Skeletal muscle Flashcards
What are the 2 main forms of muscle?
Striated
Non Striated
What types of muscle are striated?
Skeletal
Cardiac
What types of muscle are non striated?
Smooth
What is the mechanical efficacy of skeletal muscle?
20%
What are the main functions of skeletal muscle?
Movement
Posture
Stability of joints
Heat generation
What are the arrangements of muscle?
Pennete Convergent Fusiform Bipennete Multipennate Unipennate Parallel Circular
What is the Epimysium?
Outer connective tissue layer of muscle, continuous with the tendon
What is the Perimysium?
Encloses muscle fasicles
What are muscle fasicles?
Bundles of muscle fibres
What is the Endomysium?
Surrounds individual muscle fibres
What is fasciculation?
Involuntary twitching of fasicles. If common it can suggest neurological problems
What is a first class level system?
The load and force are either side of the fulcrum (Pivot) eg skull on the cervical vertebrae
Which is the most efficient type of level system?
First class level
What is a second class level system?
The load and force are on the same side of the fulcrum with the load closer to the fulcrum than the force. eg Lower leg and ankle
What is a third class level system?
The load and force are on the same side of the fulcrum, the load is further away than the force eg elbow
What are the main muscle groups?
Agonists, prime movers
Antagonists, oppose prime movers
Synergists, assist prime movers
Fixators, stabilise action of prime movers
What is compartment syndrome?
Trauma damages a blood vessel which may cause a bleed into a compartment causing a build up of pressure which presses on a nerve and causes pain.
What are the 2 types of muscle contraction?
Isotonic
Isometric
What is isotonic contraction?
Constant tension, variable muscle length. The muscle changes length and moves the load.
What are the 2 types of Isotonic contraction?
Concentric, muscle shortens eg lifting with the arm
Eccentric, muscle exerts a force while being extended eg walking downhill
What are the muscle fibre types?
Type I
Type IIa
Type IIb
What are type I muscle fibres?
Slow twitch fibres
Stain heavily - lots of mitochondria
What are type IIa muscle fibres?
Fast twitch or intermediate
Found particularly in sprinting
What are type IIb muscle fibres?
Fast twitch
Stain pale - little mitochondria
What is proprioception?
Awareness of self and allows awareness of where limbs are in 3D space
How does proprioception work?
Feedback control of muscle
Proprioceptors in muscles detect activity and feedsback via spinal cord
What are proprioceptors?
Specialised muscle fibres encased in a capsule along with nerve endings.
What is a motor unit?
A motor neuron and muscle fibre that innervates it
How do muscles and neurones communicate?
With signalling molecules in both direction
Why does the communication have to be constant?
Because if it wasn’t, the motor nerve and muscle would atrophy
What are some examples of the communication molecules?
Neurotrophin 3
Cardiotrophin 1 (type of cytokine)
IGF1
Why does muscle have a baseline tone at rest?
A baseline motor neuron activity
Retains tension in the muscle due to being an elastic tissue.
What controls the muscle tone?
The motor cortex in the cerebrum in the brain
What is Hypotonia?
Sudden loss of muscle tone/low level of muscle tone
What can cause Hypotonia?
Injury to the motor cortex in the cerebrum
Lesions of the cerebellum
Lesions of sensory afferents from muscle spindles
Degeneration of the muscle body
Lesions of lower motornneurones
What are the 2 types of summation?
Spatial
Temporal
What is Spatial summation?
Increase force of contraction by increasing the number of motor units involved. (called recruitment)
What is Temporal summation?
A series of action potentials in rapid succession causes muscle contraction. Doesn’t have enough time to relax so muscle contraction increases (Unfused tetanus)
What is a fused tetanus?
When succession of action potentials causes constant contraction.
What can mediate fused tetanus?
Toxin produced by Clostridium tetani
What does an EMG do?
Measures the electrical activity in a muscle which is a compound effect of all the muscle fibres being acgtivated in a muscle.
What can an EMG be used for?
Aiding diagnostics of certain types of motor neuron conditions
How do EMGs work?
They can show an increase in the force of muscle contraction and an increase in recruitment.
Calcium is removed to relax muscles, where does it go?
Back into the sarcoplasmic reticulum or bind to calmodulin
What does muscle contraction require?
Calcium and ATP which are needed in constant supply
What is the immediate store of ATP for a muscle?
Within the muscle, this is quickly depleted
What is the second source of ATP for a muscle?
In Creatine phosphate. Lasts for about 15 seconds.
How is Creatine phosphate a source of ATP?
Phosphorylates ADP to ATP
What is the third source of ATP for muscle?
Anaerobic glycolysis.
Why is anaerobic glycolysis not a favourable source of ATP?
Forms lactic acid which can cause lactic acidosis and cramps.
What is the favourable third source of ATP for muscles?
Aerobic respiration.
What is peripheral fatigue?
Effects peripheral muscle due to depletion of glycogen stores in the muscle.
What can cause peripheral fatigue?
Interruption of blood flow to the muscles
How does peripheral fatigue present itself?
Claudication (limping/interruption to walking)
Most common in the elderly
What is intermittent claudication?
Where there is only pain on exercise, due to ischaemia.
When can a state of continuous contraction occur?
When there is a depletion of ATP.
How does a depletion of ATP cause continuous contraction?
The myosin heads are unable to detach from actin filaments as they need ATP
What does continuous contraction cause?
Muscle stiffness
What is Rigor Mortis?
Where ATP is depleted and not replenished after death so there is stiffness. Occurs after about 3 hours and can last 72 hours
