Lecture 12: Muscle - Actions & Roles Flashcards
Muscular + _______ systems interact to produce muscle activity
- Nervous
Why does the sarcoplasmic reticulum’s structure have to be slightly different?
- Because there are nuclei all up and down the muscle fibre
What kind of messages do neurons carry?
- Electrical (action potential)
Tissue between neuron and muscle fibre…
- Neuromuscular Junction
Neuromuscular Junction features:
- Large SA
- Synaptic Cleft
- Chemicals in synaptic cleft
Steps occurring in action potential event….
- Electrical –> Chemical –> Electrical
What are t-tubules like?
- Tunnels that burrow through the muscle fibres
- Action potentials travel down t-tubules that trigger calcium release
Why is Ca2+ so important for contraction?
- Myosin head exposed, come up and attach to actin filament, contract, and detach
What is the sliding filament theory?
- Sarcomeres pulled toward each other
A motor unit is…
- A motor neuron, all it’s little nerves, and all the muscle fibres it attaches to
What’s controlling contraction?
- Electrical event
Motor unit displays _____ or ______ activation of fibres
- All or none
Force of contraction in a whole muscle depends on:
Characteristics of motor units:
- -> Size
- -> Number (increase = increase force of contraction)
- -> Rate of firing’
Muscle Attachments
- -> efforts needed for movement
- -> determines muscle role
Think of bones as_____. Joint = ____. Muscle Contraction = ______. Load = _____.
- Lever
- Pivot
- Pull
- External / Internal
Types of levers with muscle attachments:
- Stabilise Joint Position (skull + muscles @ base)
- Effective at overcoming loads (ankle)
- Large range of movement and speed (biceps)
Types of muscle action:
- Concentric
- Eccentric
- Isometric
What happens during concentric contraction?
- Muscle is active
- Change in joint position
- Muscle is shortening at the same time
- (Flexion)
What happens during isometric contraction?
- Muscle develops tension but length of muscle does not change
- eg. holding a book on hand
What happens during eccentric contraction?
- Muscle is active and developing tension
- Change in joint position
- Muscle lengthening
- (Extension)
Types of muscle role:
- Agonist
- Antagonist
- Stabiliser
- Neutraliser
Agonist:
- Muscle creating desired movement (bicep flexing, developing tension, and shortening) // concentric
Antagonist:
- Works against / with agonist, tricep + bicep
- Lengthening // eccentric
Stabiliser:
- Any time you’re keeping still
- A muscle is active to hold a joint still
Neutraliser:
- Muscle eliminates an unwanted movement (possibly caused by another muscle)
- Pronator muscles neutralise supinating effect of biceps brachii
