Skeletal, Smooth and Cardiac Muscle

Question 1

What are the three types of skeletal muscle fibres ?

Answer 1

I: Slow Oxidative (Resist Fatigue)
IIa: Fast Oxidative (Intermediate resistance to fatigue)
IIb: Fast Glycolytic (Fatigue quickly)

Question 2

What are four properties of Oxidative muscle fibres ?

Answer 2

High amount of mitochondria
High in oxidative phosphorylation
Contain Myoglobin
Red

Question 3

What are four properties of Glycolytic muscle fibres ?

Answer 3

Low amount of mitochondria
High in glycolytic enzymes and glycogen
Lower blood supply
White fibres with longer diameter

Question 4

Describe the structure of skeletal muscle

Answer 4

Striated
Muscle fibre containing many myofibrils
Bundle of fibres encased in connective tissue sheaths
Myofibril has a central sarcomere which conatins myosin and actin filaments

Question 5

Explain the mechanics of skeletal muscle contraction

Answer 5

1: Ca is released from the sarcoplasmic reticulum
2: Ca binds to the troponin on the thin filaments
3: This causes a conformational change on the trypomyosin which allows new binds sites to be uncovered allowing more Ca to bind.
4: Cross bridge moves

Question 6

What is occurring in the myosin head of the cross bridge thick filament ?

Answer 6

1: ATP binds to myosin head - limb moves away from actin.
2: ATP hydrolyses to ADP and Pi - Releases energy
3: ADP released

Question 7

Define Isomentric twitches

Answer 7

A muscle contracts with no resulting movement

Question 8

Define Isotonic twicthes

Answer 8

Concentric: Muscle shortens when contracts
Eccentric: Muscle contracts as muscle lengthens

Question 9

What length changes and zone changes occur when a skeletal muscle contracts ?

Answer 9

The size of the H zone (space between filaments) is reduced.

The I band (space between ends of thick filaments) is reduced also.

The A zone is unchanged.

Question 10

What is a motor unit ?

Answer 10

Motor neurons and muscle fibres

Question 11

Define the tension of a muscle

Answer 11

Force exerted by a muscle

Question 12

Define the load of a muscle

Answer 12

Force exerted on a muscle

Question 13

How does a muscle twitch occur ?

Answer 13

Single AP + Muscle fibre = Twitch

Question 14

What is the latent period ?

Answer 14

Time before excitation contraction starts

Question 15

What is the contraction time ?

Answer 15

Occurs between the start of tension and peak tension

Question 16

What kind of contractions have a shorter latent period but a longer contraction event ?

Answer 16

Isometric contractions

Question 17

What is occurring during a tetanic contraction ?

Answer 17

They are greater than twitch as the Ca never runs low enough for the typomyosin to re-block troponin binding sites

Question 18

What is the length-tension relationship ?

Answer 18

Less overlap of filaments = less tension

Question 19

Define optimal length (Io)

Answer 19

Muscle length for greatest isometric tension

Question 20

Define fatigue

Answer 20

Repeated muscle stimulation generates muscle fatigue which prevents the muscle from using up cats amounts of ATP/

Question 21

What are Type II muscle fibres and what are their properties ?

Answer 21

Fast twitch muscle fibres.
Use anaerobic respiration.
Less reliant on Oxygen which allows for quick generation of ATP.

Question 22

What are type I muscle fibres and what are their properties ?

Answer 22

Slow twitch muscle fibres.
Use aerobic respiration.
Which allows them to generates large amounts of ATP slowly.
The type I muscle contractions are also less likely to fatigue

Question 23

Describe the structure and functions of smooth muscle

Answer 23

No striations
Innervated by ANS
Exist in hollow organs
Thick and thin filaments

Question 24

How are the thick and thin filaments arranged in smooth muscles ?

Answer 24

Arranged diagonally across cells and anchored to membranes. They still slide to contract the muscle.

Question 25

How does a contraction occur in smooth muscle ?

Answer 25

1: Ca is released
2: Ca binds to calmodulin
3: Ca + Calmodulin activates MLCK
4: MLCK adds phosphate to myosinactivating the myosin
5: X-bridge cycle starts