muscle physiology Flashcards
which type of muscle is not striated
smooth
what causes striations in muscle
alternating dark (myosin) and light (actin) bands
what are skeletal muscle nerves innervated by
somatic NS and are voluntary
what are cardiac and smooth muscle innervated by
autonomic and involuntary
skeletal muscle has ____ contraction, _____ junction, no ___ junction, Ca from ___ ______
neurogenic, neuromuscular, no gap junctions, sarcoplasmic reticulum
cardiac muscle has ____ contraction, _____ junctions, Ca from ___ ______ and ____
myogenic, gap junctions, ECF and sarcoplasmic
what is an alpha motor unit
alpha motor neuron and all the skeletal fibres it innervates
if precision> power how many fibres to each motor unit
fewer fibres for control
if power> precision how many fibres to each motor unit
lots of fibres for more strength
what is the contractile structure of muscle
myofibril
what is the functional structure of muslce
sarcomere
what are sarcomeres and where are they
smallest component capable of performing function of that organ, between Z lines
what are the 4 zones
A band, H zone, M line, I band
describe the steps of ATP, myosin and actin
1) ATP is hydrolysed when myosin head unattached 2) ADP + P are bound to myosin and it attaches to actin 3) ADP P released causes contraction 4) ATP reattaches and original positions
what is needed for crossbridge formation
Ca and troponin
what is motor recruitment
stronger contraction of the whole muscle by using more motor units
what is asynchronous motor recruitment
not using all fibres at once to prevent muscle fatigue
what does muscle tension depend on
frequency of stimulation and sum of contractions, length of muscle fibre at start of contraction, thickness of muscle fibres
what do AP’s need to do to create contractions
fast, repetitive stimulation = contraction, single AP is just a muscle twitch.
what does rapid AP stimulation lead to
maximal contraction/ tetanic where muscle is constantly contracted (refractory period in cardiac muscle stops this)
what length do muscles need to be before contraction to reach optimal contractions
optimal length - relaxed
what are isotonic contractions
body movements and moving object - muscle tension is constant and muscle length changes.
what are isometric contractions
supporting objects in a fixed place/ posture - muscle tension develops at constant muscle strength
how is muscle tension transmitted to bone
tendons
what are the main 3 differences between types of skeletal muscle
enzyme for ATP synthesis, resistance to fatigue, activity of myosin
what are the 3 ATP pathways
high energy phosphate (creatine phosphate –> ADP), oxidative phosphorylation (when O2 present), glycolysis (when O2 not present)
describe slow oxidative type I muscle fibres
slow twitch fibres, aerobic prolonged low work eg posture and walking
describe fast oxidative type IIA muscle fibres
intermediate fibre twitches, aerobic and anaerobic, prolonged moderate work eg jogging
describe fast glycolytic type IIb muscle fibres
anaerobic, short but intense work
describe the stretch reflex when leaning to one side
‘person standing upright leans to one side, the muscle spindles in muscles on the opposite side of the vertebral column will detect stretch and contract to correct
why do we have stretch reflex
passive change to result in optimal resting muscle length
what type of feedback is stretch
negative
what are muscle spindles
sensory receptors for stretch reflex, collection of specialised muscle fibres called intrafusal
where do muscle spindles lie in muscle
run parallel to normal fibres and in the centre of the muscle
what are sensory nerve endings of muscle spindles called
annulospiral fibres
what types of motor neurones are muscle spindles supplied by, what do they do in contraction
gamma, adjust tension of spindle fibres to maintain sensitivity
does contraction of muscle spindles contribute to strengh of muscle
no
what are 4 causes of muscle impairment
intrinsic disease, disease of neuromuscular, disease of lower motor neuron, disruption of input to motor nerves
what investigations can be done for muscle disease
EMG, nerve conduction studies, CK, inflamm markers, biopsy
what are symptoms of muscle disease
muscle fatigue and weakness, delayed reaction (myotonia) after contraction, muscle pain, stiffness
what are some genetic myopathies (intrinsic disease)
reduced contractile ability, chronic degeneration, abnormal muscle membrane ions
what are acquired myopathies
inflammation eg polymyositis, non inflamm eg fibromyalgia, toxic eg alcohol
