Muscle Physiology

Question 1

Describe the difference between somatic and autonomic

Answer 1

Somatic = With conscious effort
Autonomic = Unconscious effort

Question 2

Describe skeletal muscles

Answer 2

Striation on sarcomeres (stripes of muscles)
Effector of somatic nerve system
Voluntary contraction
Neuromuscular junction - Specific, multi-nuclei (fusion)

Question 3

Describe smooth muscles

Answer 3

Elongated, no striation, effector of ANS, involuntary contraction, varicosites
(diffuse), gap junction

Question 4

Describe cardiac muscles

Answer 4

Striation, effector of ANS, involuntary contraction, gap junctions, intercalated disks

Question 5

What is the function of muscles?

Answer 5

Locomotion, maintaining posture/body position, stabilising joints, generate heat
Activate sarcoplasmic reticulum to release Ca as T-tubules have VG ion channels

Question 6

What are the components of the skeletal muscle fibres?

Answer 6

Sarcolemma (plasma membrane)
Sarcoplasm (cytoplasm)
Myofibrils
Mitochondria
Sarcoplasmic reticulum (SER)
Transverse tubules (T-tubule)

Question 7

Describe 3 ways to form muscle energy metabolism

Answer 7

Glucose (oxidation), Can use fat (oxidation), Creatine phosphate

Question 8

Describe the neuromuscular junction

Answer 8

AP to axon terminal of motor neuron, Ca2+ channels open, NT ACh released, Ligand-gated Na+ channels open when ACh binds to receptors on motor end plate (EPSP), AP generated when threshold reached, Propagation of AP on sarcolemma

Question 9

Describe the components of myofibrils

Answer 9

Striated, sarcomere (repeating functional unit bordered by z-line), thick filament (myosin), Thin filament (actin), A-band (dark), I-band (lighter)

Question 10

What is actin?

Answer 10

Contractile protein

Question 11

What is troponin?

Answer 11

Regulatory protein

Question 12

What is tropomyosin

Answer 12

Regulatory protein

Question 13

Describe the sliding filament of muscle contraction (which shortens etc)

Answer 13

Myosin/actin filaments don’t shorten, A-band remains same, I-band/H-band shorten

Question 14

Describe twitch contraction

Answer 14

Contraction produced in response to single AP, All or nothing for given muscle fibre
Can be induced for muscle fibre/motor unit/entire muscle

Question 15

What is latency in terms of twitch contraction?

Answer 15

Time delay between stimulation (nerve AP/direct electrical) - E-C coupling

Question 16

What is the contraction and relaxation phase?

Answer 16

Contraction phase - Cross-bridge cycling

Relaxation phase - Ca2+ uptake

Question 17

What is the contractile force of muscle affected by?

Answer 17

Multiple muscle fibres in contraction / Force that individual fibres produce
Fibre diameter, Changes in fibre length, Freq of stimulation, Type of muscle fibre, Extent of fatigue

Question 18

Describe frequency and summation

Answer 18

AP (2ms), contraction (10-200ms), Tension depends on [Ca2+]
Freq of stim inc, Ca2+ release more than uptake - When system is saturated (all troponin bind with Ca2+, cross-bridge cycling maxed out)

Question 19

What is tetanus?

Answer 19

Long lasting contraction

Question 20

What are the 3 major types of skeletal fibres?

Answer 20

Slow oxidative fibres
Fast oxidative fibres
Fast glycolytic fibres

Question 21

Describe muscle receptors

Answer 21

For coordinated activities, Muscle spindles (Stretch receptors, detect muscle length)
Golgi tendon organs - Detect muscle tension, protect muscle from exercise activity