Lecture 10: Form and Action and Joints Flashcards
What does form of muscle depend on?
muscle fiber length, number of muscle fibers, arrangement of muscle fibers.
Describe pennate muscle fiber structure.
Pennate fibers are arranged oblique to muscle tendon. This allows more fibers to be fit into the same area if they were parallel. However, this reduces the shortening due to length but increases the cross sectional area.
1st class lever.
Stabilise joint position. E.g. Neck
2nd class lever.
Effective at overcoming loads. E.g. Ankle
3rd class lever.
Large ROM for speed. E.g. Elbow
Describe the types of muscle action.
Concentric, Eccentric and Isometric.
Concentric - Shortening of muscle, developing tension.
Eccentric - Lengthening of muscle, releasing tension.
Isometric - Muscles have tension however there is no change in length of muscle or joint position.
Describe the types of muscle roles.
Antagonist - Works to control the movement by working eccentrically.
Agonist - Facilitates the movement by working concentrically.
Stabiliser - Works to keep a joint stable by acting isometrically, muscles have tension but joint position doesn’t change.
Neutraliser - Muscle eliminates unwanted movement caused by another movement. E.g. pronator works to neutralise the supinating effect of biceps when drinking.
Deltoid.
Deltoid crosses the shoulder joint. Works as agonist of flexion, extension and abduction. Anterior fibers produce flexion, posterior fibers extension and lateral fibers produce abduction.
Attaches to pictorial girdle (clavicle and scapula) and the humorous.
Biceps Brachii.
Biceps Brachii cross the elbow and shoulder. They work as the agonist of flexion at the shoulder and elbow. They also supinate the radioulnar joint as they insert into the radial tuberosity.
Triceps Brachii.
Cross the shoulder and elbow. Work as extensor of the elbow and shoulder as they lie on the posterior side. Don’t work as pronators as they insert into the ulna not the radius.
Iliopsoas.
Made of two muscles, the Psoas Major and iliacsus fuse together at the distal end of the hip. Produce flexion at the hip.
Gluteus Maximus.
Crosses posterior aspect of hip. Attaches to femur producing hip extention.
Quadriceps Femoris
Made of four muscles. Rectus Femoris lies most superficial with vastus lateralis, vastus medialis and vastus intermedialus lying under it. They all attach to the patella of the knee joint however the rectus Femoris also crosses the hip joint. Therefore the rectus Femoris can produce flexion of the hip and extension of the knee. The other quadriceps Femoris muscles can only produce extention of the knee.
Hamstrings.
Made of three muscles, semimembranosus, biceps Femoris and semitendinosus run over posterior side of hip and knee. Hip extensor.
Triceps Surae.
Made of gastrocnemius and soleus. Gastrocnemius cross over posterior side of ankle and knee while soleus only cross over the ankle. Gastrocnemius produces flexion of the knee and plantarflexion. Soleus only produces plantarflexion.
