Muscle 2

Question 1

Name the 2 types of twitch muscle

Answer 1

slow and fast-twitch

Question 2

Describe how the slow-twitch contracts, its contractions, time period and where it is most common

Answer 2

Slow-twitch contract more slowly, provide less powerful contractions over a longer period common in the calf

Question 3

Describe how the fast-twitch contracts, its contractions, time period and where it is most common

Answer 3

fast-twitch contracts more rapidly provide more powerful contractions over a short period common in biceps

Question 4

How are slow-twitch muscles adapted for aerobic respiration?

Answer 4

Large store of myoglobin
Rich supply of blood vessels
Numberous mitochondria

Question 5

How are fast-twitch muscles adapted for anaerobic respiration?

Answer 5

Thicker and more numerous myosin filaments
High concentration of glycogen
High con. of enzymes involved in anaerobic respiration
A store of phosphocreatine 4 energy 4 muscle contraction

Question 6

What is a neuromuscular junction?

Answer 6

where motor neurone meets skeletal muscle fibre

Question 7

What is a motor unit

Answer 7

multiple muscle fibres supplied by the motor

Question 8

What are the similarities between synapses and neuromuscular junction

Answer 8

Both have neurotransmitter transported by diffusion
Have receptors causing an influx of Na+
Use Na/K pump to repolarise axon
use enzymes to breakdown the neurotransmitter

Question 9

What are the differences between synapses and neuromuscular junction in relation to being excitatory or inhibitory

Answer 9

Neuromuscular junctions excitatory

Cholinergic synapse can be either excitatory or inhibitory

Question 10

What are the differences between synapses and neuromuscular junction in relation to linking the neurone to ____

Answer 10

Neuromuscular junctions = motor neurone

Cholinergic synapse = motor/ sensory or intermediate

Question 11

What are the differences between synapses and neuromuscular junction in relation to the state of the AP

Answer 11

Neuromuscular junctions = AP ends

Cholinergic synapse = A new AP may be produced

Question 12

What are the differences between synapses and neuromuscular junction in relation to what the Acetylcholine binds to ?

Answer 12

Neuromuscular junctions = Muscle Fibre

Cholinergic synapse = post synpatic neuone

Question 13

Skeletal muscles occur in ___ pairs

Answer 13

antagonist pairs

Question 14

Name the mechanism for the contraction of skeletal muscle

Answer 14

Sliding Filament Mechanism

Question 15

What happens to the —- during the sliding filament mechanism
I band
A band
Z-lines/ sarcomere

Answer 15

I band narrows
A band remains the same length
Sarcomere shortens

Question 16

What evidence discounts the sliding filaments mechanism

Answer 16

The A band remains the same length

Question 17

Describe how the muscle is stimulated

Answer 17

AP reaches many neuromuscular junctions so Ca 2+ channels open and then ions diffuse into the synaptic knob
Ion causes synaptic vesicles to fuse with the presynaptic membrane and release their acetylcholine into the synaptic cleft
Acetylcholine diffuses across cleft and binds with receptor and depolarise

Question 18

Describe muscle contraction

Answer 18

AP travels into fibre via T-tubles which are in contact with the ER which AT ca2+from sarcoplasm.
AP opens Ca2+ channels so ions diffuse into sarcoplasm and cause tropomyosin to pull away from the actin-binding site they were blocking.
ADP attaches to myosin head which can bind to actin and form cross-bridges.
The head changes angle pulling actin along and releasing ADP
ATP attaches to myosin causing it to unbind to actin
Ca2+ activate ATPase to supply energy for myosin head to return to original shape

Question 19

What are the T-tubules?

Answer 19

They are extensions of the cell-surface membrane and breach throughout the sarcoplasm

Question 20

Myosin is joined _____ so can move in ____

Answer 20

Myosin is joined tail to tail so can move in opposite directions

Question 21

Describe Muscle Relaxation

Answer 21

Nervous stimulation ceases
Ca2+ AT back to ER
Reabsorption of Ca2+ allows tropomyosin 2 block actin again
Myosin heads unable to bind to muscle relaxes