MSK - Muscle physiology

Question 1

whats the difference in terms of initiation and propagation of contraction in skeletal and cardiac muscle

Answer 1

skeletal = neurogenic 
cardiac = myogenic 

skeletal has NMJs, cardiac does not
skeletal has no gap junctions, cardiac does
skeletal has motor units, cardiac does not

Question 2

which muscle gets Ca2+ entirely from SR? cardiac or skeletal

Answer 2

skeletal

cardiac muscle gets Ca2+ from extracellular fluid also

Question 3

what is a motor unit

Answer 3

a single ALPHA motor neurone and all the skeletal muscle fibres it innervates

Question 4

muscles used for fine movements have more fibres per motor unit. true?

Answer 4

false - muscles used for fine movements have fewer fibres per motor unit

Question 5

what does the surface action potential have to spread down in order for Ca2+ to be released from SR

Answer 5

transverse (T)- tubules

Question 6

what does skeletal muscle tension depend on

Answer 6

1. no of motor fibres contracting within muscle

2. asynchronous motor unit recruitment during sub maximal contractions

Question 7

how is it possible to summate twitches to bring about a stronger contraction

Answer 7

the duration of AP is much shorter than duration of resulting twitch

therefore, repetitive fast stimulation of skeletal muscle gives a stronger contraction

Question 8

what can too much twitch summation result it

Answer 8

tetanus

not possible in cardiac muscle due to long refractory period

Question 9

when can maximal tetanic contractions be achieved

Answer 9

when muscle is at optimum length

this is at resting length in humans (the point of optimal overlap of actin and myosin binding sites)

Question 10

which type of muscle contraction is used in YOGA

Answer 10

isometric

Question 11

what are the 3 metabolic pathways that supply ATP in muscle fibre

Answer 11

1. transfer of high energy phosphate from creatine phosphate to ADP (this makes ATP) (the creatine transports the phosphate to muscle)
2. oxidative phosphorylation (when O2 present)
3. glycolysis (when O2 not present)

Question 12

which glycolytic fibres use anaerobic metabolism only

Answer 12

fast glycolytic (type IIx) fibres

Question 13

what does the stretch reflex aim to maintain

Answer 13

optimal muscle resting length

Question 14

how does the stretch reflex maintain optimal muscle resting length

Answer 14

by resisting passive change - the muscle that is being stretched contracts

Question 15

how does tapping muscle tendon with hammer elicit a response

Answer 15

it rapidly stretches muscle, causing contraction

Question 16

what are the special sensory receptors that detect that the muscle is being stretched and what motor neurones are they supplied by

Answer 16

intrafusal muscle spindles

supplied by gamma motor neurones

Question 17

which lumbar segment does the knee jerk assess

Answer 17

L3 - L4 (femoral)

Question 18

which sacral segment does the ankle jerk assess

Answer 18

S1-S2 (tibial)

Question 19

which cervical segment does the biceps jerk and brachioradialis test

Answer 19

C5 - C6

biceps = musculocutaneous nerve 
brachioradialis = radial nerve

Question 20

which cervical segment does the triceps jerk test

Answer 20

C6-C7 (radial)

Question 21

what is the most common type of hyaline cartilage

Answer 21

type II collagen

Question 22

what is the main difference between trabecular and cortical bone

Answer 22

trabecular bone has spaces in and around it, cortical doesn’t

Question 23

what is the purpose of the terminal bouton

Answer 23

it is found at the end of every branch of motor neurones

when AP reaches terminal bouton, ACh is released

Question 24

where is ACh synthesised from choline and acetyl CoA and by what enzyme

Answer 24

cystol

by choline acetyltransferase

Question 25

when ACh arrives at terminal of neurone, what channels open

Answer 25

Ca2+ channels open and Ca2+ gets into terminal

Question 26

what happens when Ca2+ gets into terminal

Answer 26

ACh diffuses into synaptic cleft

Question 27

what receptors does ACh activate after it travels across synapse? what affect does this have

Answer 27

nicotinic ACh receptors

causes the gate to open, causing Na+ to enter cell and K+ to exit
this depolarises membrane and generates an END PLATE POTENTIAL

Question 28

how does Lambert Eaton syndrome affect NMJ

Answer 28

AI antibodies against voltage activated Ca2+ channels

causes muscle weakness

Question 29

what pulmonary association does Lambert eaton syndrome have

Answer 29

associated with small cell lung cancer