muscles Flashcards
what is the connective tissue layer surrounding the muscle?
epimysium
describe a muscle
fascicles (bundles of muscle fibres) surrounded by the epimysium
what is the connective tissue layer that surrounds each fascicle?
the perimysium
what does calcium bind to during muscle contraction?
what does this result in?
binds to troponin
rolls tropomysin away from binding sites of actin filaments
skeletal muscle histology
very long
multinucleated
striated
cylindrical
what is the connection between the nervous system and the skeletal muscle fibre?
what neurotransmitter is released here?
neuromuscular junction
ACh
what gives skeletal muscle its striated appearance?
alternating bands of actin and myosin
what are the steps in initiating muscle contraction?
- ACh released, binds to receptors
- action potential reaches T-tubule
- sarcoplasmic reticulum releases calcium
- active site exposure, cross bridge formation
- contraction begins
describe the regeneration ability of muscle
poor regenerative ability
damage leads to fibrosis (scar tissue)
no regeneration in cardiac muscle
how do cardiac muscles store oxygen?
in myoglobin
smooth muscle features
uni-nucleated
spindle shaped
non-striated
which type of muscle cells are branched?
cardiac muscle
which type of muscle cells are not striated?
smooth muscle
ER-like organelle in muscle cells?
sarcoplasmic reticulum
what are the three types of muscle cells?
cardiac muscle
smooth muscle
skeletal muscle
what is the functional unit of contraction called?
the sarcomere
what is atrophy?
decrease in size/shrinkage of muscle size due to lack of use
give an example of an isometric contraction
carrying a bag of groceries
holding head up
what is the connective tissue layer that surrounds each muscle fibre?
the endomysium
what are the roles of muscles in the body?
- movement
- support soft tissues
- maintain posture and body position
- thermoregulation
- storage of nutrients
- guards body entrances and exits
during exercise, haemoglobin releases more oxygen to active skeletal muscles than when those muscles are at rest. why?
more heat generated
more acidic wastes generated.
both make haemoglobin release more oxygen
what is a muscle cell also known as?
a muscle fibre
what is the point of attachment that doesn’t change when muscle contracts
the origin
name the three types of myofilaments
actin
myosin
titin
cytoplasm of a muscle
sarcoplasm
point of attachment of a muscle: the end that is freely moveable
insertion
define circumduction
movement of arm in a circular motion
movement of hand in a circular motion without moving arm
what is muscle tone? what does it do?
degree of contraction or undertone in resting muscles
posture
joint stabililty
ready response state
what are the movements in the anterior-posterior plane?
flexion (smaller angle - hand towards inner arm)
extension - hand in a line with arm
hyperextension - wrist bending back towards forearm
what is agonist /antagonist with reference to muscles?
the contracted muscle is the agonist
the relaxed muscle is the antagonist
what’s the cell membrane of a muscle called?
the sarcolemma
the russian doll of muscle organisation
muscles each contain:
many fascicles which each contain:
many muscle fibres which each contain:
many myofibrils which each contain:
many myofilaments.
what is the thin myofilament called? the thick? the elastic?
actin (thin)
myosin (thick)
titin (elastic)
define hyperplasia
increase in cell number
occurs in skeletal muscle subjected to persistent increased workload (eg. weights, bodybuilding)
how are myosin heads activated in the muscle contraction process?
ATP binds to myosin head and breaks into ADP and P
myosin head is now cocked and can bind with actin when troponin binds wuth calcium
when it binds, it pulls the actin along
what is ATPs role in muscle contraction?
attaches to myosin head and releases it from the actin
ATP then breaks into ADP and P and the head is activated again
steps in initiating muscle relaxation?
- ACh broken down by AChE at neuromuscular junction
- sarcoplasmic reticulum recaptures calcium
- active sites covered, no cross bridge formation
- contraction ends
- relaxation occurs, passive return to resting length
what happens to actin and myosin, and to the sarcomere, during muscle contraction?
actin and myosin overlap, which shortens the sarcomere, causing contraction
