Muscle function Flashcards
What are muscle contractions triggered by?
Electrical events from the brain (action potentials)
How do the action potentials get to the muscle fibre?
They arise in the brain, but are conducted down the spinal cord to motor neurons in the spinal cord. These are conducted out of the CNS along motor axons to muscle fibres.
What happens when the action potential arrives from the brain at the neuromuscular junction?
A synaptic transmission occurs which results in the generation of the action potential in the postsynaptic muscle fibre.
What is the process that results in the development of force within a fibre?
excitation-contraction coupling
What type of synapse is the NMJ?
A chemical synapse (Cholinergic), so depolarisation at the nerve terminal results in the release of a neurotransmitter
What is the name of the neurotransmitter released?
Acetyle choline (ACh)
What is a synaptic transmission?
A neuron communicates with a target cell across a synapse by sending neurotransmitters to carry the action potential.
What does a chemical synaptic transmission involve?
The release of a neurotransmitter from the pre-synaptic neuron and neurontransmitter binding to a specific post-synaptic receptors.
What does ACh aid with?
Acts as a receptor on the muscle fibres post synaptic surface to initiate an action potential in the muscle fibre.
Where is the AP conducted along?
Along the surface of the muscle fibre, away from the NMJ is both directions. AP is spreading over the sarcolemma.
Where does the AP enter the muscle fibre?
Passes down the T-tubule and is conducted via the T-tubular network into the core of the fibre.
What does the AP trigger as it travels through the T-tubules?
It causes a voltage sensitive protein to change shape, which in turn opens a Ca release channel in the SR, allowing Ca ions to flood the sarcoplasm where the myofilaments are.
What does the release of Ca into the sarcoplasm promote?
The binding of Ca to a subunit of troponin molecule (troponin C)
What does the binding of Ca and troponin cause?
A change in shape of the troponin which exposes a actin binding sight. Myosin then binds actin and changes shape, where force is then generated.
