Muscle

Question 1

What are the two types of striated muscle?

Answer 1

Skeletal and Cardiac

Question 2

What are the characteristic features of skeletal muscle?

Answer 2

Multiple nuclei
Orderly arrangement of proteins
Nuclei bulge out

Question 3

What are the characteristic features of cardiac muscle?

Answer 3

One nucleus per cell
Intercalated discs
Gap junctions

Question 4

What is meant by hypertrophy?

Answer 4

Muscle fibres taking on more protein (actin and myosin) and so bulking up in appearance.

Question 5

What structure attaches muscle to bone?

Answer 5

Tendon

Question 6

What type of cells are used to replace skeletal muscle after an injury?

Answer 6

Satellite cells

Question 7

What two process help skeletal muscle to recover after injury?

Answer 7

1. Satellite cells migrating to point of injury to differentiate into new muscle cells
2. Hypertrophy of nearby muscle fibres to help take on the load.
   NB: The actual damaged skeletal muscle fibres will never recover.

Question 8

What changes occur to the appearance of the sarcomere when a muscle contracts?

Answer 8

I band reduces in width
H band reduces in width
(A band remains unchanged)

Question 9

Describe the sliding filament theory of muscle contraction.

Answer 9

Myosin heads bind to binding sites on actin filaments
On contraction, myosin heads flip, causing actin to change arrangement
Actin filaments slide over myosin filaments, moving closer to the M line- Power Stroke

Question 10

What molecules block actin binding sites and how do they work?

Answer 10

Tropomyosin partially blocks the binding sites and troponin holds it in place via cooperative blocking?

Question 11

What is required to unblock binding sites blocked by tropomyosin?

Answer 11

Calcium- Binds to troponin causing it to alter shape, pulling tropomyosin away and exposing binding site.

Question 12

What is the role of the sarcoplasmic reticulum?

Answer 12

Storage of Calcium ions

Question 13

What is the role of the transverse tubules in muscle fibres?

Answer 13

To allow conduction of signal deep into the muscle tissue

Question 14

What makes up a motor unit?

Answer 14

Muscle fibre and motor neuron

Question 15

What is the difference between an isometric and an isotonic muscle contractions?

Answer 15

Isometric contraction involves no change in muscle length.

Isotonic contraction involves muscle shortening

Question 16

How is a twitch contraction generated?

Answer 16

A single action potential applied to a muscle fibre

Question 17

What are the two roles of ATP in muscle action?

Answer 17

1. ATP used to separate myosin heads from actin binding sites, allowing a new cross- bridge cycle to begin.
2. ATP used to pump Calcium ions back into the sarcoplasmic reticulum, allowing contraction to end.

Question 18

How does fatigue occur due to high intensity/ short duration exercise?

Answer 18

1. Depolarisation and subsequent conduction failure due to increased [K+]
2. Increased [Lactic Acid] as waste product, acidifying proteins
3. [ADP + Pi] too high to allow myosin detachment from actin binding sites

Question 19

What are the two qualities which skeletal muscle fibres are characterised based on?

Answer 19

Fast/ Slow

Oxidative/ Glycolytic

Question 20

What quality of muscle fibres makes the ‘fast’ or ‘slow’?

Answer 20

ATPase activity

Question 21

What are the differences between oxidative and glycolytic muscle fibres?

Answer 21

Oxidative has high mitochondrial activity for oxidative phosphorylation. Glycolytic has low mitochondrial activity.
Oxidative has narrow diameter. Glycolytic has large diameters.
Oxidative has high vascularisation. Glycolytic has low vascularisation.
Oxidative has myoglobin. Glycolytic has glycogen and glycolytic enzymes.
Oxidative fibres are typically red. Glycolytic fibres are typically white.

Question 22

What 3 types of skeletal muscle fibres exist?

Answer 22

Slow Oxidative- Resist Fatigue
Fast Oxidative- Mild Fatigue
Fast Glycolytic- Fatigue quickly

Question 23

What nervous system innervates smooth muscle?

Answer 23

Autonomic

Question 24

How does smooth muscle contract?

Answer 24

Calcium binds to Calmodluin
Calcium-Calmodulin binds to Myosin Light Chain Kinase
This phosphorylates myosin Cross bridges using ATP
Cross bridges can then bind to Actin sites