Synapses

Resting Potential

The electrical potential across the membrane of a neuron when not transmitting an impulse, typically around -70mV.

Sodium-Potassium Pump

A mechanism that actively transports 3 Na⁺ ions out of the neuron and 2 K⁺ ions into the neuron, maintaining resting potential.

Depolarization

The phase in action potential where the membrane potential reaches the threshold (-55mV), causing Na⁺ ions to flood into the neuron.

Repolarization

The phase in action potential where Na⁺ channels close and K⁺ channels open, restoring the negative charge inside the neuron.

Hyperpolarization

An overshoot phase in action potential where the inside of the neuron becomes more negative than the resting potential due to slow closing of K⁺ channels.

Continuous Conduction

The method of action potential propagation in unmyelinated neurons, moving in a wave-like manner along the axon.

Saltatory Conduction

The rapid transmission of action potentials in myelinated neurons, where impulses "jump" between Nodes of Ranvier.

Synapse

The junction between two neurons or between a neuron and an effector cell, crucial for communication in the nervous system.

Chemical Synapses

A type of synapse where neurotransmitters are released in response to an action potential reaching the axon terminal.

Neurotransmitter Release

Triggered by the influx of Ca²⁺ ions at the axon terminal, leading to the release of neurotransmitters into the synaptic cleft.

Enzyme Breakdown

The process by which neurotransmitters are broken down by enzymes (e.g., acetylcholinesterase) after their action.

Absolute Refractory Period

A phase during which a neuron cannot fire another action potential regardless of stimulus strength due to inactivated Na⁺ channels.

Relative Refractory Period

A phase where a stronger-than-normal stimulus is required to initiate another action potential.

Role of Sodium (Na⁺)

Essential for depolarization during action potential.

Role of Potassium (K⁺)

Essential for repolarization during action potential.

Role of Calcium (Ca²⁺)

Triggers the release of neurotransmitters at synapses.

Axon Diameter

A factor affecting the speed of transmission; larger diameter fibers conduct impulses faster due to reduced resistance.

Temperature

A factor that influences the speed of transmission; higher temperatures increase ion diffusion rates.

Myelination

The presence of myelin sheaths around axons, which speeds up impulse transmission through saltatory conduction.

Excitatory Neurotransmitters

Chemicals that increase the likelihood of an action potential (e.g., acetylcholine, glutamate).

Inhibitory Neurotransmitters

Chemicals that decrease the likelihood of an action potential (e.g., GABA, glycine).

Describe the different events occurring at points A and B

A - Neurone is stimulated

B - Depolarisation/ VG Na ion channels are open, Na ions are diffusing into the neurone

What is the threshold level for this action potential

-40mV

What is the resting potential of this neurone cell membrane

-60mv

Explain the shape of the curve during the period marked X

What is the given name to the period marked X

Pd of +40mV, Na ion channels close and K ion channels open

Refractory Period

How would the graph look is a bigger stimulus triggered the action potential?

Action Potential will have the same pd values as the graph shown cuz once the threshold is reached an action potential will always fire with the same change in voltage