Structure of Neurons
Which neuronal structure primarily receives synaptic input from other neurons?
dendrites
Why are action potentials considered all or nothing?
They occur only if threshold is reached, once its reached Na_ channel activation triggers a full spike.
Oligodendrocytes produce myelin sheath. In CNS, myelin is made by oligodendrocytes and in peripheral nerves myelin is made by Schwann cells. Each Schwann cell makes one segment of myelin while each oligodendrocytes makes multiple segments of myelin that wraps around several axons.
1. Separation of ions across the cell membrane
2. Permeability of the membrane to those ions
What's the Difference between Ramon y Cajol's Neuron Doctrine with Golgi's Reticular Theory?
Golgi’s theory is that nervous system is continuous web, neurons are physically connected with no gaps, and information flows through a network of nerve cells. Ramon y Cajal’s theory is that the nervous system is made of individual/separate neurons, neurons communicate through synapses, there is a directional flow of information. Similarities: nervous system is composed of specialized cells (aka neurons), both used Golgi’s silver staining technique when developing their theories, both trying to figure out how neural communication works.
What is the main functional role of the axon hillock in neuronal signaling?
action potential initiation
During the rising phase of the action potential, which ion has the greatest increase in membrane permeability?
Sodium
Astrocytes contribute to the blood–brain barrier primarily through which structural specialization?
End‑feet that surround capillaries. Astrocytic end‑feet envelop CNS capillaries, helping regulate permeability and maintain the blood–brain barrier.
Which ion contributes most strongly to establishing the neuron's resting membrane potential?
K, its leak channels makes its equilibrium potential the major determinant of RMP
Define coding intensity
Neurons code intensity not by increasing the power of an action potential, rather by increasing the frequency of the action potential. Thus, the more frequent an action potential rises, the more intense the signal and/or neuronal communication is.
Which structural feature allows myelinated axons to conduct signals more rapidly than unmyelinated axons?
saltatory conduction between nodes of ranvier, Myelin forces action potentials to jump between nodes of Ranvier, enabling saltatory conduction and faster signaling.
Why do action potentials propagate in only one direction along the axon?
Refractory Na+ channels prevent backward propagation. This inactivation prevents backward flow.
Which glial cell type becomes activated during injury to release cytokines and clear cellular debris?
microglia
What equilibrium potential is the RMP closest to and why?
K because the membrane is more permeable to K+ than Na+ K
Fill in the blanks: The ends of microtubules are designated as “+” (______ from the _____) or “-“ (_______ the _______). Microtubules are used to ________ materials ______ the cell. ______ ______ move organelles around the cell on microtubular tracks. ______ proteins move toward the “___” end while ______ move toward the “___” end.
The ends of microtubules are designated as “+” (away from the nucleus) or “-“ (towards the nucleus). Microtubules are used to transport materials within the cell. Motor proteins move organelles around the cell on microtubular tracks. Kinesin proteins move toward the “+” end while Dyneins move toward the “-” end
Which cytoskeletal component is most responsible for maintaining the long, thin structure of axons?
microtubules, they provide structural support and serve as tracks for kinesin‑ and dynein‑mediated transport along the axon.
Which event is primarily responsible for the repolarization phase of the action potential?
Opening of voltage-gated K+ channels. Repolarization occurs mainly because voltage-gated K+ channels open, allowing K+ to exit the cell and bring the membrane potential back toward resting levels.
During development, radial glia serve as scaffolding for neuronal migration. What additional role do they take on in the mature CNS?
They differentiate into astrocytes in the mature CNS after guiding neuronal migration during development.
If extracellular K concentration increases significantly, what happens to RMP?
it becomes less negative because higher extracellular K reduces concentration gradient thus decreasing K efflux and causing depolarization
What are the 4 things that internal calcium regulates?
1. second messenger signaling
2. gating and kinetics of voltage gated channels
3. gating and kinetics of ligand gated channels
4. gene expression
A mutation disrupts the function of kinesin in a neuron, what structural consequence is most likely to occur?
Accumulation of vesicles and proteins in the soma. Kinesin mediates anterograde transport from soma to axon terminals thus if disrupted, cargo accumulates in the soma.
A neuron is experimentally manipulated so that extracellular K⁺ is doubled while voltage-gated Na⁺ channels are partially inactivated. Which statement best explains how these combined changes alter both the resting membrane potential and the likelihood of generating an action potential?
a. RMP becomes less negative, the increased Na inactivation doesnt have an effect
b. RMP becomes less negative, increased Na inactivation decreases probability of firing an action potential
c. RMP becomes more negative, increased Na inactivation doesnt have an effect
c. RMP becomes more negative, increased Na inactivation increases probability of firing an action potential
B
Increasing extracellular K⁺ depolarizes the resting membrane potential by reducing the K⁺ gradient. However, partial Na⁺ channel inactivation limits the inward Na⁺ current needed for the rising phase of the action potential, making spike initiation less likely even though the membrane is closer to threshold.
What are glia known for? 2 words
The glue!!!
Explain why the Na/K/ATPase pump is essential for maintaining the RMP over long periods?
It maintains ion gradients that would otherwise dissipate due to leak channels, ensuring RMP remains stable.
Describe the connection between primary erythromelalgia and soidum channels
PE results from a mutation in the SCN9A gene, which encodes for the Nav 1.7 voltage gated sodium channel. This sodium channel is heavily expressed in nociceptive (aka painful) dorsal root ganglion neurons and the mutations make Nav 1.7 hyperexcitable, lowering the threshold for firing and causing the burning pain, redness, and warmth.