Module 4

Question 1

Muscle types

Answer 1

Skeletal
Smooth
Cardiac

Question 2

Smooth muscle

Answer 2

Found within the walls of the gastrointestinal tract, lymphatic vessels, the urinary bladder, blood vessels, respiratory tract (bronchioles), skin and the iris

Responsible for involuntary activity: churning of food in the stomach, constriction of tubes
Contract to allow movement

Nonstriated with only one nucleus in each cell

Question 3

Cardiac muscle

Answer 3

Found only in the contractile walls of the heart
Striated
Has similar contractile properties to skeletal muscle, but appears to branch

Uninucleate: one nucleus per muscle cell
Cardiac muscle fibres interconnect at intercalated disk → allows for the electrical signal to pass from one muscle cell to another
- This movement of action potentials from one cell to another helps synchronise heart muscle contraction

Question 4

Skeletal muscle

Answer 4

Makes up 40-50% of body mass
Striated → striped in appearance
- The arrangement of contractile compartments (sarcomeres) within the muscle cells creates the striped appearance

Skeletal muscle cells are long → muscle fibres
- Skeletal muscle is controlled by the somatic nervous system
- Can be consciously influenced
- During development, muscle fibres form by fusing multiple precursor muscle cells → there are therefore multiple nuclei for each muscle fibre

Question 5

Sarcomeres

Answer 5

Arrangement of contractile compartments/the basic contractile unit of skeletal muscle
- sarcomeres typically shorten when contracting, causing them to pull onto tendons and apply force onto a bone
- this causes movement around a joint to occur
- muscle attaches to bone via connective tissue (tendon) and produces movement around joints

Question 6

Muscle cells

Answer 6

Multiple nuclei helps produce proteins and respond to when the cell needs to grow or repair → homeostasis of the cell
- Nuclei direct protein synthesis, growth, and repair along the length of the cell

Question 7

Primary function of skeletal muscle

Answer 7

To interact with our environment through the production of movement

Question 8

All skeletal muscles have

Answer 8

Contractility: the ability to shorten and thicken, and develop tension
Excitability: the ability to respond to appropriate stimuli
Extensibility: the ability to be stretched without damage
Elasticity: the ability to store some energy, and recoil the resting length

Question 9

Transverse cut

Answer 9

Connective tissue dispersed throughout the muscle

Question 10

Longitudinal section

Answer 10

Clear bundles of muscle fibres

Question 11

Microstructure of muscles

Answer 11

muscle is made up of a larger number of bundles known as fascicles of muscle fibres
- this is surrounded by connective tissue
- a single muscle fibre is very long and runs parallel to other muscle fibres in the same fascicle

Question 12

Connective tissue

Answer 12

the support system dispersed throughout muscle

Question 13

Muscle fibre

Answer 13

refers to the muscle cell
- made up of a large number of fused embryonic cells
- multinucleated
- inside each muscle fibre cell is a series of sarcomeres

Question 14

How do sarcomeres work

Answer 14

sarcomeres contain the contractile filaments that convert the electrical signal initiated in the nervous system to muscle force
- each sarcomere contains a series of thick and thin filaments that overlap during contraction
- sarcomeres from adjacent myofibrils line up, giving muscle its striated appearance

Question 15

Actin

Answer 15

thin filaments found in sarcomeres that attaches to the Z lines within the sarcomeres
- fine protein strand

Question 16

Myosin

Answer 16

thick filament found in sarcomeres that anchors at the M line in the centre of the sarcomere
- fine protein strand

Question 17

What happens when actin and myosin overlap more or less?

Answer 17

more:
whole muscle shortening occurs
- Z lines are pulled closer
- muscle is contracting

less:
whole muscle lengthening occurs