lungs / Body
Anatomy – LocationLocation / OrientationChambers / ValvesTissues: Epicardium, myocardium,
endocardium
Summary: Anatomy, cont:
Coronary ArteriesPericardium
Blood Flow Through HeartBeginning at Right Atria…Relative O2 contents
Cardiac Myocytes:Anatomy and Action Potentials
Summary: Conduction System of Heart:
SA, AV nodes, AV bundles, bundle branches, purkinje fibers
ECGCardiac Cycle:
Atrial systole - diastoleVentricular systole and diastoleHeart Sounds / Murmurs
Summary: Regulation of Cardiac Output Intrinsic Regulation:
Starling’s Law Extrinsic Regulation:
SNS, PSNS, Endocrine Exercise and Homeostasis:
Perfusion to “VITAL ORGANS” Intrinsic and Extrinsic Controls