Muscle

Question 1

how does a message transfer across the neuromuscular junction?

Answer 1

release of neurotransmitter acetylcholine into synaptic cleft

Question 2

where is acetylcholine produced?

Answer 2

the nerve terminal

Question 3

where is acetylcholine stored?

Answer 3

synaptic vesicles

Question 4

what happens after acetylcholine binds to receptors on muscle?

Answer 4

triggers end plate potential, which triggers action potentials and muscle contracts

Question 5

what breaks down acetylcholine?

Answer 5

acetylcholinesterase

Question 6

what is the neuromuscular junction?

Answer 6

a chemical synapse

Question 7

what are the types of skeletal muscle fibers?

Answer 7

slow twitch and fast twitch

Question 8

example of slow twitch muscle fiber

Answer 8

postural muscle

Question 9

example of fast twitch muscle fiber

Answer 9

extraocular muscles

Question 10

differences between slow and fast twitch muscles

Answer 10

fast twitch has:

• less mitochondria
• less myoglobin
• some oxidative metabolism
• more glycolytic metabolism
• SR highly developed
• fatigue prone

Question 11

structure of muscle

Answer 11

myofibrils surrounded by sarcoplasm outside myofilaments actin and myosin

Question 12

where is calcium stored in the muscle

Answer 12

sarcoplasmic reticulum

Question 13

what do T tubules do?

Answer 13

spread the muscle action potentials

Question 14

what is a sarcomere?

Answer 14

the contractile unit in skeletal muscle, located in myofibrils

Question 15

what are the thick and thin filaments in a sarcomere?

Answer 15

myosin = thick
actin = thin

Question 16

what connects the thick filament to the Z disk?

Answer 16

titin

Question 17

what are the protein components of the actin filament?

Answer 17

troponin and tropomyosin

Question 18

what happens within a sarcomere when a muscle contracts and relaxes?

Answer 18

• resting: actin and myosin detatched
• muscle action potential triggers calcium release
• calcium binds to troponin C
• myosin crossbridge formed
• phosphate released = power stroke
• atp attaches myosin, myosin detaches actin
• calcium pumped back to SR

Question 19

how do you alter the force of muscle contraction?

Answer 19

tetanus or recruitment of motor units

Question 20

what is tetany?

Answer 20

a sustained muscle contraction

Question 21

what is a motor unit?

Answer 21

an alpha motor neuron and all the muscle fibers innervated by that neuron

Question 22

types of muscle contraction

Answer 22

isotonic and isometric

Question 23

what is isotonic muscle contraction?

Answer 23

constant tension, muscle length changes, eg moving an object through a distance

Question 24

what is isometric muscle contraction?

Answer 24

constant length, tension doesn’t exceed the load, object does not move

Question 25

is cardiac muscle striated?

Answer 25

yes

Question 26

what is a pacemaker?

Answer 26

sinoatrial node capable of spontaneous depolarization (action potentials)

Question 27

which action potential is longer: cardiac or skeletal?

Answer 27

cardiac- stops heart from going into tetany

Question 28

what lies between myocardial cells?

Answer 28

gap junctions

Question 29

how does the action potential spread rapidly

Answer 29

coupled cells gap junctions

Question 30

why is cardiac muscle "all or nothing" ie all cells behave like one cell

Answer 30

it has no motor units

Question 31

composition of smooth muscle

Answer 31

no sarcomere, no troponin | poorly developed SR

Question 32

why is extracellular Ca important on smooth muscle

Answer 32

the sarcoplasmic reticulum is poorly developed, extracellular Ca must work with SR Ca

Question 33

what is calmodulin?

Answer 33

Ca binding protein that activates the enzyme Myosin Light Chain Kinase MLCK

Question 34

what are the types of smooth muscle?

Answer 34

single unit and multi unit

Question 35

what is a single unit smooth muscle?

Answer 35

many fibers contracting as a single unit, gap junctions important eg digestive tract

Question 36

what is a multi unit smooth muscle?

Answer 36

controlled mainly by nerve signals, individual muscle fibers stimulated by individual nerve fibers eg the eye

Question 37

what does activated MLCK do in smooth muscle?

Answer 37

activates cross bridge formation and contraction

Question 38

what does myosin phosphatase do in smooth muscle?

Answer 38

inactivates myosin cross bridge and relaxes muscle

Question 39

smooth muscle contraction mechanism

Answer 39

1. action potentials cause depolarisation 2. calcium channels open in plasma membrane 3. Ca and calmodulin activate MLCK 4. MLCK activates cross bridge formation and muscle contracts 5. myosin phosphatase inactivates cross bridge and muscle relaxes