Brain Bee Study Guide -

You are about to initiate movement. The EPSP travels down your dendrites, summing at the axon hillock — your decision zone. Here, voltage-gated sodium channels wait. The membrane potential crosses threshold (-55 mV from resting -70 mV). Bang.

The muscle fiber fires an action potential. on the T-tubule sense the voltage change and mechanically open ryanodine receptors (RyRs) on the sarcoplasmic reticulum. Calcium floods the cytosol.

Vesicles fuse. Glutamate spills into the synaptic cleft.

On the other side is your target: a in the ventral horn of the spinal cord, at the level of C5-C6 (imagine reaching for a cup). This LMN has ionotropic glutamate receptors — specifically, AMPA receptors (fast, Na+/K+) and NMDA receptors (slower, Ca2+ permeable, blocked by Mg2+ at rest). brain bee study guide

A volley of signals races up through the of the thalamus. And then — you feel it. A massive excitatory postsynaptic potential (EPSP) arrives at your basal dendrites.

Your action potential speeds down your (courtesy of oligodendrocytes in the CNS). The myelin sheaths are interrupted by Nodes of Ranvier , where saltatory conduction leaps the signal from node to node — much faster than unmyelinated axons. Step 2: The Synapse You arrive at the presynaptic terminal . Depolarization opens voltage-gated calcium channels (VGCCs) . Calcium rushes in. This triggers synaptic vesicles — loaded with glutamate — to dock at the active zone via SNARE proteins (synaptobrevin on vesicle, syntaxin and SNAP-25 on membrane).

Calcium binds to . Tropomyosin shifts away. Myosin heads — already loaded with ADP and Pi — bind to actin. Power stroke. Pi released. New ATP binds, myosin releases actin, then hydrolyzes ATP to recock the head. You are about to initiate movement

At the synapse onto the LMN, in the cleft take up excess glutamate via EAAT2 transporters , converting it to glutamine (via glutamine synthetase), sending it back to you to recycle.

Sodium floods in (phase 0: depolarization). Then, open, repolarizing you (phase 3). But a special class of calcium-dependent potassium channels ensures you have an afterhyperpolarization — a refractory period so you don't fire chaotically.

: Tight junctions between endothelial cells, supported by astrocyte end-feet. Circumventricular organs (area postrema, OVLT, etc.) lack BBB — they sample blood for toxins (vomiting center) or osmolality. Final Exam Question (Self-Test) A 65-year-old man has difficulty initiating movement, a resting "pill-rolling" tremor, and a shuffling gait. He is treated with L-DOPA. Which specific neuron population is degenerating, and what neurotransmitter do they normally release? Answer: Dopaminergic neurons in the substantia nigra pars compacta; neurotransmitter = dopamine. End of Deep Story. Use this narrative to anchor facts: imagine yourself as Pyra the pyramidal neuron, lifting the cup, and all the molecules and disorders that could help or hinder you. Good luck at the Brain Bee! 🧠🐝 The membrane potential crosses threshold (-55 mV from

The LMN fires. Its axon travels via the into the brachial plexus , then the radial nerve , finally reaching the neuromuscular junction (NMJ) of your biceps brachii . Step 3: The Neuromuscular Junction At the NMJ, the LMN releases acetylcholine (ACh) . ACh binds to nicotinic acetylcholine receptors (nAChRs) on the muscle fiber's motor end plate. These are ligand-gated ion channels — they let Na+ in, K+ out, creating an end-plate potential (EPP) .

This is a — a narrative-style, memorable walkthrough of key Brain Bee concepts, designed to help you retain neuroscience competition material by embedding facts into a vivid scenario. The Synaptic Symphony: A Brain Bee Deep Story You are a neuron. Specifically, you are a pyramidal cell in Layer 5 of the primary motor cortex (Brodmann Area 4). Your name is Pyra.

The hose is open.