Muscular System

Question 1

What are the features and example of skeletal muscle tissue

Answer 1

quadriceps
voluntary control, attached to bones, striated appearance

Question 2

what are the feature and example of cardiac muscle tissue

Answer 2

wall of the heart
Involuntary control
Striated appearance

Question 3

what are the feature and example of smooth muscle tissue

Answer 3

organs/ blood vessel
involuntary control, smooth appearance ( no striation )

Question 4

outline the types of muscle action

Answer 4

Concentric- muscle contracts ( shortens)
Eccentric- muscle elongates
Isometric- muscle contracts but no movement
Isotonic- change in length to produce force

Question 5

outline the gross structure of the skeletal muscle tissue

Answer 5

Epimysium- connective layer that surrounds the whole muscle, separates from other organs
Perimysium- surrounds bundles of fibres ( fascicles), allows for fascicles to be stimulated
Endomysium- surrounds each individual muscle fibre ( cell)

Question 6

Define the following
Sarcolemma
Myofibrils
Transverse Tubles
Sarcoplasmic Reticulum

Answer 6

Sarcolemma- cell membrane, lipid bi-layer, conducts AP
Sarcoplasmic Reticulum- network of tubular channels, propagate action potentials
Myofibrils- cylindrical functional units within fibres, run parallel to fibres long axis
Transverse Tubules- tube system between SE, pass through the fibre, propogate AP to deeper interior

Question 7

Define the folowing: Sarcomere, contractile proteins and Z line

Answer 7

Sarcomere- basic contractile unit of a myofibril, light and dark bands ( filaments) give ‘striated’ appearance
Actin- thin filament
Myosin- thick filament
Z line- separate sarcomeres, attachment site of actin

Question 8

outline the MAIN steps for the contraction of the sacromere

Answer 8

Cross bridge formation
Power Stroke
Detachment of myosin
Resetting of myosin head

Question 9

explain the cross bridge formation

Answer 9

Calcium binds to troponin
Myosin heads attach to actin binding sites
Myosin head is bound to ADP and Pi
Considered ‘energised’ and yields energy

Question 10

Explain the power stroke step

Answer 10

Myosin head releases ADP & Pi
Myosin head used energy to pull actin filament
Actin & Z discs move towards centre of sacromere

Question 11

Explain the steps of the detachment of myosin and resetting of myosin head

Answer 11

ATP is required to remove myosin, enables myosin to reset
ATP is hydrolysed into ADP + Pi
Energy released ‘energises’ the myosin head

Question 12

Outline the process of excitation- contraction coupling

Answer 12

Excitation- Motor neuron delivers action potential to muscle fibres
Chemical synapse at neuro muscular junction ( Acetycholine), triggers AP in the sarcolemma of muscle fibre
Action potential travels along sarcolemma & down T-tubules
Contraction- AP causes SR to release calcium, calcium binds to troponin

Question 13

what are the 3 main muscle fibre categories

Answer 13

Slow Oxidative ( Type I)
Fast oxidative- glycolytic ( Type IIa)
Fast glycolytic ( Type IIx)

Question 14

Outline the size principle

Answer 14

Motor Units recruited from smallest -> largest

Question 15

force generating capacity are affected by…

Answer 15

Motor unit recruitment ( magnitude & order); muscle temperature; stimulation frequency; resting length of fibres/ sacromere

Question 16

Define muscle fatigue

Answer 16

any exercise-induced reduction in the ability to exert muscle force/power, regardless of whether the task is sustained
Can have central and peripheral origins

Question 17

Define peripheral fatigue

Answer 17

loss of force producing capacity due to process at or below the neuromuscular junction
Synapse of AP, Excitation of sarcolemma & myofibrils, cross - bridge cycling

Question 18

Define central fatigue

Answer 18

loss of force producing capacity due to process above the neuromuscular junction- essentially the CNS, brain and spinal cord
activation of motor cortex, propagation of command along spinal cord and activation of motor units

Question 19

Give definition of voluntary activation of the muscle

Answer 19

Ability to generate and propagate the nerve impulse
Progressively declines through exercise= central fatigue

Question 20

What are some factors affecting muscle fatigue

Answer 20

Task related- exercise duration and intensity, dynamic vs isometric
Physiological characteristics- Biological sex, metabolic capacity

Question 21

how are central & peripheral mechanism linked by

Answer 21

Afferent feedback

Question 22

short duration, high intensity of work is mainly associated with

Answer 22

Peripheral
large disturbances to metabolic homeostasis

Question 23

longer duration of exercise is mainly associated with

Answer 23

central
progressive fall in voluntary activation