skeletal lever system

Question 1

how quick does it take a muscle to reach its max force (in seconds)?

Answer 1

0.3s

Question 2

what is the maximal tension or force a muscle can produce proportional to & what does this mean?

Answer 2

its cross sectional area
- ie the bigger the muscle, the more force it is capable of producing

Question 3

other than CSA, what is the maximum tension or force that a muscle can produce also dependent on?

Answer 3

the muscle length

Question 4

describe how muscle tension / force changes with muscle length

Answer 4

• 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

Question 5

what is agonist and antagonist muscle activity?

Answer 5

-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

Question 6

using the biceps and triceps as an example, describe the antagonist and agonist

Answer 6

-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

Question 7

what is the line of action in muscle?

Answer 7

imaginary line /the direction in which the force produced by the muscle is exerted

Question 8

where is the line of action in a fusiform type muscle?

Answer 8

-straight line joining the origin and point of insertion of the muscle
-eg biceps brachii muscle

Question 9

describe the line of action in pennate muscles

Answer 9

-pennate muscles have muscle fibres that are orientated at an angle to the tendon (oblique)

Question 10

how are pennate muscles classified?

Answer 10

-unipennate eg extensor digitorum
-bipennate - rectus femoris of thigh
-multipennate

Question 11

what is a moment or torque?

Answer 11

-a force which causes some rotational motion about a fixed point

Question 12

what is statics?

Answer 12

the study of forces acting on an object which is in equilibrium eg bones, limbs etc

Question 13

a rigid body is said to be in equilibrium if what 2 conditions are met?

Answer 13

-net force = 0
-net torque = 0

Question 14

what is the equation to measure torque?

Answer 14

torque = distance x perpendicular force

• note the torque is maximised when force is applied perpendicular to the direction of r

Question 15

how do we increase the lever?

Answer 15

• increase the force
  -increase the length of the arm

Question 16

when is the torque largest in relation to r (the lever)?

Answer 16

-the torque is largest when the force F is applied perpendicular to the direction of r

Question 17

what is a lever and fulcrum in physics?

Answer 17

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

Question 18

what does it mean if the net force = 0?

Answer 18

it means that all the forces acting on the object are balanced, resulting in no acceleration of the object in any direction

Question 19

what does it mean when the net torque force is =0?

Answer 19

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.

Question 20

what is the mechanical advantage (M.A) in relation to levers?

Answer 20

-defined as the ratio of the load force to the applied force
-M.A=Fl/Fa
-a measure of efficiency

Question 21

what does it mean if the mechanical advantage is bigger than 1? (M.A = Fi/Fa)

Answer 21

it means that the load force is greater than the applied force

Question 22

what does it mean if the M.A is less than 1?

Answer 22

it means that the load force is less than the applied force

Question 23

describe a class 1 lever

Answer 23

the fulcrum is located between the applied force and the load (resistance).
- eg a seesaw

Question 24

describe a class II lever

Answer 24

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

Question 25

describe a class III lever

Answer 25

the applied force is located between the fulcrum and the load -always a mechanical advantage

Question 26

describe M.A in all 3 classes of levers

Answer 26

-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

Question 27

give an example in the body of a class I lever

Answer 27

- 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

Question 28

describe a class II lever in the human body

Answer 28

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.

Question 29

describe a class III lever in the human body

Answer 29

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.