Tendon Units- Muscle Spindles And GTOs

Question 1

How does force occur in muscle tendon unit

Answer 1

In 3 dimensions and are transmitted through connective tissue

Question 2

How are muscle fibres oriented in muscle-tendon units

Answer 2

Oriented in the line of action of force

Question 3

What is a tendon

Answer 3

Highly organized connective tissue
Joins muscle to bone

Question 4

Physical properties of tenons

Answer 4

• tenocytes (tendon specific fibroblasts)
• dense regular connective tissue
• collagen fibres
• resists high tensile forces
• flexible so it can bend at joints
• shock absorption
• transmits muscle force to skeleton
• stretches and stores mechanical energy
• paratenon = fatty areolar tissue surrounding tendon

Question 5

What is a paratenon

Answer 5

Fatty areolar tissue surrounding tendon

Question 6

Internal vs external tendon

Answer 6

Internal- extends into muscle belly
External- extends from the muscle belly
- aponeurosis

Question 7

Properties of aponeurosis

Answer 7

• pearly white collagenous sheet
• broad, flat tendon
• pennate muscles have two aponeurosis
• thins into small tendon that attaches to bone
• stretched by forces of muscle contraction
• absorb energy and return it when recoil

Question 8

Achilles’ tendon rupture symptoms and treatment

Answer 8

• require medical attention
• severe swelling, extreme pain, burning
• recovery slow
• treatment surgery or rest/ice

Question 9

What are the two pennation angles

Answer 9

1 muscle with few long fibres in parallel with axis of shortening = produces rapid shortening but less tension

2 muscle with many short fibres at an angle to the axis of shortening = produce slow shortening but more tension

Question 10

What is PCSA

Answer 10

Physiological cross sectional area

Question 11

What is PCSA of muscle useful for

Answer 11

Estimating number of sarcomeres in parallel and estimating force generation

Question 12

PCSA equation

Answer 12

PCSA= muscle volume/ fibre length = muscle mass/ p * fibre length

Question 13

What is the shape of muscle spindles

Answer 13

Fusiform-shaped muscle fibres

Question 14

Where are muscle spindles found and what innervates them

Answer 14

Found in skeletal muscle- near tendinous insertion point and lie in parallel with regular muscle
Innervated by sensory and motor axons

Question 15

Function of muscle spindles

Answer 15

Detect changes in muscle length

Question 16

How are Extrafusal (regular) fibres are innervated

Answer 16

By a single alpha motor axon

Question 17

Function of gamma neurons

Answer 17

Regulate spindle sensitivity
- when muscle contracts the spindle shortens and is ‘unloaded’ (stops firing and becomes insensitive to further change)
- gamma stimulation counters this so intramuscular fibres shorten along with extrafusal fibres therefore maintaining there sensitivity (known as alpha gamma co-stimulation)

Question 18

What do muscle spindles monitor

Answer 18

Muscle length

Question 19

What do golgi tendon organs monitor

Answer 19

Muscle force

Question 20

Structure of golgi tendon organs

Answer 20

• Ib afferents only
• axon terminals wrap around dense connective tissue in tendons
• in series with muscle
• force is proportional to stretch (Hooke’s Law)