CIRCULATORY SYSTEM

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CIRCULATORY SYSTEM

• THE HEART

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CIRCULATORY SYSTEM

• BLOOD
• BLOOD VESSELS
• HEART

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BASIC HEART STRUCTURE

• ANIMAL HEART
• ATRIUM/ATRIA (1 OR 2)
• RECEIVE BLOOD RETURNING TO HEART
• MAMMALIAN HEART POSSESSES 2 ATRIA
• VENTRICLES (1 OR 2)
• PUMP BLOOD FROM THE HEART
• MAMMALIAN HEART POSSESSES 2 VENTRICLES

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BASIC HEART STRUCTURE

• ANIMAL HEART
• ARTERIES
• CARRY BLOOD FROM THE HEART
• ARTERY ? ARTERIOLE ? CAPILLARIES
• CAPILLARIES
• SITE OF GAS AND NUTRIENT EXCHANGE
• VEINS
• RETURN BLOOD TO THE HEART
• CAPILLARIES ? VENULES ? VEINS

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FUNCTIONS OF THE HEART

• TWO MAJOR DIVISIONS
• PULMONARY CIRCUIT
• CARRIES BLOOD TO LUNGS (GILLS)
• GAS EXCHANGE LOSE CO2, GAIN O2
• RIGHT SIDE OF MAMMALIAN HEART
• SYSTEMIC CIRCUIT
• CARRIES BLOOD TO BODY ORGANS
• GAS EXCHANGE LOSE O2, GAIN CO2
• LEFT SIDE OF MAMMALIAN HEART

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HEART STRUCTURE

• CHAMBERS
• ATRIA
• RIGHT AND LEFT
• SEPARATED BY INTERATRIAL SEPTUM
• VENTRICLES
• RIGHT AND LEFT
• SEPARATED BY INTERVENTRICULAR SEPTUM

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BLOOD FLOW THROUGH THE HEART

• RIGHT ATRIUM
• RECEIVES O2-POOR BLOOD FROM BODY
• RIGHT VENTRICLE
• RECEIVES O2-POOR BLOOD FROM RIGHT ATRIUM
• PUMPS O2-POOR BLOOD TO LUNGS
• LEFT ATRIUM
• RECEIVES O2-RICH BLOOD FROM LUNGS
• LEFT VENTRICLE
• RECEIVES O2-RICH BLOOD FROM LEFT ATRIUM
• PUMPS O2-RICH BLOOD TO BODY ORGANS

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HEART VALVES

• CONSIST OF FIBEROUS FLAPS
• ENSURE UNIDIRECTIONAL FLOW
• OPEN AND CLOSE IN RESPONSE TO PRESSURE
  DIFFERENCES BETWEEN SIDES
• ATRIOVENTRICULAR (AV) VALVES
• SEMILUNAR VALVES

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HEART VALVES

• ATRIOVENTRICULAR (AV) VALVES
• RIGHT AV VALVE
• A.K.A. TRICUSPID VALVE
• LEFT AV VALVE
• A.K.A. BICUSPID VALVE
• A.K.A. MITRAL VALVE

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HEART VALVES

• ATRIOVENTRICULAR (AV) VALVES
• ATRIUM ? VENTRICLE
• VENTRICLE RELAXED
• VALVE OPEN
• ATRIUM ? VENTRICLE BLOOD FLOW
• VENTRICLE CONTRACTS
• VENTRICLE PRESSURE INCREASES
• VALVE CLOSES
• PREVENTS BACK FLOW

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HEART VALVES

• ATRIOVENTRICULAR (AV) VALVES
• PAPILLARY MUSCLES
• CONTRACT WITH REST OF VENTRICLE
• PULL ON CHORDAE TENDINEAE
• CHORDAE TENDINEAE
• CONNECT AV VALVE CUSPS TO PAPILLARY MUSCLES OF
• REINFORCE AV VALVES
• PREVENT PROLAPSE

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HEART VALVES

• SEMILUNAR VALVES
• VENTRICLE ? ARTERY
• VENTRICLE RELAXED
• PRESSURE HIGHER IN ARTERIES
• VALVE CLOSED
• VENTRICLE CONTRACTS
• PRESSURE HIGHER IN VENTRICLE
• VALVES FORCED OPEN
• BLOOD FLOWS FROM HEART

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HEART STRUCTURE

• PERICARDIUM
• DOUBLE-WALLED SAC
• ENCLOSES HEART
• CONTAINS PERICARDIAL FLUID (5-30 ML)
• GREATLY REDUCES FRICTION

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HEART STRUCTURE

• HEART WALL
• EPICARDIUM (OUTER)
• A.K.A. VISCERAL PERICARDIUM
• MYOCARDIUM
• THICKEST LAYER
• CARDIAC MUSCLE
• ENDOCARDIUM
• SMOOTH INNER LINING
• CONTINUOUS WITH BLOOD VESSELS

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HEART STRUCTURE

• MYOCARDIUM
• THICKEST CARDIAC MUSCLE
• MUSCLE FIBERS CONNECTED BY FIBROUS (PROTEIN)
  SKELETON
• STRUCTURAL SUPPORT
• SOMETHING TO PULL AGAINST
• ELECTRICAL NONCONDUCTOR
• ALLOWS ATRIA AND VENTRICLES TO CONTRACT SEPARATELY

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CARDIAC MUSCLE STRUCTURE

• CARDIAC MUSCLE CELLS
• MYOCYTES / CARDIOCYTES
• STRIATED
• SHORT, THICK (50 100 mM x 10 - 20 mM)
• BRANCHED
• SINGLE NUCLEUS
• LESS DEVELOPED SR (SER)
• LARGER T-TUBULES (ADMIT Ca)
• JOINED VIA INTERCALATED DISKS

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CARDIAC MUSCLE STRUCTURE

• INTERCALATED DISK FEATURES
• INTERDIGITATING FOLDS
• INCREASED SURFACE AREA CONTACT
• MECHANICAL JUNCTIONS
• FASCIA ADHERENS (ACTIN)
• DESMOSOMES
• ELECTRICAL JUNCTIONS
• GAP JUNCTIONS
• ELECTRICALLY STIMULATE NEIGHBORS

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CARDIAC METABOLISM

• EXCLUSIVELY AEROBIC
• MYOGLOBIN-RICH (STORED O2)
• GLYCOGEN-RICH (STORED SUGAR)
• LARGE MITOCHONDRIA (25 VS 2)
• MULTIPLE FUELS USABLE
• VULNERABLE TO O2 DEFICIENCY
• NOT PRONE TO FATIGUE
• (AEROBIC, NO O2 DEBT, NO FATIGUE)

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CARDIAC RHYTHM

• HEARTBEAT
• INVERTEBRATES
• TRIGGERED BY NERVOUS SYTEM
• VERTEBRATES
• TRIGGERED BY HEART ITSELF

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CARDIAC RHYTHM

• CARDIAC MYOCYTES
• AUTORHYTHMIC
• SPONTANEOUS DEPOLARIZATION AT REGULAR INTERVALS
• SOME SPECIALIZED TO GENERATE ACTION POTENTIALS
• CARDIAC CONDUCTION SYSTEM
• SINOATRIAL (SA) NODE
• ATRIOVENTRICULAR (AV) NODE

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CARDIAC RHYTHYM

• SINOATRIAL (SA) NODE
• MYOCYTES IN RIGHT ATRIUM
• PACEMAKER
• INITIATES HEARTBEAT
• DETERMINES HEART RATE
• FIRING RATE REDUCED BY NERVES
• 70 80 BEATS PER MINUTE (BPM)

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CARDIAC RHYTHYM

• SINOATRIAL (SA) NODE
• CELLS LACK STABLE RESTING MEMBRANE POTENTIAL
• SPONTANEOUSLY DEPOLARIZE AND REPOLARIZE AT
  REGULAR INTERVALS (0.8 SEC)
• EACH DEPOLARIZATION INITIATES ONE HEARTBEAT
• GENERATE ACTION POTENTIAL

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CARDIAC RHYTHYM

• SA ACTION POTENTIAL
• SPREADS THROUGHOUT ATRIAL MYOCARDIUM
• ATRIA CONTRACT SIMULTANEOUSLY
• SIGNAL REACHES AV NODE (50MSEC)
• DELAYED AT AV NODE (100 MSEC)
• VENTRICLES FILL DURING DELAY

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CARDIAC RHYTHYM

• ATRIOVENTRICULAR (AV) NODE
• NEAR RIGHT AV VALVE
• ELECTRICAL GATEWAY TO VENTRICLES
• DISTRIBUTES SIGNAL TO VENTRICULAR MYOCARDIUM
• AV BUNDLE
• PURKINJE FIBERS

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CARDIAC RHYTHYM

• SIGNAL TRAVELS FROM AV THROUGH VENTRICULAR
  MYOCARDIUM
• VENTRICULES CONTRACT SIMULTANEOUSLY
• (PAPILLARY MUSCLES CONTRACT FIRST)

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CARDIAC RHYTHYM

• CARDIAC ACTION POTENTIALS
• PROLONGED DEPOLARIZATION
• 200 - 250 MSEC VS. 2 MSEC
• RESULT OF SLOW Ca CHANNELS
• SUSTAINED CONTRACTION
• LONGER REFRACTORY PERIOD
• 200 MSEC VS. 1 2 MSEC
• PREVENTS WAVE SUMMATION, TETANUS

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SYSTOLE / DIASTOLE

• SYSTOLE
• CONTRACTION OF A HEART CHAMBER
• REFERS TO VENTRICLE UNLESS OTHERWISE NOTED
• DIASTOLE
• PERIOD DURING WHICH A HEART CHAMBER RELAXES AND
  FILLS WITH BLOOD

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ELECTROCARDIOGRAM

• ELECTRICAL CURRENTS GENERATED IN THE HEART TRAVEL
  WEAKLY THROUGH ALL BODY TISSUES
• THESE CURRENTS CAN BE MEASURED USING ELECTRODES
  APPLIED TO THE SKIN

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• P WAVE
• SIGNAL FROM SA NODE DEPOLARIZES ATRIA
• ATRIAL SYSTOLE 100 MSEC AFTER P WAVE BEGINS

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• QRS COMPLEX
• FIRING OF THE AV NODE
• ONSET OF VENTRICULAR DEPOLARIZATION
• ATRIAL REPOLARIZATION / DIASTOLE OBSCURED
• VENTRICULAR SYSTOLE IMMEDIATELY AFTER

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• S T SEGMENT
• MYOCARDIAL ACTION POTENTIAL PLATEAU
• VENTRICLES ARE CONTRACTING
• BLOOD EJECTED FROM VENTRICLES

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• T WAVE
• VENTRICULAR REPOLARIZATION BEFORE DIASTOLE
• (REPOLARIZATION TAKES LONGER THAN DEPOLARIZATION)

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HEART SOUNDS

• FIRST AND SECOND HEART SOUNDS
• S1 AND S2
• LUBB-DUPP
• OCCUR IN CONJUNCTION WITH HEART VALVES CLOSING
• BLOODSTREAM TURBULENCE
• THIRD HEART SOUND (S3)
• SOMETIMES HEARD IN CHILDREN AND ADOLESCENTS

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CARDIAC CYCLE

• ATRIAL SYSTOLE
• ATRIAL DYASTOLE
• VENTRICULAR SYSTOLE
• VENTRICULAR DIASTOLE
• QUIESCENT PERIOD

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CARDIAC CYCLE

• QUIESCENT PERIOD
• NO CONTRACTION OF ANY HEART CHAMBERS
• ATRIA ARE FILLING

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CARDIAC CYCLE

• ATRIAL SYSTOLE
• SA NODE FIRES
• ATRIA DEPOLARIZE
• P WAVE OF ECG PRODUCED
• ATRIA CONTRACT
• BLOOD PRESSURE IN ATRIA INCREASES
• BLOOD FORCED INTO VENTRICLES

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CARDIAC CYCLE

• ISOVOLUMETRIC CONTRACTION
• ATRIA REPOLARIZE, RELAX
• ATRIA IN DIASTOLE FOR REMAINDER
• VENTRICLES DEPOLARIZE, CONTRACT
• VENTRICULAR PRESSURE INCREASES
• AV VALVES CLOSE
• HEART SOUND S1
• NO BLOOD EJECTED YET

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CARDIAC CYCLE

• VENTRICULAR EJECTION
• VENTRICULAR PRESSURE EXCEEDS ARTERIAL PRESSURE
• SEMILUNAR VALVES OPEN
• BLOOD EJECTED INTO ARTERIES
• NOT ALL BLOOD EXPELLED
• AMOUNT EJECTED STROKE VOLUME
• EJECTION FRACTION

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CARDIAC CYCLE

• ISOVOLUMETRIC RELAXATION
• EARLY IN VENTRICULAR DIASTOLE
• BLOOD BRIEFLY FLOWS BACKWARDS
• SEMILUNAR VALVES CLOSE
• HEART SOUND S2
• AV VALVES NOT YET OPEN
• NO BLOOD TAKEN IN YET

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CARDIAC CYCLE

• VENTRICULAR FILLING
• VENTRICULAR PRESSURE DROPS
• AV VALVES OPEN
• VENTRICLES BEGIN TO FILL
• HEART SOUND S3
• (COMPLETELY FILLED BY ATRIAL SYSTOLE)
• P WAVE PRODUCED

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CARDIAC OUTPUT

• HEART RATE (HR) (BEATS/MIN)
• 75 BPM AT REST
• STROKE VOLUME (SV)
• 70 ML/BEAT AT REST
• CARDIAC OUTPUT (CO)
• CO HR SV
• 75 70 5,000 ML/MIN AT REST
• CARDIAC OUTPUT IS NOT CONSTANT

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CARDIAC OUTPUT

• CARDIAC OUTPUT IS NOT CONSTANT
• RESTING
• 5 LITERS/MIN RESTING (TOTAL VOLUME)
• VIGOROUS EXERCISE
• 21 LITERS/MIN IN GOOD CONDITION
• 35 LITERS/MIN OLYMPIC ATHLETE
• CO HR SV,
• CO INCREASED BY HR OR SV INCREASE

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CARDIAC OUTPUT

• HEART RATE
• EASILY MEASURED (PULSE)
• 70 80 AVERAGE RESTING RATE
• TACHYCARDIA RESTING gt100 BPM
• BRACHYCARDIA RESTING lt60 BPM
• REGULATED BY NERVOUS SYSTEM

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CARDIAC OUTPUT

• HEART RATE
• REGULATED BY CARDIAC CENTER OF MEDULLA OBLONGATA
• CARDIOACCELATORY CENTER
• CARDIOINHIBITORY CENTER

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CARDIAC OUTPUT

• HEART RATE
• CARDIOACCELATORY CENTER
• THORACIC SPINAL CORD
• CARDIAC ACCELERATOR NERVES
• SECRETE NOREPINEPHRINE
• BINDS TO RECEPTORS IN HEART
• INCREASES HEART RATE

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CARDIAC OUTPUT

• HEART RATE
• CARDIOINHIBITORY CENTER
• VAGUS NERVES
• SECRETE ACETYLCHOLINE
• SEND SIGNALS TO AV AND SA NODES
• FIRE LESS FREQUENTLY
• INTRINSIC HEART RATE IS 100 BPM

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CARDIAC OUTPUT

• HEART RATE
• CARDIAC CENTER RECEIVES INPUT FROM MULTIPLE
  SOURCES
• PROPRIORECEPTORS
• PHYSICAL ACTIVITY
• BARORECEPTORS
• BLOOD PRESSURE
• CHEMORECEPTORS
• pH, O2, CO2

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CARDIAC OUTPUT

• STROKE VOLUME
• GOVERNED BY THREE FACTORS
• PRELOAD
• CONTRACTILITY
• AFTERLOAD

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CARDIAC OUTPUT

• STROKE VOLUME
• PRELOAD
• VENTRICULAR MYOCARDIUM TENSION PRIOR TO
  CONTRACTION
• SKELETAL MUSCLES MASSAGE VEINS AND INCREASE
  VENOUS RETURN
• MORE TENSION WHEN MYOCARDIUM CONTRACTS
• MORE FORCEFUL CONTRACTION
• MORE BLOOD EXPELLED

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CARDIAC OUTPUT

• CONTRACTILITY
• CONTRACTION FORCE FOR A GIVEN PRELOAD
• MYOCYTES MORE RESPONSIVE TO STIMULATION
• AFFECT Ca CONCENTRATIONS
• (Ca REQUIRED FOR MUSCLE EXCITATION /
  CONTRACTION)

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CARDIAC OUTPUT

• CONTRACTILITY
• Ca CONCENTRATIONS INCREASED BY
• EPINEPHRINE, NOREPINEPHRINE
• GLUCAGON, cAMP
• DIGITALIS

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CARDIAC OUTPUT

• AFTERLOAD
• BLOOD PRESSURE IN ARTERIES JUST OUTSIDE OF
  SEMILUNAR VALVES
• INCREASED AFTERLOAD REDUCES STROKE VOLUME
• CAUSED BY ANYTHING IMPEDING ARTERIAL CIRCULATION

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CARDIAC OUTPUT

• EFFECTS OF EXERCISE
• INCREASED CARDIAC OUTPUT
• VENTRICULAR HYPERTROPHY
• INCREASED STROKE VOLUME
• PROPRIORECEPTORS
• SIGNALS FROM MUSCLES/JOINTS
• INCREASED VENOUS RETURN
• INCREASED PRELOAD