Cardiovascular Control During Exercise

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Cardiovascular Control During Exercise

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Cardiovascular Functions

• Delivery
• Oxygen and nutrients
• Removal
• CO2 and metabolic wastes
• Transport
• hormones
• Maintenance
• Body temperature
• Fluid leves and pH
• Prevention
• infection

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The Heart

• Blood flow through the heart (fig 8.1)
• The myocardium
• interconnected cardiac muscle
• hypertrophy of left ventrical
• The cardiac conduction system (fig 8.3)
• Autoconduction the ability to generate its own
  electrical signal rythmically without neural
  stimuation.
• SA node (pacemaker) sends the electrical impulse
  to the atria and reaches the AV node.
• AV node conducts the impulse from the atria into
  the ventricals through the ....
• AV bundle and Perkinji fibers where it travels
  along the septum and to the ventrical walls
  starting at the Apex.

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The Heart

• Extrinsic control of heart activity
• the parasympathetic nervous system
• decreases H.R. force of heart contraction
• the sympathetic nervous system
• increases H.R. force of heart contraction
• the endocrine system release norepinephrine and
  epinephrine to increase H.R.
• The ECG (fig 8.4)
• records the electrical activity of the heart
• the P wave atrial depolarization
• the QRS complex ventricular depolarization
• the T wave ventricular repolarization

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The ECG
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Cardiac Arrhythmias

• Bradycardia slow heart
• Resting H.R. lt 60
• Tachycardia fast heart
• Resting H.R. gt 100
• Symptoms include
• Fatigue
• Dizziness
• Lightheadedness
• Fainting
• Premature ventricular contraction skipped beat
• Ventricular Fibrillation uncoordinated beat

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The Heart

• The Cardiac Cycle includes all of the events
  between two consecutive cycles
• Diastole relaxation phase
• Systole contraction phase
• Stroke Volume (SV) the amount of blood ejected
  from the left ventrical (fig 8.5).
• SV EDV - ESV
• end diastolic volume (EDV)
• end systolic volume (ESV)
• ejection fraction (EF) (SV / EDV) X
  100
• cardiac output (Q) HR X SV

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The Vascular System

• Method Aorta --gt Arteries --gt Arterioles --gt
  Capillaries --gtVenuoles --gt Veins --gt Vena Cava
• Coronary arteries
• Return of blood to the heart
• breathing increases thoracic pressure
• muscles create a pumping action
• valves prevent backflow

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The Vascular System

• Distribution of blood (fig 8.6)
• autoregulation the vessels ability to detect the
  local chemical changes and regulate its own blood
  flow to meet the needs of the tissues.
• extrensic neural control regulated largely by
  the sympathetic nervous system by constricting
  blood vessels of lesser need.
• redistribution of venous blood creating more
  available blood to meet the needs of the body.
• During Exercise blood is redirected to the areas
  where it is needed most
• Muscles receive up to 80

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The Vascular System

• Redistribution of Venous Blood
• 64 of blood pools in the veins waiting for the
  need.
• Blood pressure
• systolic / diastolic
• Measured sitting and supine/prone
• control weight loss, diet, exercise, meds
• Hypertension 140 / 100
• Hypotension 100 / 60

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The Blood

• Functions
• Transportation of nutrients, hormones, etc.
• Temperature regulation
• Maintain (pH) balance
• Blood volume and composition
• Men 5 - 6 L, Women 4 - 5 L
• composition (fig 8.8)
• 55 plasma
• 90 water
• 45 hematocrit
• red blood cells transport oxygen primarily bound
  to their hemoglobin (iron).
• White blood cells
• platelets

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The Blood

• Blood viscosity refers to the thickness of the
  blood.
• increased viscosity restricts blood flow but
  increases oxygen carrying capacity.
• decreased viscosity increases blood flow but
  decreases oxygen carrying capacity.

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Cardiovascular Response to Exercise

• Increased stroke volume (fig 8.11)
• only up to 40-60 of maximal capacity then
  plateaus (caused by reduced filling time at
  higher h.r. ?)
• increased volume of venous blood return
• increased muscle pumping of venous blood
• increased breathing (thoracic pressure)
• supine positions
• increased ventrical enlargement capacity
• Frank-Starling law when the ventricle stretches
  more, it will contract with more force.
• increased ventrical contractility
• aortic or pulmonary artery pressure

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Cardiovascular Response to Exercise

• Increased heart rate / cardiac output (fig 8.10)
• Anticipatory response (increased heart rate
  before exercise)
• Caused by the release of epinephrine
• Steady state heart rate during steady exercise
• Maximum heart rate 220 - age

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Cardiovascular Response to Exercise

• Redistribution of blood to the working muscles by
  reducing blood flow to the kidneys, stomach,
  liver and intestines.
• Redistribution of blood to the skin in order to
  maintain body temperature.
• Increased metabolic rate of working muscles
• Autoregulation is triggered by low muscle Po2
• Cardiovascular drift increased H.R. compensates
  for a decreased S.V. from a decreased total blood
  volume to maintain Q.
• redistribution
• decreased blood plasma

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Cardiovascular Response to Exercise

• Systolic B.P. increases with intensity
• valsalva during resistance exercise
• increased use of upper body musculature
• Diastolic B. P. does not change

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Cardiovascular Responses to Exercise

• Increased A-V O2 difference representing the
  amount of O2 extracted from the blood to be used
  by the muscles.
• Decreased plasma volume decreased performance
  increased blood pressure forces water from the
  vascular system to the interstitial spaces.
• increased intramuscular osmotic pressure attracts
  fluid to the muscles.
• sweating
• Increased blood viscosity
• decreasing O2 transport
• Decreased blood pH level