muscle physiology

Question 1

which type of muscle is not striated

Answer 1

smooth

Question 2

what causes striations in muscle

Answer 2

alternating dark (myosin) and light (actin) bands

Question 3

what are skeletal muscle nerves innervated by

Answer 3

somatic NS and are voluntary

Question 4

what are cardiac and smooth muscle innervated by

Answer 4

autonomic and involuntary

Question 5

skeletal muscle has ____ contraction, _____ junction, no ___ junction, Ca from ___ ______

Answer 5

neurogenic, neuromuscular, no gap junctions, sarcoplasmic reticulum

Question 6

cardiac muscle has ____ contraction, _____ junctions, Ca from ___ ______ and ____

Answer 6

myogenic, gap junctions, ECF and sarcoplasmic

Question 7

what is an alpha motor unit

Answer 7

alpha motor neuron and all the skeletal fibres it innervates

Question 8

if precision> power how many fibres to each motor unit

Answer 8

fewer fibres for control

Question 9

if power> precision how many fibres to each motor unit

Answer 9

lots of fibres for more strength

Question 10

what is the contractile structure of muscle

Answer 10

myofibril

Question 11

what is the functional structure of muslce

Answer 11

sarcomere

Question 12

what are sarcomeres and where are they

Answer 12

smallest component capable of performing function of that organ, between Z lines

Question 13

what are the 4 zones

Answer 13

A band, H zone, M line, I band

Question 14

describe the steps of ATP, myosin and actin

Answer 14

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

Question 15

what is needed for crossbridge formation

Answer 15

Ca and troponin

Question 16

what is motor recruitment

Answer 16

stronger contraction of the whole muscle by using more motor units

Question 17

what is asynchronous motor recruitment

Answer 17

not using all fibres at once to prevent muscle fatigue

Question 18

what does muscle tension depend on

Answer 18

frequency of stimulation and sum of contractions, length of muscle fibre at start of contraction, thickness of muscle fibres

Question 19

what do AP’s need to do to create contractions

Answer 19

fast, repetitive stimulation = contraction, single AP is just a muscle twitch.

Question 20

what does rapid AP stimulation lead to

Answer 20

maximal contraction/ tetanic where muscle is constantly contracted (refractory period in cardiac muscle stops this)

Question 21

what length do muscles need to be before contraction to reach optimal contractions

Answer 21

optimal length - relaxed

Question 22

what are isotonic contractions

Answer 22

body movements and moving object - muscle tension is constant and muscle length changes.

Question 23

what are isometric contractions

Answer 23

supporting objects in a fixed place/ posture - muscle tension develops at constant muscle strength

Question 24

how is muscle tension transmitted to bone

Answer 24

tendons

Question 25

what are the main 3 differences between types of skeletal muscle

Answer 25

enzyme for ATP synthesis, resistance to fatigue, activity of myosin

Question 26

what are the 3 ATP pathways

Answer 26

high energy phosphate (creatine phosphate –> ADP), oxidative phosphorylation (when O2 present), glycolysis (when O2 not present)

Question 27

describe slow oxidative type I muscle fibres

Answer 27

slow twitch fibres, aerobic prolonged low work eg posture and walking

Question 28

describe fast oxidative type IIA muscle fibres

Answer 28

intermediate fibre twitches, aerobic and anaerobic, prolonged moderate work eg jogging

Question 29

describe fast glycolytic type IIb muscle fibres

Answer 29

anaerobic, short but intense work

Question 30

describe the stretch reflex when leaning to one side

Answer 30

‘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

Question 31

why do we have stretch reflex

Answer 31

passive change to result in optimal resting muscle length

Question 32

what type of feedback is stretch

Answer 32

negative

Question 33

what are muscle spindles

Answer 33

sensory receptors for stretch reflex, collection of specialised muscle fibres called intrafusal

Question 34

where do muscle spindles lie in muscle

Answer 34

run parallel to normal fibres and in the centre of the muscle

Question 35

what are sensory nerve endings of muscle spindles called

Answer 35

annulospiral fibres

Question 36

what types of motor neurones are muscle spindles supplied by, what do they do in contraction

Answer 36

gamma, adjust tension of spindle fibres to maintain sensitivity

Question 37

does contraction of muscle spindles contribute to strengh of muscle

Answer 37

no

Question 38

what are 4 causes of muscle impairment

Answer 38

intrinsic disease, disease of neuromuscular, disease of lower motor neuron, disruption of input to motor nerves

Question 39

what investigations can be done for muscle disease

Answer 39

EMG, nerve conduction studies, CK, inflamm markers, biopsy

Question 40

what are symptoms of muscle disease

Answer 40

muscle fatigue and weakness, delayed reaction (myotonia) after contraction, muscle pain, stiffness

Question 41

what are some genetic myopathies (intrinsic disease)

Answer 41

reduced contractile ability, chronic degeneration, abnormal muscle membrane ions

Question 42

what are acquired myopathies

Answer 42

inflammation eg polymyositis, non inflamm eg fibromyalgia, toxic eg alcohol