MSK- physiology Flashcards
What do “dark bands” refer to in muscle fibers?
Myosin filaments
What do “light bands” refer to in muscle fibers?
Actin filaments
Skeletal muscle features
Motor units, striated, voluntary control, neuromuscular junctions, no gap junctions
Purpose of skeletal muscle
Movement, posture, heat production, metabolism, respiratory movement
what is a motor unit
A single alpha motor neuron and all the skeletal muscle fibres it innervates
Power>precision
More fibres per motor unit
Myosin is darker/lighter
Darker
Actin is darker/lighter
Lighter
what are sarcomeres
Functional unit of the muscle
Muscle tension sliding filaments theory
Sliding of actin filaments on myosin filaments
Calcium is released from where in skeletal muscle fibres when surface action potential spreads down what?
Lateral sacs of sarcoplasmic reticulum, t-tubules
Factors determining graduation of muscle tension
-No of muscle fibres contracting within muscle
-tension developed by each contracting muscle fibre
Tension developed by each contracting muscle fibre depends on
-frequency of stimulation and summation
- length of muscle fibre at onset of contraction
-thickness of muscle fibre
What happens when skeletal muscle is stimulated once
Twitch produced
What happens when muscle fibres are stimulated so rapidly there is no opportunity to relax at all between stimuli
Tetanus occurs
Optimum length of skeletal muscle is approximately the length of what
It’s resting length
Isotonic contraction
Muscle tension remains constant as muscle length changes (body movements and maintaining objects)
Isometric contraction
Muscle tension develops at constant muscle length (body posture etc)
Main source of energy that supplies ATP when oxygen is present
oxidative phosphorylation
Main source that supplies ATP when oxygen is not present
glycolysis
Type 1 skeletal muscle fibre
Slow oxidative fibres
Type 2a skeletal muscle fibres
Fast oxidative muscle fibres
Type 2b skeletal muscle fibres
Fast glycolytic fibres
Type 1 fibres aka
Slow twitch fibres
Type 2a fibres aka
Intermediate twitch fibres
Type 2b fibres aka
Fast twitch fibres
Type 1 fibres used
Posture, walking
Type 2a used
Jogging etc
Type 2b used
High intensity
what is the stretch reflex
Simplest monosynaptic spinal reflex
Muscle spindles aka
Intrafusal fibres
Ordinary muscle fibres aka
Extrafusal muscle fibres
what are muscle spindles
A collection of specialised muscle fibres which act as sensory receptors for the stretch reflex
where are muscle spindles located
Within belly of muscles
what are fibrous joints
Bones United by fibrous tissue, doesn’t allow any movement, eg skulls in adults
what are cartilaginous joints
Bones United by cartilage, allows limited movement, eg intervertebral disc
what are synovial joints
Separated by a cavity containing synovial fluid and United by a fibrous capsule
what are simple synovial joints
joints that have 1 pair of articular surfaces
what are compound synovial joints
joints with more than one pair of articular surfaces
Functions of joints
Structural support, purposeful motion
Purposeful motion purpose
Stress distribution, confer stability, joint lubrication
Synovial fluid purposes
Lubrication, prevents wear and tear, movement, nutrition
Normal synovial fluid is what colour
Colourless
when does red synovial fluid occur
Traumatic synovial tap and haemorrhagic arthritis
WBC count of synovial fluid increases in:
Inflammatory and septic arthritis
what does repeated wear and tear result in
Osteoarthritis
Synovial fluid proliferation and inflammation is a result of what
Rheumatoid arthritis
Decomposition of salt crystals eg uric acid =
Gouty arthritis
