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
Neutralisers GO OVER THIS
- muscle eliminates an unwanted movement caused by another muscle
E.g: biceps brachiii - Pronator muscles neutralise supinating effect of biceps brachii
Biceps brachii
- two headed muscle
- shoulder, flexion (Attatches anterialy to scapular and elbow)
- elbo, flexion
- attatches to radius (radial tuberosity) to allow supernation
Triceps brachii
3 headed muscle
- runs posterior causing extension
- muscle runs into olecraron
- elbow extension
- shoulder extension
Deltoid
- attachment to clavicle then scapular (pectoral girdle)
- attatchemnt to shaft of humerus as well
Shoulder:
- flexion (anterior fibres)
- abduction (lateral fibres
- extension (posterior fibres)
Iliopsoas
- Psoas runs down vertebra into hip and joins up iliacus and together run down to hip joint and sit anterior for flexion
Gluteus maximus
Attachment to femur
Attachment to large tendon
Hip
- extension
Sits posterior
Quadriceps femoris : Rectus femoris
Recuts femoris:
KNEE - attaches to anterior thus extending
- also flexes hip, only one to cross hip joint
Quadriceps femoris (other 3)
4 headed straight muscle of femur
Vasti muscles:
- lateralis
- intermedius
- medialis
(Anterior on quad helping with flexion)))))))))???????????
Hamstrings
3 muscles involved - all 3 attach to hip bone
- biceps femoris
- semi-membranosus
- semi tendinosus
Hip:
- extension - runs posterior
Knee:
- flexion - runs posterior
- rotation when knee is flexed
Tibialis anterior
Ankle
- Doriflexion - runs anterior to ankle causing Dorsiflexion
Foot:
- inversion - runs to medial side of joint causing inversion
Triceps surae
Gastrocnemius and soleus
Ankle:
- plantarflexion as it runs posterior
(Gastrocnemius also flexes knee, only one to cross knee joint)
