CIRCULATORY AND RESPIRATORY SYSTEMS
Homeostasis- maintaining constant internal conditions
under changing environmental conditions
Organ systems that supply tissues must have reserve
capacity: increase or decrease supply when
physiological demand changes
Supply of oxygen to metabolizing tissues  integrated
function of circulatory and respiratory systems
Integration of cardiac and respiratory function with
demands of metabolizing muscles is performed by the
autonomic nervous system
fluctuation in
blood pressure
drops with
distance from
heart –
pressure
damping
blood pressure
drops with
distance from
heart
Blood pressure - systole vs. diastole
- systole - maximum contraction - pressure generation
- diastole - relaxation – refilling of chambers with venous
blood
Increasing cardiac output - reserve capacity
1. increase stroke volume - volume pumped per contraction
2. increase heart rate
Blood pressure is affected by:
a. amount of heart contraction
b. stroke volume
c. peripheral resistance
- all circulatory routes not open simultaneously
- more routes open  lower resistance
- autonomic nervous system controls heart
contractions and patterns of blood flow
For 2 subjects, measure:
1) Resting heart rate, systolic, and diastolic blood pressure
2) Exercise vigorously for 3-5 minutes
3) Measure blood pressure and heart rate immediately
following exercise
Expected changes after exercise:
Blood pressure: depends on fitness level
- well-conditioned individuals: blood pressure may decrease
due to opening up more routes for blood flow to muscles –
reduced peripheral resistance
- sedentary individuals: increased ventricle contraction 
increase blood pressure
Pulse rate: increase; amount varies based on fitness
RESPIRATORY RESERVES – ability to increase volume of
gas exchanged when needed
Negative pressure breathers - aspiration mechanism
- partial vacuum in lungs created by expanding volume of
chest cavity
Amount of expansion increases with demand:
1) low level activity - diaphragm alone
2) moderate levels of activity
- intercostal muscles expand,
compress rib cage
3) extreme activity
- abdominal, trunk
muscles move viscera
up and down
Reserve capacity – two ways to increase gas exchange
1) increase tidal volume - volume of gas moved in and out
of lungs in each breathing cycle
2) increase breathing rate
Tidal volume - increases from rest  exertion
- increased inhalation – inspiratory reserve
- increased exhalation – expiratory reserve
inspiratory
reserve
resting
tidal volume
maximal tidal volume
expiratory
reserve
The maximum tidal volume is called vital capacity
- the greatest volume of air that can be moved in and out with a
single breath
Spirometer - measures only expiration volumes; do not inhale
3 measurements:
A) inhale normally, then expel as much air as possible into
spirometer  resting tidal volume + expiratory reserve
B) exhale normally, then expel as much air as possible into
spirometer  expiratory reserve only
C) inhale maximally, then expel as much air as possible into
spirometer  vital capacity = the sum of inspiratory reserve,
expiratory reserve, and tidal volume
A – B = resting tidal volume
C – A = inspiratory reserve
Compare your vital capacity with average:
Dubois chart – average (expected) vital capacity for man or
woman of given height and weight
Look up your weight and height – chart gives you surface area
of body (in square meters)
- multiply x 2 for women, x2.5 for men = expected vital
capacity in Liters (gender conversion factor)
- calculate % difference from average - your measured vital
capacity vs. the expected average for someone of your size
Example:
- your vital capacity is 4.25L (measured with spirometer)
- expected vital capacity is 4.0L (calculated from Dubois
chart)
% difference = (4.25- 4.0)/ 4.0 x 100 = (0.25/4) x 100 =
+ 6.25%
RESPIRATORY RATE AND VOLUME
Total volume of gas exchange = volume x frequency of
breaths
Respiratory minute volume
= tidal volume x number of breaths/minute
Measure respiratory rate before and after vigorous exercise
Estimate:
Resting minute volume = resting tidal volume x resting
respiration rate
Exertion minute volume = vital capacity x after exercise
respiration rate
TO DO:
1. Table 1 and 2. Collect BP and heart rate data before and
after exercise for 2 members of your group.
2. Table 3 and 4. Measure respiratory volumes and %
deviation from average for 2 individuals. Take the
average of 3 readings for each measured volume.
3. Table 5. Respiratory minute volume, before and after
exercise.
TO TURN IN NEXT WEEK:
1. Tables 1-5, and paragraph of interpretation of each.
What do these data tell you about the mechanics, function,
or reserve capacity of the heart and respiratory system?
How does the autonomic nervous system affect these
systems? Why?