BPK 142 Study Guide - Final Guide: Alveolar Pressure, Premature Ventricular Contraction, Pulmonary Circulation
25 Jun 2017
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BPK 142 Final Exam – Lecture
Lecture 6: Biomechanics
IV. Newton’s Laws of Motion
1. First Law - Law of Inertia - “A body will maintain a state of rest or constant velocity unless acted
on by an external force that changes the state.” The amount of inertia a body possesses is directly
proportional to its mass.
2. Second Law - Law of Acceleration - “force equals mass X acceleration” – F = ma
3. Third Law - Law of Reaction - “When one body exerts a force on a second body, the second
body exerts a reaction force that is equal in magnitude and opposite in direction on the first
body.”
• Momentum
• A mechanical quantity that is important in situations involving collisions.
• Momentum = mass X velocity
V. Work and Power Relations
Work = force X distance
Units of work - 1.0 Nm = 1.0 J (joule)
Power = work per unit of time = Fdt
= force X velocity
Units of power = watts - 1.0 W = 1.0 J/s.
VI. Walking Versus Running
Differences between walking and running:
1. In running there is a period when both feet are off the ground. Consider running as a series of
jumps.
2. In running, there is no period when both feet are in contact with the ground at the same time
3. In running, the stance phase is a much smaller portion of the total gait cycle than in walking.
Running speed = stride length X stride rate
• Length of stride is dependent primarily upon leg length and the power of the stride. Leg speed
(frequency) is mostly dependent on speed of muscle contraction and neuromuscular coordination
(skill) in running.
• Running mechanics vary from person to person and they vary in the same person running at
different speeds.
• At slow running speeds, complete foot contact is used. As running speed increases, the amount
of foot contact becomes less.
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• At slower running speeds, runners tend to run more erectly, whereas at full speed, the typical
sprinter leans forward at about 15 degrees from the perpendicular.
Lecture 7: Pulmonary Structure and Function
I. Anatomy of the Respiratory System
• Respiratory system consists of nose, pharynx, larynx, trachea, bronchi, and lungs.
• Bronchi - primary, secondary, and tertiary bronchi ---> terminal and respiratory bronchioles ---
> alveolar ducts ---> alveoli.
• With branching, supportive cartilage is gradually replaced by smooth muscle.
• Contraction and relaxation of this smooth muscle constricts or dilates the bronchioles --> major
effects on airway resistance.
• The conducting airways lead inspired air to the alveoli.
• Volume of conducting airways = anatomic dead space (VD) - 150 mL
• Alveoli - small, thin walled sacs that have capillary beds in their walls; site of gas molecule
(O2 & CO2) exchange between air and blood; there are millions (300) of alveoli
o Continuous capillary – less exchange of material
o Discontinuous capillary – more exchange of material
• Respiratory membrane – alveolar-capillary membranes that separate the air molecules in the
alveoli from the blood in the capillaries - average thickness is 0.6 micrometers. Fick’s Law of
Diffusion
o Fick’s Law of Diffusion = tells us about how our body works, how it evolved, and
how it is affected by disease
• The respiratory membrane has a very large surface area – 70 square meters in the normal adult
- size of tennis court.
• Lungs - contain conducting airways, alveoli, blood vessels, elastic tissue.
II. Mechanics of Breathing
• Molecules move from areas of high pressure or concentration to areas of low pressure or
concentration.
• Boyle's Law - the pressure of a gas is inversely proportional to its volume. P1V1 = P2V2
• The movement of air into and out of the lungs results from a pressure difference between the
pulmonary air and the atmosphere.
• Inspiration - active process - diaphragm descends and external intercostal muscles contract thus
increasing the volume of the thoracic cavity decreased pressure in thoracic cavity causing a
one or two mm Hg drop in intra-alveolar pressure at rest compared to the outside atmospheric
pressure air molecules move through the respiratory tubes into the lungs from the
atmosphere following the pressure gradient.
• Inspiratory muscles, when they work their hardest, can produce a negative pressure as great as -
30 mm Hg below atmospheric pressure within the alveoli.
o Negative pressure refers to the outside
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• Expiration - passive process at rest. Secondary muscles, such as abdominal muscles become
involved in exercise.
• Forced expiration can produce intra-alveolar pressure as great as +50 mm Hg above
atmospheric pressure.
• During exercise, mouth breathing tends to replace nasal breathing - less resistance to airflow.
• Air that enters the respiratory passages via either the nose or the mouth is quickly saturated
with water vapor and warmed to body temperature, 37 degrees centigrade, even under
conditions when very cold air is inspired.
• Compliance – the amount of volume change in the lung for a given change in alveolar
pressure.
III. Lung Volumes
• Vital Capacity (VC): the greatest volume of gas that can be expelled by voluntary effort after
maximal inspiration – sum of IC and ERV
• Inspiratory Capacity (IC): the maximal volume of gas that can be inspired from the resting
end-expiratory position
• Expiratory Reserve Volume (ERV): the maximal volume that can be exhaled from the
resting end-expiratory position
• Functional Residual Capacity (FRC): the volume of gas remaining in the lungs at the end of
a quiet exhalation – composed of: ERV + RV
• Residual Volume (RV): the volume of gas remaining in the lungs after forced expiration
• Total Lung Capacity (TLC): the volume of gas in the lungs at the time of maximal
inspiration – composed of: VC (IC +ERV) + RV
• Residual Volume – Total Lung Capacity Ratio [(RV/TLC) x 100]: the percentage of the
total lung capacity occupied by residual volume – 20-30%
• Tidal Volume (VT): the volume of gas inspired or expired with each breath at rest or during
any stated activity
• Minute Ventilation (VE): the volume of gas either inspired or expired (but not both) per
minute at rest or during an stated activity – VT x # breaths/min
• Maximum Breathing Capacity (MBC): the maximum volume of air which may be breathed
during maximum effort – estimated from 12 second period of hyperventilation at rest;
volume/minute – multiply 12 second value by 5
• Forced Expiratory Volume in One Second (FEV1.0): the volume of air expired during the
first 1.0 seconds of a forced vital capacity maneuver – which is where the subject is instructed
to expire as hard and as fast as possible for four seconds
• Valsalva Maneuver: making volume in thorax smaller, pressure increase blood no longer
gets into thorax so blood doesn’t get out cuts blood to brain pass out
• Normal values at rest:
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Document Summary
Units of work - 1. 0 nm = 1. 0 j (joule) Power = work per unit of time = fd t. Units of power = watts - 1. 0 w = 1. 0 j/s. Differences between walking and running: in running there is a period when both feet are off the ground. Running speed = stride length x stride rate: length of stride is dependent primarily upon leg length and the power of the stride. As running speed increases, the amount of foot contact becomes less: at slower running speeds, runners tend to run more erectly, whereas at full speed, the typical sprinter leans forward at about 15 degrees from the perpendicular. Lecture 7: pulmonary structure and function: anatomy of the respiratory system, respiratory system consists of nose, pharynx, larynx, trachea, bronchi, and lungs, bronchi - primary, secondary, and tertiary bronchi ---> terminal and respiratory bronchioles --- Size of tennis court: lungs - contain conducting airways, alveoli, blood vessels, elastic tissue.
