Introduction to the muscular system Flashcards
what are muscles?
the largest soft tissues
List the structures of the muscle from outermost to innermost structures
- muscle
- fascia
- muscle fibres
- sarcomere
- myofibril
- filaments containing actin and myosin
main functions (abilities/properties) of muscles:
Movement
- excitability: ability to respond to stimulus
- contractibility: ability to contract
- extensibility: ability of muscle to be stretched without tearing
- elasticity: ability of muscle to return to its normal shape
What do muscled produce?
What do muscles require to perform their functions (muscle contraction)?
- muscles produce heat energy
- they require energy, predominantly powered by oxidation of fats and carbohydrates,
- these chemical reactions produce ATP (adenosine triphosphate) which are used up by myosin filaments during muscle contraction
3 types of muscles + describe
smooth muscle (visceral):
- spindle shaped, nonstriated, uninucleated (1 nucleus) fibres
- occurs in walls of internal organs (GI tract, uterus, eye, blood vessels)
- involuntary system
skeletal muscle: long cylindrical system
- has striated alternating light and dark pattern, tubular, multinucleated fibres
- usually attached to skeleton
- voluntary system
- function: movement, heat, posture
cardiac muscle:
- striated, branched, uninucleated fibres
- occurs in walls of heart and adjacent great vessels like aorta
- involuntary system
- function: pumps blood continuously
function of skeletal muscles
Skeletal Muscles:
- voluntary movement:
pull bones (body movement)
pull skin (facial expression)
How does the muscle function to contract? (Process)
- a signal is sent from the brain along a bundle of nerves (nervous system)
- the electronic and chemical message passes quickly from nerve cell to nerve cell until it arrives at motor end plate (terminal axon)
- synaptic vesicles containing neurotransmitter ACh (acetylcholine) are released into synapse (aka synaptic cleft)
- ACh binds to receptors on muscle and they receive the information to contract
- message is distributed to all cells in the fibre connected to the nerve
- chemical (neurotransmitter) to mechanical (muscle contraction) energy
Connective tissue wrappings of skeletal muscle
- fascia: on outside of epimysium
- epimysium: covers the entire skeletal muscle (many fascicles)
- perimysium: around a fascicle (bundle of fibres)
- endomysium: around a single muscle fibre
the collection of the epimysium, perimysium and endomysium for the tendon which attaches to the bone
Naming of muscles classified by:
- shape
- number of heads
- attachments
- action
Shape:
- deltoid (triangular)
- teres (rounded)
- rectus (straight)
No. of heads:
- biceps 2
- triceps 3
- quadriceps 4
Attachments:
- coracobrachialis (from coracoid to arm)
Action:
- flexor digitorum: flexion of digits
Shapes of skeletal muscles according to direction of muscle fibres:
Parallel: have parallel fascicles; stronger pull
(rectus abdominis, sartorius)
Convergent: broad at origin and tapering to a narrower insertion; less pull than parallel
(pectoralis major)
Pennate: uni, bi, multi- . Fascicles insert obliquely (diagonally) on a tendon; produce more tension (more muscle fibres)
(extensor digitorum longus, rectus femoris and deltoid)
Circular: ring around body opening, sphincter
(orbicularis oris)
Fusiform parallel muscle: muscle belly fibres arranged parallel to each other and attached to a tendon at either end
(biceps brachii)
Describe prime mover, synergist and antagonist
prime mover (agonist): initiates action / provides primary force driving the action
synergist: assists action (can fixtate and stabalize bone)
antagonist: muscle in opposition to a prime mover, it provides resistance or reverses a given movement
Head muscles
- frontalis
- cranial aponeurosis
- occipitalis
- temporalis
- orbicularis oculi
- zygomaticus (facial expression, draws the angle of the mouth superiorly and posteriorly to allow one to smile)
- depressor / anguli oris (facial muscle that allows a person to move the corners of their mouth, specifically downward)
- sternocleidomastoid (rotation of the head to the opposite side and flexion of the neck)
Chewing:
- buccinator
- masseter
- orbicularis oris
- platysma
- trapezius
Neck Muscles
- suprahyoid muscles
- infrahyoid muscles
Muscles of inspiration and expiration
Inspiration:
- external intercostals contract to elevate ribs (rib cage expands)
- diaphragm contracts (moves down) to expand thoracic walls
Expiration:
- internal intercostals contracts to pull ribs down (rib cage gets smaller)
- diaphragm relaxes (moves up) to reduce thoracic cavity
Label inferior and anterior view of diaphragm
What is diaphragm shaped like?
inferior view:
- central tendon
- foramen for aorta
- foramen for esophagus
- foramen for (inferior) vena cava
diaphragm is shaped like a parachute
