Principles of Muscular System

Question 1

3 types of muscle tissue and, basically, how they are different to each other

Answer 1

Smooth, cardiac, skeletal

Question 2

Examples of smooth muscle

Answer 2

Walls of organs e.g. walls of bronchioles/bronchi

Question 3

Where in the heart is cardiac muscle?

Answer 3

Walls

Question 4

Examples of skeletal muscle

Answer 4

Biceps, gross muscles

Question 5

3 roles of skeletal muscle

Answer 5

Moving organs/structures, postural (found around spine), voluntary movement (locomotion) (e.g. muscles in limbs)

Question 6

What does locomotion require in terms of muscle function? What allows for this function?

Answer 6

Requires contraction of muscle fibres/cells. Contraction done by contractile proteins called myofilaments

Question 7

Name the 2 myofilaments/contractile proteins

Answer 7

Myosin and Actin

Question 8

Divide muscles into their most fundamental part

Answer 8

Muscle consists of fascicles, which are bundles of muscle fibres, which are bundles of myofibrils, which are made up of myofilaments.

Question 9

Describe fully the microstructure of skeletal muscle

Answer 9

Elongated, multinucleated cells/fibres with peripheral nuclei. Cells are grouped into fascicles. Endomysium surrounds each fibre, perimysium divides muscles into fascicles and epimysium wraps around the whole muscle

Question 10

Where is the basement membrane in relation to the sarcolemma? What is the basement membrane continuous with?

Answer 10

Basement membrane is above sarcolemma and is continuous with the endomysium

Question 11

What is the sarcoplasm?

Answer 11

The muscle cell’s cytoplasm

Question 12

What is the sarcolemma?

Answer 12

Muscle fibre’s cell membrane

Question 13

Which myofilament is thick and which is thin?

Answer 13

Myosin is thick, actin is thin

Question 14

Relate the contraction of sarcomere to the movement of myofilaments.

Answer 14

Contraction occurs because of the movement of myosin along the actin.

Question 15

What is the sarcomere?

Answer 15

Smallest functional unit of a skeletal muscle fibre

Question 16

What is the layout of the sarcomere when fully contracted?

Answer 16

Z lines closer, actin filament ends overlap, H zone disappears, I zone narrower, A zone unchanged

Question 17

What does the M region contain?

Answer 17

Only contains myosin

Question 18

What does the I region contain?

Answer 18

Only contains actin

Question 19

What does the Z line mark?

Answer 19

The end of the sarcomere

Question 20

Where is actin attached to the sarcomere?

Answer 20

Anchored at Z line

Question 21

Describe what happens on a whole-muscle level when sarcomeres contract

Answer 21

Shortening of sarcomeres shortens muscle, which occurs between origin and insertion of muscle. This leads to movement of bone or joint.

Question 22

What is a ‘head’ of a muscle?

Answer 22

A part of a muscle with its own origin

Question 23

4 parameters of biceps brachii

Answer 23

Origin: Long head- supraglenoid tubercle of scapula. Short head- coracoid process of scapula. Insertion: Radius. Action: flexion of elbow joint, shoulder joint and radio-ulnar joints. Nerve supply: musculocutaneous nerve.

Question 24

4 parameters of deltoid

Answer 24

Origin: clavicle, acromion and spine of scapula. Insertion: deltoid tuberosity of humerus. Action: abduction of shoulder joint. Nerve supply: Axillary nerve.

Question 25

Give 6 muscle fibre arrangements

Answer 25

Flat, pennate, fusiform, quadrate, circular, multi-headed/multi-bellied

Question 26

Motor end plate

Answer 26

Where motor nerve meets muscle

Question 27

Describe how impulses arrive at muscle and cause contraction

Answer 27

When impulse reaches motor end plate, acetylcholine neurotransmitter released to cross the neuromuscular junction to fibre. Impulse spreads into sarcolemma and passes down T-tubules so impulse penetrates the whole muscle fibre so that the whole muscle fibre contracts simultaneously. When impulse reaches fibre, calcium is released from sarcoplasmic reticulum to allow contraction

Question 28

What is the neuromuscular junction?

Answer 28

The gap between motor end plate and muscle fibre

Question 29

Satellite cells

Answer 29

Myogenic cells located between sarcolemma and basement membrane of muscle fibres in skeletal muscle. Normally dormant in adults but act as reserve population of cells, proliferating in response to injury and giving rise to regenerated muscle and more satellite cells. If cell is injured, satellite cells move to injured cell and proliferate.