Skeletal Lever Systems

Question 1

how are muscles able to generate a force

Answer 1

Muscles made of many long thin fibres. When stimulated by electrical impulses from the CNS, the muscle contracts briefly - exert a force.

Question 2

The maximum tension (force) a muscle can produce is ….

Answer 2

is proportional to the cross sectional area of the muscle at its widest point

Question 3

when is maximum tension achieved

Answer 3

when muscle is stimulated in its relaxed state

Question 4

maximum tension of most muscles

Answer 4

30-40 N/cm2

Question 5

when does maximum tension decrease significantly

Answer 5

significantly if the muscle is elongated or shortened.

Question 6

what does joint articulation usually involve

Answer 6

Joint articulation usually involves using groups of muscles (i.e. normal muscle action and antagonistic muscle action

Question 7

line of action of a fusiform

Answer 7

straight line joining the point of insertion of muscle w/ origin

Question 8

line of action of pennate muscles

Answer 8

like a feather

in direction of fibres - diagonally

Question 9

pennate muscles can produce what kind of lines of action and what does that allow?

Answer 9

Such muscles (multipennate or combinations of pennate or bipennate) can produce oblique (& many) different lines of action. (This allows total muscle force to be minimized

Question 10

lever

Answer 10

apply one force and gives a different force

Question 11

how do levers operate

Answer 11

thru application of moments and torques

longer r is the more torque is applied more leverage

Question 12

moment or torque

Answer 12

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

Question 13

statics

Answer 13

the study of forces acting on an object which is in Equilibrium, i.e. bridges, bones and limbs, etc.

Question 14

a rigid body is in equilibrium when 2 conditions are met.

Answer 14

net force = 0

net torque = 0

Question 15

torque

Answer 15

the quantity which indicates the ability of a force to cause rotation, i.e

Question 16

torque formula

Answer 16

P (pivot) = rFsin0
(radius?/distance)
F = force applied

Question 17

when is the torque largest

Answer 17

The torque is largest when the force F is applied PERPENDICULAR to the direction of r.

Question 18

how to reduce the applied torque

Answer 18

This distance should be minimized to reduce the applied torque, i.e. a much lower torque required to be produced by the back muscles

Question 19

mechanical advantage

Answer 19

measure of efficiency

a ratio of the load force to the applied force

Question 20

levers are examples of ..

Answer 20

simple machines where a force (Fa) is applied to lift or balance a load force (Fl).

Question 21

scale of mechanical advantage

Answer 21

can be >1 or <1 depending on whether the lever is efficient or not

Question 22

3 classes of lever

Answer 22

Class I
Class II
Class III

Question 23

Class I lever

Answer 23

FULCRUM is between load(Fl) and applied force(Fa)/effort

both forces need to be in the same direction otherwise it is a propellors

Question 24

Class II lever

Answer 24

Fl is between the fulcrum and Fa

Fa Fl fulcrum

Question 25

Class III lever

Answer 25

Fa is between fulcrum and Fl

Fl Fa fulcrum

Question 26

mechanical advantage of Class I lever is

Answer 26

more, less or equal to 1

Question 27

mechanical advantage of Class II lever is

Answer 27

always greater than 1

applied force is always further out - always efficient

Question 28

mechanical advantage of Class III lever is

Answer 28

always less than 1 - always inefficient