Nervous System- Skeletal muscle and contraction Flashcards
What are the three types of muscle in the body and name an example of each?
1) Cardiac- heart
2) Skeletal muscle- attached to bone i.e. biceps
3) Smooth muscle- blood vessels
What are the muscle fibres called that make up the muscle?
Myofibrils
What are the 2 types of protein filament that make up myofibrils?
1) Myosin- thicker and made up of long rod shaped fibres with bulbous ends.
2) Actin- thinner and consists of 2 strands which are twisted around one another
What are the coloured bands in myofibrils?
1) Anisotropic- contain both actin and myosin so look darker as they overlap
2) Isotropic- only contain actin which looks lighter
Where is the Z line located?
The centre of the Isotropic bands
What is the H zone?
The region in the centre of the sarcomere which contains only myosin so is light in colour
What are the 2 types of muscle fibre?
1) Slow twitch- slow contraction, poor power, adapted for endurance and aerobic respiration
2) Fast twitch fibres- fast contraction, increased power for short periods of time
What are the adaptations of slow twitch fibres?
Lot of mitochondria, rich supply of blood vessels, rich supply of glycogen and large store of myoglobin
What are the adaptations of fast twitch fibres?
Thicker and more numerous myosin filaments, high concentration of enzymes used in anaerobic respiration, a large store of phosphocreatine which provides phosphate to make ATP
What is the evidence for the sliding filament mechanism?
1) I band becomes narrower
2) Z lines become closer to one another
3) H band becomes narrower
4) A band does not change (this is determined by the width of myosin)
What are the 3 stages of muscle contraction?
1) Stimulation (refer to action potential)
2) Contraction
3) Relaxation
What causes muscle contraction?
1) Action potential moves through t tubules
2) The sarcoplasmic reticulum opens Ca2+ channels
3) Ca2+ ions to diffuse out into the muscle
4) Ca2+ ions cause tropomyosin to change shape which exposes binding sites on actin
5) ADP from the myosin head forms a cross bridge with actin
6) Myosin head changes shape causing actin to slide and the ADP is lost
7) ATP attaches to the myosin head
8) ATPase hydrolyses ATP, so energy released changes myosin head back to original shape- ADP and Pi are reformed
What cause muscle relaxation?
Active transport of Ca2+ ions back into sarcoplasmic reticulum
Lack of Ca2+ ions allows tropomyosin to establish original position
What are the roles of the mitochondria at the synapse?
1) Movement of vesicles to membrane
2) Active transport of ions
3) Provide energy for ionic pump
4) Synthesis of acetylcholine
5) Reabsorption of acetylcholine from the cleft
Why is ATP a suitable energy source for cells to use?
1) Releases small amount of energy so little is lost as heat
2) Releases energy on the spot
3) Rapidly resynthesized
4) Not lost from the cell
