Lecture 10 - Form And Actions At Joints

Question 1

“Muscle form determines function” depends on….

Answer 1

1. Length of muscle fibres
2. Number of muscle fibres
3. Arrangement of muscle fibres

Question 2

Explain the importance on the length of muscle fibres

Answer 2

The length of muscle fibres will affect the range of movement that the muscle has

Question 3

Explain the importance of the number of muscle fibres

Answer 3

The more muscle fibres a muscle have the more force the muscle holds. More muscle fibres means more tension, which results in more force. The more fibres, the stronger the muscle

Question 4

Explain the arrangement of muscle fibres and the two arrangements and their properties

Answer 4

The way the muscle is arrangement will affect the muscles movement. Fibres arranged vertically between muscle tendons are parallel. Fibres that are oblique to muscle tendon (diagonally spaced) are pennate. If we arrange in a pennate, more fibres can be fit into the same space

Question 5

What are the three different orientations of pennate muscle arrangement?

Answer 5

1. Unipennate
2. Bupennate (two different cross sections - tibialis anterior)
3. Multi pennate (multiple cross sections - quadriceps)

Question 6

What are the 4 anatomical levers?

Answer 6

Muscles contract to make movement.

1. Bones = lever
2. Joint = pivot or fulcrum
3. Muscle contraction = pull/applied force
4. Load = external or internal

Question 7

What are the three classes of anatomical levers?

Answer 7

1. First = stabilize joint position e.g see-saw, scissors (the neck)
2. Second = effective at overcoming loads e.g wheelbarrow, bottle opener (ankle joint plantar flexion - fulcrum is ball of foot, the load is the ankle joint and the applied force is the gastrocnemius)
3. Third = large range of movement and speed e.g tweezers, fishing rod (flexion at the elbow joint) fulcrum is holding fishing rod, load is the fish and the pull is moving the fishing rod)

Question 8

What are they three types of muscle action?

Answer 8

1. Concentric
2. Eccentric
3. Isometric

Question 9

What is concentric contraction?

Answer 9

When your muscle is active and is developing tension and the muscle shortens.

• change in joint position
• shortening of muscle

Question 10

What is eccentric contraction?

Answer 10

When your muscle is active and is developing tension but lengthens.

• change in joint position
• Lengthening of muscle

Question 11

What is isometric contraction?

Answer 11

The muscle is active and develops tension but it doesn’t change length.

• no change in joint position
• no change in length or muscle
• important for holding a joint still/steady

Question 12

Muscles can have different roles at a joint. What are the types of muscle roles and their properties?

Answer 12

1. Agonist (causing the joint to change e.g bicep in flexion)
2. Antagonist (opposite to the agonist and will act eccentrically and will lengthen the muscle to give control)
3. Stabilizer (when a muscle is active to hold a joint still - e.g holding a heavy book)
4. Neutralizer (muscle eliminates an unwanted movement caused by another muscle - e.g pronator muscles neutralize in the forearm supinating effect of biceps brachii)

Question 13

What are the properties of the bicep brachii?

Answer 13

The bicep brachii is a two headed muscle which three movements at three different joints.

1. Shoulder - flexion
2. Elbow - flexion
3. Radioulna joints - supination

Question 14

What are the properties of the tricep brachii?

Answer 14

The tricep brachii is a three headed muscle of the arm (long head, lateral head and medial head) it is involved with shoulder extension and elbow extension

Question 15

What are the properties of the deltoid?

Answer 15

The deltoid is attached to the pectoral girdle and attachment to shaft of humerus.

1. Flexion (anterior fibres)
2. Abduction (lateral fibres)
3. Extension (posterior fibres)

Question 16

What are the properties of the iliopsoas?

Answer 16

The iliopsoas is made up of two muscles. The psoas major is by your vertebrae and merges with the iliacus at the hip bone then attaches to the femur. It sits anterior to the hip so will perform hip flexion

Question 17

What are the properties of the gluteus Maximus?

Answer 17

The gluteus maximus attaches to the sacrum/coccyx and attaches to the femur. It is posterior to the hip so it’s role is to perform hip extension

Question 18

What are the properties of the quadriceps femoris?

Answer 18

There are four different heads in the quadriceps femoris. The first is the recurs femoris which is the superficial muscle. Underneath this are three muscles called the vasti muscles. These are the lateralis, intermedius and the medialis. All four muscles attach to the patella through the tibia. Our quadriceps are our knee extenders

Question 19

What are the properties of the hamstrings?

Answer 19

There are three muscles within the hamstring. The bicep femoris, semi membranous and the semi tendinous. All three cross at the hip joint and help hip extension

Question 20

What are the properties of the tibialis anterior?

Answer 20

The tibialis anterior runs from the tibia and fibula and crosses the ankle interiorly. It is responsible for dorsiflexion and foot inversion

Question 21

What are the properties of the triceps surae?

Answer 21

The triceps surae are a three headed muscle of your leg and are the gastrocnemius and soleus muscles. The superficial muscle is the gastrocnemius which attaches to the femur and crosses posteriorly to the knee joint and therefore helps with knee flexion. The soleus is flat and doesn’t cross the knee. These muscles join together and form a thick tendon called calacanean tendon. This is here for plantar flexion

Question 22

What muscles form the calcanean tendon?

Answer 22

The gastrocnemius and the soleus (triceps surae)