Principles of Muscular System Flashcards
3 types of muscle tissue and, basically, how they are different to each other
Smooth, cardiac, skeletal
Examples of smooth muscle
Walls of organs e.g. walls of bronchioles/bronchi
Where in the heart is cardiac muscle?
Walls
Examples of skeletal muscle
Biceps, gross muscles
3 roles of skeletal muscle
Moving organs/structures, postural (found around spine), voluntary movement (locomotion) (e.g. muscles in limbs)
What does locomotion require in terms of muscle function? What allows for this function?
Requires contraction of muscle fibres/cells. Contraction done by contractile proteins called myofilaments
Name the 2 myofilaments/contractile proteins
Myosin and Actin
Divide muscles into their most fundamental part
Muscle consists of fascicles, which are bundles of muscle fibres, which are bundles of myofibrils, which are made up of myofilaments.
Describe fully the microstructure of skeletal muscle
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
Where is the basement membrane in relation to the sarcolemma? What is the basement membrane continuous with?
Basement membrane is above sarcolemma and is continuous with the endomysium
What is the sarcoplasm?
The muscle cell’s cytoplasm
What is the sarcolemma?
Muscle fibre’s cell membrane
Which myofilament is thick and which is thin?
Myosin is thick, actin is thin
Relate the contraction of sarcomere to the movement of myofilaments.
Contraction occurs because of the movement of myosin along the actin.
What is the sarcomere?
Smallest functional unit of a skeletal muscle fibre
What is the layout of the sarcomere when fully contracted?
Z lines closer, actin filament ends overlap, H zone disappears, I zone narrower, A zone unchanged
What does the M region contain?
Only contains myosin
What does the I region contain?
Only contains actin
What does the Z line mark?
The end of the sarcomere
Where is actin attached to the sarcomere?
Anchored at Z line
Describe what happens on a whole-muscle level when sarcomeres contract
Shortening of sarcomeres shortens muscle, which occurs between origin and insertion of muscle. This leads to movement of bone or joint.
What is a ‘head’ of a muscle?
A part of a muscle with its own origin
4 parameters of biceps brachii
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.
4 parameters of deltoid
Origin: clavicle, acromion and spine of scapula. Insertion: deltoid tuberosity of humerus. Action: abduction of shoulder joint. Nerve supply: Axillary nerve.
Give 6 muscle fibre arrangements
Flat, pennate, fusiform, quadrate, circular, multi-headed/multi-bellied
Motor end plate
Where motor nerve meets muscle
Describe how impulses arrive at muscle and cause contraction
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
What is the neuromuscular junction?
The gap between motor end plate and muscle fibre
Satellite cells
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.
