muscles

Question 1

what is a muscle

Answer 1

a muscle is a tissue as it is composed of many similar cells working together collectively

Question 2

what is the function of a muscle

Answer 2

contraction

Question 3

how to describe contraction

Answer 3

comparatively fast, fatigues rapidly and is under conscious control.
skeletal muscles is under the control of the somatic nervous system (voluntary)

Question 4

information of skeletal muscles

Answer 4

made up of bundles of fibres, have striped appearance (also called striated muscle).
each fibre contains many myofibrils running the length of the fibre.

Question 5

what are myofibrils made of

Answer 5

made of multinucleate cells

Question 6

myofibril structure consists of….

Answer 6

I band made of Actin (shortens during contraction)
A band made of actin and myosin (stays same during contraction)
sarcomere - z line to z line (shortens during contraction)

Question 7

what are actin

Answer 7

thin filaments, globular protein

• many link together to form a chain
• 2 chains twist together to form actin filament

Question 8

what are myosin

Answer 8

thick filaments, fibrous protein

• has a tail attached to M line
• several lie in a bundle to form a myosin filament
• heads form cross bridges between actin and myosin

Question 9

what does the neuromuscular junction do

Answer 9

• it is the point at which the motor nuerone synapses with msucle
• neurotransmitter acetylcholine produced at axon terminals
• acetylcholine diffuses through gap and fuses with receptors on post-synpatic membrane
• post-synaptic membrane is highly folded to form motor end plate - large surface area
• this causes depolarisation of membrane at motor-end plate
• depolarisation goes down t-tubules causing calcium ions to move out of sarcoplasmic reticulum
• therefore causing a CONTRACTION OF MYOFIBRILS

Question 10

examples of other fibrous proteins

Answer 10

typomyosin - twists around actin chains

troponin - attaches to actin chains at regular intervals

Question 11

what is the muscular-ratchet mechanism

Answer 11

• myosin heads stick out and they contain ATPase (hydrolyses ATP to ADP + Pi)
• action potential arrives, myosin heads engage into binding sites on actin filaments
• ATP hydrolyses to ADP + Pi and energy is released causing the heads to swivel, rowing the actin past myosin.
• heads release, return to original position and rejoin and repeat action.
• when muscle relaxes, heads disengage.

Question 12

what is oxygen debt

Answer 12

when exercising, oxygen is needed for aerobic respiration. there is a limit to the volume of oxygen that can be taken in.
during intense exercise, muscles will not receive enough oxygen so will have to respire anaerobically.
during anaerobic respiration, pyruvate is reduced to lactate using hydrogen from reduced NAD. meaning a build up of lactic acid.
whe oxygen is available again, the lactate can be oxidesed back into pyruvate by liver.
this extra oxygen needed is called the oxygen debt.

Question 13

what does a build of lactic acid cause

Answer 13

cramps, muscle fatigue

Question 14

what is the main energy source used during exercise

Answer 14

glycogen, a branched molecule made up of alpha glucose with 1-4 glycosidic linkages. stored in muscle and liver

Question 15

information about glycogen

Answer 15

may become limiting, if used up the fat reserves will be used. body will always respire some fat to conserve glycogen.

Question 16

What is carbohydrate loading?

Answer 16

increasing the glycogen content of the liver and muscle.
7 days before event, perform exhaustive exercise to all but deplete your energy stores
next 2-3 days cut back on carbs and do low exercise to keep carb level low.
3-4 days before event, eat very high car diet. glycogen stores in muscle will become full as possible

Question 17

info about muscle types

Answer 17

2 fibre types occuring together in varying combinations depend on

• genetics of person
• training
• location of muscle

Question 18

what are slow twitch fibres

Answer 18

used largely in aerobic (endurance) exercises.
more efficient at using oxygen (oxidative phosphorylation) to generate more ATP
used for continuous extended muscle contraction over a long time
e.g marathon running, aerobics, jogging

Question 19

What are fast twitch fibres

Answer 19

used largely in anaerobic metabolism - depends on glycolysis and anaerobic respiration to create ATP
generates short burst of strength/speed
e.g sprinting, high jump, javelin throw.

Question 20

differences of slow and fast twich fibres

Answer 20

slow twitch - 
- ATP via aerobic respiration
- lots of mitochondria
-many capillaries
-smaller diameter
- contains myoglobin
fast twitch - 
- ATP via anaerobic respiration
- few mitochondria
- little myoglobin
- few capilarries
- larger diameter to slow twitch.