Muscle

Question 1

what are the 5 muscle functions?

Answer 1

heat production
Production of body movements
Stabilisation of body positions - posture
Regulation of organ volume
Movement of substances internally

Question 2

muscle includes what parts in the body?

Answer 2

muscle fibres, connective tissue, nerves & blood vessels

Question 3

what is muscle skeletal wrapped in?

Answer 3

epimysium

Question 4

what is the difference between perimysium and endomysium?

Answer 4

perimysium surrounds fibre bundles called fascicles.
endomysium surrounds each individual fibre.

Question 5

what type of cell are muscle fibres made up of?

Answer 5

elongated cylindrical cells.

Question 6

what is the muscle sarcolemma known as?

Answer 6

the plasma membrane.

Question 7

what is the sarcoplasm in muscle?

Answer 7

cytoplasm - contains myoglobin which is related to haemoglobin

Question 8

what is the endoplasmic reticulum known as in muscle?

Answer 8

sarcoplasmic reticulum. - stores calcium ions.

Question 9

what are myofibrils and where can you find them in muscle?

Answer 9

Thick (myosin) and thin (actin) protein filaments. Found along entire length of cell.

Question 10

what is the H-zone in sarcomere?

Answer 10

middle zone, only thick filaments.(myosin)

Question 11

what is the l-band in sarcomere.

Answer 11

inner parts bside z disc, only thin filaments. (actin)

Question 12

what is the a band in sarcomere?

Answer 12

the whole length of thick filaments (myosin)

Question 13

thick filaments (myosin) in myofibril are composed of what?

Answer 13

a myosin tail and myosin heads (moveable).

Question 14

thin filaments (actin) found in myofibril are composed of what?

Answer 14

actin (yellow bobbles), troponin (grey double bobbles), tropomyosin (stems)

Question 15

what does myosin binding site on thin filament (actin) bind to?

Answer 15

the myosin head on thick filament. (during contraction)

Question 16

what are thin filaments (actin) binded to?

Answer 16

z-discs.

Question 17

what does tropomyosin on thin filament (actin) do?

Answer 17

tropomyosin blocks binding site at rest.

Question 18

what happens during muscle contraction?

Answer 18

actin molecules and z discs are pulled and slide towards H- zone. both h and I zones narrow.

Question 19

what triggers muscle fibres?

Answer 19

a motor neuron. neuron + triggered fibres = motor unit.

Question 20

what is a neuronal ending to a muscle fibre called?

Answer 20

neuromuscular junction.

Question 21

between the synaptic end bulb and motor end plate (muscle area) is what?

Answer 21

synaptic cleft.

Question 22

what happens at the neuromuscular junction?

Answer 22

Release of the neurotransmitter, acetylcholine (ACh)
Diffuses across cleft
Activation of ACh receptors on sarcolemma
Generation of Muscle Action Potential
Repeats with each nerve action potential
Breakdown of ACh by the enzyme acetylcholinesterase

Question 23

how is muscle contraction initiated?

Answer 23

Muscle action potential
Ca2+ released from Sarcoplasmic Reticulum (SR)
4 Ca2+ bind to troponin
Moves tropomyosin off actin sites
Myosin binds to actin and starts contraction cycle

Question 24

explain contraction cycle.

Answer 24

Myosin binds to actin & releases phosphate group (forming crossbridges)
Crossbridge swivels releasing ADP & shortening sarcomere (power stroke)
ATP binds to Myosin => release of myosin from actin
ATP broken down to ADP & Pi => activates myosin head to bind and start again
Repeats as long as Ca2+ concentration is high

Question 25

during muscle relaxation calcium ions are transported back to SR, what does this process involve?

Answer 25

active transport and use of ATP. Tropomyssin covers actin binding site.

Question 26

Describe aerobic respiration

Answer 26

Production of ATP in mitochondria Requires oxygen and carbon substrate Produces CO2 and H2O and heat.

Question 27

limiting factors of muscle fatigue include:

Answer 27

Ca2+ Creatine Phosphate Oxygen Build up of acid Neuronal failure

Question 28

what happens to muscles after exercise.

Answer 28

Lactic acid converted back to glucose in liver Creatine Phosphate and ATP resynthesised Oxygen binds to deoxymyoglobin

Question 29

what are the 3 types of muscle fibre.

Answer 29

Slow oxidative (SO)- small diameter & red large amounts of myoglobin and mitochondria ATP production primarily oxidative Fatigue resistant Fast oxidative- glycolytic (FOG) Large diameter = many myofibrils Many mitochondria and high glycolytic capacity Fast glycolytic fibres (FG) white, fast & powerful and fast fatiguing For strong, short term use

Question 30

Ties of muscles contraction

Answer 30

If force is constant and the muscle shortens = Isotonic Contraction If length is constant and the force varies = Isometric Contraction The latter is often a postural muscle activity

Question 31

what does strength exercise do for fast glycolytic fibres

Answer 31

increases size and strength of them.