6.3 Muscle Coordination

Question 1

What are the 3 types of muscle?

Answer 1

1. Skeletal/striated
2. Smooth
3. Cardiac

Question 2

Main characteristic of smooth muscle

Answer 2

Voluntary

Question 3

Where is smooth muscle found?

Answer 3

All blood vessels except capillaries
Digestive system (stomach, oesophagus, small & large intestine)

Question 4

Is smooth muscle voluntary or involuntary?

Answer 4

Involuntary

Question 5

Big to small: muscle structure

Answer 5

Muscle bundle ➞ muscle fibre ➞ myofibril

Question 6

What does the longitudinal cross section of a myofibril look like?

Answer 6

Bands of dark & light

Question 7

What does the circular cross section of a myofibril look like?

Answer 7

Dots of actin & myosin randomly scattered

Question 8

Actin vs myosin

Answer 8

Actin: light
Myosin: thick, heavy, dense

Question 9

Sarcomere

Answer 9

Functional unit of muscle.
Each myofibril contains sarcomeres divided by Z lines.

Question 10

Z line

Answer 10

Cluster of protein molecules.
Divides myofibril into sarcomeres.
Where actin filaments bind.

Question 11

M line

Answer 11

Cluster of protein molecule in MIDDLE of sarcomere.
Where myosin filaments bind.

Question 12

I band

Answer 12

Where ONLY actin filaments are

Question 13

A band

Answer 13

Where myosin filaments are regardless of overlap

Question 14

H zone

Answer 14

Within A band, myosin only

Question 15

Describe an actin filament in detail

Answer 15

Made of two strands of actin linked together by tropomyosin.
Troponin is interspersed between tropomyosin.

Question 16

Describe a myosin filament in detail

Answer 16

Has little “heads” on each end that are curved upwards
Made up of multiple myosin strands

Question 17

3rd source of ATP (apart from aerobic & anaerobic respiration)

Answer 17

Phosphocreatine!

Question 18

How does phosphocreatine produce ATP?

Answer 18

It is hydrolysed into phosphate ion and creatine.
Phosphate ion is added to ADP which is produced in muscle contractions

Question 19

Neuromuscular junction: what happens after neurotransmitters diffuse across?

Answer 19

1. Neurotransmitter binds to receptor on Na channels in muscle
2. Na ions move into muscle
3. Sarcolemma becomes depolarised
4. T-tubules (which go deep into the myofibrils) also become depolarised
5. This releases Ca ions from the sarcoplasmic reticulum into myofibrils

Question 20

First step when interpreting micrographs of a myofibril

Answer 20

IDENTIFY Z LINES

Question 21

Main differences between muscle relaxation & contraction in terms of actin & myosin?

Answer 21

Relaxed: NO LINKAGES between actin & myosin
Contracted: Linkages form

Question 22

What happens during muscle contraction?

Answer 22

1. Sliding filament theory: actin & myosin filaments slide past each other
2. A bands stay the same length
3. I bands & H zones shorten
4. Z lines move closer together
5. Sarcomere decreases in length