Muscle Contractions

Question 1

What are muscles?

Answer 1

Muscles are effectors that contract in response to nerve impulses, due to a stimuli

Question 2

What are the three types of muscles?

Answer 2

Cardiac muscles
smooth muscles
Skeletal muscles

Question 3

What are cardiac muscles?

Answer 3

Muscles found within the heart, they are myogenic as contractions arise from within the heart itself

Question 4

What are smooth muscles? Where are they found

Answer 4

Found in the wall of tubular organs
They are involuntary, unscripted and unstriated
Contracts slowly, fatigues slowly

Question 5

What are skeletal muscles? Where are the found?

Answer 5

Attached to bones via inelastic, connective tissue
Voluntary, striped, striated
Contracts rapidly, fatigues rapidly

Question 6

What is antagonistic muscle action? In which muscles does it occur?

Answer 6

Where two muscles work in a pairs around an incompressible skeleton/bone. They work to move bones around joints.
As one muscle contracts and shortens, the other relaxes and returns to its normal shape

Question 7

Describe the gross structure of the skeletal muscles

Answer 7

• tendons attach to either side of the muscle, so attach them to bones
• muscles are made up of bundles of muscle fibres (muscle cells surrounded by a cell plasma membrane) bound by connective tissue
• muscle cells consist of many myofibrils

Question 8

What would be seen if you were to look at a myofibrils under an electron microscope?

Answer 8

Repeated light and darl bands would be displayed
The light bands (I bands) contains only thin actin filaments
The dark bands (A bands) contains only mainly thick myosin filaments, and some overlapping actin filaments
Sarcomeres are marked by Z lines

Question 9

What are myofibrils made of?

Answer 9

Repeated functional units called sarcomeres
Contains thin actin filaments and thick myosin filaments

Question 10

What are sarcomeres?

Answer 10

Repeating functional units found in myofibrils

Question 11

What is the structure of myosin (in myofibrils)?

Answer 11

Made of a tail and a globular head
The tails are specifically shaped to bind to each other to form a thick filament
The globular heads stick out in all directions, and form actomyosin bridges (cross-links) with adjacent actin filaments

Question 12

What is the structure of actin (in myofibrils)?

Answer 12

Made of two helical strands of globular actin molecules, that twist round each other
Associated with to regulatory proteins- troponin and tropomyosin
Tropomyosin is a fibrous protein that wraps around the actin filaments