Transcript Cardiac & Respiratory Dynamics - CHOW

Cardiac & Respiratory Dynamics
Vascular System
Carry blood away from heart
Arteries  Arterioles  Capillaries
Carry blood to heart
Capillaries  Venules  Veins  Large Veins
Venous Return
• One-way valves
– Ensure blood goes back to the
heart and not backwards
• Skeletal muscle pump
– Low pressure in veins 
skeletal contracts to increase
pressure
• Thoracic pump
– Difference in pressure between
2 cavities
– Each breath taken, pressure in
chest cavity low, abdominal
pressure increases
– Blood from abdominal to
thoracic cavity
• Venoconstiction
– Nervous system sends signal to
veins to slightly constrict
Cardiac Cycle
• Diastole – phase of relaxation
• Systole – phase of contraction
Systolic blood pressure –
measure in arteries during
contraction (120 mm Hg)
Diastolic blood pressure –
measure in arteries during
contraction (80mm Hg)
Normal person: 120/80 mmHg
Hypertension: >140/90 mmHg
– Elevated blood pressure
Blood
• Erythrocytes (red blood cells)
– Transport O2 and CO2
– Contain hemoglobin  bind O2 and CO2
• Leukocytes (white blood cells)
– Protect body from diseases
– Contain platelets  blood clotting
Cardiovascular Dynamics
Cardiac Output
• Volume of blood pumped out of the left
ventricle in 1 minute (L/min)
• Factors: stroke volume & heart rate
Cardiac
Output
(L/min)
Q = SV x HR
Stroke
Volume (mL)
Heart Rate
(beats/min)
• Stroke Volume (SV)
– Amount of blood ejected from left ventricle in
single beat
Stroke
Volume
(mL)
SV = LVEDV – LVESV
Left
Ventricular
End-Systolic
Volume (mL)
Left Ventricular
Diastolic Volume (mL)
• Heart Rate (HR)
– Number of times hear beats in one minute
Maximum Heart Rate = 220 – age (years)
How do you increase Q?
↑ Heart Rate
↑ Stroke Volume
Increase SV or HR?
• Preferred way: ↑ stroke volume
• Heart pushes more blood volume with each
pump in left ventricle
• Heart can beat fewer times
• Less stress on heart
• Athlete has lower heart rate and beats less
than a sedentary person
Cardiovascular Training
• Cardiac output increase linearly with exercise
intensity
• Body needs more oxygen = more blood is
needed to be pumped to body
• Aerobic training
• Increase in ventricular volume & thickness of
ventricular wall
• ↑ ventricular volume = ↑stroke volume
Respiratory Dynamics
Pulmonary Ventilation
• Rate and/or intensity of work being done = air in
and out of the body
Ventilation (VE)
• Inspiration + expiration
• Volume of air moved by lungs in 1 minute
Ventilation
(L/min)
VE = VT x ƒ
Tidal Volume (L)
– volume of air
in each breath
Respiratory Frequency
(breaths/min) – # of
breaths taken per
minute
Oxygen Uptake
• Amount of oxygen consumed by body during
cellular respiration
• Measure as volume of oxygen consumed in
given time (VO2)
• Increases with activity
• VO2max – maximal volume of oxygen that can
be supplied to and consumed by body