Action potentials, synapses, and neural integration

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Where does the first action potential occur in a neuron?
Or, where does the action potential begin in a neuron?

At the axon hillock

What are neurotransmitters?

Chemical messengers that carry signals between nerve cells in the brain and body

What prevents action potentials from moving backwards?

The refractory period and the sequential nature of ion diffusion

What are glia cells

any of the cells that hold nerve cells in place and help them work the way they should

What is the function of myelin sheaths?

They insulate axons, preventing ion movement and increasing signal speed

Which cells form myelin sheaths in the PNS?

Schwann cells

What is saltatory conduction?

A process where the action potential jumps between unmyelinated nodes, increasing speed

What disease results from the destruction of myelin?

Multiple sclerosis

What would happen if the myelin sheath was damaged?

The action potential would fire, but the signal may be lost traveling down the axon

What are the functions of astrocytes?

• structural support

• metabolic functions

• blood-brain barrier maintenance

• neurotransmitter regulation

What is the role of oligodendrocytes?

The provide myelination in the CNS, insulating multiple neurons at a time

Where does a chemical neuron signal occur?

Between neurons via neurotransmitters

Where does an electrical neuron signal occur?

Within the neuron

What is exocytosis in neural communication?

The process of vesicles fusing with the presynaptic membrane to release neurotransmitters

What are ligand-gated ion channels

Channels that open or close when neurotransmitters bind to them, affecting ion flow

What does EPSP stand for?

Excitatory postsynaptic potential

What does the excitatory postsynaptic potential do

A positive change in the membrane potential that increases the likelihood of neuron firing

What does IPSP stand for?

Inhibitory postsynaptic potential

What does the inhibitory postsynaptic potential do?

A negative change in membrane potential that decreases the likelihood of neuron firing

What is neural integration?

A process of a neuron combining multiple inputs to decide whether to fire

What is temporal summation?

Multiple signals from the same neuron occuring in rapid succession to trigger an action potential

What is spatial summation?

Signals from multiple neurons combing to reach the action potential threshold

What triggers the release of neurotransmitters at the synapse?

The influx of calcium ions through voltage-gated calcium channels in the presynaptic neuron

Where is calcium concentration higher before neurotransmitter release?

Outside the synapse

How does calcium cause neurotransmitter release

they enter the synaptic terminal, causing vesicles to move, fuse with the membrane, and release neurotransmitters

What would happen if calcium voltage-gated ion channels were blocked

It would prevent neurotransmitter release, reducing the likelihood of the postsynaptic neuron firing

What is influx in calcium?

Calcium ions move into the cell

What is efflux of calcium?

Calcium ions move out of the cell

Where are the nodes of ranvier?

On the axon with the myelin sheaths

What is the function of a node of ranvier

essential for the transmission of electrical impulses along the axons

What does the arrival of an inhibitory postsynaptic potential do?

ligand-gated Cl- channels open allowing chloride ions to flow into the postsynaptic neuron

What does the arrival of an excitatory postsynaptic potential do?

ligand-gated Na+ channels open, allowing sodium ions to flow into the postsynaptic neuron

What activates the ligand gated ion channels

EPSP and IPSP

What activates the voltage gated ion channels

The difference in charge of the interior and exterior of the cell

If IPSP and an EPSP of equal magnitude fired, would it fire?

No