The Musculoskeletal System

Question 1

what is the axial and appendicular systems.

Answer 1

axial: sternum, skull, ribs, spine (vertebrae)
appendicular: bones of the appendages (arms and legs) and the girdles (shoulder and pelvic) that connects them with the axial skeleton
- pelvis, femur, tibia, ulna, humerus

Question 2

what is the vertebral column?

Answer 2

intervetebral discs separate the vertebrae form one another.
top and bottom of each disc has a layer of hyaline cartilage. they are used to absorb shock and create spaces between vertebrae

Question 3

what is the atlas and the axis?

Answer 3

atlas: first cervical vertebra, supports the skull
axis: second cervical vertebra, enables pivot movement of the head

Question 4

what is the thoracic vertebrae?

Answer 4

supports ribs and have special structures for rib head and tubercle attachment

Question 5

what is the lumbar vertebrae?

Answer 5

the largest and strongest in the vertebral column. they support the body’s weight.

Question 6

what are the benefits of compact and spongy bone?

Answer 6

compact bone is good at providing protection and support.

spongy bone is lightweight and provides tissue support

Question 7

what are joints?

Answer 7

a part of the body where two or more bones meet to allow movement
- joints may be supported by fibrous structures (ligaments) connecting one bone to another

Question 8

what are tendons?

Answer 8

fibrous connective tissue that connects muscle to bone

Question 9

what are synovial joints?

Answer 9

most common type of joint, allows for ‘free movement’

Question 10

what type of cells do bones consist of?

Answer 10

osteoprogenitor cells (bone stem cells able to differentiate into other types of cells)
osteoblasts (bone-building cells that secrete matrix)
osteocytes (mature bone cells)
osteoclasts (remodel bones and cause them to release calcium)

Question 11

what movements do synovial joints allow?

Answer 11

• gliding (e.g. at the wrist)
• angular movements (flexion, extension, abduction, adduction, circumduction)
• rotation (head, neck and lower limb)

Question 12

what would happen if there was no synovial fluid?

Answer 12

synovial fluid is a slippery fluid that occupies all free spaces within the joint capsule
- it reduces friction, without it the joint surfaces would rub away as a result of friction

Question 13

what happens to joints as humans age?

Answer 13

• decreased production of synovial fluid
• thinning of articular cartilage
• loss of ligament length and flexibility

Question 14

describe homeostasis in bones, ageing and bone tissue

Answer 14

although bones stop growing in length by adulthood, bone continually renews itself throughout life.
Spongy bone is replaced every 3-4 years and compact bone roughy every 10 years.

Question 15

how does movement occur?

Answer 15

movement is produced by muscle contraction pulling, via a tendon, on one muscle while relaxation of the opposing muscle occurs
- coordination of motor activity is essential for any purposeful movement to occur

Question 16

what are muscle cells, and what do they contain?

Answer 16

muscle cells are cylindrical and called muscle fibres. each muscle fibre contains muscle filaments or myofilaments
- these can be thick or thin and aid in muscle contraction

Question 17

briefly explain the sliding filament mechanism.

Answer 17

myosin pulls on action, causing the thin filament to slide inward

• consequently, Z discs move toward each other and the sarcomere shortens
• thanks to structural proteins, there is a transmission of a force throughout the entire muscle, resulting in whole muscle contraction

Question 18

what are troponin and tropomyosin? what role do they play in muscle contraction?

Answer 18

the sliding of the muscle filaments is triggered by an intracellular rise in calcium ion levels.
troponin binding of calcium moves tropomyosin away from myosin-binding sites on actin - allowing cross bridge binding
- this concept connects the events of a muscle action potential with the sliding filament mechanism

Question 19

what would happen in a patient with low calcium levels?

Answer 19

hypocalcaemia - muscle cramps, spasms, tremors or tetany from prolonged contraction. muscular and nervous system hyper excited

Question 20

state characteristics and role of smooth muscle in muscle contractions.

Answer 20

smooth muscles contractions start more slowly and last longer than skeletal and cardiac muscle contractions.

• can shorten and stretch to a greater extent
• provides elasticity, contractility and support
• found in the walls of blood vessels, around hollow organs, and in layers around the digestive, respiratory, circulatory and reproductive tracts

Question 21

what is the neuromuscular junction?

Answer 21

the events at the neuromuscular junction produce a muscle action potential.

• voltage-gated calcium channels open resulting in an influx of calcium. This causes exocytosis of neurotransmitter (NT) into the synaptic cleft. NT binds to ligand-gated Na+ channels on the motor endplate which cause an influx of Na+ into the muscle. This depolarises it and results in Ca+ release from the sarcoplasm reticulum.