week 6 lab 13,14,15,16 Flashcards
What is a lever?
A rigid bar that turns about an axis
In the body, the bones represent the bars and the joints are the axes.
What are the three parts of a lever?
- Force point
- Resistance point
- Fulcrum
What is the force point in a human body lever system?
The insertion point of the muscle of interest on a bone
What is the resistance point in a human body lever system?
The center of gravity of the moving body segment plus any external weight
Define the force arm (FA) of a lever.
The perpendicular distance from the fulcrum to the line of action of the force acting on the force point
Define the resistance arm (RA) of a lever.
The perpendicular distance from the fulcrum to the line of action of the resistance acting on the resistance point
Give an example of a first-class lever in the human body.
The triceps muscle acting at the elbow joint
What distinguishes second-class levers?
The resistance point is located between the force point and the fulcrum
What is a third-class lever?
A lever with its force point located between the resistance point and the fulcrum
What is the main advantage of third-class levers in the human body?
They permit speed and distance of movement at the sacrifice of force
What is the Principle of Levers?
A lever will balance when the product of the force times the distance from the point of application of the force to the fulcrum equals the resistance times the distance from the point of application of the resistance to the fulcrum
What does the equation F x FA = R x RA represent?
The balance condition of a lever
What is mechanical advantage (MA)?
The ratio between the force arm and the resistance arm of a lever
If the force arm is three times as long as the resistance arm, what is the mechanical advantage?
Three to one
True or False: Second-class levers are always force levers.
True
True or False: Third-class levers are always speed levers.
True
What is the center of gravity (CG)?
The point where the sum of all turning moments of the particles acting individually is exactly zero
How is the center of gravity defined in the human body?
- The point of intersection of the three cardinal planes
- The point of exact center around which the body may rotate freely
- The point around which the weight is equal on all opposite sides
What is the reaction board method used for?
Determining the center of gravity of the human body in any position when it is not moving
What equipment is typically used to measure the center of gravity?
- Reaction board
- Tape measure
- Accurate weighing scale
What is the significance of the angle of pull of the biceps muscle in calculations?
It simplifies calculations by allowing the assumption of a 90-degree angle
What must be done to balance a lever?
The product of force and force arm must equal the product of resistance and resistance arm
Fill in the blank: The force of gravity acts upon all particles in a given mass, resulting in a net effect considered as one acting at a point called the _______.
Center of gravity
What does it mean when the resistance arm is longer than the force arm?
The lever favors speed and range of motion at the sacrifice of force
What is the distance between knife edges on the reaction board denoted as?
L
L is measured in centimeters.
What is the mass of the unloaded reaction board denoted as?
R1
R1 is measured in kilograms.
What is the mass of the reaction board plus the subject denoted as?
R2
R2 is measured in kilograms.
What is the equation to calculate the distance of the center of gravity from the feet in the transverse plane?
Y = (F2 x L) / (F1 + F2) = F2L / M
Y represents the distance from the body’s center of gravity to the footboard.
What percentage of the subject’s height does the center of gravity represent in the example given?
55%
The subject’s height is 170 cm.
What are the two main phases in the gait cycle?
- Stance phase
- Swing phase
What is defined as the time when the plantar surface of the foot touches the ground?
Foot-flat
What event occurs when the heel loses contact with the ground?
Heel-off
In running, what is the term for the period when both feet are off the surface?
Flight phase
What is the average velocity of a runner calculated as?
Average velocity = average stride length x average stride frequency
For example, if stride length is 3.0 meters and frequency is 2.0 strides per second, the velocity is 6.0 m/s.
What is the difference between ‘stride length’ and ‘step length’?
- Stride length: distance between two foot strikes of the same foot
- Step length: distance between the foot strike of one foot and the other foot
What muscles are involved in the stance phase during heel strike?
Active muscles include the gluteus medius, quadriceps, and hamstrings
These muscles help stabilize the body during the initial contact with the ground.
What is the definition of ‘stride time’?
The time taken to complete one stride
What is the role of the hamstring muscle group during the gait cycle?
The hamstrings stabilize the leg during the swing phase and assist in deceleration
What is the purpose of the GaitCD software in gait analysis?
To study muscle activation during one gait cycle
What is indicated by the green line in the ‘Ground forces’ picture during gait analysis?
The length of the green line indicates the magnitude of the ground reaction force
What is the role of the diaphragm muscle in the respiratory system?
It aids in inhalation by contracting and expanding the thoracic cavity
What is the function of the aortic valve?
To prevent backflow of blood from the aorta into the left ventricle
Fill in the blank: The __________ is the main muscle responsible for inhalation.
diaphragm
True or False: In running, there is a period where both feet are in contact with the surface at the same time.
False
What major arteries supply blood to the arms?
- Subclavian artery
- Axillary artery
- Brachial artery
- Radial artery
- Ulnar artery
What are the major veins in the systemic circulation?
- Superior vena cava
- Inferior vena cava
- Coronary sinus
- Internal jugular vein
- External jugular vein
What is the function of the aortic arch?
It distributes oxygenated blood from the heart to the body.
The aortic arch branches into major arteries that supply blood to the head, neck, and arms.
Trace a drop of blood from the aortic arch to the right ankle. List the major arteries involved.
Aortic arch, brachiocephalic artery, right common carotid artery, right subclavian artery, thoracic aorta, abdominal aorta, right femoral artery, popliteal artery, posterior tibial artery.
This pathway illustrates the systemic circulation route.
What are the main structures of the heart that should be labeled?
Ventricles, atria, aortic valve, tricuspid valve, bicuspid (mitral) valve, pulmonary arteries, pulmonary veins, superior vena cava, inferior vena cava.
Proper labeling helps in understanding heart anatomy and blood flow.
How does blood return to the right atrium?
Through the superior and inferior vena cava.
The vena cavae are major veins that carry deoxygenated blood back to the heart.
True or False: One should stop abruptly after vigorous exercise.
False.
Cooling down helps prevent dizziness and allows the heart rate to return to normal gradually.
Why is the wall of the left ventricle thicker than the wall of the right ventricle?
It needs to generate higher pressure to pump blood throughout the entire body.
The right ventricle pumps blood only to the lungs, requiring less pressure.
Define ‘atria’ and ‘ventricles’.
Atria are the upper chambers of the heart; ventricles are the lower chambers.
Atria receive blood, while ventricles pump blood out of the heart.
List the vessels that enter or exit the atria and ventricles.
- Atria: superior vena cava, inferior vena cava, pulmonary veins
- Ventricles: pulmonary arteries, aorta
This organization is crucial for understanding heart function and blood flow.
Describe the importance of elasticity and contractility of arteries.
They help maintain blood pressure and regulate blood flow.
Elasticity allows arteries to expand and recoil, while contractility helps in controlling blood distribution.
Where is the heart located in the thoracic cavity?
Between the lungs, slightly to the left of the midline.
This location is essential for its protective function and efficient blood pumping.
Why are heart valves important?
They prevent backflow of blood and ensure unidirectional flow.
Leaky valves can lead to inefficient blood circulation and heart problems.
Why are artery walls thicker than those of corresponding veins?
Arteries need to withstand higher pressure from the heart’s pumping action.
The structure of arteries supports their role in carrying oxygenated blood under pressure.
