Heart Valves

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Heart Valves

• Atrioventricular valves
• Tricuspid and Bicuspid
• Prevent backflow into the atria when ventricles
  are contracting
• Semilunar valves
• Pulmonary and Aortic semilunar valves
• Prevent backflow into the ventricles when they
  are relaxing

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Mechanisms to aid in return of blood to heart

• One way Valves
• Open to allow blood through then close to prevent
  backflow
• Skeletal muscle contractions
• Help to pump blood through by constricting veins
  and squeezing blood
• Breathing
• Help to pump blood through by constricting veins
  and squeezing blood

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Problems with blood return

• Fainting
• Standing still too long without moving
  particularly your lower body
• less blood circulating because of accumulation in
  veins already have low blood pressure
• Varicose veins
• stretching of veins caused by accumulation of
  blood
• weak valves (allowed pooling of blood), standing
  too much
• Light headedness from lifting
• improper breathing

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Heart sounds

• Heart valves closing during each heartbeat create
  stereotypical sound lub-dup
• LUB two atroventricular valves close during
  ventricular contraction
• DUP two semilunar valves close during
  ventricular relaxation

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Heartbeat conduction

• Myogenic
• The ability of the heart to contract is a
  property of the heart muscle itself it is not
  dependent on the body's nervous system
• But brain does control the rate

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Heartbeat
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Conduction of heartbeat 0.85 sec
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Electrical and Contractile Sequence of the Heart
Beat

• SA node fires, initiating an impulse that rapidly
  travels across the atria
• Atria contract almost simultaneously (as a unit)
  forcing blood across the valves and into the
  ventricles
• Signal passes on to the septum separating right
  and left halves of the heart Atrioventricular
  node
• AV node delays conduction of impulses from the
  atria to the ventricle (to ensure complete atrial
  contraction before ventricles begin contraction)

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• AV node transfers signal to rapid conduction
  pathway called the bundle of His
• Bundle branches divide into right and left halves
  going to right and left ventricles respectively
• Bundle of His accelerates the impulse and passes
  it down the interventricular septum to the
  Purkinje fibers
• Purkinje fibers carry the impulse deep into the
  ventricular myocardial walls
• Ventricles contract simultaneously (as a unit),
  forcing the AV valves shut, and pumping the blood
  into the aorta on the left and the pulmonary
  arteries on the right

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Extrinsic control of heartbeat

• Nervous Control of Heartbeat
• Cardiac center in medulla oblongata can alter
  heartbeat through autonomic nervous system
• Parasympathetic system promotes normal responses
  including slowing down heartbeat
• Sympathetic system promotes stress responses
  including speeding up heartbeat
• Need for oxygen, increase in blood pressure, etc.
  may activate systems

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Hormones in heartbeat

• Chemical messengers (hormones) called
  catecholamines, which consist of adrenaline
  (epinephrine) and noradrenaline (norepinephrine)
  help to speed up heart rate
• Acetylcholine, has the opposite effect, causing
  the heart rate to slow

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Heart rate (72 beats/min)

• Factors age, gender, exercise, body temp.
• fetus 140-160 beats per min (FYI)
• faster in women
• Exercise raises heart rate
• increases systemic blood pressure and routes more
  blood to the working muscles.
• Trained athletes may be as low as 40-60 beats per
  min.

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Blood Pressure

• The pressure the blood exerts against any unit
  area of the blood vessel walls
• Systolic (heart contracting) Less than 120mm Hg
• Diastolic (pressure at the moment your heart
  relaxes to permit blood flow into its chambers)
  Less than 80mm Hg
• Normal blood pressure written as 120/80mmHg

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Measured in the arteries
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Sounds of Korotkoff

• Cuff tightens it cuts off the blood flow to your
  arm. As pressure is released, a thump is heard
  (Systolic). This is what we hear as the LUB
  sound
• As the cuff is loosened further, the pressure
  continues to fall and the lighter thumps are
  heard as the blood finds it easy to push pass the
  cuff. Thumping stops (Diastolic). This is what we
  hear as the DUP sound

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ECG (Electrocardiogram)

• Recording of electrical changes during a cardiac
  cycle

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ECG

• Normal heartbeat
• Is the result of an electrical impulse
• Originates in a specialized area in the wall of
  the right atrium called the SinoAtrial node
• SinoAtrial node (a.k.a) SA node (a.k.a) Pace Maker

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ECG

• P wave-electrical activity initiated by SA node
  causing atria to contract
• QRS wave-impulses to stimulate ventricle to
  contract
• T wave- electrical recovery of ventricles

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Arrhythmia (Irregular heart beat)

• Problems that affect the electrical system of the
  heart muscle
• Irregularities in initiation or conduction of
  impulses
• Results in abnormal heart beat
• Cause the heart to pump less effectively
• Occurs due to
• coronary artery disease, high blood pressure,
  diabetes, smoking, excessive use of alcohol, drug
  abuse and stress

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Irregular heart beats Too slow

• Bradycardia
• heart rate slower than 60 beats per minute
• Result
• low body temp, certain drugs, brain edema after
  head trauma
• In endurance type athletes, heart rate can lower
  and still provide the same cardiac output

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Irregular heart beats Too fast

• Tachycardia
• abnormally fast heart rate, over 100 beats per
  minute
• Due to
• stress, elevated body temp, stress, certain drugs
  or heart disease. Can promote fibrillation
• Rapid and irregular or out of phase contractions
• Defibrillation - strong electrical shock

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Heart Murmur

• Small deformity in valve blood passes back into
  the atria after the valves have closed
• Produces a swishing noise
• Reduce efficiency of blood flow
• Can hinder persons ability to sustain normal
  activity levels

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Emergency Defibrillation

• Heart attack induces ventricular fibrillation
• Regain normal rhythm
• CPR (Cardio-Pulmonary Resuscitation)