Muscular contraction+microstructure

Question 1

How is smooth muscle controlled?

Answer 1

Involuntary control from ANS

Question 2

How is cardiac muscle controlled?

Answer 2

Circulating chemicals and ANS

Question 3

How is skeletal muscle controlled?

Answer 3

Voluntary control-To bring about movement

Question 4

Label types of muscle fibres

Answer 4

Parallel
Fusiform
Triangular

Question 5

Label types of muscle fibre

Answer 5

Unipennate
Bipennate
Multipennate

Question 6

Answer 6

Question 7

Answer 7

Question 8

What is the present in the sarcoplasm?

Answer 8

Myoglobin
Mitochondria

Question 9

What are myofibres composed of?

Answer 9

Myofilaments(Actin, myosin)

Question 10

What is the Z-disc?

Answer 10

Actin base chain-separate sarcomeres

Question 11

What is the H-zone?

Answer 11

Zone where only myosin is present

Question 12

Diameter of a myofibril

Answer 12

1-2um

Question 13

Do myofilaments and myofibrils extend along the whole length of the myfibres?

Answer 13

Myofilaments don’t
Myofibrils do

Question 14

What is the A-band?

Answer 14

Whole length of actin chain

Question 15

What is the I-band

Answer 15

Zone with only actin

Question 16

What is the structure of a myosin filament?

Answer 16

2 globular heads
Single tail formed by 2 a-helices
-Several hundred form 1 filament

Question 17

What 2 other molecules exist on the actin chain?

Answer 17

Troponin
Tropomyosin

Question 18

What occurs to the H zone, I band and A-zone during contraction

Answer 18

H zone decreases/disappears
I band decreases
A band stays same

Question 19

What enzyme breaks down ACh in an NM junction

Answer 19

Acetylcholine esterase

Question 20

How is the ryanodine receptor opened?

Answer 20

Dihydropyridine (DHP) receptor in T-tubule membrane: senses ΔV & changes shape of the protein linked to ryanodine receptor

Question 21

How do muscle contractions stop through Ca2+ removal?

Answer 21

Ca2+ is actively transported into the SR continuously while action potentials continue. ATP- driven pump (uptake rate < or = release rate).

Question 22

For muscle contraction control, where are the upper and lower motor neurones?

Answer 22

Upper-brain
lower-Brainstem and spinal cord

Question 23

Approximately how many neurones and muscle fibres do humans have?

Answer 23

Humans have approximately 420,000 motor neurons and 250 million skeletal muscle fibres.

Question 24

Roughly how many muscle fibres does each motor neurone innervate/

Answer 24

600

Question 25

What does stimulation of a motor unit lead to?

Answer 25

Contraction of all the muscles innervated by that motor neurone

Question 26

What does this table show?

Answer 26

Huge variation in ratio of neurone to muscle fibres innervated

Question 27

Characteristics of a Type I motor unit

Answer 27

**Slow** smallest diameter cell bodies small dendritic trees thinnest axons slowest conduction velocity

Question 28

Characteristics of a Type IIa motor unit

Answer 28

**Fast fatigue resistant** larger diameter cell bodies larger dendritic trees thicker axons faster conduction velocity

Question 29

Characteristics of a Type IIb motor unit

Answer 29

**Fast fatiguable** larger diameter cell bodies larger dendritic trees thicker axons faster conduction velocity

Question 30

Answer 30

Question 31

What method can tell you the variety in muscle fibre types?

Answer 31

ATPase staining method

Question 32

How are motor units classified?

Answer 32

Tension generated Speed of contraction Fatiguability of the motor unit

Question 33

Generally what order are motor units recruited in?

Answer 33

Slow Fast fatigue resistant Fast fatiguable

Question 34

Outline the 2 methods by which motor unit activation is regulated?

Answer 34

**Recruitment** Smaller motor units are recruited first, as more force is needed more(larger) units are recruited -**Allows for fine movement e.g writing** **Rate coding** Slower units fire at a slower frequency as firing speed increases, force generated increases -**Summation occurs when firing frequency is too fast for the muscle to relax in between contractions**

Question 35

2 functions of neurotrophic factors

Answer 35

Prevent neuronal death Promote growth of neurons after injury

Question 36

What occurs if a fast and slow twitch muscle are cross innervated?

Answer 36

The slow one becomes fast and vice versa

Question 37

Label types of contraction

Answer 37

Isometric Concentric Eccentric

Question 38

Outline how ageing affects the proportion of muscle fibre types?

Answer 38

Loss of type I and II fibres but also **preferential loss of type II fibres**. This results in a larger proportion of type I fibres in aged muscle (evidence from slower contraction times).

Question 39

What most likely occurs to muscles in terms of type switching with training?

Answer 39

IIB to IIA

Question 40

What can cause a shift from type I to type II muscle fibres?

Answer 40

Severe deconditioning Spinal cord injury Spaceflight micorgravity