MSK Session 2 (Lecture 2.1) Flashcards
What are the functions of skeletal muscle?
1) Movement
2) Posture
3) Stability of joints
4) Heat generation
What are the 7 arrangements of skeletal muscle?
1) Circular
2) Convergent
3) Parallel
4) Unipennate
5) Bipennate
6) Multipennate
7) Fusiform
What is fasciculation? Can it be harmful?
Involuntary local twitch of a muscle fibre caused by a spontaneous depolarization of a lower motor neuron. Can be benign and harmless or can be indicative of motor neurone disease?
Describe and give an example of a first class lever.
Where the fulcrum is in the middle with the force and load on either side. It is very efficient e.g. moving head upwards by contraction of neck muscles
Describe and give an example of a second class lever.
Load is in the middle with the force being at one end and the fulcrum being at the other. It is efficient e.g. gastrocnemius elevating heel of foot.
Describe and give an example of a third class lever.
The fulcrum is at one end with the resistance and force on the same side near the fulcrum. e.g. biceps brachii flexing forearm
What are the four muscle groups?
1) Agonists
2) Antagonists
3) Synergists
4) Fixators
Define an agonist.
Prime movers (main muscles responsible for a particular movement)
Define an antagonist.
Oppose prime movers
Define synergists.
Assist prime movers (neutralise extra motion) e.g. side motion
Define fixators.
Stabalizes action of prime mover e.g. fixes non-moving joint when prime mover acting over two joints.
What is compartment syndrome?
Build up of pressure in one of the body’s compartments containing muscles and nerves. This causes nerve compression and in severe cases muscle and nerve ischaemia.
What are the two types of muscle contraction?
1) Isotonic
2) Isometric
Describe isotonic contraction and its two subdivisions
Constant tension, variable muscle length
1) Concentric - muscle shortens
2) Eccentric - muscle exerts force while being extended
Describe isometric contraction.
Constant length, variable tension e.g. hand grip
State the three types of muscle fibre.
1) Type 1 (slow oxidative) - red
2) Type 2a (fast oxidative) - intermediate
3) Type 2b (fast glycolytic) - white
Describe type 1 fibres.
Aerobic High myoglobin Many mitochondria Rich capillary supply Fatigue resistant
Describe type 2a fibres.
Aerobic High myoglobin Many mitochondria Rich capillary supply Moderate fatigue resistance
Describe type 2b fibres
Anaerobic glycolysis Low myoglobin Few mitochondria Poor capillary supply Rapidly fatigable
What is proprioception ? Where can proprioceptors be found?
Feedback control of muscle tension and movement. Proprioceptors can be found in muscle spindles which are located in the muscle belly sensing how stretched the muscle is. They travel along afferent sensory nerves towards the brain.
What is a motor unit? Describe how it can affect fine vs crude control of muscles.
A motor neurone and the muscle fibres it innervates.
If a motor neurone innervates fewer muscles then this will give rise to fine control as there would be individual fibre recruitment rather than inervating 1000s of muscle fibres giving crude control.
Give examples of signalling molecules that communicate between nerve and muscle.
Neurotrophin-3, cardiotrophin-1, IGF1
What determines muscle tone?
1) Motor neurone activity
2) Muscle elasticity
How can hypotonia arise? List 3 different causes.
Hypotonia is a low level of muscle tone
1) Cerebral or spinal neural shock
2) Lesion of lower motor neurones e.g. polyneuritis
3) Primary degeneration of muscle e.g. myopathies
What is spatial summation?
More motor neurones activated so more muscle fibres recruited to develop more force
What is temporal summation?
Increased frequency of action potentials to muscle fibres over time. Can cause tetanus if constant stimulation occurs leading to prolonged muscle contraction. (e.g. Clostridium tetani)
