muscle physiology

Question 1

Which muscle types are striated?

Answer 1

skeletal and cardiac

Question 2

Skeletal muscles are innervated by the ____ nervous system

Answer 2

somatic

Question 3

Cardiac and smooth muscles are innervated by the ____ nervous system

Answer 3

autonomic

Question 4

What is the sole source of Calcium in skeletal muscles?

Answer 4

sarcoplasmic reticulum

Question 5

What is the origin of Calcium in cardiac muscle?

Answer 5

Extra cellular fluid

and Sarcoplasmic reticulum (Ca-induced Ca release)

Question 6

What is a motor unit?

Answer 6

A single Alpha Motor neurone and all the muscle fibres it innervates

Question 7

What are the levels of organisation of skeletal muscle?

Answer 7

whole muscle -> muscle fibre -> myofibril -> sarcomere -> Actin (thin) / Myocin (thick)

Question 8

What is the A-band of the sarcomere?

Answer 8

thick filaments with portions of overlapping thin filaments

Question 9

What is the H-zone

Answer 9

the portion of the A-band (myosin/thick filament) where the thin filaments do not reach

Question 10

What is the M-line?

Answer 10

It extends vertically down the middle of the H-zone

Question 11

What is the I-Band?

Answer 11

The portion of the thin filaments which do not overlap with the thick filaments

Question 12

What is the function of Calcium in muscle contraction?

Answer 12

induces cross bridge formation between myosin head and actin filament

Question 13

What are T-tubules? How are they involved in contraction induction?

Answer 13

invaginations of the surface membrane that dip into the muscle fibre

Action potential in T-tubules induces Ca release from sarcoplasmic reticulum

Question 14

How does Calcium enables cross bridge formation?

Answer 14

1. Ca binding to troponin triggers the release of troponin-tropomyosin complex
2. The cross bridge binding sites on actin are now exposed

Question 15

What is the function of ATP in muscle contraction?

Answer 15

ATP phosphorylation energises the myosin heads

-once bound to actin, ADP+Pi are released, new ATP binds, inducing the power stroke

Question 16

What factors define the gradation of skeletal muscle tension?

Answer 16

• number of muscle fibres
• frequency of stimulation and summation of contractions
• length of fibre at the onset of contraction
• thickness of muscle fibre

Question 17

Skeletal muscle twitch is much _____ than the action potential.

Answer 17

longer

Question 18

Restimulation of skeletal muscle before the end of contraction results in …

Answer 18

summation of contraction

Question 19

What feature of the cardiac muscle AP prevents its tetanisation?

Answer 19

long refractory period

Question 20

What muscle length is optimal for cross bridge formation?

Answer 20

resting muscle length

Question 21

What are the 2 types of muscle contraction?

Answer 21

Isotonic contraction

Isometric contraction

Question 22

What is isotonic contraction use for? What is happening to tension and muscle length?

Answer 22

• body movements
• moving objects

Tension is constant;
muscle length changes

Question 23

What are isometric contractions used for?

Answer 23

• supporting objects in fixed position

- maintaining body posture

Question 24

What happens to tension and muscle length during isometric contraction?

Answer 24

Muscle tension develops at constant muscle length

Question 25

What are the 3 muscle fibre types?

Answer 25

Type I - Slow-oxidative
Type IIa - Fast-oxidative
Type IIx - Fast0glycolytic

Question 26

What are Type I fibres used for?

Answer 26

Prolonged low work aerobic activity

Question 27

Type IIa fibres use what metabolism?

Answer 27

both aerobic and anaerobic (walking)

Question 28

What are Type IIa fibres used for?

Answer 28

prolonged moderate work (jogging)

Question 29

What are the Type IIx fibres used for?

Answer 29

high intensity activities (jumping)

-use anaerobic metabolism

Question 30

What is the receptor involved in the Stretch reflex?

Answer 30

Muscle spindle

Question 31

Where and with what neurons do the afferent neurons activated by the muscle spindle synapse?

Answer 31

synapse at the spinal cord with alpha motor neurons

Question 32

What are the efferent neurons that stimulate the contraction in stretch reflex?

Answer 32

Alpha motor neurons