Skeletal Muscle (physiology) Flashcards
Are Skeletal muscles voluntary or involuntary muscles?
-voluntary
Where do our thoughts of voluntarily movement come from?
- Primary motor cortex
- sends to
What is the neuromuscular junction?
- synapse between somatic motor neuron and skeletal muscle fiber
Where is the origin of the motor neuron (cell body) of the neuromuscular junction?
- anterior horn of the spinal cord
What happens at the axon terminal directly above the muscle fiber?
- relay message by
- releasing neurotransmitter (ACh) to bind on the sarcolemma
The sarcolemma contains what kind of tubules?
-transverse tubule (t-tubule)
What is the function of the motor end plate?
-increase surface area for receptors to accept the neurotransmitters (ACh) from the vesicles
What is the goal of the neurotransmitter (ACh) being released into the muscle fiber?
-excite the muscle fiber for contraction
What type of receptor is needed for the muscle fiber to be excited?
- nicotinic cholinergic receptor
- when ACh binds, Sodium comes in , and a little K+ leaves
Once the muscle is excited it leads to what process?
-excitation-contraction coupling
What is the muscle fiber threshold?
-50mv
What is an end plate potential?
- localized depolarization (EPP)
- due to entry of NA+ ion
What kind of electrical signal does End plate potential give off?
- EPSP (excitatory postsynaptic potential)
- is a graded potential
Where is the end plate potential created?
Motor end plate
Can graded potentials be summed?
Yes
Where is the action potential created on the muscle fiber? Where does it go after?
- sarcolemma
- T tubule
Once the action potential reaches the t-tubule, which receptor conformed (altered)?
- DHP receptor (dihydropyridine) #3
- voltage sensitive
- linked to the sarcoplasmic reticulum
The DHP receptor (dihydropyridine) opens which ion channel in the sarcoplasmic reticulum?
- RyR Ca2+ (ryanodine Ca2+ release channels) #4
- Ca2+ enters cytoplasm
Once Ca2+ is released in the cytoplasm, where do they bind to?
- Ca2+ binds to troponin (of the thin filament) #5
- allows actin-myosin binding
Explain how the filaments are arranged in a relaxed state (not contracted)
- myosin head cocked
- tropomyosin partially blocks binding site on actin
- myosin is weakly bound to actin
-no calcium ions are available in a relaxed state