Skeletal Muscle Physiology 1

Question 1

What are muscles capable of?

Answer 1

of developing tension and producing movement through contraction

Question 2

Are smooth muscles striated?

Answer 2

No

Question 3

What kind of muscle are skeletal and cardiac?

Answer 3

striated muscle

Question 4

What causes the light and dark bands in striate muscles?

Answer 4

light - actin thin filaments

dark - myocin thick filaments

Question 5

What innervates skeletal muscles?

Answer 5

Somatic nervous system and are therefore subject to voluntary control

Question 6

What kind of nerve innervates cardiac and smooth muscle?

Answer 6

autonomic nervous system - involuntary

Question 7

List the functions of skeletal muscle

Answer 7

• Maintenance of posture
• Purposeful movement in relation to external environment
• Respiratory movements
• Heat production - shivering
• Contribution to whole body metabolism

Question 8

What is a motor unit?

Answer 8

The motor unit is a single alpha motor neuron and all the skeletal muscle fibres it innervates

Question 9

Why do muscles which serve fine movements have fewer fibres per motor unit? Give examples of these muscles

Answer 9

because precision is more important than strength

intrinsic hand muscles and extra-occular muscles

Question 10

What is a sarcomere?

Answer 10

Functional unit made up of actin and myocin filaments

Question 11

What do actin and myocin form?

Answer 11

cytoskeletal elements of skeletal muscle

Question 12

Why are there no gap junctions in skeletal muscle?

Answer 12

to allow rapid propagation of AP through muscle cells

Question 13

Does Ca induced Ca release occur in cardiac or skeletal muscles or both?

Answer 13

cardiac muscles only

Question 14

In skeletal muscle, where does the Ca required for excitation contraction coupling come from?

Answer 14

Entirely from the lateral sacs of the sarcoplasmic reticulum

Question 15

What is excitation contraction coupling?

Answer 15

process whereby the surface action potential results in activation of the contractile mechanism of the muscle fibre

Question 16

After the AP is initiated, where does it spread down in skeletal muscle?

Answer 16

the tranverse (T)-tubules - this traiggers the release of Ca from the lateral sacs of SR

Question 17

Which molecule acts as the neurotransmitter at the neuromuscular junction?

Answer 17

Acetylcholine

Question 18

What is the function of myofibrils?

Answer 18

contractile structures made up of actin and myocin filaments arranged into sarcomeres

Question 19

How long are skeletal muscles?

Answer 19

Usually extend the entire length of muscle

Question 20

What are skeletal muscles usually attached to?

Answer 20

attached to bone by means of a tendon

Question 21

What actually is a functional unit of an organ?

Answer 21

The smallest component capable of performing all the functions of that organ

Question 22

What separates sarcomeres?

Answer 22

Z line

Question 23

What are the 4 zones of sarcomeres?

Answer 23

A-band
H-zone
M-line
I-band

Question 24

How is muscle tension produced?

Answer 24

Sliding filaments theory - sliding of actin filaments on myocin filaments

Question 25

What does force generation within muscles depend on?

Answer 25

ATP-dependent interaction between thick (myosin) and thin (actin) filaments

Question 26

When is Ca2+ needed?

Answer 26

• switch on cross bridge formation
• Ca2+ is the link between excitation and contraction
• Ca2+ is entirely derived from sarcoplasmic reticulum in skeletal muscle

Question 27

When is ATP required?

Answer 27

during muscle contraction to power cross bridges

during relaxation to release cross bridges and to pump Ca2+ back into the sarcoplasmic reticulum