Lecture Ten : Muscle III - Form and Actions at Joints
13 important questions on Lecture Ten : Muscle III - Form and Actions at Joints
Explain the 3 factors that affect muscle contraction/function?
- Length of muscle fibres : longer fibres can contract more (greater range of movement). Fibres can shorten up to 50% of their resting length during contraction.
- Number of muscle fibres : By increasing the number of muscle fibres, you increase the cross-sectional area of the muscle which is directly proportional to tension (can produce more contractile force).
- Arrangement of fibres : parallel or pennate(oblique) to the line of pull.
- PARALLEL : Increased shortening but can fit fever fibres in a given space (lower contractile force produced).
- PENNATE : Decreased shortening but can fit more fibres in a given space (higher contractile force produced).
Explain the different anatomical levers ?
- Lever = Bone
- Pivot/fulcrum = Joint
- Load = External or Internal force
- Pulling force = from muscle
Explain the 3 different Muscle Actions ?
- Concentric : Develops tension, muscle shortens and changes joint position.
- Isometric : Develops tension, but no change in muscle length or joint position.
- Eccentric : Develops tension, muscle lengthens and changes in joint position.
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Explain the 4 different types of Muscle Roles and give an example for each ?
E.g Biceps branchii when lifting a weight.
2. Antagonist : Contracts eccentrically
E.g Triceps branchii when lifting a weight.
3. Stabilizer : Contracts isometrically
E.g Biceps branchii while holding a weight (not moving).
4. Neutralizer : Eliminates unwanted movement of another muscle.
Describe What a Deltoid muscle is ?
- Location : Lateral side of the shoulder joint.
- Origin : Pectoral girdle (scapula and clavicle).
- Insertion : Humerus.
- Concentric action/s :
- Anterior belly : Flexion at the shoulder.
- Posterior belly : Extension of the shoulder.
- Medial belly : Abduction of the shoulder.
Describe What are Biceps branchii muscles ?
- Location : Anterior of the radioulnar and elbow joints.
- Origin : Scaula.
- Insertion : Radial tuberosity.
- Concentric action/s : Flexion at the elbow and supination at the radioulnar joint.
Describe What are Triceps branchii muscles ?
- Location : Posterior of the elbow joint.
- Origin : Scapula and humerus.
- Insertion : Ulna.
- Concentric action/s : Extension at the elbow.
Describe What is a Illiopsoas muscle ?
- Location : Anterior of the hip joint.
- Origin : T12 - L5 vertebrae and anterior surface of the pelvis.
- Insertion : Femur.
- Concentric action/s : Flexion at the hip.
Explain What the Gluteus Maximus muscles are ?
- Location : Posterior to the hip joint.
- Origin : Pelvis and sacrum.
- Insertion : Iliotibial band and femur.
- Concentric action/s : Extension at the hip.
Explain What is a Quadriceps femoris muscle ?
- Location :
- VM, VI & VL : Anterior to the knee joint.
- Origin :
- VM, VI & VL : Femur.
- Insertion : Tibia and the patella tendon.
- Concentric action/s :
- RF : Flexion of the hip and extension of the knee.
- VM , VI & VL : Extension of the knee.
Describe the Hamstrings Muscle Group ?
- Location : Posterior of the hip and knee joint.
- Origin : Pelvis and femur.
- Insertion : Tibia and Fibula.
- Concentric action/s : Extension of the hip, flexion of the knee and rotation at the knee (when flexed).
Describe the Tibialis Anterior Muscle ?
- Location : Anterior of the ankle joint.
- Origin : Tibia.
- Insertion : Medial tarsals.
- Concentric action/s : Dorsiflexion.
Describe the Triceps Surae Muscle ?
- Location :
- S : Posterior to the ankle joint.
- Origin :
- G : Femur.
- S : Tibia and Fibula.
- Insertion : Calcaneus (heel bone) by Achilles tendon.
- Concentric action/s :
- G : Plantarflexion of the ankle and flexion at the knee.
- S : Plantarflexion at the ankle.
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