ORTHO 112 Wrist Injury

Question 1

What is the function of a tendon?

Answer 1

Links muscle to bone, transmits force. Allows muscle belly to be some distance from site of action. Enables muscle pull to be accurately focuses. Reinforces joint capsure

Question 2

What is the area called where tendon inserts on the bone and what is present there to reduce risk of wear and tear?

Answer 2

enthesis and fibrocartilage

Question 3

What is the function of ligaments?

Answer 3

Link bone to bone, hold joint together, passive mechanical functions, proprioreception, muscle attachments

Question 4

What is a motor unit?

Answer 4

A single motor neurone and all the muscle fibres innervated by it

Question 5

What is a motor neurone pool?

Answer 5

All motor neurones that supply one whole muscle

Question 6

What is the NMJ?

Answer 6

terminus of axon and motor end plate of muscle fibre/cell

Question 7

What does a muscle fibre contain?

Answer 7

Many nuclei, sarcoplasm, sarcolemma, T-tubules, sarcoplasmic reticulum and motor end plate

Question 8

What is the sarcoplasm?

Answer 8

The muscular cytoplasm

Question 9

What is sarcolemma and describe it?

Answer 9

The muscle fibre membrane
Outer coat: thin polysaccharide/collagen layer that attaches to tendons
Inner plasma membrane

Question 10

What are T-tubules?

Answer 10

Deep invaginations of sarcolemma into centre of fibre to allow the inner speedy depolarisation

Question 11

What is the sarcoplasmic reticulum?

Answer 11

Enlarged endoplasmic reticulum assoc. with t-tubules and releases calcium on stimulation

Question 12

What is the motor end plate?

Answer 12

Sarcolemma directly under axon with infoldings to increase the SA

Question 13

What is a myofibril?

Answer 13

an intracellular fibril of multiple protein layers

Question 14

Describe the 4 myofibril proteins?

Answer 14

Myosin- thick protein, multiple heads that bind to actin and use ATP to recock heads
Actin - thin filaments
Tropomyosin - lies over actin filaments and blocks myosin binding sites
Troponin bound by calcium, changing its shape so that it pulls tropomyosin out of the way

Question 15

What are myofilaments?

Answer 15

Single protein chains

Question 16

Describe the sarcomere and it’s bands

Answer 16

Contractile unit of the muscle extending from one z line to the next
Abands: dark and stay constant on contraction
I bands: light and reduce length on contraction

Question 17

Influx of what cation causes depolarisation at the NMJ?

Answer 17

Na+

Question 18

What cation causes release of the NT?

Answer 18

Calcium

Question 19

What is the neurotransmitter released into the synaptic cleft at the NMJ?

Answer 19

AcH - acetylcholine

Question 20

What receptors does acetylcholine bind to at the NMJ and what does it subsequently cause?

Answer 20

binds to nicotinic receptors and causes Na+ influx into the muscle sarcoplasm

Question 21

Once depolarisation of the muscle sarcoplasm has reached threshold post-synaptically what potential is generated?

Answer 21

end-plate potential which spreads over the sarcolemma

Question 22

What structure does the endplate potential penetrate?

Answer 22

T-tubules

Question 23

What cation in the sarcoplasm stimulates what cations release in the sarcoplasmic reticulum?

Answer 23

Na+ stimulates calcium release in the sarcoplasmic reticulum

Question 24

Once calcium has been released from the sarcoplasmic reticulum, where does it diffuse into and to what protein does it bind?

Answer 24

It diffuses into myofibrils and binds to troponin

Question 25

What does troponin do?

Answer 25

Pulls tropomyosin out of the way clearing the myosin binding site

Question 26

What does myosin head bind to to form a cross bridge?

Answer 26

Actin

Question 27

What binds to myosin to allow it to dissociate from actin?

Answer 27

ATP

Question 28

What splitting allows the myosin head to “recock”

Answer 28

ATP into ADP and Pi

Question 29

Name the 4 ATP sources in Skeletal muscle

Answer 29

Phosphocreatinine, Anaerobic respiration, aerobic respiration, free fatty acids

Question 30

What does muscle contraction strength depend on?

Answer 30

The number of motor units recruited and the frequency of impulses

Question 31

What is an hypotonic muscle contraction?

Answer 31

Shortening - load or weight on the muscle remains the same whilst the muscle shortens

Question 32

What is an isometric muscle contraction?

Answer 32

Stays the same length - despite contraction of the muscle the load remains in constant position supported by the muscle

Question 33

What is eccentric muscle contraction?

Answer 33

Lengthening - force against against muscle is greater than that exerted by contraction

Question 34

What are the 3 main muscle fibre types?

Answer 34

Type 1, Type 2a and Type 2b

Question 35

Describe Type 1 muscle fibres

Answer 35

Slow twitch, oxidative fibre. Red, high myoglobin, well vascularised and resistant to fatigue

Question 36

Describe Type 2a muscle fibres

Answer 36

Fast twitch, oxidative fibre, red, high ,myoglobin and well vascularised but glycogen stores for anaerobic respiration also

Question 37

Describe type 2b muscle fibres

Answer 37

Fast twitch, glycolytic fibre, white, low myoglobin, low vascularity, few mitochondria, large glycogen stores, fatigue rapidly