skeletal lever system Flashcards
how quick does it take a muscle to reach its max force (in seconds)?
0.3s
what is the maximal tension or force a muscle can produce proportional to & what does this mean?
its cross sectional area
- ie the bigger the muscle, the more force it is capable of producing
other than CSA, what is the maximum tension or force that a muscle can produce also dependent on?
the muscle length
describe how muscle tension / force changes with muscle length
- the max tension of most muscles is achieved when the muscle is stimulated in its relaxed state - ie at its free length
- if it is shortened or stretched too much, much less tension will be produced as the actin & myosin filaments won’t be at the optimal length
what is agonist and antagonist muscle activity?
-refers to the coordinated action of muscles that work together to produce movement around a joint.
- the agonist is responsible for generating the movement
-the antagonist is acting in opposition and acts to slow down and control the movement
using the biceps and triceps as an example, describe the antagonist and agonist
-agonist - biceps - flexing the elbow joint - when performing a biceps curl - the biceps shortens to bring arm up
-antagonist - triceps - during elbow flexion, the triceps relaxes to allow the movement to occur smoothly
what is the line of action in muscle?
imaginary line /the direction in which the force produced by the muscle is exerted
where is the line of action in a fusiform type muscle?
-straight line joining the origin and point of insertion of the muscle
-eg biceps brachii muscle
describe the line of action in pennate muscles
-pennate muscles have muscle fibres that are orientated at an angle to the tendon (oblique)
how are pennate muscles classified?
-unipennate eg extensor digitorum
-bipennate - rectus femoris of thigh
-multipennate
what is a moment or torque?
-a force which causes some rotational motion about a fixed point
what is statics?
the study of forces acting on an object which is in equilibrium eg bones, limbs etc
a rigid body is said to be in equilibrium if what 2 conditions are met?
-net force = 0
-net torque = 0
what is the equation to measure torque?
torque = distance x perpendicular force
- note the torque is maximised when force is applied perpendicular to the direction of r
how do we increase the lever?
- increase the force
-increase the length of the arm
when is the torque largest in relation to r (the lever)?
-the torque is largest when the force F is applied perpendicular to the direction of r
what is a lever and fulcrum in physics?
rigid bar or beam that pivots around a fixed point called a fulcrum
-eg sea saw, the fulcrum is the point where the seasaw pivots
what does it mean if the net force = 0?
it means that all the forces acting on the object are balanced, resulting in no acceleration of the object in any direction
what does it mean when the net torque force is =0?
it means that the object is not experiencing any tendency to rotate in either direction. All the torques acting on the object are balanced or cancel each other out.
what is the mechanical advantage (M.A) in relation to levers?
-defined as the ratio of the load force to the applied force
-M.A=Fl/Fa
-a measure of efficiency
what does it mean if the mechanical advantage is bigger than 1? (M.A = Fi/Fa)
it means that the load force is greater than the applied force
what does it mean if the M.A is less than 1?
it means that the load force is less than the applied force
describe a class 1 lever
the fulcrum is located between the applied force and the load (resistance).
- eg a seesaw
describe a class II lever
load is located between the fulcrum and the applied force.
- eg a wheelbarrow
- always provide a mechanical advantage as the load force is greater than the applied force
describe a class III lever
the applied force is located between the fulcrum and the load
-always a mechanical advantage
describe M.A in all 3 classes of levers
-M.A of class I lever can be greater than , less than or equal to 1- can either be efficient or inefficient
-M.A of class II lever is always greater than 1 - always efficient
-M.A of class III lever is always less than 1
give an example in the body of a class I lever
- nodding your head
-your skull/ head serves as the lever
-the joint at the base of your skull - atlanto-occiptal joint serves as the fulcrum - the muscles at the back of your neck are the applied force
- the weight of your head acts as a load force
describe a class II lever in the human body
When you stand on your tiptoes, your foot serves as the lever, the balls of your feet serve as the fulcrum, the weight of your body serves as the load, and the calf muscles provide the effort. The effort is applied farther from the fulcrum (ankle joint) than the load, giving you a mechanical advantage in lifting your body.
describe a class III lever in the human body
When you flex your forearm at the elbow joint to lift a weight (like a dumbbell), your forearm serves as the lever, the elbow joint serves as the fulcrum, the weight of the dumbbell serves as the load, and the bicep muscle provides the effort. In this case, the effort is applied closer to the fulcrum than the load, but it allows for a greater range of motion and speed in lifting the weight.
