Muscle Physiology 1

Question 1

What are the 3 types of muscles in the body ?

Answer 1

Skeletal, cardiac and smooth muscles

Question 2

Skeletal and cardiac muscle is striated and smooth muscle is unstriated - T/F?

Answer 2

True

Question 3

What is the control over skeletal, cardiac and smooth muscles

Answer 3

• Skeletal muscle control is voluntary
• Cardiac and smooth muscles control is involuntary

Question 4

What are the physiological functions of skeletal muscle ?

Answer 4

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

Question 5

What are skeletal muscles organised into and describe this

Answer 5

Oragnised into motor units -

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

Question 6

What does the muscles per motor neurone depend on ?

Answer 6

Depends on the function served by that muscle - due to the fact that the fewer fibres supplied by a single motor neurone the more percise fine movements it can carry out

Question 7

What are the different levels of organisation of muscles ?

Answer 7

Question 8

What are some of the important differences between skeletal and cardiac muscles:

What intiated and propagates contraction

Excitation contraction coupling (whats the link between excitation and contraction)

Gradiation of contraction (what makes them stronger or weaker)

Answer 8

Question 9

What does the pic show and what type of muscle are these present in ?

Answer 9

Neuromuscular junctions present in skeletal muscle

Question 10

What does this pic show and what type of muscle are they present in ?

Answer 10

Gap junctions present in cardiac muscle

Question 11

What is excitation contraction coupling ?

Answer 11

It is the process by which the surface AP results in activation of the contractile mechanism of the muscle fibre

Question 12

Describe the steps of excitation contraction coupling in skeletal muscle

Answer 12

1. Acetylcholine relased at neuromusclar junction
2. AP generated in response which goes down T-tubules of muscle cells
3. AP in T-tubules causes relase of Ca²⁺ from the sarcoplasmic recticulum
4. Ca2+ binds to tropnin on actin filaments
5. Tropomyosin is therefore physically moved aside to uncover cross-binding bridges on actin filament
6. Myosin cross-bridges attach to actin and bend pulling actin filaments towards the centre of sarcomere (contraction)
7. When no longer AP Ca2+ is taken back up in the sarcoplasmic recticulum
8. Ca2+ no longer bound to troponin, tropomyosin slips back to original postition over binding sites on actin, contraction ends, actin slides back to original resting place

Question 13

What is the neurotrasmitter at the neuromuscular junction in skeletal muscles ?

Answer 13

Acetylcholine

Question 14

Appreciate this pic of T-tubules

Answer 14

Question 15

What is ATP required for in terms of skeletal muscle contraction (excitiation-contraction coupling)

Answer 15

Required for pulling actin filaments towards the centre of the sarcomere

Question 16

Describe the structure of muscles

Answer 16

• Muscles are comprised of parallel muscles fibres
• Each muscle fibre is made up of myofibrils
• Myofibrils have alternating segments of actin and myosin fibres

Question 17

Match the appearance of myosin and actin:

• Thin and lighter in appearance
• Thick and darker in appearance

Answer 17

• Thin and lighter in appearance - actin
• Thick and darker in appearance - myosin

Question 18

What structure is actin and myosin arranged into?

Answer 18

Arranged into sarcomeres

Question 19

What is the functional unit of skeletal muscles and define what is meant by functional unit

Answer 19

• Functional unit is the smallest component capable of performing all the functions of that organ
• Sarcomere is the functional unit of skeletal muscles

Question 20

What is the sarcomere found between ?

Answer 20

Two Z-lines

Question 21

What are the 4 different zones of the sarcomere ?

Answer 21

Think HAMI

• H - lighter area within middle of A band, where thin filaments don’t reach
• A - Made up of thick filaments along with portions of thin filaments that overlap in both ends of thick filaments
• M - extends vertically down middle of A band within centre of H zone
• I - Consists of remaining portion of thin filaments that do not project in A-band

Question 22

Learn the zones of the sarcomere under the microscope

Answer 22

Question 23

What is ATP required for in terms of muscle movements ?

Answer 23

It is required for contraction and relaxation

Question 24

What is Ca2+ required for in terms of muscle movements ?

Answer 24

Required for cross-bridge formation

Question 25

Appreciate the relation of actin and mysoin filaments to each other

Answer 25