Lab 1 Flashcards
What is the role of the axon hillock in a neuron?
Integration zone of neuron that sums up all electrical signals and decides whether to generate action potential
The axon hillock is crucial for determining if the neuron will fire.
What do the nodes of Ranvier do?
Propagate action potentials by allowing K+/Na+ to diffuse between myelin
Nodes of Ranvier are gaps in the myelin sheath that facilitate rapid signal transmission.
What happens when K+ leaves the cell?
Intracellular fluid (ICF) becomes more negative, leading to repolarization
What effect does Na+ entering the cell have?
Intracellular fluid (IF) becomes more positive, leading to depolarization
Depolarization is a key step in the generation of action potentials.
What is the threshold potential for generating an action potential?
Minimum membrane potential needed is -55mV
Reaching this threshold is crucial for the neuron to fire.
What is the effect of adding K+ to the extracellular fluid (ECF)?
Less K+ leaves the cell, leading to depolarization
This can influence neuronal excitability.
What is the effect of adding Na+ to the extracellular fluid (ECF)?
More Na+ wants to enter the cell, leading to depolarization
This increases the likelihood of reaching the threshold potential.
What is lidocaine and its effect on action potentials?
Reversible and temporary, blocks sodium channels at the hillock and on the axon, resulting in inability to generate action potential
Lidocaine is often used as a local anesthetic.
What is TTX and its effect on action potentials?
Irreversible and permanent, blocks sodium channels on the axon only, resulting in inability to propagate action potential
TTX is a potent neurotoxin found in pufferfish.
Fill in the blank: The axon hillock is the _______ zone of a neuron.
integration
Define the threshold potential.
The minimum membrane potential needed to generate an action potential.
Where are synaptic vesicles found on the neuron?
Axon terminals.
Describe the steps of an action potential.
- Resting Potential (-70 mV): Na⁺/K⁺ pump keeps cell ICF inside.
- Threshold (-55 mV): Stimulus opens Na⁺ channels; must reach threshold to fire.
- Depolarization (+30 mV): Na⁺ influx makes ICF positive.
- Repolarization: K⁺ channels open; K⁺ exits, restoring negativity.
- Hyperpolarization: K⁺ channels stay open too long; ICF becomes even more negative.
- Return to Resting Potential: Na⁺/K⁺ pump restores balance.
Place the steps of the action potential in order:
1. Depolarization (+30 mV): Na⁺ influx makes ICF positive.
2. Return to Resting Potential: Na⁺/K⁺ pump restores balance.
3. Threshold (-55 mV): Stimulus opens Na⁺ channels; must reach threshold to fire.
4. Resting Potential (-70 mV): Na⁺/K⁺ pump keeps cell ICF inside.
5. Hyperpolarization: K⁺ channels stay open too long; ICF becomes even more negative.
6. Repolarization: K⁺ channels open; K⁺ exits, restoring negativity.
4 - 3 - 1 - 6 - 5 - 2
What is the mechanism of action for the anaesthetics lidocaine and TTX?
They block voltage-gated Na+ channels, preventing action potential.
When does the absolute refractory period begin?
When Na+ channels open/When the threshold potential is reached/When membrane reaches -55mV
When does the relative refractory period begin? When does it end?
When Na+ channels reset/When Na+ channels close/When membrane returns to -55mV.
It ends when membrane potential returns to resting -70mV
Fill in the blanks.
Word Bank:
Spinal nerves & vetebral arteries
Spinous process
Spinal cord
Superior articular process
Transverse process
Transverse foramen
