Neuromuscular Junction PDF

# Neuromuscular Junction ## Biochemical Pathway - **Start:** Nervous system - **Finish:** Muscular system **1. Define Action Potential:** - Molecular level: K+ (potassium ion), Na (sodium ion). - How cells talk to each other: Analogy: Stadium wave - It's an action: Movement of ions across a membr...

# Neuromuscular Junction ## Biochemical Pathway - **Start:** Nervous system - **Finish:** Muscular system **1. Define Action Potential:** - Molecular level: K+ (potassium ion), Na (sodium ion). - How cells talk to each other: Analogy: Stadium wave - It's an action: Movement of ions across a membrane - Not a thing → It's an *Action Potential* **2. Diagram of Neuromuscular Junction:** - **Neuron:** Contains a synaptic vesicle with the neurotransmitter acetylcholine (ACh). - **Muscle:** Contains the opening of a T-tubule and a muscle fiber with myofibrils. - **Synaptic Cleft:** Space between the neuron and the muscle. - **Muscle End Plate:** Contains ACh receptors. **3. Step-by-Step Breakdown of Pathway:** 1. Signal starts the action potential on the neural cell. 2. Action potential arrives at the synaptic vesicle. 3. Synaptic vesicle fuses with the cell membrane and dumps ACh into the synaptic gap. 4. ACh moves across the space and binds to the receptor on the muscle cell. This causes the cell membrane to allow ions to move across → Action Potential. ## Neuromuscular Junction - Background - Remember: A muscle fiber is another word for a *muscle cell*. - A muscle fiber has 5 important *organelles* you need to understand. - **Myofibril:** The individual proteins that make up a muscle fiber. - **Sarcolemma:** The muscle fiber cell membrane. - **Sarcoplasmic Reticulum:** Regulates levels of calcium ions (Ca??) in the muscle fiber. - **Releases** calcium ions when a muscle fiber is stimulated by an impulse. - **Does not** release calcium ions when there is no electrical impulse. - **T-Tubules:** Part of the sarcolemma that protrudes *deep* into the muscle fiber interior. - **Sarcoplasmic Reticulum:** Binding sites on the muscle fiber that receive *neurotransmitters*. ## Neuromuscular Junction Vocabulary - **Motor Neurons:** Neurons that deliver impulses from the *brain* to the *muscles* to stimulate skeletal muscle fibers to *contract*. - **Action Potential:** An electrical impulse that travels through a *motor neuron* and a *neuron*. - **Neuromuscular Junction:** Where the *motor neuron* comes together with a *muscle fiber*. - **Axon Terminal:** The end of the *axon* of a neuron that sends an impulse *away*. - **Synaptic Cleft:** The space between the *axon terminal* of a motor neuron and a *muscle fiber*. - **Neurotransmitter:** A chemical message released by *neurons*. - **Acetylcholine (ACh):** The neurotransmitter that motor neurons use to tell skeletal muscle to *contract*.