Muscles 3 Flashcards
How does skeletal muscle cause movement at synovial joints
- attaches to bone (lever)
- muscle structure (length, number and arrangement of muscle fibres)
- type of contraction (roles/action)
- crosses joint (location)
4 parts that make bones and muscle anatomical levers
Bones = lever
Joint = pivot or fulcrum
Muscle contraction = pull/applied force
Load = external or internal
Types of levers with muscle attachments
Lever arrangement determines function
First = stabilise joint position
- e.g: see-saw, scissors
- how you nod your head
Second = effective at overcoming loads
- wheelbarrow, bottle opener
- plantar flexion at the ankle joint (gastrocnemius)
Third = larger range of movement and speed, not as big load
- tweezers, fishing
- flexion at the elbow joint (flexion at the elbow joint)
Muscle form determines function, muscle form depends on
1: Length of muscle fibres
2: Number of muscle fibres
3: Arrangement of muscle fibres
Length of muscle fibres: how it determines function
- fibres can shorten up to 50% of resting length
- large ROM required = must have long muscle fibres
If you want a larger range of movement, you need lots of long muscle fibres to contract a lot and bring bones closer together
Number of muscle fibres: how it determines function
Tension (force) is directly proportional to the cross-sectional area (CSA)
Greater number of fibres =
- greater CSA
- greater tension
The more muscle fibres fitted into muscle, the more tension it can generate thus the heavier it can lift
Arrangement of muscle fibres: how it determines function
Fibres arranged vertically between muscle tendons - parallel
Fibres oblique to muscle tendon - pennate
- pennate = more fibres into same space
- reduced shortening as pennate will only shorten half the shortest fibre - not big ROM
- greater CSA thus muscle can generate more tension and overcome more weight
3 types of pennate
- unipennarte
- bipennate
- multi pennate
Three types of muscle contraction
- concentric
- essentric
- isometric
Concentric
- muscle is active, develops tension
- tension is greater then the load
- muscle shortens
- change in joint position
- angle decreases
Biceps brachii - elbow joint
Elbow flexion: biceps brachii contracts concentrically
Eccentric
- muscle is active, develops tension
- tension is lesser then the load
- muscle elongates
- pull in opposite direction by another muscle/gravity
- change in joint position
- angle increases
Elbow extension: biceps brachii contracts eccentrically
Isometric
- muscle is active, develops tension
- tension does not outweigh load (=)
- no change in length of muscle
- no change in joint position
- no change in angle
Holding the elbow joint still: biceps brachii contracts isometrically
Different roles of muscles at a joint:
- Agonist
- Anagonisy
- Stabiliser
- Neutraliser
Agonists and Atagonists
Agonist (biceps brachii) act concentrically to create movemnt at a joint, (bicep brachii shortens)
Antagonist (triceps brachii) act eccentrically to oppose and control the movement (triceps brachii lengthens)
AGONIST = DRIVER = ACT CONCENTRICALLY
ANTAGONIST = OPPOSE = ACT ECCENTRICALLY
They can switch depending on what’s happening at the joint
Stabilisers
- when a muscle is active to hold a joint still it is a stabiliser
E.g: holding a heavy book - biceps brachii role = stabiliser
- biceps brachii action = isometric
No change in length of muscle
